Funded by NIH P40 OD010952, the Korein Foundation, a University of Miami Fellowship to SLC and a Maytag fellowship to ATK. The authors gratefully acknowledge the staff of the National Resource for Aplysia, as well as Lauren Simonitis and Hannah Peck, who provided micrographs for a figure.

1. Cell Preparation
<ol>
 <li>On Day 1, weigh and anesthetize animal.
 <ol>
 <li>Weigh a 30 g-1 kg animal. Anesthetize in 5-10 animal volumes of 1:1 seawater:isotonic MgCl . 6H20 for 1 hr with aeration such as an electric aquarium air pump with attached airstone.</li>
 </ol>
 </li>
 <li>Prepare dissection supplies.
 <ol>
 <li>Assemble clean dissection tray with stainless steel straight pins, such as fabric pins. Assemble several Petri dishes containing artificial seawater (ASW; see Tables 1 and 3) + penicillin/ streptomycin (P/S).</li>
 <li>Have ready a low power microscope. Have clean dissection instruments ready, such as ribbed nose and fine surgical forceps, and fine and large surgical scissors. Spray the instruments with 70% isopropol alcohol before use and allow to dry.</li>
 </ol>
 </li>
 <li>Position animal on dissection tray.
 <ol>
 <li>Position animal ventral side down in the dissection tray. Pin animal through edges of body wall and parapodial borders, but avoid tail and head, to expose the dorsal surface and the genital groove</li>
 <li>Rinse the dorsal surface in slow-running cold tap water. Apply a light stream of 70% isopropol alcohol from a squeeze bottle along the genital groove and over the top of the head.</li>
 </ol>
 </li>
 <li>Make the initial incision.
 <ol>
 <li>Using a low power microscope (see Table 2) and reflected light to observe the point where the genital groove originates from the anterior shell margin, tautly hold with ribbed-nose forceps a fold of tissue to the left of this origin, while snipping a shallow hole all the way through the smooth, flat area of body wall just to the right of the genital groove with fine angled scissors.</li>
 <li>Hemolymph should be observed to pour from the hole, sometimes carrying with it the abdominal ganglion and stomach.</li>
 </ol>
 </li>
 <li>Expand the incision.
 <ol>
 <li>Use large scissors to expand the incision anteriorly to a point between the rhinophores, while pulling upward with the lower blade to avoid nicking the gut. The internal organs will be observed to spill out of the incision.</li>
 </ol>
 </li>
 <li>Remove the ganglia.
 <ol>
 <li>Reposition the tray and refocus the microscope on the head region.</li>
 <li>Using clean forceps and fine scissors, remove the head ganglia by severing at one point the nerves that form the head ganglia into a ring around the esophagus to remove pleural-pedal and cerebral ganglia as a group.</li>
 <li>Remove the buccal ganglion that adheres to the ventral side of the esophagus.</li>
 <li>Remove the abdominal ganglion by cutting the 4 large nerve connectives that issue from this ganglion.</li>
 </ol>
 </li>
 <li>Isolate ganglia of interest.
 <ol>
 <li>Trim head ganglia apart, leaving a length of connectives attached to each ganglion of interest that is equal to at least the diameter of the ganglion; this will retard enzyme over-digestion of the cells of interest in the next step.</li>
 <li>Put each target ganglion through 2 rinses of ASW + P/S, moving between rinses with clean forceps.</li>
 <li>If targeting the PVC cells, leave the right pleural hemiganglion attached to the right pedal hemiganglion, and similarly leave the left pleural hemiganglion attached to the left pedal hemiganglion.</li>
 <li>Discard unwanted ganglia and the rest of the animal according to accepted research practice.</li>
 </ol>
 </li>
 <li>Enzymatically digest the ganglia.
 <ol>
 <li>For each ganglion, prepare 1 ml of enzyme solution consisting of 3.75 mg dispase, 1 mg hyaluronidase and 0.3 g collagenase type XI per ml of ASW + P/S in a 15 ml polypropylene conical tube.</li>
 <li>Place rinsed ganglia in enzyme solution and attach the cap tightly. Place the tube on its side on a rotary shaker (see Table 2) at slow speed for 13-5 hr overnight at approximately 23 &deg;C (room temperature).</li>
 </ol>
 </li>
 <li>Prepare the culture dishes.
 <ol>
 <li>Before microdissection (Day 2), prepare poly-D-lysine (PDL)-coated culture dishes in a tissue culture hood. Add ~0.5 ml PDL (0.2 mg/ml of sterile water) to the center of a 35 mm dish for ~25 min.</li>
 <li>Rinse PDL 3x with sterile water. Allow to dry. UV-sterilize the plates.</li>
 </ol>
 </li>
 <li>Day 2 Isolate neurons.
 <ol>
 <li>Fill the center of 35 mm dishes that were PDL-coated and UV sterilized with approximately 0.5 ml of ASW + P/S to create an island of media inside the otherwise dry dish. This can be done on the bench, outside the tissue culture hood. One dish should be prepared for each cell cluster originating from a hemiganglion.</li>
 <li>Have ready a 100 mm diameter dissection dish made by sylgard-coating and curing a 5 mm deep dissection surface, outfitted with fine dissection pins of several sizes to be used as pins and probes (see Table 3). Rinse this dish with 70% isopropol alcohol, then with ASW + P/S, and finally fill it with ASW + P/S.</li>
 </ol>
 </li>
 <li>Prepare microdissection of digested ganglia.
 <ol>
 <li>Pour the enzyme solution containing the digested pleural-pedal and buccal ganglia into the dissection dish.</li>
 <li>Place the dish on the stage of the microscope against a black surface under reflected light.</li>
 <li>Using the attached connective tissue, pin down each pleural-pedal hemiganglion dorsal side up. The tissues will be soft and intolerant of stretching.</li>
 </ol>
 </li>
 <li>Microdissect PVC neurons.
 <ol>
 <li>Using 2 pairs of clean fine forceps, and holding a fine dissection pin in one pair of forceps as a probe, isolate the PVC cells from a pleural hemiganglion. Enzyme digestion will have removed or broken apart the connective tissue sheath covering the PVC cluster, yet the cells will adhere to one another.</li>
 <li>Use the probe to detach these cells from the pedal-pleural connective18, then let the cell cluster fall to the bottom of the dissection dish.</li>
 </ol>
 </li>
 <li>Transfer neurons to culture dish.
 <ol>
 <li>Transfer the cell cluster to a prepared 35 mm culture dish by gently sucking up the cluster into the tip of a slightly fire polished disposable glass Pasteur pipette, then dispensing it slowly into the media island in a culture dish, being careful to avoid introducing air bubbles into the pipette. Repeat isolation of the PVC cluster of the other hemiganglion and place into a separate culture dish.</li>
 </ol>
 </li>
 <li>Microdissect and transfer BSC neurons.
 <ol>
 <li>Pin out the buccal ganglion ventral side up, with care to spare the cells of interest. Repeat step 1.12 with the 2 BSC cell clusters of the buccal ganglion10.</li>
 <li>Isolation of PVC and BSC neurons will produce 4 culture dishes containing neuron clusters: 2 dishes containing BSC clusters and 2 dishes containing PVC clusters. Discard the rest of the ganglia and set aside the 100 mm dissection dish.</li>
 </ol>
 </li>
 <li>Dissociate the cell clusters.
 <ol>
 <li>Place a culture dish containing cells on the stage of the low power microscope and remove the cover.</li>
 <li>Dissociate the PVC cluster by gently flicking the bottom of the culture dish adjacent to the cell cluster with a fine dissection pin held in forceps. Flicking is digging the tip of the pin into the plastic of the bottom of the dish as though trying to dig out a fleck of plastic. When friction with the plastic releases the pin point, a percussion wave is produced through the medium that breaks apart the nearby clump of cells.</li>
 <li>5-10 flicks may be needed to nearly completely dissociate the cells, but it is better to leave small clusters of cells rather than to flick too much lest the cells be destroyed by mechanical sheer.</li>
 <li>Replace cover and repeat with other culture dishes.</li>
 </ol>
 </li>
 <li>Store cell cultures.
 <ol>
 <li>Place the culture dishes containing media islands in their centers with dissociated cells into a large container that permits air circulation, such as a 150 x 25 mm round plastic Petri dish, and place this dish in an incubator set to 17 &deg;C.</li>
 <li>Install in the chamber an open dish of water as a source of humidity. Leave undisturbed overnight. The cells will adhere to the poly-D-lysine coating in the center of the dish.</li>
 </ol>
 </li>
 <li>Flood culture dishes.
 <ol>
 <li>On Day 3, Gently flood the dishes with 2.5 ml of ASW + P/S. Examine and count the cells using an inverted cell culture microscope. Store in the 17 &deg;C incubator.</li>
 </ol>
 </li>
</ol>
2. Electrophysiology
The method is standard patch clamping that has been described in numerous texts (e.g. Sakmann and Neher, 1995)16. This protocol will work on cells &le;100 pF capacitance, or cells &lt;60 &mu;m diameter during days 3 and 4 of the protocol. Cells without processes are optimal for recording. The following special considerations apply:
<ol>
 <li>Larger cells can be accommodated with the configuration setting on the Axopatch 200B amplifier set to &beta;=0.1. Activation of very large currents may cause cells to escape voltage clamp. ASW solutions substituted for salt content (e.g. a fraction of the NaCl substituted with impermeable N-methy-D-glucamine chloride) may be used to reduce whole cell current amplitude.</li>
 <li>Fiber-filled borosilicate patch pipettes pulled on a pipette puller and backfilled halfway with intracellular solution (ICS) consisting of 450 mM KCl and other salts (see Table 1) are suitable, and should have resistance of approximately 0.5-1 MOhms. If isolation of specific ionic currents is desired, for example, Na+ currents in the absence of K currents, K+ in this solution can be replaced with other ions such as Cs+. Cl- replacement of ICS with an impermeant anion is also warranted if a more natural ICS is desired9.</li>
 <li>The cells are robust with &gt;1 hr-long recordings possible at room temperature. Recording is optimal on days 3 and 4 of the protocol, corresponding to 24-48 hr in culture. After 48 hr there is difficulty forming gigaOhm seals, perhaps because of elaboration of a glycocalyx on the cell surface, and space clamp problems caused by process outgrowth. The cells are useful, however, for non-patch clamp studies, such as toxicology, that can be completed in &lt;14 d.</li>
 <li>ASW and other solutions to be dispensed from the gravity fed solution device, as well as intracellular solution, should be filtered through a syringe-mounted 0.2 &mu;m Acrodisk filter (Table 3) to eliminate fine particles that interfere with gigaOhm seal formation.</li>
 <li>Desensitization occurs when using agonists such as D-Aspartate (D-Asp), therefore ~1-2 min between applications of agonists is recommended. Conversely, potentiation is often observed with rapid repeated application of agonists such as L-Glutamate (L-Glu).</li>
 <li>Agonist activated currents such as L-Glu can be studied by applying agonists with the picospritzer pipette. This pipette is pulled the same as the patch pipette and contains agonist in ASW. When the tip of this pipette is positioned below the outflow pipe of the gravity fed solution device, and at a 45&deg; angle from the outflow pipe (Figure 2F), agonist will be quickly washed away from the cell, and desensitization will be minimized. The agonist pipette should create an angle of 90&deg; or more relative to the patch pipette.</li>
</ol>

<ol>
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A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physiological+evidence+that+D-Aspartate+activates+a+current+distinct+from+ionotropic+glutamate+receptor+currents+in+Aplysia+californica.">Physiological evidence that D-Aspartate activates a current distinct from ionotropic glutamate receptor currents in Aplysia californica.</a> J. Neurophysiol. 106 (4), 1629-1636 (2011).</li><li>Carlson, S. L., Kempsell, A. T., Fieber, L. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pharmacological+evidence+that+D-Aspartate+activates+a+current+distinct+from+ionotropic+glutamate+receptor+currents+in+Aplysia+californica.">Pharmacological evidence that D-Aspartate activates a current distinct from ionotropic glutamate receptor currents in Aplysia californica.</a> Br. Behav. 2 (4), 391-401 (2012).</li><li>Fieber, L. 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L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Habituation+in+Aplysia:+The+Cheshire+Cat+of+neurobiology.">Habituation in Aplysia: The Cheshire Cat of neurobiology.</a> Neurobiol. Learn. Mem. 92, 147-154 (2009).</li><li>Hawkins, R. D., Abrams, T. W., Carew, T. J., 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=A+Cellular+Mechanism+of+Classical+Conditioning+in+Aplysia:+Activity-Dependent+Amplification+of+Presynaptic+Facilitation.">A Cellular Mechanism of Classical Conditioning in Aplysia: Activity-Dependent Amplification of Presynaptic Facilitation.</a> Science, New. 219 (4583), 400-405 (1983).</li><li>Ichinose, M., Sawada, M., Maeno, T., McAdoo, D. 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S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Persistent+Ca2++current+contributes+to+a+prolonged+depolarization+in+Aplysia+bag+cell+neurons.">Persistent Ca2+ current contributes to a prolonged depolarization in Aplysia bag cell neurons.</a> J. Neurophysiol. 102 (6), 3753-3765 (2009).</li><li>Schacher, S., Proshansky, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neurite+regeneration+by+Aplysia+neurons+in+dissociated+cell+culture:+modulation+by+Aplysia+hemolymph+and+the+presence+of+the+initial+axonal+segment.">Neurite regeneration by Aplysia neurons in dissociated cell culture: modulation by Aplysia hemolymph and the presence of the initial axonal segment.</a> J. Neurosci. 3 (12), 2403-2413 (1983).</li><li>Walters, E. T., Byrne, J. H., Carew, T. J., 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=Mechanoafferent+neurons+innervating+tail+of+Aplysia.+I.+Response+properties+and+synaptic+connections.">Mechanoafferent neurons innervating tail of Aplysia. I. Response properties and synaptic connections.</a> J. Neurophysiol. 50 (6), 1522-1542 (1983).</li><li>Wilson, G. F., Richardson, F. C., Fisher, T. E., Olivera, B. M., Kaczmarek, L. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+and+characterization+of+a+Ca(2+)-sensitive+nonspecific+cation+channel+underlying+prolonged+repetitive+firing+in+Aplysia+neurons.">Identification and characterization of a Ca(2+)-sensitive nonspecific cation channel underlying prolonged repetitive firing in Aplysia neurons.</a> J. Neurosci. 16 (11), 3661-3671 (1996).</li><li>White, B. H., Nick, T. 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The authors declare that they have no competing financial interests.

The dissociation techniques described here yield sensory neuron cultures containing 50-100 isolated neurons interspersed with small numbers of glia and other unidentified cells. The most critical steps in the protocol are the time the ganglia remain in enzyme solution, and flicking, the dissociation of the digested cell clusters to break apart the cluster into individual cells. Enzyme digestion (step 1.8) must be optimized at the available temperature. At 23 &deg;C with slow shaking, 13 hr is sufficient for digest...

The marine opistobranch mollusk, Aplysia, has been a useful neurobiological model for many decades. It is best known as a model of habituation and classical conditioning 7, 8. Studies on learning and memory in this model won the Nobel Prize for Physiology or Medicine in 2000 for Eric R. Kandel, in a prize he shared with Arvid Carlsson and Paul Greengard 10. Studies involving electrical recordings from reduced preparations, in which elements of the nervous system of this invertebrate are dissected from the animal with nerves and muscles left attached, have helped elucidate the roles of individual neurons in Aplysia. Identification of precise molecular mechanisms that constitute learning in Aplysia however, often employed another technique, long-term co-cultures of a sensory neuron and a motoneuron, obtained one by one from individual donor animals and allowed to form a synapse in the culture dish 21.
We and others 1, 3, 6, 14, 15, 16 have exploited the ease with which identified neurons can be targeted in this model as well as their endurance in long-term experiments to make dissociated short term cultures of clusters of nominally homogeneous neurons in which we study ionic currents under voltage clamp in the patch clamp configuration. Many Aplysia neurons stand up to repeated rounds of patch clamping to allow time for long-lasting experimental manipulations. The technique is useful for neurons such as the neurosecretory bag cells of the abdominal ganglion, and the sensory neurons of the pleural and buccal ganglia whose dissociation we describe here, but not for very large neurons &gt;60 &mu;m diameter, such as L7 or R2 of the abdominal ganglion. We do not employ Aplysia serum in our cultures, unlike the sensory-motoneuron co-cultures described elsewhere. Most neurons obtained using this procedure will be without processes for the first 48 hr in culture, facilitating whole cell voltage recording, but will then sprout and elaborate axons and other processes for approximately 14 days before dying from lack of nutrients and/or growth factors.
This technique produces primary cultures of 50-100 neurons per dish from physiologically documented regions of the buccal and pleural ganglia. This protocol is useful for researchers studying aspects of single cell physiology in experiments that require numerous experimental replicates per animal. It produces a matched pair of cultures due to the anatomical separation of the target cells into left and right hemiganglia, permitting studies that benefit from matched treatment and control cultures.
The protocol targets buccal S cluster (BSC) neurons of the buccal ganglion, and pleural ventrocaudal (PVC) neurons of the pleural ganglion. These cells are an appropriate size for whole cell voltage recordings and display robust glutamatergic responses. The discussed methodology is appropriate for most ganglia in the Aplysia nervous system.

<table border="1">
 <tbody>
 <tr>
 <td>Name of Reagent/Material</td>
 <td>Company</td>
 <td>Catalog Number</td>
 <td>Comments</td>
 </tr>
 <tr>
 <td>Artificial seawater ASW</td>
 <td>Sigma-Aldrich</td>
 <td>assorted</td>
 <td>(mM): 417 NaCl, 10 KCl, 10 CaCl2 (2 H2O), 5MgCl2 (6H2O), 15 HEPES-NaOH, pH 7.6</td>
 </tr>
 <tr>
 <td>Intracellular solution</td>
 <td>Sigma</td>
 <td>assorted</td>
 <td>(mM): 450 KCl, 2.9 CaCl2 (2 H2O), 2.5 MgCl2 (6 H2O), 5 Na2ATP, 10 EGTA, and 40 HEPES-KOH, pH 7.4</td>
 </tr>
 <tr>
 <td>Poly-D-lysine</td>
 <td>Sigma</td>
 <td>P6407</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>penicillin/streptomycin added to ASW at 1:100</td>
 <td>Lonzo Walkersville, Inc.</td>
 <td>17-603E</td>
 <td>5,000 Units/ml penicillin plus 5,000 mg/ml streptomycin</td>
 </tr>
 <tr>
 <td>Neutral dispase II</td>
 <td>Roche Diagnostics</td>
 <td>10165859001</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>hyaluronidase</td>
 <td>Sigma-Aldrich</td>
 <td>H4272</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>collagenase type XI</td>
 <td>Sigma-Aldrich</td>
 <td>C9407</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>L-Glutamate (L-Glu)</td>
 <td>Sigma-Aldrich</td>
 <td>49601-100G</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>D-Aspartate (D-Asp)</td>
 <td>Sigma-Aldrich</td>
 <td>11200-10G</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>N-methyl-D-aspartate (NMDA)</td>
 <td>Biomol</td>
 <td>100002-268</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>L-Asp</td>
 <td>Sigma</td>
 <td>A6683-25G</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-propionic acid (AMPA)</td>
 <td>Sigma</td>
 <td>A6816-5MG</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>L-Glu R antagonists</td>
 <td>various</td>
 <td>various</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>agar</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>kynurenate</td>
 <td>Sigma-Aldrich</td>
 <td>61250</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>APV</td>
 <td>Sigma-Aldrich</td>
 <td>A5282</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>DL-2-Amino-5-phosphonopentanoic acid (NMDAR antagonist)</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>2-propanol</td>
 <td>VWRSP</td>
 <td>BDH1133</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Chloriding solution</td>
 <td>Sigma</td>
 <td>assorted</td>
 <td>25 g FeCl3 + 25 ml concentrated HCl + 50 ml H2O</td>
 </tr>
 <tr>
 <td>Sylgard silicone 2-part polymer</td>
 <td>World Precision Instruments (WPI)</td>
 <td>SYL184</td>
 <td>Provides pin-out surface for small dissection dishes</td>
 </tr>
 <tr>
 <td>0-40x zoom magnification microscope for dissections</td>
 <td>Wild</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Techniquip 150 Watts Fiber Optic Illuminator</td>
 <td>Microoptics of Florida</td>
 <td>TQ FOI-150</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>RotoMix 50800 orbital mixer</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Nikon Diaphot inverted phase-contrast microscope with 4x, 20x (optional) &amp; 40x objectives</td>
 <td>SR Research Ltd.</td>
 <td>Eyelink II</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Tektronix digital oscilloscope</td>
 <td>SR Research Ltd.</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>pClamp 10 data acquisition and analysis software</td>
 <td>Molecular Devices</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>PC with Windows XP or higher operating system</td>
 <td>PC Solutions</td>
 <td>&nbsp;</td>
 <td>Thinkserver with solid state hard drives (80GB) and low noise monitors</td>
 </tr>
 <tr>
 <td>Flaming/Brown P87 micropipette puller</td>
 <td>Sutter Instruments, Novato, CA</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Axon Instruments Axopatch 200B clamp amplifier with a capacitance compensation range of 1-1000 pF; preamplifier</td>
 <td>Molecular Devices, Sunnyvale, CA</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Axon instruments electrode holder assembly for Axopatch 200B preamplifier</td>
 <td>Molecular Devices, Sunnyvale, CA</td>
 <td>CV203BU</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Digidata 1200 A/D converter</td>
 <td>Molecular Devices, Sunnyvale, CA</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Picospritzer, powered by N2 adjustable for pressure and duration</td>
 <td>Parker Hannifin, Cleveland, OH</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>TMC Micro-G Vibration isolation table</td>
 <td>Ametek</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Faraday cage</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>custom manufacture</td>
 </tr>
 <tr>
 <td>Burleigh Piezoelectric Clamshell Micromanipulators</td>
 <td>Burleigh Instruments; Thorlabs</td>
 <td>&nbsp;</td>
 <td>presently PCS-5000; -6000 series + mounts</td>
 </tr>
 <tr>
 <td>Narishige M-152 manual manipulators (for perfusion system and picospritzer)</td>
 <td>Narishige USA</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Filament pipette glass,1.5 mm OD, 0.84 mm ID -</td>
 <td>WPI</td>
 <td>1B150-3</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>3 inch length</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Ag/AgCl half cell</td>
 <td>WPI</td>
 <td>EP4</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>15 ml centrifuge tubes, 35-2097 BD Falcon* Centrifuge Tubes</td>
 <td>VWRSP</td>
 <td>21008-918</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Angled Scissors</td>
 <td>Fine Science Tools</td>
 <td>15006-09</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Dumostar Fine forceps</td>
 <td>Fine Science Tools</td>
 <td>11295-00</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>35 mm falcon tissue culture dishes</td>
 <td>VWRSP</td>
 <td>25382-064</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>falcon 150 x 25 mm tissue culture dishes; 1013</td>
 <td>VWRSP</td>
 <td>1013</td>
 <td>also can be made into small dissection dishes with sylgard</td>
 </tr>
 <tr>
 <td>sylgard</td>
 <td>WPI</td>
 <td>SYL184</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>animal dissection tray</td>
 <td>various</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>15 ml centrifuge tubes, 35-2097 BD Falcon</td>
 <td>VWRSP</td>
 <td>21008-918</td>
 <td>For 6-bore gravity-fed perfusion system</td>
 </tr>
 <tr>
 <td>Aluminum clips with screw hole ends</td>
 <td>hardware store</td>
 <td>&nbsp;</td>
 <td>For perfusion system</td>
 </tr>
 <tr>
 <td>23 gauge needles (manually file off points)</td>
 <td>VWRSP</td>
 <td>&nbsp;</td>
 <td>For perfusion system</td>
 </tr>
 <tr>
 <td>Polyethylene tubing 0.022"ID x 0.042"OD; 427411</td>
 <td>Becton-Dickinson</td>
 <td>&nbsp;</td>
 <td>For perfusion system</td>
 </tr>
 <tr>
 <td>H-7 pipette stand/holder for microcap perfusion array</td>
 <td>Narishige USA</td>
 <td>&nbsp;</td>
 <td>For perfusion system</td>
 </tr>
 <tr>
 <td>one-way valves</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>For perfusion system</td>
 </tr>
 <tr>
 <td>Drummond Microcaps 1 &mu;l</td>
 <td>VWRSP</td>
 <td>&nbsp;</td>
 <td>For perfusion system</td>
 </tr>
 <tr>
 <td>18 gauge needles for suction (filed off points)</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Polyethylene tubing</td>
 <td>Cole Parmer</td>
 <td>4.27436E+11</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>fine dissection pins</td>
 <td>Fine Science Tools</td>
 <td>26002-20</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>capillary tubes</td>
 <td>Kimble 71900-100</td>
 <td>&nbsp;</td>
 <td>fire-polished and U-shaped in a Bunsen burner flame and filled with 3% agar in ECS</td>
 </tr>
 <tr>
 <td>modeling clay</td>
 <td>craft store</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>dish holder for microscope stage with isolated ground bath</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>Custom manufacture</td>
 </tr>
 <tr>
 <td>pasteur pipettes</td>
 <td>VWRSP</td>
 <td>14672-412</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>pipette bulbs</td>
 <td>VWRSP</td>
 <td>53283-911</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>acrodisk syringe filters</td>
 <td>VWRSP</td>
 <td>28144-040</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>thick-walled 1.5 mm diameter borosilicate filament glass</td>
 <td>WPI</td>
 <td>1B150F-3</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>High purity nitrogen cylinder and bifurcating regulator</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 </tbody>
</table>
Tables 1-3. Lists of Reagents, Materials, and Equipment.

isolation of sensory neurons of aplysia californica for patch clamp recordings of glutamatergic currents

The marine gastropod mollusk Aplysia californica has a venerable history as a model of nervous system function, with particular significance in studies of learning and memory. The typical preparations for such studies are ones in which the sensory and motoneurons are left intact in a minimally dissected animal, or a technically elaborate neuronal co-culture of individual sensory and motoneurons. Less common is the isolated neuronal preparation in which small clusters of nominally homogeneous neurons are dissociated into single cells in short term culture. Such isolated cells are useful for the biophysical characterization of ion currents using patch clamp techniques, and targeted modulation of these conductances. A protocol for preparing such cultures is described. The protocol takes advantage of the easily identifiable glutamatergic sensory neurons of the pleural and buccal ganglia, and describes their dissociation and minimal maintenance in culture for several days without serum.

The locations of the sensory neurons within the ganglia that are targeted in this protocol, the BSC and PVC neurons are shown in Figure 1. The BSC neurons are located in 2 symmetrical oval clusters on the ventral side of the buccal ganglion, the surface that faces away from the buccal mass in the intact ganglion (Figure 1A). The PVC neurons form bilateral, V-shaped clusters that wrap around the dorsal surface of the pleural ganglion toward the central axis (Figure 1B). T...

Watch this Scientific Journal Video about Isolation of Sensory Neurons of Aplysia californica for Patch Clamp Recordings of Glutamatergic Currents at JoVE.com

Isolation of Sensory Neurons of Aplysia californica for Patch Clamp Recordings of Glutamatergic Currents

We describe the dissection of the nervous system of the marine sea hare Aplysia after anesthesia, the isolation of neurons for short term-tissue culture, and recordings of single cell ion currents via the patch clamp technique.

Isolation of Sensory Neurons of Aplysia californica for Patch Clamp Recordings of Glutamatergic Currents

The marine gastropod mollusk Aplysia californica has a venerable  history as a model of nervous system function, with particular significance in  studies ...

isolation-sensory-neurons-aplysia-californica-for-patch-clamp

Research

JoVE Journal

Neuroscience

12.2K Views.  University of Miami. We describe the dissection of the nervous system of the marine sea hare Aplysia after anesthesia, the isolation of neurons for short term-tissue culture, and recordings of single cell ion currents via the patch clamp technique.

Video: Isolation of Sensory Neurons of Aplysia californica for Patch Clamp Recordings of Glutamatergic Currents

Electrode Fabrication and Implantation in Aplysia californica for Multi-channel Neural and Muscular Recordings in Intact, Freely Behaving Animals

Recording from key nerves and muscles of Aplysia during feeding behavior allows us to study the patterns of neural control in an intact animal. Simultaneously recording from multiple nerves and muscles gives us precise information about the timing of neural activity. Previous recording methods have worked for two electrodes, but the study of additional nerves or muscles required combining and averaging the recordings of multiple animals, which made it difficult to determine fine details of timing and phasing, because of variability from response to response, and from animal to animal. Implanting four individual electrodes has a very low success rate due to the formation of adhesions that prevent animals from performing normal feeding movements. We developed a new method of electrode fabrication that reduces the bulk of the electrodes inside the animal allowing for normal feeding movements. Using a combination of glues to attach the electrodes results in a more reliable insulation of the electrode which lasts longer, making it possible to record for periods as long as a week. The fabrication technique that we describe could be extended to incorporate several additional electrodes, and would be applicable to vertebrate animals.

Electrode Fabrication and Implantation in Aplysia californica for Multi-channel Neural and Muscular Recordings in Intact, Freely Behaving Animals

A technique is described for implanting four in vivo electrodes to monitor the neuromuscular control of feeding behavior in Aplysia californica.

Recording from key nerves and muscles of Aplysia during feeding behavior allows us to study the patterns of neural control in an intact animal.  ...

Patch Clamp Recordings from Mouse Retinal Neurons in a Dark-adapted Slice Preparation

Our visual experience is initiated when the visual pigment in our retinal photoreceptors absorbs photons of light energy and initiates a cascade of intracellular events that lead to closure of cyclic-nucleotide-gated channels in the cell membrane. The resulting change in membrane potential leads in turn to reductions in the amount of neurotransmitter release from both rod and cone synaptic terminals. To measure how the light-evoked change in photoreceptor membrane potential leads to downstream activity in the retina, scientists have made electrophysiological recordings from retinal slice preparations for decades1,2. In the past these slices have been cut manually with a razor blade on retinal tissue that is attached to filter paper; in recent years another method of slicing has been developed whereby retinal tissue is embedded in low gelling temperature agar and sliced in cool solution with a vibrating microtome3,4. This preparation produces retinal slices with less surface damage and very robust light-evoked responses. Here we document how this procedure can be done under infrared light to avoid bleaching the visual pigment.

Here we describe a procedure for generating dark-adapted slices of the mouse retina for electrophysiological recordings.

Our visual experience is initiated when the visual pigment in our retinal photoreceptors absorbs photons of light energy and initiates a cascade of ...

Live-imaging of PKC Translocation in Sf9 Cells and in Aplysia Sensory Neurons

Protein kinase Cs (PKCs) are serine threonine kinases that play a central role in regulating a wide variety of cellular processes such as cell growth and learning and memory. There are four known families of PKC isoforms in vertebrates: classical PKCs (&alpha;, &beta;I, &beta;II and &gamma;), novel type I PKCs (&#949; and &eta;), novel type II PKCs (&delta; and &theta;), and atypical PKCs (&zeta; and &iota;). The classical PKCs are activated by Ca2+ and diacylclycerol (DAG), while the novel PKCs are activated by DAG, but are Ca2+-independent. The atypical PKCs are activated by neither Ca2+ nor DAG. In Aplysia californica, our model system to study memory formation, there are three nervous system specific PKC isoforms one from each major class, namely the conventional PKC Apl I, the novel type I PKC Apl II and the atypical PKC Apl III. PKCs are lipid-activated kinases and thus activation of classical and novel PKCs in response to extracellular signals has been frequently correlated with PKC translocation from the cytoplasm to the plasma membrane. Therefore, visualizing PKC translocation in real time in live cells has become an invaluable tool for elucidating the signal transduction pathways that lead to PKC activation. For instance, this technique has allowed for us to establish that different isoforms of PKC translocate under different conditions to mediate distinct types of synaptic plasticity and that serotonin (5HT) activation of PKC Apl II requires production of both DAG and phosphatidic acid (PA) for translocation 1-2. Importantly, the ability to visualize the same neuron repeatedly has allowed us, for example, to measure desensitization of the PKC response in exquisite detail 3. In this video, we demonstrate each step of preparing Sf9 cell cultures, cultures of Aplysia sensory neurons have been described in another video article 4, expressing fluorescently tagged PKCs in Sf9 cells and in Aplysia sensory neurons and live-imaging of PKC translocation in response to different activators using laser-scanning microscopy.

In this video, we demonstrate visualization of PKC translocation in living cells using fluorescently tagged PKCs.

Protein kinase Cs (PKCs) are serine threonine kinases that play a central role in regulating a wide variety of cellular processes such as cell growth and ...

Patch Clamp Recordings in Inner Ear Hair Cells Isolated from Zebrafish

Patch clamp analyses of the voltage-gated channels in sensory hair cells isolated from a variety of species have been described previously1-4 but this video represents the first application of those techniques to hair cells from zebrafish. Here we demonstrate a method to isolate healthy, intact hair cells from all of the inner ear end-organs: saccule, lagena, utricle and semicircular canals. Further, we demonstrate the diversity in hair cell size and morphology and give an example of the kinds of patch clamp recordings that can be obtained. The advantage of the use of this zebrafish model system over others stems from the availability of zebrafish mutants that affect both hearing and balance. In combination with the use of transgenic lines and other techniques that utilize genetic analysis and manipulation, the cell isolation and electrophysiological methods introduced here should facilitate greater insight into the roles hair cells play in mediating these sensory modalities.

The purpose of this video is to demonstrate procedures for obtaining healthy, intact hair cells from the inner ear organs of adult zebrafish and then using them for patch clamp studies aimed at characterizing the biophysical properties of their voltage-gated channels.

Patch  clamp analyses of the voltage-gated channels in sensory hair cells isolated  from a variety of species have been described previously1-4 but this  ...

Extracellularly Identifying Motor Neurons for a Muscle Motor Pool in Aplysia californica

In animals with large identified neurons (e.g. mollusks), analysis of motor pools is done using intracellular techniques1,2,3,4. Recently, we developed a technique to extracellularly stimulate and record individual neurons in Aplysia californica5. We now describe a protocol for using this technique to uniquely identify and characterize motor neurons within a motor pool.
This extracellular technique has advantages. First, extracellular electrodes can stimulate and record neurons through the sheath5, so it does not need to be removed. Thus, neurons will be healthier in extracellular experiments than in intracellular ones. Second, if ganglia are rotated by appropriate pinning of the sheath, extracellular electrodes can access neurons on both sides of the ganglion, which makes it easier and more efficient to identify multiple neurons in the same preparation. Third, extracellular electrodes do not need to penetrate cells, and thus can be easily moved back and forth among neurons, causing less damage to them. This is especially useful when one tries to record multiple neurons during repeating motor patterns that may only persist for minutes. Fourth, extracellular electrodes are more flexible than intracellular ones during muscle movements. Intracellular electrodes may pull out and damage neurons during muscle contractions. In contrast, since extracellular electrodes are gently pressed onto the sheath above neurons, they usually stay above the same neuron during muscle contractions, and thus can be used in more intact preparations.
To uniquely identify motor neurons for a motor pool (in particular, the I1/I3 muscle in Aplysia) using extracellular electrodes, one can use features that do not require intracellular measurements as criteria: soma size and location, axonal projection, and muscle innervation4,6,7. For the particular motor pool used to illustrate the technique, we recorded from buccal nerves 2 and 3 to measure axonal projections, and measured the contraction forces of the I1/I3 muscle to determine the pattern of muscle innervation for the individual motor neurons.
We demonstrate the complete process of first identifying motor neurons using muscle innervation, then characterizing their timing during motor patterns, creating a simplified diagnostic method for rapid identification. The simplified and more rapid diagnostic method is superior for more intact preparations, e.g. in the suspended buccal mass preparation8 or in vivo9. This process can also be applied in other motor pools10,11,12 in Aplysia or in other animal systems2,3,13,14.

Extracellularly Identifying Motor Neurons for a Muscle Motor Pool in Aplysia californica

In animals with large identified neurons (e.g. mollusks), analysis of motor pools is done using intracellular techniques1,2,3,4. Recently, we developed a technique to extracellularly stimulate and record individual neurons in Aplysia californica5. We now describe a protocol for using this technique to uniquely identify and characterize motor neurons within a motor pool.

In animals with large  identified neurons (e.g. mollusks), analysis of motor pools is done using  intracellular techniques1,2,3,4. Recently,  we developed ...

Patch Clamp Recordings from Embryonic Zebrafish Mauthner Cells

Mauthner cells (M-cells) are large reticulospinal neurons located in the hindbrain of teleost fish. They are key neurons involved in a characteristic behavior known as the C-start or escape response that occurs when the organism perceives a threat. The M-cell has been extensively studied in adult goldfish where it has been shown to receive a wide range of excitatory, inhibitory and neuromodulatory signals1. We have been examining M-cell activity in embryonic zebrafish in order to study aspects of synaptic development in a vertebrate preparation. In the late 1990s Ali and colleagues developed a preparation for patch clamp recording from M-cells in zebrafish embryos, in which the CNS was largely intact2,3,4. The objective at that time was to record synaptic activity from hindbrain neurons, spinal cord neurons and trunk skeletal muscle while maintaining functional synaptic connections within an intact brain-spinal cord preparation. This preparation is still used in our laboratory today. To examine the mechanisms underlying developmental synaptic plasticity, we record excitatory (AMPA and NMDA-mediated)5,6 and inhibitory (GABA and glycine) synaptic currents from developing M-cells. Importantly, this unique preparation allows us to return to the same cell (M-cell) from preparation to preparation to carefully examine synaptic plasticity and neuro-development in an embryonic organism. The benefits provided by this preparation include 1) intact, functional synaptic connections onto the M-cell, 2) relatively inexpensive preparations, 3) a large supply of readily available embryos 4) the ability to return to the same cell type (i.e. M-cell) in every preparation, so that synaptic development at the level of an individual cell can be examined from fish to fish, and 5) imaging of whole preparations due to the transparent nature of the embryos.

We have developed an intact brain-spinal cord preparation to record and monitor electrical activity via patch clamp recording from the Mauthner neurons and other reticulospinal cells in zebrafish embryos. Thus, we are able to record excitatory and inhibitory synaptic currents, voltage-gated channel activity and action potentials from key neurons in a developing embryo.

Mauthner cells (M-cells) are large  reticulospinal neurons located in the hindbrain of teleost fish. They are key  neurons involved in a characteristic ...

Perforated Patch-clamp Recording of Mouse Olfactory Sensory Neurons in Intact Neuroepithelium: Functional Analysis of Neurons Expressing an Identified Odorant Receptor

Analyzing the physiological responses of olfactory sensory neurons (OSN) when stimulated with specific ligands is critical to understand the basis of olfactory-driven behaviors and their modulation. These coding properties depend heavily on the initial interaction between odor molecules and the olfactory receptor (OR) expressed in the OSNs. The identity, specificity and ligand spectrum of the expressed OR are critical. The probability to find the ligand of the OR expressed in an OSN chosen randomly within the epithelium is very low. To address this challenge, this protocol uses genetically tagged mice expressing the fluorescent protein GFP under the control of the promoter of defined ORs. OSNs are located in a tight and organized epithelium lining the nasal cavity, with neighboring cells influencing their maturation and function. Here we describe a method to isolate an intact olfactory epithelium and record through patch-clamp recordings the properties of OSNs expressing defined odorant receptors. The protocol allows one to characterize OSN membrane properties while keeping the influence of the neighboring tissue. Analysis of patch-clamp results yields&#160;a precise quantification of ligand/OR interactions, transduction pathways and pharmacology, OSNs&#39; coding properties and their modulation at the membrane level.&#160;

Analyzing the physiological properties of olfactory sensory neurons still faces technical limitations. Here we record them through perforated patch-clamp in an intact preparation of the olfactory epithelium in gene-targeted mice. This technique allows the characterization of membrane properties and responses to specific ligands of neurons expressing defined olfactory receptors.

Analyzing the physiological responses of olfactory sensory neurons (OSN) when stimulated with specific ligands is critical to understand the basis of ...

Whole-cell Patch-clamp Recordings in Brain Slices

Whole-cell patch-clamp recording is an electrophysiological technique that allows the study of the&#160;electrical properties of a substantial part of the neuron. In this configuration, the micropipette is in tight contact with the cell membrane, which prevents current leakage and thereby provides more accurate ionic current measurements than the previously used intracellular sharp electrode recording method. Classically, whole-cell recording can be performed on neurons in various types of preparations, including cell culture models, dissociated neurons, neurons in brain slices, and in intact anesthetized or awake animals. In summary, this technique has immensely contributed to the understanding of passive and active biophysical properties of excitable cells. A major advantage of this technique is that it provides information on how specific manipulations (e.g., pharmacological, experimenter-induced plasticity) may alter specific neuronal functions or channels in real-time. Additionally, significant opening of the plasma membrane allows the internal pipette solution to freely diffuse into the cytoplasm, providing means for introducing drugs, e.g., agonists or antagonists of specific intracellular proteins, and manipulating these targets without altering their functions in neighboring cells. This article will focus on whole-cell recording performed on neurons in brain slices,&#160;a preparation that has the advantage of recording neurons in relatively well preserved brain circuits, i.e., in a physiologically relevant context. In particular,&#160;when combined with appropriate pharmacology, this technique is a powerful tool allowing identification of specific neuroadaptations that occurred following any type of experiences, such as learning, exposure to drugs of abuse, and stress. In summary, whole-cell patch-clamp recordings in brain slices provide means to measure in ex vivo preparation long-lasting changes in neuronal functions that have developed in intact awake animals.

This protocol describes basic procedural steps for performing whole-cell patch-clamp recordings. This technique allows the study of&#160;the electrical behavior of neurons, and when performed in brain slices, allows the assessment of various neuronal functions from neurons that are still integrated in relatively well preserved brain circuits.

Whole-cell patch-clamp recording is an electrophysiological technique that allows the study of the&#160;electrical properties of a substantial part of the ...

Subcellular Patch-clamp Recordings from the Somatodendritic Domain of Nigral Dopamine Neurons

Dendrites of dopaminergic neurons receive and convey synaptic input, support action potential back-propagation and neurotransmitter release. Understanding these fundamental functions will shed light on the information transfer in these neurons. Dendritic patch-clamp recordings provide the possibility to directly examine the electrical properties of dendrites and underlying voltage-gated ion channels. However, these fine structures are not easily accessible to patch pipettes because of their small diameter. This report describes a step-by-step procedure to collect stable and reliable recordings from the dendrites of dopaminergic neurons in acute slices. Electrophysiological measurements are combined with post hoc recovery of cell morphology. Successful experiments rely on improved preparation of slices, solutions and pipettes, adequate adjustment of the optics and stability of the pipette in contact with the recorded structure. Standard principles of somatic patch-clamp recording are applied to dendrites but with a gentler approach of the pipette. These versatile techniques can be implemented to address various questions concerning the excitable properties of dendrites.

Subcellular patch-clamp recordings offer the possibility to investigate the functional properties of dendrites. However these fine structures are not easily accessible due to their small diameter. The protocol described here aims to facilitate the collection of stable and reliable recordings from the dendrites of dopamine neurons in slices in vitro.

Dendrites of dopaminergic neurons receive and convey synaptic input, support action potential back-propagation and neurotransmitter release. Understanding ...

Whole-cell Patch-clamp Recordings for Electrophysiological Determination of Ion Selectivity in Channelrhodopsins

Over the past decade, channelrhodopsins became indispensable in neuroscientific research where they are used as tools to non-invasively manipulate electrical processes in target cells. In this context, ion selectivity of a channelrhodopsin is of particular importance. This article describes the investigation of chloride selectivity for a recently identified anion-conducting channelrhodopsin of Proteomonas sulcata via electrophysiological patch-clamp recordings on HEK293 cells. The experimental procedure for measuring light-gated photocurrents demands a fast switchable &#8211; ideally monochromatic &#8211; light source coupled into the microscope of an otherwise conventional patch-clamp setup. Preparative procedures prior to the experiment are outlined involving preparation of buffered solutions, considerations on liquid junction potentials, seeding and transfection of cells, and pulling of patch pipettes. The actual recording of current-voltage relations to determine the reversal potentials for different chloride concentrations takes place 24 h to 48 h after transfection. Finally, electrophysiological data are analyzed with respect to theoretical considerations of chloride conduction.

This article describes how the ion selectivity of channelrhodopsin is determined with electrophysiological whole-cell patch-clamp recordings using HEK293 cells. Here, the experimental procedure for investigating chloride selectivity of an anion-selective channelrhodopsin is demonstrated. However, the procedure is transferable to other channelrhodopsins of distinct selectivity.