Name: quantitative autoradiographic method for determination of regional rates of cerebral protein synthesis in vivo
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Description: Watch this Scientific Journal Video about Quantitative Autoradiographic Method for Determination of Regional Rates of Cerebral Protein Synthesis In Vivo at JoVE.com

The authors would like to acknowledge Zengyan Xia for the genotyping of the mice, Tom Burlin for the processing of amino acids and films, and Mei Qin for performing some of the rCPS experiments. This research was supported by the Intramural Research Program of the NIMH, ZIA MH00889. RMS was also supported by an Autism Speaks Postdoctoral Fellowship 8679 and a FRAXA Postdoctoral Fellowship.

Note: All animal procedures were approved by the National Institute of Mental Health Animal Care and Use Committee and were performed according with the National Institutes of Health Guidelines on the Care and Use of Animals.
An overview of the protocol is presented in Figure 1.
1. Surgically implant catheters in a femoral vein and artery for administration of the tracer and collection of timed arterial blood samples, respectively. Comple...

<ol>
	<li>West, A. E., 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+regulation+of+neuronal+gene+expression.">Calcium regulation of neuronal gene expression.</a> Proceedings of the National Academy of Sciences of the United States of America. 98, 11024-11031 (2001).</li><li>Siegel, G., Agranoff, B., Albers, R. W., Fisher, S., Uhler, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Basic Neurochemistry. , (1999).</li><li>Nguyen, P. V., Abel, T., Kandel, E. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Requirement+of+a+critical+period+of+transcription+for+induction+of+a+late+phase+of+LTP.">Requirement of a critical period of transcription for induction of a late phase of LTP.</a> Science. 265, 1104-1107 (1994).</li><li>Mao, Z., Bonni, A., Xia, F., Nadal-Vicens, M., Greenberg, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuronal+activity-dependent+cell+survival+mediated+by+transcription+factor+MEF2.">Neuronal activity-dependent cell survival mediated by transcription factor MEF2.</a> Science. 286, 785-790 (1999).</li><li>Pfeiffer, B. E., Huber, K. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Current+advances+in+local+protein+synthesis+and+synaptic+plasticity.">Current advances in local protein synthesis and synaptic plasticity.</a> The Journal of Neuroscience: the Official Journal of the Society for Neuroscience. 26, 7147-7150 (2006).</li><li>Smith, C. B., Deibler, G. E., Eng, N., Schmidt, K., Sokoloff, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+of+local+cerebral+protein+synthesis+in+vivo:+influence+of+recycling+of+amino+acids+derived+from+protein+degradation.">Measurement of local cerebral protein synthesis in vivo: influence of recycling of amino acids derived from protein degradation.</a> Proceedings of the National Academy of Sciences of the United States of America. 85, 9341-9345 (1988).</li><li>Schmidt, K. C., Smith, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Resolution,+sensitivity+and+precision+with+autoradiography+and+small+animal+positron+emission+tomography:+implications+for+functional+brain+imaging+in+animal+research.">Resolution, sensitivity and precision with autoradiography and small animal positron emission tomography: implications for functional brain imaging in animal research.</a> Nuclear Medicine and Biology. 32, 719-725 (2005).</li><li>Banker, G., Cotman, C. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characteristics+of+different+amino+acids+as+protein+precursors+in+mouse+brain:+advantages+of+certain+carboxyl-labeled+amino+acids.">Characteristics of different amino acids as protein precursors in mouse brain: advantages of certain carboxyl-labeled amino acids.</a> Archives of Biochemistry and Biophysics. 142, 565-573 (1971).</li><li>Frerichs, K. U., 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=Suppression+of+protein+synthesis+in+brain+during+hibernation+involves+inhibition+of+protein+initiation+and+elongation.">Suppression of protein synthesis in brain during hibernation involves inhibition of protein initiation and elongation.</a> Proceedings of the National Academy of Sciences of the United States of America. 95, 14511-14516 (1998).</li><li>Abrams, R. M., Burchfield, D. J., Sun, Y., Smith, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rates+of+local+cerebral+protein+synthesis+in+fetal+and+neonatal+sheep.">Rates of local cerebral protein synthesis in fetal and neonatal sheep.</a> The American Journal of Physiology. 272, R1235-R1244 (1997).</li><li>Nakanishi, H., 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=Positive+correlations+between+cerebral+protein+synthesis+rates+and+deep+sleep+in+Macaca+mulatta.">Positive correlations between cerebral protein synthesis rates and deep sleep in Macaca mulatta.</a> The European Journal of Neuroscience. 9, 271-279 (1997).</li><li>Sun, Y., Deibler, G. E., Sokoloff, L., Smith, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+regional+rates+of+cerebral+protein+synthesis+adjusted+for+regional+differences+in+recycling+of+leucine+derived+from+protein+degradation+into+the+precursor+pool+in+conscious+adult+rats.">Determination of regional rates of cerebral protein synthesis adjusted for regional differences in recycling of leucine derived from protein degradation into the precursor pool in conscious adult rats.</a> Journal of Neurochemistry. 59, 863-873 (1992).</li><li>Scammell, T. E., Schwartz, W. J., Smith, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=No+evidence+for+a+circadian+rhythm+of+protein+synthesis+in+the+rat+suprachiasmatic+nuclei.">No evidence for a circadian rhythm of protein synthesis in the rat suprachiasmatic nuclei.</a> Brain Research. 494, 155-158 (1989).</li><li>Smith, C. B., Eintrei, C., Kang, J., Sun, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+thiopental+anesthesia+on+local+rates+of+cerebral+protein+synthesis+in+rats.">Effects of thiopental anesthesia on local rates of cerebral protein synthesis in rats.</a> The American Journal of Physiology. 274, E852-E859 (1998).</li><li>Sun, Y., Deibler, G. E., Smith, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+axotomy+on+protein+synthesis+in+the+rat+hypoglossal+nucleus:+examination+of+the+influence+of+local+recycling+of+leucine+derived+from+protein+degradation+into+the+precursor+pool.">Effects of axotomy on protein synthesis in the rat hypoglossal nucleus: examination of the influence of local recycling of leucine derived from protein degradation into the precursor pool.</a> Journal of Cerebral Blood Flow and Metabolism: Official Journal of the International Society of Cerebral Blood Flow and Metabolism. 13, 1006-1012 (1993).</li><li>Smith, C. B., Yu, W. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rates+of+protein+synthesis+in+the+regenerating+hypoglossal+nucleus:+effects+of+testosterone+treatment.">Rates of protein synthesis in the regenerating hypoglossal nucleus: effects of testosterone treatment.</a> Neurochemical Research. 19, 623-629 (1994).</li><li>Orzi, F., Sun, Y., Pettigrew, K., Sokoloff, L., Smith, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+acute+and+delayed+effects+of+prior+chronic+cocaine+administration+on+regional+rates+of+cerebral+protein+synthesis+in+rats.">Effects of acute and delayed effects of prior chronic cocaine administration on regional rates of cerebral protein synthesis in rats.</a> The Journal of Pharmacology and Experimental Therapeutics. 272, 892-900 (1995).</li><li>Nadel, J., 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=Voluntary+exercise+regionally+augments+rates+of+cerebral+protein+synthesis.">Voluntary exercise regionally augments rates of cerebral protein synthesis.</a> Brain Research. 1537, 125-131 (2013).</li><li>Sun, Y., 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=Rates+of+local+cerebral+protein+synthesis+in+the+rat+during+normal+postnatal+development.">Rates of local cerebral protein synthesis in the rat during normal postnatal development.</a> The American Journal of Physiology. 268, R549-R561 (1995).</li><li>Smith, C. B., Sun, Y., Sokoloff, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+aging+on+regional+rates+of+cerebral+protein+synthesis+in+the+Sprague-Dawley+rat:+examination+of+the+influence+of+recycling+of+amino+acids+derived+from+protein+degradation+into+the+precursor+pool.">Effects of aging on regional rates of cerebral protein synthesis in the Sprague-Dawley rat: examination of the influence of recycling of amino acids derived from protein degradation into the precursor pool.</a> Neurochemistry International. 27, 407-416 (1995).</li><li>Ingvar, M. C., Maeder, P., Sokoloff, L., Smith, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effects+of+aging+on+local+rates+of+cerebral+protein+synthesis+in+rats.">The effects of aging on local rates of cerebral protein synthesis in rats.</a> Monographs in Neural Sciences. 11, 47-50 (1984).</li><li>Sare, R. M., Huang, T., Burlin, T., Loutaev, I., Smith, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Decreased+rates+of+cerebral+protein+synthesis+measured+in+vivo+in+a+mouse+model+of+Tuberous+Sclerosis+Complex:+unexpected+consequences+of+reduced+tuberin.">Decreased rates of cerebral protein synthesis measured in vivo in a mouse model of Tuberous Sclerosis Complex: unexpected consequences of reduced tuberin.</a> Journal of Neurochemistry. 145, 417-425 (2018).</li><li>Liu, Z. H., Huang, T., Smith, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lithium+reverses+increased+rates+of+cerebral+protein+synthesis+in+a+mouse+model+of+fragile+X+syndrome.">Lithium reverses increased rates of cerebral protein synthesis in a mouse model of fragile X syndrome.</a> Neurobiology of Disease. 45, 1145-1152 (2012).</li><li>Qin, M., 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=Altered+cerebral+protein+synthesis+in+fragile+X+syndrome:+studies+in+human+subjects+and+knockout+mice.">Altered cerebral protein synthesis in fragile X syndrome: studies in human subjects and knockout mice.</a> Journal of Cerebral Blood Flow and Metabolism: Official Journal of the International Society of Cerebral Blood Flow and Metabolism. 33, 499-507 (2013).</li><li>Qin, M., Kang, J., Burlin, T. V., Jiang, C., Smith, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Postadolescent+changes+in+regional+cerebral+protein+synthesis:+an+in+vivo+study+in+the+FMR1+null+mouse.">Postadolescent changes in regional cerebral protein synthesis: an in vivo study in the FMR1 null mouse.</a> The Journal of Neuroscience: the Official Journal of the Society for Neuroscience. 25, 5087-5095 (2005).</li><li>Qin, M., 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=R-Baclofen+Reverses+a+Social+Behavior+Deficit+and+Elevated+Protein+Synthesis+in+a+Mouse+Model+of+Fragile+X+Syndrome.">R-Baclofen Reverses a Social Behavior Deficit and Elevated Protein Synthesis in a Mouse Model of Fragile X Syndrome.</a> The International Journal of Neuropsychopharmacology. 18, pyv034 (2015).</li><li>Qin, M., 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=Cerebral+protein+synthesis+in+a+knockin+mouse+model+of+the+fragile+X+premutation.">Cerebral protein synthesis in a knockin mouse model of the fragile X premutation.</a> ASN Neuro. 6, (2014).</li><li>Smith, C. B., Kang, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cerebral+protein+synthesis+in+a+genetic+mouse+model+of+phenylketonuria.">Cerebral protein synthesis in a genetic mouse model of phenylketonuria.</a> Proceedings of the National Academy of Sciences of the United States of America. 97, 11014-11019 (2000).</li><li>Reivich, M., Jehle, J., Sokoloff, L., Kety, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+of+regional+cerebral+blood+flow+with+antipyrine-14C+in+awake+cats.">Measurement of regional cerebral blood flow with antipyrine-14C in awake cats.</a> Journal of Applied Physiology. 27, 296-300 (1969).</li></ol>

We present a quantitative method for determination of regional rates of cerebral protein synthesis (rCPS) in vivo in experimental animals. This method has considerable advantages over existing methods: 1. Measurements are made in the awake behaving animal, so they reflect ongoing processes in the functioning brain. 2. Measurements are made by means of quantitative autoradiography affording the ability to determine rCPS in all regions and subregions of the brain simultaneously. 3. The kinetic model of the method takes int...

Protein synthesis is&#160;an important biological process required for long-term adaptive change in the nervous system1. Inhibiting protein synthesis blocks long-term memory storage in both invertebrates and vertebrates2. Protein synthesis is essential for maintenance of the late phases of some forms of long-term potentiation (LTP) and long-term depression (LTD)3, neuronal survival during development4, and for general maintenance of the neuron and its synaptic connections5. Measurement of rates of brain protein synthesis may be an important tool with which to study adaptive changes as well as neurodevelopmental disorders and disorders related to learning and memory.
We have developed a method to quantify rates of cerebral protein synthesis in vivo in an awake animal that offers inherent advantages over other techniques that estimate rates in ex vivo or in vitro preparations of brain tissue6. Foremost is the applicability to measurements in the intact brain in an awake animal. This is a key consideration because it allows measurements with synaptic structure and function in place and without concerns about post mortem effects. Moreover, the quantitative autoradiographic approach that we employ achieves a high degree of spatial localization. Whereas the energy of 14C is such that we cannot localize the tracer at the subcellular or cellular level, we can measure rates in cell layers and small brain regions such as hypothalamic nuclei, with approximately a 25 &#181;m resolution7.
One challenge of in vivo measurements with radiotracers is to ensure that radiolabel measured is in the product of the reaction of interest rather than unreacted labeled precursor or other extraneous labeled metabolic products6. We chose L-[1-14C]-leucine as the tracer amino acid because it is either incorporated into protein or rapidly metabolized to 14CO2, which is diluted in the large pool of unlabeled CO2 in brain resulting from the high rate of energy metabolism8. Moreover, any 14C not incorporated into protein exists primarily as free [14C]-leucine, which over the 60 min experimental period, is almost entirely cleared from the tissue6. Proteins are then fixed to tissue with formalin and subsequently rinsed with waterto remove any free [14C]-leucine before autoradiography.
Another important consideration is the issue of the dilution of the specific activity of the precursor amino acid pool by unlabeled amino acids derived from tissue proteolysis. We have shown that in adult rat and mouse, about 40% of the precursor leucine pool for protein synthesis in the brain comes from amino acids derived from protein breakdown6. This must be included in the computation of regional rates of cerebral protein synthesis (rCPS) and must be confirmed in studies in which this relationship may change. The theoretical basis and the assumptions of the method have been presented in detail elsewhere6. In this paper, we focus on the procedural issues of the application of this methodology.
This method has been employed for the determination of rCPS in ground squirrels9, sheep10, rhesus monkeys11, rats12,13,14,15,16,17,18,19,20,21, a mouse model of Tuberous Sclerosis complex22, a mouse model of fragile X syndrome23,24,25,26, fragile X premutation mice27, and a mouse model of phenylketonuria28. In this manuscript, we present the procedures for measurement of rCPS with the in vivo autoradiographic L-[1-14C]-leucine method. We present rCPS in brain regions of an awake control mouse. We also demonstrate that in vivo administration of anisomycin, an inhibitor of translation, abolishes protein synthesis in the brain.

<table>
	<tbody>
		<tr>
			<td>Mice</td>
			<td>The Jackson Laboratory</td>
			<td>003024</td>
			<td>Fmr1 knockout breeding pairs</td>
		</tr>
		<tr>
			<td>Anisomycin</td>
			<td>Tocris Bioscience</td>
			<td>1290</td>
			<td></td>
		</tr>
		<tr>
			<td>Microhematocrit Tubes</td>
			<td>Drummond Scientific</td>
			<td>1-000-3200-H</td>
			<td>capillary tubes</td>
		</tr>
		<tr>
			<td>Critoseal Capillary Tube Sealant</td>
			<td>Leica Microsystems</td>
			<td>39215003</td>
			<td>sealant putty</td>
		</tr>
		<tr>
			<td>Glass vial inserts</td>
			<td>Agilent</td>
			<td>5183-2089</td>
			<td>used to collect blood samples</td>
		</tr>
		<tr>
			<td>Digi-Med Blood Pressure Analyzer</td>
			<td>Micro-Med Inc.</td>
			<td>BPA-400</td>
			<td>blood pressure analyzer</td>
		</tr>
		<tr>
			<td>Bayer Breeze 2 Blood Glucose Monitoring System</td>
			<td>Bayer Breeze</td>
			<td>9570A</td>
			<td>glucose meter</td>
		</tr>
		<tr>
			<td>Gastight syringe</td>
			<td>Hamilton Co.</td>
			<td>1710</td>
			<td>tuberculin glass syringe</td>
		</tr>
		<tr>
			<td>HeatMax HotHands-2 Hand Warmers</td>
			<td>HeatMax</td>
			<td>Model HH2</td>
			<td>warming pads</td>
		</tr>
		<tr>
			<td>Heparin Lock Flush Solution</td>
			<td>Fresenius Kabi USA, LLC</td>
			<td>504505</td>
			<td>heparin saline</td>
		</tr>
		<tr>
			<td>Clear animal container</td>
			<td>Instech</td>
			<td>MTANK/W</td>
			<td>animal enclosure</td>
		</tr>
		<tr>
			<td>Spring tether</td>
			<td>Instech</td>
			<td>PS62</td>
			<td>catheter tube/rodent attachment</td>
		</tr>
		<tr>
			<td>Swivel</td>
			<td>Instech</td>
			<td>375/25</td>
			<td>hooks to spring tether</td>
		</tr>
		<tr>
			<td>Swivel arm and mount</td>
			<td>Instech</td>
			<td>SMCLA</td>
			<td>hooks to swivel and animal enclosure</td>
		</tr>
		<tr>
			<td>Tether button</td>
			<td>Instech</td>
			<td>VAB62BS/22</td>
			<td>attaches to bottom of spring tether</td>
		</tr>
		<tr>
			<td>Stainless steel tube</td>
			<td>Made in-house</td>
			<td>N/A</td>
			<td>used to snake catheters through mouse</td>
		</tr>
		<tr>
			<td>Matrx VIP 3000</td>
			<td>Matrx</td>
			<td>91305430</td>
			<td>isoflurane vaporizer</td>
		</tr>
		<tr>
			<td>Isoflurane</td>
			<td>Stoelting Co.</td>
			<td>50207</td>
			<td>isoflurane/halothane adsorber</td>
		</tr>
		<tr>
			<td>Clippers</td>
			<td>Oster Finisher</td>
			<td>Model 59</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical skin hooks</td>
			<td>Made in-house (??)</td>
			<td>N/A (??)</td>
			<td></td>
		</tr>
		<tr>
			<td>0.9% Sodium Chloride Saline</td>
			<td>APP Pharmaceuticals LLC</td>
			<td>918610</td>
			<td></td>
		</tr>
		<tr>
			<td>Forceps</td>
			<td>Fine Science Tools</td>
			<td>11274-20</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical scissors</td>
			<td>Fine Science Tools</td>
			<td>14058-11</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscissors</td>
			<td>Fine Science Tools</td>
			<td>15000-00</td>
			<td></td>
		</tr>
		<tr>
			<td>UNIFY silk surgical sutures</td>
			<td>AD Surgical</td>
			<td>#S-S618R13</td>
			<td>6-0 USP, non-absorbable</td>
		</tr>
		<tr>
			<td>PE-8 polyethylene tubing</td>
			<td>SAI Infusion Technologies</td>
			<td>PE-8-25</td>
			<td></td>
		</tr>
		<tr>
			<td>Syringe</td>
			<td>Becton Dickinson and Co.</td>
			<td>309659</td>
			<td>1cc/mL</td>
		</tr>
		<tr>
			<td>PE-10 polyethylene tubing</td>
			<td>Clay Adams</td>
			<td>427400</td>
			<td></td>
		</tr>
		<tr>
			<td>MCID Analysis</td>
			<td>Imaging Research Inc.</td>
			<td>Version 7.0</td>
			<td>optical density analysis</td>
		</tr>
		<tr>
			<td>Gelatin-coated slides (75x25mm)</td>
			<td>FD Neurotechnologies</td>
			<td>PO101</td>
			<td></td>
		</tr>
		<tr>
			<td>Cryostat</td>
			<td>Leica</td>
			<td>CM1850</td>
			<td></td>
		</tr>
		<tr>
			<td>Super RX-N medical x-ray film</td>
			<td>Fuji</td>
			<td>47410-19291</td>
			<td></td>
		</tr>
		<tr>
			<td>Hypercassettes (8x10 in)</td>
			<td>Amersham Pharmacia Biotech</td>
			<td>11649</td>
			<td></td>
		</tr>
		<tr>
			<td>[1-14C]leucine</td>
			<td>Moravek</td>
			<td>MC404E</td>
			<td></td>
		</tr>
		<tr>
			<td>Microcentrifuge tube</td>
			<td>Sarstedt Aktiengesellschaft &#38; Co.</td>
			<td>72.692.005</td>
			<td>used to deproteinize blood samples</td>
		</tr>
		<tr>
			<td>Glass pasteur pipette</td>
			<td>Wheaton</td>
			<td>357335</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass wool</td>
			<td>Sigma-Aldrich</td>
			<td>18421</td>
			<td></td>
		</tr>
		<tr>
			<td>Nitrogen</td>
			<td>NIH Supply Center</td>
			<td>6830009737285</td>
			<td></td>
		</tr>
		<tr>
			<td>Scintillation fluid</td>
			<td>CytoScint</td>
			<td>882453</td>
			<td></td>
		</tr>
		<tr>
			<td>Liquid scintilllation counter</td>
			<td>Packard Tri-Carb</td>
			<td>2250CA</td>
			<td></td>
		</tr>
		<tr>
			<td>Amino acid analyzer</td>
			<td>Pickering Laboratories</td>
			<td>Pinnacle PCX</td>
			<td></td>
		</tr>
		<tr>
			<td>HPLC unit</td>
			<td>Agilent Technologies</td>
			<td>1260 Infinity</td>
			<td>include 1260 Bio-Inert Pump</td>
		</tr>
		<tr>
			<td>Surgical microscope</td>
			<td>Wild Heerbrugg</td>
			<td>M650</td>
			<td></td>
		</tr>
		<tr>
			<td>Sulfosalicylic acid</td>
			<td>Sigma-Aldrich</td>
			<td>MKBS1634V</td>
			<td>5-sulfosalicylic acid dihydrate</td>
		</tr>
		<tr>
			<td>Norleucine</td>
			<td>Sigma</td>
			<td>N8513</td>
			<td></td>
		</tr>
		<tr>
			<td>1.0 N HCl</td>
			<td>Sigma-Aldrich</td>
			<td>H9892</td>
			<td></td>
		</tr>
		<tr>
			<td>[H3]leucine</td>
			<td>Moraevk</td>
			<td>MC672</td>
			<td></td>
		</tr>
		<tr>
			<td>Falcon tube</td>
			<td>Thermo Scientific</td>
			<td>339652</td>
			<td>50 mL conical centrifuge tubes</td>
		</tr>
		<tr>
			<td>Stopwatch</td>
			<td>Heuer Microsplit</td>
			<td>Model 1000</td>
			<td>1/100 min</td>
		</tr>
		<tr>
			<td>Euthanasia Solution</td>
			<td>Vet One</td>
			<td>H6438</td>
			<td></td>
		</tr>
		<tr>
			<td>Northern Light Precision Illuminator</td>
			<td>Imaging Research Inc.</td>
			<td>Model B95</td>
			<td>fluorescent light box</td>
		</tr>
		<tr>
			<td>Micro-NIKKOR 55mm f/2.8</td>
			<td>Nikon</td>
			<td>1442</td>
			<td>CDD camera</td>
		</tr>
	</tbody>
</table>

quantitative autoradiographic method for determination of regional rates of cerebral protein synthesis in vivo

Protein synthesis is required for development and maintenance of neuronal function and is involved in adaptive changes in the nervous system. Moreover, it is thought that dysregulation of protein synthesis in the nervous system may be a core phenotype in some developmental disorders. Accurate measurement of rates of cerebral protein synthesis in animal models is important for understanding these disorders. The method that we have developed was designed to be applied to the study of awake, behaving animals. It is a quantitative autoradiographic method, so it can yield rates in all regions of the brain simultaneously. The method is based on the use of a tracer amino acid, L-[1-14C]-leucine, and a kinetic model of the behavior of L-leucine in the brain. We chose L-[1-14C]-leucine as the tracer because it does not lead to extraneous labeled metabolic products. It is either incorporated into protein or rapidly metabolized to yield 14CO2 which is diluted in a large pool of unlabeled CO2 in the brain. The method and the model also allow for the contribution of unlabeled leucine derived from tissue proteolysis to the tissue precursor pool for protein synthesis. The method has the spatial resolution to determine protein synthesis rates in cell and neuropil layers, as well as hypothalamic and cranial nerve nuclei. To obtain reliable and reproducible quantitative data, it is important to adhere to procedural details. Here we present the detailed procedures of the quantitative autoradiographic L-[1-14C]-leucine method for the determination of regional rates of protein synthesis in vivo.

Here we show a representative experiment demonstrating the effects of prior administration of a protein synthesis inhibitor on rCPS. Anisomycin in normal saline was administered to an adult C57/BL6 male wild-type mouse subcutaneously (100 mg/kg) 30 min prior to initiation of rCPS determination. Effects of anisomycin treatment compared to a vehicle-treated control animal show that rCPS is almost undetectable in the anisomycin-treated mouse (Figure 4). These da...

Watch this Scientific Journal Video about Quantitative Autoradiographic Method for Determination of Regional Rates of Cerebral Protein Synthesis In Vivo at JoVE.com

Quantitative Autoradiographic Method for Determination of Regional Rates of Cerebral Protein Synthesis In Vivo

Protein synthesis is&#160;a critical biological process for cells. In brain, it is required for adaptive changes. Measurement of rates of protein synthesis in the intact brain requires careful methodological considerations. Here we present the L-[1-14C]-leucine quantitative autoradiographic method for determination of regional rates of cerebral protein synthesis in vivo.

Protein synthesis is required for development and maintenance of neuronal function and is involved in adaptive changes in the nervous system. Moreover, it ...

Measurement of regional rates of brain protein synthesis can trace the response of the brain to long term changes such that occur during development and neuroplasticity. Our method has the advantages that measurements are fully quantitative, and they are made in the awake behaving animal. The quantitative autoradiographic technique permits measurements in all brain regions simultaneously.Demonstrating the procedure will be Anita Torossian, a post-baccalaureate fellow in my laboratory, and Tianjian Huang, our animal surgeon. Begin this procedure with preparation for surgery as detailed in the text protocol. Once on the surgery stage, use surgical scissors to make a one centimeter incision from the upper medial portion of the left thigh rostrally towards the midline revealing the femoral artery and vein.Retract loose skin with surgical skin hooks above and on either side of the incision. Secure the skin hooks by taping them to the surgery stage. Apply sterile 0.9%sodium chloride to the exposed area to maintain adequate moisture.Use forceps to blunt dissect, separating the connective tissue around a small section of the femoral artery and vein. Carefully separate the artery and vein. Now use forceps to thread one strand of absorbable suture under both the femoral vein and artery at the most lateral point of the incision.Pull the suture halfway through so the ends are even. At a more proximal point to the groin, use forceps to thread a second suture under only the femoral vein. Gently tie a half-knot that will be used to restrict blood flow.At a point between strand A and strand B, use forceps to thread a third suture under only the femoral vein. Gently tie a full knot that will be used to restrict blood flow. Be careful not to tear the vein.Gently tug on strand B to restrict blood flow. Use a hemostat to gently tug strand B to maintain blood restriction. Now, connect the non-cut end of the PE tubing to a 32 gauge needle and a one millimeter syringe filled with heparinized saline.Flush the catheter to remove air bubbles. Cut a small hole in the restricted area of the femoral vein with micro scissors, and carefully insert the angled end of the flushed PE eight tubing toward strand B.Once inserted, release strand B's tension and guide the catheter further up the vein. Tighten strand B around the vein containing the catheter.Using strand C, tie an additional knot around the catheter. Make sure this knot does not capture the femoral artery. Gently pull back on the syringe barrel to partially fill the tubing with blood to ensure that the catheter has been implanted properly before inserting a PE 10 catheter into the left femoral artery using the same procedure.Once both the femoral vein and artery catheters have been secured, tie strand A into a knot around both catheters. After cutting all excess sutures and removing skin hooks, flush the arterial catheter with heparinized saline to prevent clotting. Cauterize the ends of both catheters to create a seal.Place the mouse in the prone position and make a small incision at the base of the neck applying saline to the exposed area. Insert a hollow metal rod subdermally from the neck incision to the femoral incision. Snake the catheters through the hollow rod and out of the neck incision.After removing the hollow rod, close the femoral incision with suture followed by post-surgical analgesia. Snake the catheters through a 30 centimeter flexible hollow tube to make the spring tether before suturing the button of the spring tether under the skin followed by post-surgical analgesia. Move the mouse into a clear cylindrical container with a swivel mount and arm to house the mouse during the recovery period.Place a hand warmer under the container to keep the mouse warm. Ensure that the mouse is in a normal physiological state at the outset of the experiment by taking samples as detailed in the text protocol. To administer the tracer intravenously, use a Y-connector with a syringe holding the C 14 labeled leucine tracer connected to one arm, and a syringe with 100 to 200 microliters of sterile saline to flush the venous line connected to the other arm.Connect the Y-connector to the venous line. Initiate the study by simultaneously starting a stop watch, injecting the tracer, and collecting timed arterial blood samples. Flush the venous line with saline immediately following injection.Collect blood samples one through seven continuously throughout the first two minutes of the experiment in the same manner. After collecting the seven samples, collect 30 microliters of dead space blood before each remaining sample. Samples eight through 14 are collected at three, five, 10, 15, 30, 45, and 60 minutes respectively.At some point during the experiment, process three tubes for internal standards containing tritiated leucine and norleucine as detailed in the text protocol. To quantify plasma leucine concentrations, use an HPLC system with a sodium cation exchange column and post column derivatization with orthophthalaldehyde and flourometric detection. The area under the leucine curve is proportional to the concentration of leucine in the sample.Use comparison with standards to quantify leucine concentrations in the samples. Then use a liquid scintillation counter to quantify disintegrations per minute of tritium and C 14 in the plasma samples. Use these concentrations to construct the clearance curve of C 14 labeled leucine from the circulation and the time course of its specific activity in the arterial plasma.From the graph, calculate the integrated C 14 labeled leucine specific activity in the arterial plasma. To perform quantitative autoradiography, prepare brain sections 20 microns in thickness. Section brain by means of a cryostat at minus 20 degrees celsius.Thaw mount sections on gelatin coated slides. After fixation of slides, arrange slides in an X-ray film cassette along with a set of previously calibrated C 14 labeled methyl methacrylate standards. In a dark room and under safe light, place a piece of X-ray film, emulsion-side down over the sides and standards.Seal the cassette and place it in a black changing bag. Develop the films according to the manufacturer's instructions. Automated film development is not recommended because the background may be uneven and can affect quantification.Construct a calibration curve of optical density versus tissue C 14 concentration based on the optical density values of the set of calibrated standards on the film. Fit these data to a polynomial equation. Either a second or third degree polynomial equation fits very well.To analyze specific brain regions, locate the region of interest or ROI in six to eight sections by comparison with a brain atlas. Record the optical density of the pixels within an ROI in all sections. Based on the calibration curve, compute the tissue C 14 concentration in each pixel.Finally, compute the regional rates of cerebral protein synthesis from the average tissue C 14 concentration in the ROI in the integral of the ratios of arterial plasma concentrations of unlabeled and labeled leucine at times t and lamba. The fraction of leucine in the tissue precursor pool that comes from the plasma. Shown here are representative images from a vehicle treated animal compared with an animal treated with anisomycin, an inhibitor of protein synthesis.Rates of protein synthesis are proportional to the level of darkness in the image. Anisomycin drastically reduces the measured rates of brain protein synthesis indicating the specificity of this method. Here, digitized autoradiograms are shown from an awake behaving mouse at the level of the hippocampus and hypothalamus.The darker regions have higher regional rates of cerebral protein synthesis. Shown here is a digitized autoradiogram from an awake behaving control mouse at the level of the dorsal hippocampus. Rates of cerebral protein synthesis are color-coated in the images according to the color bar.While attempting this procedure, it's important to be sure that animals are in a normal physiological state during the measurements. Our methodology has already demonstrated disregulation of protein synthesis in neurodevelopmental disorders like Fragile X syndrome. It may also be a useful marker for degenerative changes and conditions like Alzheimer's disease.The protein synthesis method can be used in conjunction with immune histochemistry in alternating sections to correlate changes in proteins synthesis with regional changes in specific proteins. In summary, the quantitative autoradiographic L-1 C 14 leucine method is ideal for accurate determination of regional rates of protein synthesis in vivo. It offers considerable advantages in terms of accuracy and its applicability to in vivo conditions.

quantitative-autoradiographic-method-for-determination-regional-rates

Research

JoVE Journal

Neuroscience

Methods for Study of Neuronal Morphogenesis: Ex vivo RNAi Electroporation in Embryonic Murine Cerebral Cortex

The cerebral cortex directs higher cognitive functions. This six layered structure is generated in an inside-first, outside-last manner, in which the first born neurons remain closer to the ventricle while the last born neurons migrate past the first born neurons towards the surface of the brain1. In addition to neuronal migration2, a key process for normal cortical function is the regulation of neuronal morphogenesis3. While neuronal morphogenesis can be studied in vitro in primary cultures, there is much to be learned from how these processes are regulated in tissue environments.
We describe techniques to analyze neuronal migration and/or morphogenesis in organotypic slices of the cerebral cortex4,6. A pSilencer modified vector is used which contains both a U6 promoter that drives the double stranded hairpin RNA and a separate expression cassette that encodes GFP protein driven by a CMV promoter7-9. Our approach allows for the rapid assessment of defects in neurite outgrowth upon specific knockdown of candidate genes and has been successfully used in a screen for regulators of neurite outgrowth8. Because only a subset of cells will express the RNAi constructs, the organotypic slices allow for a mosaic analysis of the potential phenotypes. Moreover, because this analysis is done in a near approximation of the in vivo environment, it provides a low cost and rapid alternative to the generation of transgenic or knockout animals for genes of unknown cortical function. Finally, in comparison with in vivo electroporation technology, the success of ex vivo electroporation experiments is not dependant upon proficient surgery skill development and can be performed with a shorter training time and skill.

Methods for Study of Neuronal Morphogenesis: Ex vivo RNAi Electroporation in Embryonic Murine Cerebral Cortex

To conduct a rapid assessment of the function of genes in the development of cerebral cortex, we describe methods involving the ex vivo electroporation of plasmids co-expressing inhibitory RNA (RNAi) and GFP in murine embryonic cortex. This protocol is amenable to the study of various aspects of neurodevelopment such as neurogenesis, neuronal migration and neuronal morphogenesis including dendrite and axon outgrowth.

The cerebral cortex directs higher cognitive functions. This six layered structure is generated in an inside-first, outside-last manner, in which the ...

Functional Neuroimaging Using Ultrasonic Blood-brain Barrier Disruption and Manganese-enhanced MRI

Although mice are the dominant model system for studying the genetic and molecular underpinnings of neuroscience, functional neuroimaging in mice remains technically challenging. One approach, Activation-Induced Manganese-enhanced MRI (AIM MRI), has been used successfully to map neuronal activity in rodents 1-5. In AIM MRI, Mn2+ acts a calcium analog and accumulates in depolarized neurons 6,7. Because Mn2+ shortens the T1 tissue property, regions of elevated neuronal activity will enhance in MRI. Furthermore, Mn2+ clears slowly from the activated regions; therefore, stimulation can be performed outside the magnet prior to imaging, enabling greater experimental flexibility. However, because Mn2+ does not readily cross the blood-brain barrier (BBB), the need to open the BBB has limited the use of AIM MRI, especially in mice.
One tool for opening the BBB is ultrasound. Though potentially damaging, if ultrasound is administered in combination with gas-filled microbubbles (i.e., ultrasound contrast agents), the acoustic pressure required for BBB opening is considerably lower. This combination of ultrasound and microbubbles can be used to reliably open the BBB without causing tissue damage 8-11.
Here, a method is presented for performing AIM MRI by using microbubbles and ultrasound to open the BBB. After an intravenous injection of perflutren microbubbles, an unfocused pulsed ultrasound beam is applied to the shaved mouse head for 3 minutes. For simplicity, we refer to this technique of BBB Opening with Microbubbles and UltraSound as BOMUS 12. Using BOMUS to open the BBB throughout both cerebral hemispheres, manganese is administered to the whole mouse brain. After experimental stimulation of the lightly sedated mice, AIM MRI is used to map the neuronal response.
To demonstrate this approach, herein BOMUS and AIM MRI are used to map unilateral mechanical stimulation of the vibrissae in lightly sedated mice 13. Because BOMUS can open the BBB throughout both hemispheres, the unstimulated side of the brain is used to control for nonspecific background stimulation. The resultant 3D activation map agrees well with published representations of the vibrissae regions of the barrel field cortex 14. The ultrasonic opening of the BBB is fast, noninvasive, and reversible; and thus this approach is suitable for high-throughput and/or longitudinal studies in awake mice.

A technique is described for broadly opening the blood-brain barrier in the mouse using microbubbles and ultrasound. Using this technique, manganese can be administered to the mouse brain. Because manganese is an MRI contrast agent that accumulates in depolarized neurons, this approach enables imaging of neuronal activity.

Although mice are the dominant model system for studying the genetic and molecular underpinnings of neuroscience, functional neuroimaging in mice remains ...

Dual Electrophysiological Recordings of Synaptically-evoked Astroglial and Neuronal Responses in Acute Hippocampal Slices

Astrocytes form together with neurons tripartite synapses, where they integrate and modulate neuronal activity. Indeed, astrocytes sense neuronal inputs through activation of their ion channels and neurotransmitter receptors, and process information in part through activity-dependent release of gliotransmitters. Furthermore, astrocytes constitute the main uptake system for glutamate, contribute to potassium spatial buffering, as well as to GABA clearance. These cells therefore constantly monitor synaptic activity, and are thereby sensitive indicators for alterations in synaptically-released glutamate, GABA and extracellular potassium levels. Additionally, alterations in astroglial uptake activity or buffering capacity can have severe effects on neuronal functions, and might be overlooked when characterizing physiopathological situations or knockout mice. Dual recording of neuronal and astroglial activities is therefore an important method to study alterations in synaptic strength associated to concomitant changes in astroglial uptake and buffering capacities. Here we describe how to prepare hippocampal slices, how to identify stratum radiatum astrocytes, and how to record simultaneously neuronal and astroglial electrophysiological responses. Furthermore, we describe how to isolate pharmacologically the synaptically-evoked astroglial currents.

The preparation of acute brain slices from isolated hippocampi, as well as the simultaneous electrophysiological recordings of astrocytes and neurons in stratum radiatum during stimulation of schaffer collaterals is described. The pharmacological isolation of astroglial potassium and glutamate transporter currents is demonstrated.

Astrocytes form together with neurons tripartite synapses, where they integrate and modulate neuronal activity. Indeed, astrocytes sense neuronal inputs ...

A Method for High Fidelity Optogenetic Control of Individual Pyramidal Neurons In vivo

Optogenetic methods have emerged as a powerful tool for elucidating neural circuit activity underlying a diverse set of behaviors across a broad range of species. Optogenetic tools of microbial origin consist of light-sensitive membrane proteins that are able to activate (e.g., channelrhodopsin-2, ChR2) or silence (e.g., halorhodopsin, NpHR) neural activity ingenetically-defined cell types over behaviorally-relevant timescales. We first demonstrate a simple approach for adeno-associated virus-mediated delivery of ChR2 and NpHR transgenes to the dorsal subiculum and prelimbic region of the prefrontal cortex in rat. Because ChR2 and NpHR are genetically targetable, we describe the use of this technology to control the electrical activity of specific populations of neurons (i.e., pyramidal neurons) embedded in heterogeneous tissue with high temporal precision. We describe herein the hardware, custom software user interface, and procedures that allow for simultaneous light delivery and electrical recording from transduced pyramidal neurons in an anesthetized in vivo preparation. These light-responsive tools provide the opportunity for identifying the causal contributions of different cell types to information processing and behavior.

A Method for High Fidelity Optogenetic Control of Individual Pyramidal Neurons In vivo

The recent development of neuroscience tools that combine genetics and optics, termed "optogenetics", enables control over neural circuit activity with an unprecedented level of spatial and temporal resolution. Here we provide a protocol for integrating in vivo recording with optogenetic manipulation of genetically-defined subsets of prefrontal cortical and subicular pyramidal neurons.

Optogenetic methods  have emerged as a powerful tool for elucidating neural circuit activity  underlying a diverse set of behaviors across a broad range ...

A Dual Tracer PET-MRI Protocol for the Quantitative Measure of Regional Brain Energy Substrates Uptake in the Rat

We present a method for comparing the uptake of the brain&#39;s two key energy substrates: glucose and ketones (acetoacetate [AcAc] in this case) in the rat. The developed method is a small-animal positron emission tomography (PET) protocol, in which&#160;11C-AcAc and 18F-fluorodeoxyglucose (18F-FDG) are injected sequentially in each animal. This dual tracer PET acquisition is possible because of the short half-life of 11C (20.4 min). The rats also undergo a magnetic resonance imaging (MRI) acquisition seven days before the PET protocol. Prior to image analysis, PET and MRI images are coregistered to allow the measurement of regional cerebral uptake (cortex, hippocampus, striatum, and cerebellum). A quantitative measure of 11C-AcAc and 18F-FDG brain uptake (cerebral metabolic rate; &#956;mol/100 g/min) is determined by kinetic modeling using the image-derived input function (IDIF) method. Our new dual tracer PET protocol is robust and flexible; the two tracers used can be replaced by different radiotracers to evaluate other processes in the brain. Moreover, our protocol is applicable to the study of brain fuel supply in multiple conditions such as normal aging and neurodegenerative pathologies such as Alzheimer&#39;s and Parkinson&#39;s diseases.

Small-animal positron emission tomography enables the assessment of the brain&#39;s two main energy substrates:&#160;glucose and ketones. In the present method, 11C-acetoacetate and 18F-fluorodeoxyglucose are injected sequentially in each animal, and their uptake is measured quantitatively in specific brain regions determined from the magnetic resonance images.

We present a method for comparing the uptake of the brain&#39;s two key energy substrates: glucose and ketones (acetoacetate [AcAc] in this case) in the ...

Inducing Plasticity of Astrocytic Receptors by Manipulation of Neuronal Firing Rates

Close to two decades of research has established that astrocytes in situ and in vivo express numerous G protein-coupled receptors (GPCRs) that can be stimulated by neuronally-released transmitter. However, the ability of astrocytic receptors to exhibit plasticity in response to changes in neuronal activity has received little attention. Here we describe a model system that can be used to globally scale up or down astrocytic group I metabotropic glutamate receptors (mGluRs) in acute brain slices. Included are methods on how to prepare parasagittal hippocampal slices, construct chambers suitable for long-term slice incubation, bidirectionally manipulate neuronal action potential frequency, load astrocytes and astrocyte processes with fluorescent Ca2+ indicator, and measure changes in astrocytic Gq GPCR activity by recording spontaneous and evoked astrocyte Ca2+ events using confocal microscopy. In essence, a &#8220;calcium roadmap&#8221; is provided for how to measure plasticity of astrocytic Gq GPCRs. Applications of the technique for study of astrocytes are discussed. Having an understanding of how astrocytic receptor signaling is affected by changes in neuronal activity has important implications for both normal synaptic function as well as processes underlying neurological disorders and neurodegenerative disease.

Here we describe an adaptation of protocols used to induce homeostatic plasticity in neurons for the study of plasticity of astrocytic G protein-coupled receptors. Recently used to examine changes in astrocytic group I mGluRs in juvenile mice, the method can be applied to measure scaling of various astrocytic GPCRs, in tissue from adult mice in situ and in vivo, and to gain a better appreciation of the sensitivity of astrocytic receptors to changes in neuronal activity.

Close to two decades of research has established that astrocytes in situ and in vivo express numerous G protein-coupled receptors (GPCRs) that can be ...

Determination of Photoreceptor Cell Spectral Sensitivity in an Insect Model from In Vivo Intracellular Recordings

Intracellular recording is a powerful technique used to determine how a single cell may respond to a given stimulus. In vision research, intracellular recording has historically been a common technique used to study sensitivities of individual photoreceptor cells to different light stimuli that is still being used today. However, there remains a dearth of detailed methodology in the literature for researchers wishing to replicate intracellular recording experiments in the eye. Here we present the insect as a model for examining eye physiology more generally. Insect photoreceptor cells are located near the surface of the eye and are therefore easy to reach, and many of the mechanisms involved in vision are conserved across animal phyla. We describe the basic procedure for in vivo intracellular recording of photoreceptor cells in the eye of a butterfly, with the goal of making this technique more accessible to researchers with little prior experience in electrophysiology. We introduce the basic equipment needed, how to prepare a live butterfly for recording, how to insert a glass microelectrode into a single cell, and finally the recording procedure itself. We also explain the basic analysis of raw response data for determining spectral sensitivity of individual cell types. Although our protocol focuses on determining spectral sensitivity, other stimuli (e.g., polarized light) and variations of the method are applicable to this setup.

Determination of Photoreceptor Cell Spectral Sensitivity in an Insect Model from In Vivo Intracellular Recordings

The electrophysiological technique of intracellular recording is demonstrated and used to determine spectral sensitivities of single photoreceptor cells in the compound eye of a butterfly.

Intracellular recording is a powerful technique used to determine how a single cell may respond to a given stimulus. In vision research, intracellular ...

In Vivo Gene Transfer to Schwann Cells in the Rodent Sciatic Nerve by Electroporation

The formation of the myelin sheath by Schwann cells (SCs) is essential for rapid conduction of nerve impulses along axons in the peripheral nervous system. SC-selective genetic manipulation in living animals is a powerful technique for studying the molecular and cellular mechanisms of SC myelination and demyelination in vivo. While knockout/knockin and transgenic mice are powerful tools for studying SC biology, these methods are costly and time consuming. Viral vector-mediated transgene introduction into the sciatic nerve is a simpler and less laborious method. However, viral methods have limitations, such as toxicity, transgene size constraints, and infectivity restricted to certain developmental stages. Here, we describe a new method that allows selective transfection of myelinating SCs in the rodent sciatic nerve using electroporation. By applying electric pulses to the sciatic nerve at the site of plasmid DNA injection, genes of interest can be easily silenced or overexpressed in SCs in both neonatal and more mature animals. Furthermore, this in vivo electroporation method allows for highly efficient simultaneous expression of multiple transgenes. Our novel technique should enable researchers to efficiently manipulate SC gene expression, and facilitate studies on SC development and function.

In Vivo Gene Transfer to Schwann Cells in the Rodent Sciatic Nerve by Electroporation

Here, we present an in vivo technique for gene transfer to Schwann cells (SCs) in the rodent sciatic nerve. This simple technique is useful for investigating signaling mechanisms involved in the development and maintenance of myelinating SCs.

The formation of the myelin sheath by Schwann cells (SCs) is essential for rapid conduction of nerve impulses along axons in the peripheral nervous ...

Lateral Chronic Cranial Window Preparation Enables In Vivo Observation Following Distal Middle Cerebral Artery Occlusion in Mice

Focal cerebral ischemia (i.e., ischemic stroke) may cause major brain injury, leading to a severe loss of neuronal function and consequently to a host of motor and cognitive disabilities. Its high prevalence poses a serious health burden, as stroke is among the principal causes of long-term disability and death worldwide1. Recovery of neuronal function is, in most cases, only partial. So far, treatment options are very limited, in particular due to the narrow time window for thrombolysis2,3. Determining methods to accelerate recovery from stroke remains a prime medical goal; however, this has been hampered by insufficient mechanistic insights into the recovery process. Experimental stroke researchers frequently employ rodent models of focal cerebral ischemia. Beyond the acute phase, stroke research is increasingly focused on the sub-acute and chronic phase following cerebral ischemia. Most stroke researchers apply permanent or transient occlusion of the MCA in mice or rats. In patients, occlusions of the MCA are among the most frequent causes of ischemic stroke4. Besides proximal occlusion of the MCA using the filament model, surgical occlusion of the distal MCA is probably the most frequently used model in experimental stroke research5. Occlusion of a distal (to the branching of the lenticulo-striate arteries) MCA branch typically spares the striatum and primarily affects the neocortex. Vessel occlusion can be permanent or transient. High reproducibility of lesion volume and very low mortality rates with respect to the long-term outcome are the main advantages of this model. Here, we demonstrate how to perform a chronic cranial window (CW) preparation lateral to the sagittal sinus, and afterwards how to surgically induce a distal stroke underneath the window using a craniotomy approach. This approach can be applied for sequential imaging of acute and chronic changes following ischemia via epi-illuminating, confocal laser scanning, and two-photon intravital microscopy.

Lateral Chronic Cranial Window Preparation Enables In Vivo Observation Following Distal Middle Cerebral Artery Occlusion in Mice

Surgical occlusion of a distal middle cerebral artery branch (MCAo) is a frequently used model in experimental stroke research. This manuscript describes the basic technique of permanent MCAo, combined with the insertion of a lateral cranial window, which offers the opportunity for longitudinal intravital microscopy in mice.

Focal cerebral ischemia (i.e., ischemic stroke) may cause major brain injury, leading to a severe loss of neuronal function and consequently to a host of ...

Bioluminescence Imaging of Neuroinflammation in Transgenic Mice After Peripheral Inoculation of Alpha-Synuclein Fibrils

To study the prion-like behavior of misfolded alpha-synuclein, mouse models are needed that allow fast and simple transmission of alpha-synuclein prionoids, which cause neuropathology within the central nervous system (CNS). Here we describe that intraglossal or intraperitoneal injection of alpha-synuclein fibrils into bigenic Tg(M83+/-:Gfap-luc+/-) mice, which overexpress human alpha-synuclein with the A53T mutation from the prion protein promoter and firefly luciferase from the promoter for glial fibrillary acidic protein (Gfap), is sufficient to induce neuropathologic disease. In comparison to homozygous Tg(M83+/+) mice that develop severe neurologic symptoms beginning at an age of 8 months, heterozygous Tg(M83+/-:Gfap-luc+/-) animals remain free of spontaneous disease until they reach an age of 22 months. Interestingly, injection of alpha-synuclein fibrils via the intraperitoneal route induced neurologic disease with paralysis in four of five Tg(M83+/-:Gfap-luc+/-) mice with a median incubation time of 229 &#177;17 days. Diseased animals showed severe deposits of phosphorylated alpha-synuclein in their brains and spinal cords. Accumulations of alpha-synuclein were sarkosyl-insoluble and colocalized with ubiquitin and p62, and were accompanied by an inflammatory response resulting in astrocytic gliosis and microgliosis. Surprisingly, inoculation of alpha-synuclein fibrils into the tongue was less effective in causing disease with only one of five injected animals showing alpha-synuclein pathology after 285 days. Our findings show that inoculation via the intraglossal route and more so via the intraperitoneal route is suitable to induce neurologic illness with relevant hallmarks of synucleinopathies in Tg(M83+/-:Gfap-luc+/-) mice. This provides a new model for studying prion-like pathogenesis induced by alpha-synuclein prionoids in greater detail.

Peripheral injection of alpha-synuclein fibrils into the peritoneum or tongue of Tg(M83+/-:Gfap-luc+/-) mice, which express human alpha-synuclein with the familial A53T mutation and firefly luciferase, can induce neuropathology, including neuroinflammation, in their central nervous system.