This work has been supported by NINDS, RO1NS52699 and MH84874 to SA. 
We would like to thank Dr. Dave Featherstone (Department of Biological Sciences, University for Illinois at Chicago) for providing us with the suture glue used in the immunohistochemistry work. We thank Michael Alpert for his comments and proofreading of the manuscript.

1. Preparation of Poly-D-lysine Hydrobromide
<ol>
	<li>Prepare 1 mg/ml poly-D-lysine hydrobromide in 0.1 M borate buffer (pH 8.5).</li>
	<li>Aliquot and store at -20 &#176;C.</li>
</ol>
2. Poly-lysine Coating of Coverslips
Note: Carry out all cleaning and coating steps in a laminar flow chamber.
<ol>
	<li>Place coverslips in a Petri dish containing 1 N Hydrochloric acid (HCl) for 2 hr.</li>
	<li>Aspirate all HCl and rinse with 70% Ethanol (EtOH) 2-3x.</li>
	<li>Leave in 70% EtOH for 1 hr.</li>
	<li>Aspirate all 70% EtOH and rinse with 100% EtOH 2-3x.</li>
	<li>Leave in 100% EtOH for 2 hr. Aspirate all EtOH.</li>
	<li>Blot dry with filter paper and air dry for a few seconds.</li>
	<li>Place O/N in 1 mg/ml poly-lysine solution.</li>
	<li>Rinse coverslips next day with Millipore water 4-5x.</li>
	<li>Air dry poly-lysine coated coverslips on glass rollers in a clean Petri dish.</li>
	<li>For immunohistochemistry, use 35 x 10 mm Petri dish lids. Prepare sylgard (polydimethylsilioxane, PDMS) lined dishes by pouring PDMS (elastomer and curing agent 10:1 by weight) into the dish to a thickness of 0.3 cm and allow to set at 30 &#176;C O/N. Once this has set, cut a 2 cm by 1 cm inset into the PDMS. Clean and coat the inset with poly-lysine following the same steps as mentioned above for coverslips.</li>
	<li>Store poly-lysine coated coverslips and dishes covered inside the laminar flow chamber until use (up to 2 weeks, but achieve best adhesive results by preparing periodically every 3-4 days).</li>
	<li>Prepare a PDMS block, to pin the spinal cord in the vibrating tissue slicer. Mix Elastomer A and Elastomer B 1:1 by weight. Pour into a 100 x 15 mm Petri dish and allow to set O/N at 30 &#176;C. Cut a rectangular piece of the PMDS and glue it to the slicing base plate using epoxy glue. Allow the glue to set fixing the PDMS in place and slice multiple thin sections off the surface to obtain a flat surface to pin the tissue on.</li>
</ol>
3. Acute Dissociation of Lamprey Spinal Cord to Yield Isolated Reticulospinal Axons
<ol>
	<li>Anesthetize an ammoecoete or adult lamprey (Petromyzon marinus) with tricaine methanesulphonate (MS-222; 100 mg/L). Add anesthetic into the water, in a plastic cup covered by a lid, containing the lamprey to be sacrificed.</li>
	<li>Decapitate lamprey in cold (4 &#176;C) Ringer&#8217;s solution of the following composition (in mM): 130 NaCl, 2.1 KCl, 2.6 CaCl2, 1.8 MgCl2, 4 HEPES, 4 dextrose (pH 7.6, osmolarity 270 mOsm) and remove body wall muscles to expose dorsal surface of spinal cord.</li>
	<li>Remove meninx primitiva from the dorsal surface of the spinal cord using fine forceps. Do not remove ventral meninx primitiva at this stage.</li>
	<li>Cut spinal cord into 1 cm long pieces.</li>
	<li>Pin a spinal cord piece using fine insect pins, dorsal side facing up, on a PDMS lined slicing base plate (see 2.12) in a vibrating tissue slicer chamber containing ice-cold Ringer&#8217;s solution.</li>
	<li>Remove a central section of the dorsal column of the spinal cord by slicing along the rostro-caudal axis with the blade, leaving behind intact dorsal column sections on the rostral and caudal ends to serve as handles during the dissociation process Figure 2a&#160;and Figure 2b. Use slowest speed setting that permits slicing and a depth setting that removes only the dorsal column leaving the underlying reticulospinal axon column undamaged Figure 2b.</li>
	<li>Incubate sliced spinal cord pieces at RT for 45 min&#160;in a cocktail of 1 mg/ml protease (Type XIV from Streptomyces griseus) and 1 mg/ml collagenase prepared (Type IA from Clostridium histolyticum) in Ringer&#8217;s solution (adapted from El Manira &#38; Bussi&#232;res, 1997 17).</li>
	<li>Pin enzyme-treated spinal cord pieces using fine pins in a PDMS lined Petri dish containing cold (4 &#176;C) Ringer&#8217;s solution.</li>
	<li>Remove ventral meninx primitiva with fine forceps.</li>
	<li>Cut lateral tracts of spinal cord with a scalpel blade at the midpoint of the sliced dorsal section leaving the central column of reticulospinal axons intact in the spinal cord Figure 2d.</li>
	<li>Place a drop of immersion oil on the lens.</li>
	<li>Place the poly-lysine coated coverslip (Figure 3a, top piece, red rectangle) in the slot of the recording chamber Figure 3 and apply vacuum grease to all edges (space between red and blue rectangles in Figure 3a, to facilitate a seal. Screw the top into place. Place the chamber in the inset on the recording rig.</li>
	<li>Add Ringer&#8217;s solution into the recording chamber using a Pasteur pipette.</li>
	<li>Connect the outflow tubing of the pressure bottle containing antifreeze solution to the thermoelectric cooling device input tubing. Connect the output tubing of the thermoelectric cooling device to the input end of the outer cooling jacket and the output end to the reservoir Figure 3b.</li>
	<li>Place one piece of spinal cord at a time in the recording chamber and gently separate the spinal cord maintaining it along the coverslip at all times using Teflon coated forceps until axons are isolated Figure 2e&#160;and Figure 2f.</li>
	<li>Bring the recording solution temperature to 10 &#176;C by passing the pressurized (nitrogen gas is pushed into the bottle) antifreeze solution (by displacement), via the thermoelectric cooling device, through the outer cooling jacket of the recording chamber Figure 3b.</li>
	<li>Allow axons to recover for 1 hr post dissociation at 10 &#176;C.</li>
</ol>
<img alt="Figure 2" fo:content-width="4in" src="/files/ftp_upload/51925/51925fig2highres.jpg" width="400" /> 
Figure&#160;2. Schematic description of dissociation protocol for isolation of reticulospinal axons. (a) Removal of dorsal column. The arrow indicates the direction of slicing of the tissue. The dorsal horns are marked by the alphabet D (red font color), while the ventral horns by the alphabet V (red font color). (b) Dorsal column removed in the central portion of the spinal cord exposing the reticulospinal axons (green lines). The ventral horns, which remain intact after the slicing process, are marked by the alphabet V (red font color). (c) 45 min&#160;treatment with protease and collagenase enzymes cocktail (1 mg/ml). (d) Cutting of lateral tracts of the spinal cord; indicating position, direction and extent of lateral cut. (e) Mechanical dissociation of spinal cord. Arrows indicate position of forceps and direction of separation force during dissociation. (f) Representative example of dissociated reticulospinal axon preparation. Green arrows mark regions of acutely dissociated reticulospinal axons without any postsynaptic processes.
<img alt="Figure 3" fo:content-width="5in" src="/files/ftp_upload/51925/51925fig3highres.jpg" width="500" /> 
Figure&#160;3. Schematic of recording chamber for electrophysiology experiments. Dimensions provided are in inches. Red rectangle shown in basepiece diagram (a)&#160;indicates positioning of coverslip in the coverslip groove in the basepiece. The region between the red and blue rectangle, shown in the basepiece diagram (a)&#160;is where the high vacuum grease is applied. (b) shows the assembled recording chamber.
4. Labeling and Identification of Presynaptic Terminals with FM 1-43
<ol>
	<li>Label presynaptic terminals, by incorporating FM 1-43 into vesicles during synaptic exo-endocytosis during high K+ depolarization. Perfuse preparation with 5 &#181;M FM 1-43 (in 5 ml Ringer&#8217;s solution containing 30 mM KCl).</li>
	<li>Perfuse preparation with 1 mg/ml Advasep-7 (in 5 ml Ringer&#8217;s solution) to remove excess FM dye)18.</li>
	<li>Perfuse preparation with Ringer&#8217;s solution for 15 min&#160;to washout any remant dye and the Advasep.</li>
	<li>Image with 100 X oil immersion lens (NA 1.25) on an inverted fluorescence microscope, in conjunction with a digital CCD camera and image acquisition software Micromanager, using standard fluorescence imaging protocols.</li>
	<li>Identify fluorescently labeled presynaptic terminals to target for recording Figure 4c&#160;and Figure 4d.</li>
</ol>
5. Immunohistochemistry of Isolated Reticulospinal Axons
<ol>
	<li>Fill dish inset (Protocol section 2.10.) with divalent-ion (Ca2+ and Mg2+) free Ringer&#8217;s solution.</li>
	<li>Fabricate patch pipettes in a P-87 micropipette puller. Place a small amount of suture glue at one end of the poly-lysine inset using a patch pipette (1.5 mm outer diameter glass) and suction (using a silicone tubing 0.89 mm inner diameter with a micropipette tip attached to the suction end).</li>
	<li>Carry out dissociations using the same procedure as mentioned in protocol section 3 Figure 2. Place one end of the spinal cord on the suture glue and press gently with forceps to adhere it strongly to the surface. Place another drop of suture glue at the other end of the inset and gently stretch the spinal cord until axons are dissociated and adhere the free spinal cord end by dragging it gently over the suture glue. Fix in place by gentle pressing down with the forceps.</li>
	<li>Exchange divalent free Ringer&#8217;s solution with regular Ringer&#8217;s solution by perfusion.</li>
	<li>Allow axons to recover for 20 min&#160;post dissociation at 10 &#176;C.</li>
	<li>Fix dissociated axons in 4% paraformaldehyde (PFA) {prepared in Phosphate Buffer Saline (PBS, (mM) NaCl 137,&#160;KCl 2.7, Na2HPO4 10, KH2PO4 1.8, pH 7.4)} for 20 min. Filter PFA solution prior to use by passing through a 0.2 &#181;M syringe filter.</li>
	<li>Wash out the PFA by perfusing 0.1 M glycine (in PBS) for 10 min.</li>
	<li>Incubate in 0.1% Triton-X (in PBS) for 10 min.</li>
	<li>Wash by perfusing PBS for 20 min.</li>
	<li>Block with 5% non-fat milk (in PBS) for 6 hr at 4 &#176;C.</li>
	<li>Add in primary antibody to VGCC of interest (1:200 dilution in PBS) and incubate for 20 hr at 4 &#176;C.</li>
	<li>Wash by perfusing PBS for 20 min.</li>
	<li>Block with 5% non-fat milk (in PBS) for 10 min&#160;at 4 &#176;C.</li>
	<li>Add in secondary antibody (1:400 dilution in PBS) and incubate in dark for 2 hr at 4 &#176;C.</li>
	<li>Wash by perfusing with PBS for 20 min.</li>
	<li>Block with 1% Bovine Serum Albumin (in PBS) for 20 min.</li>
	<li>Add in Alexa Fluor 488 phalloidin (5 Units/&#181;l working concentration; stock prepared in methanol 200 Units/ml).</li>
	<li>Wash by perfusing with PBS for 20 min.</li>
	<li>Image using 100X water immersion lens on confocal microscope.</li>
</ol>
6. Electrophysiological Recording
<ol>
	<li>Fabricate aluminosilicate glass patch pipettes (pipette resistance 2-5 M&#937;) in a P-87 micropipette puller. Design patch pipette such that pipette tip encompasses entire presynaptic terminal diameter.</li>
	<li>PDMS coat patch pipettes by dipping the patch pipette under 50-60 psi pressure into PDMS23 (attach a silicone tubing, 0.89 mm inner diameter, connected to a nitrogen gas cylinder, to the back end of the patch pipette) and dry using a heat gun. Alternately, manually coat the pipette with PDMS, applying coating as close to the tip as possible, under a compound microscope.</li>
	<li>Fire polish patch pipettes using a microforge (a custom built platinum filament fitted onto the stage of a compound microscope).</li>
	<li>Identify isolated axons demonstrating labeled presynaptic terminals by fluorescence microscopy.</li>
	<li>Fill recording solution (designed to isolate Ca2+ currents; 10 mM CaCl2 or 90 mM BaCl2 as charge carrier, HEPES buffered pH 7.6, osmolarity 270 mOsm) into the patch pipette using a syringe.</li>
	<li>Insert patch pipette into the pipette holder and position above bath using a motorized manipulator MP225. Gently lower the patch pipette into the bath and position against the face of a fluorescently identified presynaptic terminal.</li>
	<li>Advance the patch pipette slowly until contact is made with the membrane. At this point, achieve a gigaohm seal by gentle mouth suction through a tube attached to the pipette holder.</li>
	<li>To achieve the extremely low background noise levels required for recording single channel Ca2+ currents, use an Axopatch 200B with a cooled headstage for the recordings. Sample data at 20-50 kHz and filter using a 5 kHz Bessel filter. Carry out data acquisition using an Axograph X.</li>
	<li>Use a standard step protocol, in increments of 10 mV as stimulus. Incorporate a pre-pulse in the protocol, preceding the step protocol, to ensure maximal activation of Ca2+ channels. Incorporate a 10 mV leak step into the step protocol for post-analysis subtraction of leak currents.</li>
</ol>

<ol>
	<li>Katz, B., Miledi, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+timing+of+calcium+action+during+neuromuscular+transmission.">The timing of calcium action during neuromuscular transmission.</a> Journal of Physiology. 189 (3), 535-544 (1967).</li><li>Sabatini, B. L., Regehr, W. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Timing+of+neurotransmission+at+fast+synapses+in+the+mammalian+brain.">Timing of neurotransmission at fast synapses in the mammalian brain.</a> Nature. 384 (6605), 170-172 (1996).</li><li>Augustine, G. J., Adler, E. M., Charlton, M. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+calcium+signal+for+transmitter+secretion+from+presynaptic+nerve+terminals.">The calcium signal for transmitter secretion from presynaptic nerve terminals.</a> Annals of the New York Academy of Sciences. 635, 365-381 (1991).</li><li>Zucker, R. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calcium+and+transmitter+release.">Calcium and transmitter release.</a> Journal of Physiology Paris. 87 (1), 25-36 (1993).</li><li>Delaney, K. R., Shahrezaei, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Uncaging+Calcium+in+Neurons.">Uncaging Calcium in Neurons.</a> Cold Spring Harbor protocols. (12), (2013).</li><li>Paradiso, K., Wu, W., Wu, L. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methods+for+patch+clamp+capacitance+recordings+from+the+calyx.">Methods for patch clamp capacitance recordings from the calyx.</a> Journal of Visualized Experiments. (6), 244 (2007).</li><li>Stanley, E. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+calyx-type+synapse+of+the+chick+ciliary+ganglion+as+a+model+of+fast+cholinergic+transmission.">The calyx-type synapse of the chick ciliary ganglion as a model of fast cholinergic transmission.</a> Canadian Journal of Physiology and Pharmacology. 70, S73-S77 (1992).</li><li>Church, P. J., Stanley, E. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single+L+type+calcium+channel+conductance+with+physiological+levels+of+calcium+in+chick+ciliary+ganglion+neurons.">Single L type calcium channel conductance with physiological levels of calcium in chick ciliary ganglion neurons.</a> The Journal of Physiology. 496 (Pt 1), 59-68 (1996).</li><li>Stanley, E. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single+calcium+channels+and+acetylcholine+release+at+a+presynaptic+nerve+terminal.">Single calcium channels and acetylcholine release at a presynaptic nerve terminal.</a> Neuron. 11 (6), 1007-1011 (1993).</li><li>Weber, A. M., Wong, F. K., Tufford, A. R., Schlichter, L. C., Matveev, V., Stanley, E. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=N-type+Ca(2+)+channels+carry+the+largest+current+implications+for+nanodomains+and+transmitter+release.">N-type Ca(2+) channels carry the largest current implications for nanodomains and transmitter release.</a> Nature Neuroscience. 13 (11), 1348-1350 (2010).</li><li>He, L., Wu, X. S., Mohan, R., Wu, L. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two+modes+of+fusion+pore+opening+revealed+by+cell+attached+recordings+at+a+synapse.">Two modes of fusion pore opening revealed by cell attached recordings at a synapse.</a> Nature. 444 (7115), 102-105 (2006).</li><li>Sheng, J., He, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calcium+channel+number+critically+influences+synaptic+strength+and+plasticity+at+the+active+zone.">Calcium channel number critically influences synaptic strength and plasticity at the active zone.</a> Nature Neuroscience. 15 (7), 998-1006 (2012).</li><li>Photowala, H., Freed, R., Alford, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Location+and+function+of+vesicle+clusters,+active+zones+and+Ca2++channels+in+the+lamprey+presynaptic+terminal.">Location and function of vesicle clusters, active zones and Ca2+ channels in the lamprey presynaptic terminal.</a> The Journal of Physiology. 569. 569 (Pt 1), 119-135 (2005).</li><li>Rovainen, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synaptic+interactions+of+reticulospinal+neurons+and+nerve+cells+in+the+spinal+cord+of+the+sea+lamprey.">Synaptic interactions of reticulospinal neurons and nerve cells in the spinal cord of the sea lamprey.</a> Journal of Comparative Neurology. 154 (2), 207-223 (1974).</li><li>Takahashi, M., Freed, R., Blackmer, T., Alford, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calcium+influx+independent+depression+of+transmitter+release+by+5+HT+at+lamprey+spinal+cord+synapses.">Calcium influx independent depression of transmitter release by 5 HT at lamprey spinal cord synapses.</a> The Journal of Physiology. 532 (2), 323-336 (2001).</li><li>Stanley, E. F., Goping, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+a+calcium+current+in+a+vertebrate+cholinergic+presynaptic+nerve+terminal.">Characterization of a calcium current in a vertebrate cholinergic presynaptic nerve terminal.</a> The Journal of Neuroscience. 11 (4), 985-993 (1991).</li><li>El Manira, A., Bussi&#232;res, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calcium+channel+subtypes+in+lamprey+sensory+and+motor+neurons.">Calcium channel subtypes in lamprey sensory and motor neurons.</a> Journal of Neurophysiology. 78 (3), 1334-1340 (1997).</li><li>Kay, A. R., Alfonso, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+synaptic+activity+in+intact+brain+and+slices+with+FM1+43+in+C+elegans+lamprey+and+rat.">Imaging synaptic activity in intact brain and slices with FM1 43 in C elegans lamprey and rat.</a> 24 (4), 809-817 (1999).</li><li>Betz, W. J., Bewick, G. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+analysis+of+synaptic+vesicle+recycling+at+the+frog+neuromuscular+junction.">Optical analysis of synaptic vesicle recycling at the frog neuromuscular junction.</a> Science. 255 (5041), 200-203 (1992).</li><li>Bleckert, A., Photowala, H., Alford, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dual+pools+of+actin+at+presynaptic+terminals.">Dual pools of actin at presynaptic terminals.</a> Journal of Neurophysiology. 107 (12), 3479-3492 (2012).</li><li>Gustafsson, J. S., Birinyi, A., Crum, J., Ellisman, M., Brodin, L., Shupliakov, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrastructural+organization+of+lamprey+reticulospinal+synapses+in+three+dimensions.">Ultrastructural organization of lamprey reticulospinal synapses in three dimensions.</a> The Journal of Comparative Neurology. 450 (2), 167-182 (2002).</li><li>Broadie, K., Featherstone, D. E., Chen, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrophysiological+Recording+in+the+Drosophila+Embryo.">Electrophysiological Recording in the Drosophila Embryo.</a> Journal of Visualized Experiments. (27), (2009).</li><li>Rae, J. L., Levis, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+method+for+exceptionally+low+noise+single+channel+recordings.">A method for exceptionally low noise single channel recordings.</a> Pfl&#252;gers Archiv European Journal of Physiology. 420 (5-6), 618-620 (1992).</li></ol>

The authors do not have any competing financial interests or other conflicts of interest to disclose.

Our dissociation protocol is significant by yielding isolated reticulospinal axons devoid of postsynaptic projections Figure 2f, but which nevertheless retain functional presynaptic terminals Figure 4c&#160;and Figure 4d. The absence of postsynaptic processes opposing the presynaptic terminal permits direct recording access to the presynaptic release face membrane at single presynaptic terminals, previously not possible in central synapses and successfully achieved in on...

Synaptic transmission is an extremely rapid and precise process. Action potential invasion of the presynaptic terminal leads to opening of VGCCs located in the release face membrane, the resulting increase in presynaptic Ca2+ acting as the trigger for vesicle fusion and neurotransmitter release1. All of these steps occur within hundreds of microseconds2, and hence require tight spatial coupling of VGCCs to the vesicle fusion machinery3. Presynaptic Ca2+ fluxes have been primarily characterized through imaging approaches using Ca2+ sensitive dyes4. Incorporating Ca2+ buffers that modulate Ca2+ in presynaptic neurons has been used to indirectly characterize the relationship between presynaptic calcium and neurotransmission3. In addition, modulating the presynaptic free Ca2+&#160;concentration by uncaging Ca2+ 5 or recording macroscopic Ca2+ currents have been used in conjunction with measures of vesicle fusion and/or release; such as capacitance measurements6 or postsynaptic responses2 to address the same question. However, characterizing Ca2+ currents directly at the release face, the specialized section of the presynaptic membrane where membrane depolarization is translated into Ca2+&#160;currents triggering synaptic vesicle fusion and neurotransmitter release, is integral to obtaining a precise measure of the Ca2+ requirement for synaptic vesicle fusion. In addition, the ability to directly characterize Ca2+ currents at individual presynaptic terminals, coupled with accurate simultaneous measurements of vesicle fusion and release allows a precise elucidation of the timing relationship between the time course of the action potential, presynaptic Ca2+&#160;current, vesicle fusion and release. Access to the release face membrane is not available in the majority of presynaptic terminals due to close apposition by the postsynaptic dendrites. This inaccessibility has been a major obstacle in the characterization of VGCCs since it prevents direct measurements of current at individual presynaptic terminals. Direct characterization of presynaptic Ca2+ currents at individual presynaptic terminals has thus far not been possible in central synapses and has only been achieved in two calyceal type presynaptic terminals; calyx-type synapse of the chick ciliary ganglion7-10 and rat calyces11,12. In all other presynaptic terminals including the giant reticulospinal synapse in the lamprey spinal cord13, the lack of access to the presynaptic release face membrane has necessitated the use of indirect approaches such as Ca2+&#160;imaging to study presynaptic Ca2+&#160;fluxes.
<img alt="Figure 1" fo:content-width="5in" src="/files/ftp_upload/51925/51925fig1highres.jpg" width="500" /> 
Figure&#160;1. Lamprey giant reticulospinal synapse. (a) Cross-section of lamprey spinal cord indicating dorso-ventral orientation. Reticulospinal axons are marked with green asterix. (b)&#160;3-D reconstruction of the reticulospinal synapse in the lamprey spinal cord showing presynaptic reticulospinal axon making numerous en passant contacts (marked by green arrows) onto the postsynaptic neuron13. Presynaptic terminals have been labeled with Alexa Fluor 488 hydrazide conjugated phalloidin (green), while the postsynaptic neuron has been filled with Alexa Fluor 568 hydrazide (red).
Lamprey giant reticulospinal axons, located in the ventral region of the spinal cord parallel to the rostral-caudal axis Figure 1a, form multiple enpassant synaptic contacts onto neurons of the spinal ventral horn14&#160;Figure 1b13. Macroscopic whole-cell Ca2+ currents have been recorded from reticulospinal axons in the intact spinal cord13,15. However, previous blind attempts at direct measurement of Ca2+&#160;currents in reticulospinal axons in the intact lamprey spinal cord using cell-attached patch clamp technique have proven unsuccessful13 due to lack of access to the presynaptic release face membrane owing to the opposing postsynaptic processes Figure 1b. The release face membrane has been previously made accessible by removal of the postsynaptic neuron11, mechanical perturbation of the synapse prior to recording12 or enzymatic treatment coupled with mechanical dissociation16. Given the complex organization of the spinal cord, it would prove extremely difficult to identify the postsynaptic neuron and retract it mechanically or perturb the synapse. Hence, we decided to use enzymatic treatment17 followed by mechanical dissociation.
Using this approach, we have developed an acutely dissociated preparation of the lamprey spinal cord that yields viable isolated reticulospinal axons with functional presynaptic terminals devoid of any postsynaptic processes, thereby providing unrestricted access to individual presynaptic terminals. In conjunction with a standard inverted microscope and fluorescence imaging, it enables us to identify and target individual fluorescently-identified presynaptic terminals, with a patch pipette containing a recording solution that isolates Ca2+ currents FIgure 4c&#160;and Figure 4d, for recording using cell-attached voltage-clamp technique. Ca2+ currents have been recorded directly at the presynaptic release face membrane of individual presynaptic terminals Figure 4f. This is a significant breakthrough in the field of synaptic transmission since it is the first such recording to be carried out at central synapses.

<table border="0" cellpadding="0" cellspacing="0" width="713">
	<tbody>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Name of Material/ Equipment</td>
			<td style="width:211px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:167px;">Comments/Description</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">0.2 &#181;m syringe filter</td>
			<td style="width:211px;">EMD Millipore</td>
			<td style="width:119px;">SLGV004SL</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">22x60 mm coverslips</td>
			<td style="width:211px;">Fisherbrand</td>
			<td style="width:119px;">12545J</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Advasep-7</td>
			<td style="width:211px;">Cydex Pharmaceuticals</td>
			<td style="width:119px;">ADV7</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Alexa Fluor 488 Phalloidin</td>
			<td style="width:211px;">Invitrogen/Life Technologies</td>
			<td style="width:119px;">A12379</td>
			<td></td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:216px;">Alexa-633 conjugated goat anti-rabbit secondary antibody</td>
			<td style="width:211px;">Invitrogen/Life Technologies</td>
			<td style="width:119px;">A21070</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Antifreeze</td>
			<td style="width:211px;">Prestone</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Boric acid</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td style="width:119px;">B7660</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Bovine Serum Albumin</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td style="width:119px;">A7906</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Bright field light source</td>
			<td style="width:211px;">Dolan-Jenner</td>
			<td style="width:119px;">Fiberlite 180</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Calcium chloride</td>
			<td style="width:211px;">Sigma Aldrich</td>
			<td style="width:119px;">C4901</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Collagenase Type IA from Cloristridium histolyticum</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td style="width:119px;">C9891</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Cover slip</td>
			<td style="width:211px;">Fisher-Scientific</td>
			<td style="width:119px;">12-545-J</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Dextrose</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td style="width:119px;">D9559</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Digital CCD Camera</td>
			<td style="width:211px;">Hamamatsu</td>
			<td style="width:119px;">C8484-03G01</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Dissection fine forceps</td>
			<td style="width:211px;">Fine Science Tools</td>
			<td style="width:119px;">91150-20</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Dissection forceps</td>
			<td style="width:211px;">Fine Science Tools</td>
			<td style="width:119px;">11251-20</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Dissection microscope</td>
			<td style="width:211px;">Leica Biosystems</td>
			<td style="width:119px;">Leica MZ 12</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Dissection scissors</td>
			<td style="width:211px;">Fine Science Tools</td>
			<td style="width:119px;">15025-10</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Dissection scissors fine</td>
			<td style="width:211px;">Fine Science Tools</td>
			<td style="width:119px;">91500-09</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Dissection scissors ultra fine</td>
			<td style="width:211px;">Fine Science Tools</td>
			<td style="width:119px;">15000-08</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">FM 1-43</td>
			<td style="width:211px;">Invitrogen/Life Technologies</td>
			<td style="width:119px;">T3163</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Glycine</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td style="width:119px;">G7126</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">HEPES</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td style="width:119px;">H7523</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">High vacuum grease</td>
			<td style="width:211px;">Dow-Corning</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Hydrochloric acid</td>
			<td style="width:211px;">Fisherbrand</td>
			<td style="width:119px;">SA-56-500</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Immersion oil</td>
			<td style="width:211px;">Fisher-Scientific</td>
			<td style="width:119px;">M2000</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Industrial grade Nitrogen gas tank</td>
			<td style="width:211px;">Praxair</td>
			<td style="width:119px;">UN1066</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Insect pins</td>
			<td style="width:211px;">Fine Science Tools</td>
			<td style="width:119px;">26002-10</td>
			<td></td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;width:216px;">Liquid suture glue</td>
			<td>Braun Veterinary Cair Division</td>
			<td style="width:119px;">8V0305</td>
			<td>The suture glue we used in our experiments was provided to us by another lab. It is no longer manufactured. We have sourced a Histoacryl Suture Glue for future use from Aesculap (Ts1050071FP)</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Magnesium chloride</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td style="width:119px;">M2670</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Methanol</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td align="right" style="width:119px;">154903</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Non-fat dry milk</td>
			<td style="width:211px;">Cell Signaling Technology</td>
			<td style="width:119px;">9999S</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">P-87 Micropipette puller</td>
			<td style="width:211px;">Sutter Instruments</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Paraformaldehyde</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td style="width:119px;">P6148</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Perfusion pump</td>
			<td style="width:211px;">Cole-Palmer</td>
			<td style="width:119px;">Masterflex C/L</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Petri dish 100x15 mm</td>
			<td style="width:211px;">Fisher-Scientific</td>
			<td align="right" style="width:119px;">875712</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Petri dish 35x10 mm</td>
			<td style="width:211px;">Fisher-scientific</td>
			<td align="right" style="width:119px;">875712</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Poly-D-lysine hydrobromide</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td style="width:119px;">P1024</td>
			<td>MW &#62; 300000</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Potassium chloride</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td style="width:119px;">P9333</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Potassium phosphate monobasic</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td style="width:119px;">P5379</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Primary antibodiesR-type calcium channel</td>
			<td style="width:211px;">Alomone Labs</td>
			<td style="width:119px;">ACC-006</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Protease Type XIV from Streptomyces griseus</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td style="width:119px;">P5147</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Scalpel blades</td>
			<td style="width:211px;">World Precision Instruments&#160;</td>
			<td align="right" style="width:119px;">500240</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Schot Duran Preesure Bottle</td>
			<td style="width:211px;">Fisher-Scientific</td>
			<td style="width:119px;">09-841-006</td>
			<td></td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:216px;">Silicone tubing for glue application</td>
			<td style="width:211px;">Cole-Palmer</td>
			<td>07625-26</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Slicing base plate</td>
			<td style="width:211px;">Leica Biosystems</td>
			<td align="right" style="width:119px;">14046327404</td>
			<td></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:216px;">Slicing chamber</td>
			<td style="width:211px;">Leica Biosystems</td>
			<td align="right">1.4046E+10</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Sodium chloride</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td style="width:119px;">S7653</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Sodium hydroxide</td>
			<td style="width:211px;"></td>
			<td style="width:119px;">S8045</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Sodium phosphate dibasic</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td style="width:119px;">S9763</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Sodium tetraborate</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td style="width:119px;">B3545</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Sylgard 160 Silicone Elastomer Kit</td>
			<td style="width:211px;">Dow Corning&#160;</td>
			<td style="width:119px;">SYLGARD&#174; 160</td>
			<td>To prepare, mix elastomer A and elastomer B 10:1 by weight</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:216px;">Sylgard 184 Silicone Elastomer Kit</td>
			<td style="width:211px;">Dow Corning</td>
			<td style="width:119px;">SYLGARD&#174; 184&#160;</td>
			<td>To prepare, mix elastomer and curing agent 10:1 by weight</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Teflon coated forceps</td>
			<td style="width:211px;">Fine Science Tools</td>
			<td style="width:119px;">11626-11</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Tricaine methanesulphonate</td>
			<td style="width:211px;">Sigma-Aldrich</td>
			<td style="width:119px;">A5040</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Vibratome blades</td>
			<td style="width:211px;">World Precision Instruments&#160;</td>
			<td style="width:119px;">BLADES</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:216px;">Xenon lamp</td>
			<td style="width:211px;">Nikon</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

acute dissociation of lamprey reticulospinal axons to enable recording from the release face membrane of individual functional presynaptic terminals

Synaptic transmission is an extremely rapid process. Action potential driven influx of Ca2+&#160;into the presynaptic terminal, through voltage-gated calcium channels (VGCCs) located in the release face membrane, is the trigger for vesicle fusion and neurotransmitter release. Crucial to the rapidity of synaptic transmission is the spatial and temporal synchrony between the arrival of the action potential, VGCCs and the neurotransmitter release machinery. The ability to directly record Ca2+&#160;currents from the release face membrane of individual presynaptic terminals is imperative for a precise understanding of the relationship between presynaptic Ca2+&#160;and neurotransmitter release. Access to the presynaptic release face membrane for electrophysiological recording is not available in most preparations and presynaptic Ca2+&#160;entry has been characterized using imaging techniques and macroscopic current measurements &#8211; techniques that do not have sufficient temporal resolution to visualize Ca2+ entry. The characterization of VGCCs directly at single presynaptic terminals has not been possible in central synapses and has thus far been successfully achieved only in the calyx-type synapse of the chick ciliary ganglion and in rat calyces. We have successfully addressed this problem in the giant reticulospinal synapse of the lamprey spinal cord by developing an acutely dissociated preparation of the spinal cord that yields isolated reticulospinal axons with functional presynaptic terminals devoid of postsynaptic structures. We can fluorescently label and identify individual presynaptic terminals and target them for recording. Using this preparation, we have characterized VGCCs directly at the release face of individual presynaptic terminals using immunohistochemistry and electrophysiology approaches. Ca2+ currents have been recorded directly at the release face membrane of individual presynaptic terminals, the first such recording to be carried out at central synapses.

This dissociation protocol yields healthy and functional isolated reticulospinal axons devoid of postsynaptic projections Figure 2f, but which nevertheless retain functional presynaptic terminals capable of evoked synaptic vesicle exo-and endocytosis Figure 4c&#160;and Figure 4d. Sections of the isolated regions of the reticulospinal axons can be clearly identified under light microscopy to be clear of any other neuronal processes allowing unrestricted access to the reti...

Watch this Scientific Journal Video about Acute Dissociation of Lamprey Reticulospinal Axons to Enable Recording from the Release Face Membrane of Individual Functional Presynaptic Terminals at JoVE.c

Acute Dissociation of Lamprey Reticulospinal Axons to Enable Recording from the Release Face Membrane of Individual Functional Presynaptic Terminals

Recording Ca2+ currents at the presynaptic release face membrane is key to a precise understanding of Ca2+ entry and neurotransmitter release. We present an acute dissociation of the lamprey spinal cord that yields functional isolated reticulospinal axons, permitting recording directly from the release face membrane of individual presynaptic terminals.

Synaptic transmission is an extremely rapid process. Action potential driven influx of Ca2+&#160;into the presynaptic terminal, through voltage-gated ...

acute-dissociation-lamprey-reticulospinal-axons-to-enable-recording

Research

JoVE Journal

Neuroscience

8.7K Views.  University of Illinois at Chicago. Recording Ca2+ currents at the presynaptic release face membrane is key to a precise understanding of Ca2+ entry and neurotransmitter release. We present an acute dissociation of the lamprey spinal cord that yields functional isolated reticulospinal axons, permitting recording directly from the release face membrane of individual presynaptic terminals. 

Video: Acute Dissociation of Lamprey Reticulospinal Axons to Enable Recording from the Release Face Membrane of Individual Functional Presynaptic Terminals

The Subventricular Zone En-face: Wholemount Staining and Ependymal Flow

The walls of the lateral ventricles contain the largest germinal region in the adult mammalian brain. The subventricular zone (SVZ) in these walls is an extensively studied model system for understanding the behavior of neural stem cells and the regulation of adult neurogenesis. Traditionally, these studies have relied on classical sectioning techniques for histological analysis. Here we present an alternative approach, the wholemount technique, which provides a comprehensive, en-face view of this germinal region. Compared to sections, wholemounts preserve the complete cytoarchitecture and cellular relationships within the SVZ. This approach has recently revealed that the adult neural stem cells, or type B1 cells, are part of a mixed neuroepithelium with differentiated ependymal cells lining the lateral ventricles. In addition, this approach has been used to study the planar polarization of ependymal cells and the cerebrospinal fluid flow they generate in the ventricle. With recent evidence that adult neural stem cells are a heterogeneous population that is regionally specified, the wholemount approach will likely be an essential tool for understanding the organization and parcellation of this stem cell niche.

The lateral ventricle walls contain the largest germinal region in the adult mammalian brain. Traditionally, studies on neurogenesis in this region have relied on classical sectioning techniques for histological analysis. Here we present an alternative approach, the wholemount technique, which provides a comprehensive, en-face view of this germinal region.

The walls of the lateral ventricles contain the largest germinal region in the adult mammalian brain. The subventricular zone (SVZ) in these walls is an ...

Vibrodissociation of Neurons from Rodent Brain Slices to Study Synaptic Transmission and Image Presynaptic Terminals

Mechanical dissociation of neurons from the central nervous system has the advantage that presynaptic boutons remain attached to the isolated neuron of interest. This allows for examination of synaptic transmission under conditions where the extracellular and postsynaptic intracellular environments can be well controlled. A vibration-based technique without the use of proteases, known as vibrodissociation, is the most popular technique for mechanical isolation. A micropipette, with the tip fire-polished to the shape of a small ball, is placed into a brain slice made from a P1-P21 rodent. The micropipette is vibrated parallel to the slice surface and lowered through the slice thickness resulting in the liberation of isolated neurons. The isolated neurons are ready for study within a few minutes of vibrodissociation. This technique has advantages over the use of primary neuronal cultures, brain slices and enzymatically isolated neurons including: rapid production of viable, relatively mature neurons suitable for electrophysiological and imaging studies; superior control of the extracellular environment free from the influence of neighboring cells; suitability for well-controlled pharmacological experiments using rapid drug application and total cell superfusion; and improved space-clamp in whole-cell recordings relative to neurons in slice or cell culture preparations. This preparation can be used to examine synaptic physiology, pharmacology, modulation and plasticity. Real-time imaging of both pre- and postsynaptic elements in the living cells and boutons is also possible using vibrodissociated neurons. Characterization of the molecular constituents of pre- and postsynaptic elements can also be achieved with immunological and imaging-based approaches.

This report demonstrates a technique for mechanical isolation of individual viable neurons retaining attached presynaptic boutons. Vibrodissociated neurons have the advantages of rapid production, excellent pharmacological control and improved space-clamp without influence from neighboring cells. This method can be used for imaging of synaptic elements and patch-clamp recording.

Mechanical dissociation of neurons from the central nervous system has the advantage that presynaptic boutons remain attached to the isolated neuron of ...

Voltage-sensitive Dye Recording from Axons, Dendrites and Dendritic Spines of Individual Neurons in Brain Slices

Understanding the biophysical properties and functional organization of single neurons and how they process information is fundamental for understanding how the brain works. The primary function of any nerve cell is to process electrical signals, usually from multiple sources. Electrical properties of neuronal processes are extraordinarily complex, dynamic, and, in the general case, impossible to predict in the absence of detailed measurements. To obtain such a measurement one would, ideally, like to be able to monitor, at multiple sites, subthreshold events as they travel from the sites of origin on neuronal processes and summate at particular locations to influence action potential initiation. This goal has not been achieved in any neuron due to technical limitations of measurements that employ electrodes. To overcome this drawback, it is highly desirable to complement the patch-electrode approach with imaging techniques that permit extensive parallel recordings from all parts of a neuron. Here, we describe such a technique - optical recording of membrane potential transients with organic voltage-sensitive dyes (Vm-imaging) - characterized by sub-millisecond and sub-micrometer resolution. Our method is based on pioneering work on voltage-sensitive molecular probes 2. Many aspects of the initial technology have been continuously improved over several decades 3, 5, 11. Additionally, previous work documented two essential characteristics of Vm-imaging. Firstly, fluorescence signals are linearly proportional to membrane potential over the entire physiological range (-100 mV to +100 mV; 10, 14, 16). Secondly, loading neurons with the voltage-sensitive dye used here (JPW 3028) does not have detectable pharmacological effects. The recorded broadening of the spike during dye loading is completely reversible 4, 7. Additionally, experimental evidence shows that it is possible to obtain a significant number (up to hundreds) of recordings prior to any detectable phototoxic effects 4, 6, 12, 13. At present, we take advantage of the superb brightness and stability of a laser light source at near-optimal wavelength to maximize the sensitivity of the Vm-imaging technique. The current sensitivity permits multiple site optical recordings of Vm transients from all parts of a neuron, including axons and axon collaterals, terminal dendritic branches, and individual dendritic spines. The acquired information on signal interactions can be analyzed quantitatively as well as directly visualized in the form of a movie.

An imaging technique for monitoring of membrane potential changes with sub-micrometer spatial and sub-millisecond temporal resolution is described. The technique, based on laser excitation of voltage-sensitive dyes, allows measurements of signals in axons and axon collaterals, terminal dendritic branches, and individual dendritic spines.

Understanding the biophysical properties and functional organization of single neurons and how they process information is fundamental for understanding ...

Laser Nanosurgery of Cerebellar Axons In Vivo

Only a few neuronal populations in the central nervous system (CNS) of adult mammals show local regrowth upon dissection of their axon. In order to understand the mechanism that promotes neuronal regeneration, an in-depth analysis of the neuronal types that can remodel after injury is needed. Several studies showed that damaged climbing fibers are capable of regrowing also in adult animals1,2. The investigation of the time-lapse dynamics of degeneration and regeneration of these axons within their complex environment can be performed by time-lapse two-photon fluorescence (TPF) imaging in vivo3,4. This technique is here combined with laser surgery, which proved to be a highly selective tool to disrupt fluorescent structures in the intact mouse cortex5-9.
This protocol describes how to perform TPF time-lapse imaging and laser nanosurgery of single axonal branches in the cerebellum in vivo. Olivocerebellar neurons are labeled by anterograde tracing with a dextran-conjugated dye and then monitored by TPF imaging through a cranial window. The terminal portion of their axons are then dissected by irradiation with a Ti:Sapphire laser at high power. The degeneration and potential regrowth of the damaged neuron are monitored by TPF in vivo imaging during the days following the injury.

Laser Nanosurgery of Cerebellar Axons In Vivo

Two-photon imaging, coupled to laser nanodissection, are useful tools to study degenerative and regenerative processes in the central nervous system with subcellular resolution. This protocol shows how to label, image, and dissect single climbing fibers in the cerebellar cortex in vivo.

Only a few neuronal populations in the central nervous system (CNS) of adult mammals show local regrowth upon dissection of their axon. In order to ...

Measuring Spinal Presynaptic Inhibition in Mice By Dorsal Root Potential Recording In Vivo

Presynaptic inhibition is one of the most powerful inhibitory mechanisms in the spinal cord. The underlying physiological mechanism is a depolarization of primary afferent fibers mediated by GABAergic axo-axonal synapses (primary afferent depolarization). The strength of primary afferent depolarization can be measured by recording of volume-conducted potentials at the dorsal root (dorsal root potentials, DRP). Pathological changes of presynaptic inhibition are crucial in the abnormal central processing of certain pain conditions and in some disorders of motor hyperexcitability. Here, we describe a method of recording DRP in vivo in mice. The preparation of spinal cord dorsal roots in the anesthetized animal and the recording procedure using suction electrodes are explained. This method allows measuring GABAergic DRP and thereby estimating spinal presynaptic inhibition in the living mouse. In combination with transgenic mouse models, DRP recording may serve as a powerful tool to investigate disease-associated spinal pathophysiology. In vivo recording has several advantages compared to ex vivo isolated spinal cord preparations, e.g. the possibility of simultaneous recording or manipulation of supraspinal networks and induction of DRP by stimulation of peripheral nerves.

Measuring Spinal Presynaptic Inhibition in Mice By Dorsal Root Potential Recording In Vivo

GABAergic presynaptic inhibition is a powerful inhibitory mechanism in the spinal cord important for motor and sensory signal integration in spinal cord networks. Underlying primary afferent depolarization can be measured by recording of dorsal root potentials (DRP). Here we demonstrate a method of in vivo recording of DRP in mice.

Presynaptic inhibition is one of the most powerful inhibitory mechanisms in the spinal cord. The underlying physiological mechanism is a depolarization of ...

Imaging Ca2+ Dynamics in Cone Photoreceptor Axon Terminals of the Mouse Retina

Retinal cone photoreceptors (cones) serve daylight vision and are the basis of color discrimination. They are subject to degeneration, often leading to blindness in many retinal diseases. Calcium (Ca2+), a key second messenger in photoreceptor signaling and metabolism, has been proposed to be indirectly linked with photoreceptor degeneration in various animal models. Systematically studying these aspects of cone physiology and pathophysiology has been hampered by the difficulties of electrically recording from these small cells, in particular in the mouse where the retina is dominated by rod photoreceptors. To circumvent this issue, we established a two-photon Ca2+ imaging protocol using a transgenic mouse line that expresses the genetically encoded Ca2+ biosensor TN-XL exclusively in cones and can be crossbred with mouse models for photoreceptor degeneration. The protocol described here involves preparing vertical sections (&#8220;slices&#8221;) of retinas from mice and optical imaging of light stimulus-evoked changes in cone Ca2+ level. The protocol also allows &#8220;in-slice measurement&#8221; of absolute Ca2+ concentrations; as the recordings can be followed by calibration. This protocol enables studies into functional cone properties and is expected to contribute to the understanding of cone Ca2+ signaling as well as the potential involvement of Ca2+ in photoreceptor death and retinal degeneration.

Imaging Ca2+ Dynamics in Cone Photoreceptor Axon Terminals of the Mouse Retina

We describe a protocol to monitor Ca2+ dynamics in the axon terminals of cone photoreceptors using an ex-vivo&#160;slice preparation of the mouse retina. This protocol allows comprehensive studies of cone Ca2+ signaling in an important mammalian model system, the mouse.

Retinal cone photoreceptors (cones) serve daylight vision and are the basis of color discrimination. They are subject to degeneration, often leading to ...

Live Imaging of Nicotine Induced Calcium Signaling and Neurotransmitter Release Along Ventral Hippocampal Axons

Sustained enhancement of axonal signaling and increased neurotransmitter release by the activation of pre-synaptic nicotinic acetylcholine receptors (nAChRs) is an important mechanism for neuromodulation by acetylcholine (ACh). The difficulty with access to probing the signaling mechanisms within intact axons and at nerve terminals both in vitro and in vivo has limited progress in the study of the pre-synaptic components of synaptic plasticity. Here we introduce a gene-chimeric preparation of ventral hippocampal (vHipp)&#8211;accumbens (nAcc) circuit in vitro that allows direct live imaging to analyze both the pre- and post-synaptic components of transmission while selectively varying the genetic profile of the pre- vs post-synaptic neurons. We demonstrate that projections from vHipp microslices, as pre-synaptic axonal input, form multiple, reliable glutamatergic synapses with post-synaptic targets, the dispersed neurons from nAcc. The pre-synaptic localization of various subtypes of nAChRs are detected and the pre-synaptic nicotinic signaling mediated synaptic transmission are monitored by concurrent electrophysiological recording and live cell imaging. This preparation also provides an informative approach to study the pre- and post-synaptic mechanisms of glutamatergic synaptic plasticity in vitro.

We developed a gene-chimeric preparation of ventral hippocampal &#8211; accumbens circuit in vitro that allows direct live imaging to analyze presynaptic mechanisms of nicotinic acetylcholine receptors (nAChRs) mediated synaptic transmission. This preparation also provides an informative approach to study the pre- and post-synaptic mechanisms of synaptic plasticity.

Sustained enhancement of axonal signaling and increased neurotransmitter release by the activation of pre-synaptic nicotinic acetylcholine receptors ...

Recording Synaptic Plasticity in Acute Hippocampal Slices Maintained in a Small-volume Recycling-, Perfusion-, and Submersion-type Chamber System

Even though experiments on brain slices have been in use since 1951, problems remain that reduce the probability of achieving a stable and successful analysis of synaptic transmission modulation when performing field potential or intracellular recordings. This manuscript describes methodological aspects that might be helpful in improving experimental conditions for the maintenance of acute brain slices and for recording field excitatory postsynaptic potentials in a commercially available submersion chamber with an outflow-carbogenation unit. The outflow-carbogenation helps to stabilize the oxygen level in experiments that rely on the recycling of a small buffer reservoir to enhance the cost-efficiency of drug experiments. In addition, the manuscript presents representative experiments that examine the effects of different carbogenation modes and stimulation paradigms on the activity-dependent synaptic plasticity of synaptic transmission.

This protocol describes the stabilization of the oxygen level in a small volume of recycled buffer and methodological aspects of recording activity-dependent synaptic plasticity in submerged acute hippocampal slices.

Even though experiments on brain slices have been in use since 1951, problems remain that reduce the probability of achieving a stable and successful ...

In Vivo Single-Molecule Tracking at the Drosophila Presynaptic Motor Nerve Terminal

An increasing number of super-resolution microscopy techniques are helping to uncover the mechanisms that govern the nanoscale cellular world. Single-molecule imaging is gaining momentum as it provides exceptional access to the visualization of individual molecules in living cells. Here, we describe a technique that we developed to perform single-particle tracking photo-activated localization microscopy (sptPALM) in Drosophila larvae. Synaptic communication relies on key presynaptic proteins that act by docking, priming, and promoting the fusion of neurotransmitter-containing vesicles with the plasma membrane. A range of protein-protein and protein-lipid interactions tightly regulates these processes and the presynaptic proteins therefore exhibit changes in mobility associated with each of these key events. Investigating how mobility of these proteins correlates with their physiological function in an intact live animal is essential to understanding their precise mechanism of action. Extracting protein mobility with high resolution in vivo requires overcoming limitations such as optical transparency, accessibility, and penetration depth. We describe how photoconvertible fluorescent proteins tagged to the presynaptic protein Syntaxin-1A can be visualized via slight oblique illumination and tracked at the motor nerve terminal or along the motor neuron axon of the third instar Drosophila larva.

In Vivo Single-Molecule Tracking at the Drosophila Presynaptic Motor Nerve Terminal

Here we illustrate how single molecule photo-activated localization microscopy can be carried out on the motor nerve terminal of a live Drosophila melanogaster third instar larva.

An increasing number of super-resolution microscopy techniques are helping to uncover the mechanisms that govern the nanoscale cellular world. ...

Single Synapse Indicators of Glutamate Release and Uptake in Acute Brain Slices from Normal and Huntington Mice

Synapses are highly compartmentalized functional units that operate independently on each other. In Huntington&#39;s disease (HD) and other neurodegenerative disorders, this independence might be compromised due to insufficient glutamate clearance and the resulting spill-in and spill-out effects. Altered astrocytic coverage of the presynaptic terminals and/or dendritic spines as well as a reduced size of glutamate transporter clusters at glutamate release sites have been implicated in the pathogenesis of diseases resulting in symptoms of dys-/hyperkinesia. However, the mechanisms leading to the dysfunction of glutamatergic synapses in HD are not well understood. Improving and applying synapse imaging we have obtained data shedding new light on the mechanisms impeding the initiation of movements. Here, we describe the principle elements of a relatively inexpensive approach to achieve single synapse resolution by using the new genetically encoded ultrafast glutamate sensor iGluu, wide-field optics, a scientific CMOS (sCMOS) camera, a 473 nm laser and a laser positioning system to evaluate the state of corticostriatal synapses in acute slices from age appropriate healthy or diseased mice. Glutamate transients were constructed from single or multiple pixels to obtain estimates of i) glutamate release based on the maximal elevation of the glutamate concentration [Glu] next to the active zone and ii) glutamate uptake as reflected in the time constant of decay (TauD) of the perisynaptic [Glu]. Differences in the resting bouton size and contrasting patterns of short-term plasticity served as criteria for the identification of corticostriatal terminals as belonging to the intratelencephalic (IT) or the pyramidal tract (PT) pathway. Using these methods, we discovered that in symptomatic HD mice ~40% of PT-type corticostriatal synapses exhibited insufficient glutamate clearance, suggesting that these synapses might be at risk to excitotoxic damage. The results underline the usefulness of TauD as a biomarker of dysfunctional synapses in Huntington mice with a hypokinetic phenotype.

We present a protocol to evaluate the balance between glutamate release and clearance at single corticostriatal glutamatergic synapses in acute slices from adult mice. This protocol uses the fluorescent sensor iGluu for glutamate detection, a sCMOS camera for signal acquisition and a device for focal laser illumination.