We thank Joung Jang and Xin Guan for technical assistance. We thank Dr. Rory McQuiston of Virginia Commonwealth University for setting up our first patch clamp rig and advices on experimental procedures. We thank Dr. Samuel Wu for suggestions on voltage clamp recording. The work is supported by NIH grants EY013811, EY022228 and a vision core grant EY002520. C-KC is the Alice R. McPherson Retina Research Foundation Endowed Chair at the Baylor College of Medicine.

Ethical approval &#8211; procedures involving animal subjects were conducted in accordance with the rules and regulations of the National Institutes of Health guidelines for research animals, as approved by the institutional animal care and use committee of Baylor College of Medicine.
1. External and Internal Solutions
<ol>
	<li>Use mammalian Ringer&#39;s solution during retina dissection and as the external solution in subsequent electrophysiological recording. Prepare the mammalian Ringer&#39;s solution from 10x stock solution (without calcium) on the day of recording, and add CaCl2 drop-wise after 15 min of carbogenation (95% O2 and 5% CO2). The final 1x solution contains (in mM): 120 NaCl, 5 KCl, 25 NaHCO3, 0.8 Na2HPO4, 0.1 NaH2PO4, 2 CaCl2, 1 MgSO4 and 10 D-glucose.</li>
	<li>Use two internal solutions to characterize SAC oscillations. Test the usefulness of prepared solutions in prolonged whole-cell patch clamp recordings on adult mouse RGCs and store the verified batches in 500 &#181;l aliquots at -20 &#176;C until use.
	<ol>
		<li>For recording membrane potential oscillation, use a potassium-based internal solution that contains (in mM): 125 K-gluconate, 8 NaCl, 4 ATP-Mg, 0.5 Li-GTP, 5 EGTA, 10 HEPES and 0.2% biocytin (w/v). Adjust pH to 7.3 with KOH.</li>
		<li>For recording excitatory and inhibitory postsynaptic currents, use a cesium-based internal solution that contains (in mM): 100 Cs-methanesulfonate, 8 NaCl, 4 ATP-Mg, 0.5 Li-GTP, 5 EGTA, 10 HEPES and 0.2% biocytin (w/v). Adjust pH to 7.3 with CsOH.</li>
	</ol>
	</li>
</ol>
2. Preparation for the Day of Recording
<ol>
	<li>To prepare a nitrocellulose membrane with open holes, manually punch the membrane with a customized puncher made from a blunted 16 G syringe needle and flatten the membrane between two clean glass plates. For a whole-mount retina, make a central hole 0.2 mm in diameter and surround it by 4 larger holes that are 1-1.2 mm in diameter.</li>
	<li>To make a customized backfill filament for loading internal solution into electrodes, melt a 10 &#181;l pipette tip in the middle and gently lengthen the melted portion until it cools and hardens. Just prior to use, use a clean razor blade to trim the filament until it is slightly longer than the patch pipettes.</li>
	<li>Pull patch pipettes in a programmable puller from borosilicate glass tube with an internal filament. Manufacture the micropipettes on the day of experiment and use them immediately. 
	NOTE: For recording SACs, we use the following puller setting: heat: 484; pull: 0; velocity: 25; delay time: 1; pressure: 400 and a ramp value of 462. The O.D. and I.D. of the borosilicate tubes are 1.65 mm and 1.0 mm, respectively. Resistance of the pipettes is 10-14 M&#937;.</li>
	<li>One hr before tissue harvest, thaw a tube of internal solution by shaking it on a vortex for &#62;30 min.</li>
</ol>
3. Retina Dissection
<ol>
	<li>Anesthetize the animal by 4% isoflurane in oxygen until the animal loses responsiveness to a toe pinch. Sacrifice the animal by cervical dislocation.</li>
	<li>Cut both eyeballs off the optic nerves at 1-2 mm away from the optic nerve heads with straight-pointed iris scissors.</li>
	<li>Roll the eyeballs on a clean paper towel to remove blood and then immerse them in carbogenated mammalian Ringer&#39;s solution. Punch a hole on the limbus with a 23 G needle and bisect the eyeballs by cutting along the limbus with micro-scissors. Remove the cornea and lens using fine forceps.
	<ol>
		<li>For retinal whole-mount, gently peel the entire retina off the pigmented epithelium with fine forceps and make four 1.5-2 mm orthogonal cuts from the edge toward the optic nerve head.</li>
	</ol>
	</li>
	<li>Immerse a punched nitrocellulose membrane into the dish and gently drag the retina over it with the GCL side up. Place the optic nerve head into the center hole when preparing a whole-mount retina. Transfer the membrane with the retina into another clean dish. Gently flatten the retina with a fine paint brush to look like a Maltese cross and lay all four edges over the holes.
	<ol>
		<li>If a fraction of the retina is to be examined at a time, cut each eyecup prepared from Step 3.3 into 3-4 pieces with a razor blade with the pigmented epithelium remains attached. Protect the unused pieces from light in carbogenated external solution and use them within 12 hr.</li>
	</ol>
	</li>
	<li>Blot the nitrocellulose membrane with a piece of dry filter paper and remove the vitreous and inner limiting membrane with forceps and a paint brush.</li>
	<li>Make sure that all retinal edges are fully attached to the membrane before transferring the assembly into the recording chamber with a sealed glass cover slip at the bottom. Secure the membrane with vacuum grease to the cover slip and rehydrate the retina with the external solution. Be careful not to trap any air bubbles underneath the assembly.</li>
	<li>Set the chamber onto the stage of an upright microscope. Perfuse the chamber with warm (34-35 &#176;C) carbogenated external solution at a rate of ~3 ml per min.</li>
	<li>Examine the retina under a 10x objective lens first, and then use a 60x water-immersion lens to see GCL and INL neurons under differential interference contrast (DIC) and/or epifluorescence. To visualize tdTomato-expressing SACs, use a white LED light source in combination with an excitation filter of 554 nm and an emission filter of 581 nm.</li>
</ol>
4. Whole-cell Patch Clamp Recording from Flat-mount Retina
<ol>
	<li>Filter the internal solution through a syringe filter into the custom backfill filament.</li>
	<li>Insert the filament into a freshly pulled micropipette and dispense the internal solution near the tip until the solution covers the silver electrode wire for &#62;5 mm. Fasten the micropipette onto an electrode holder with a suction pole, through which pressure inside the electrode can be adjusted by pushing or pulling the plunger of a tube-connected 10 ml plastic syringe.</li>
	<li>Find the pipette under the objective and bring it down to ~100 &#181;m above the retina. Under the current-follower mode (I = 0), use DC offset to zero the standing DC voltage signal. Measure the pipette resistance under the current clamp (IClamp) mode by injecting fixed amplitude square wave currents through the pipette while it is in the bath and neutralize the difference by turning the Raccess knob. Use the reading on the Raccess knob to calculate pipette resistance by the Ohm&#39;s law.</li>
	<li>Slowly bring the electrode to ~10 &#181;m above the retina. Apply positive pressure to the electrode. Watch the reflection change near the pipette tip as it approaches the retina. Quickly but gently force the pipette into the GCL and reduce the positive pressure immediately.</li>
	<li>Move the pipette toward a labeled neuron. Avoid contacting other neurons, blood vessels and endfeet of Muller cells. Apply more positive pressure if needed to prevent electrode clogging.</li>
	<li>Position the pipette tip near the midline of a labeled neuron until a dimple is visible. Release the positive pressure and allow the plasma membrane to bounce back onto the pipette tip.</li>
	<li>Apply 20 to 120 pA negative currents to the pipette to help the formation of a giga-ohm seal. Apply a gentle suction if necessary to pull the plasma membrane into the pipette. Wait 5 min after seal formation to rupture the cell membrane. This allows the spilled internal solution to be cleared by superfusion. Rupture the membrane by a gentle suction.</li>
	<li>After the membrane rupture and while in the current clamp mode, switch on bridge balance and adjust it using the Raccess knob. 
	NOTE: For a small cell like the SAC, only slight adjustment is needed, if any. Alternatively, record excitatory and inhibitory postsynaptic currents in the voltage clamp mode (VClamp) by holding the cell at reversal potentials of chloride (around -75 mV) and glutamate (around 0 mV), respectively. Check and adjust pipette position if needed to accommodate occasional retina and/or micromanipulator drift.</li>
	<li>To record membrane potential or current change before, during and after pharmacological treatment, prepare synaptic blockers (e.g., CNQX, AP5, picrotoxin, tubocurarine, etc.) and channel modulators (e.g., flupirtine, dopamine, meclofenamic acid, etc.) fresh on the day of experiment from frozen stocks. Dilute the drugs with carbogenated Ringer&#39;s solution. Apply them in a batch manner through perfusion.</li>
	<li>After recording, gently remove the pipette from the soma. Transfer the assembly from the chamber to a clean dish. Detach and re-attach the retina onto another flattened nitrocellulose membrane without punched holes to ensure retina flatness during fixation.</li>
	<li>Fix the retina by immersing it in 4% paraformaldehyde for 30 min at RT. Remove the retina from the nitrocellulose membrane and rinse it extensively with 1x PBS. Reveal the morphology of the recorded cells by O/N staining with dye-conjugated streptavidin diluted in 1x PBS with 0.4% Triton X-100 at 4 &#176;C14. Mount the retina in antifade medium and observe recorded cells using a scanning confocal microscope. 
	NOTE: Procedures involving paraformaldehyde, which is volatile and toxic, should be conducted in a draft chamber for safety.</li>
</ol>

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The authors have nothing to disclose.

Many labs have recorded from GCL neurons in the flat-mount preparation15-18, but our procedures allow recording from INL neurons. We hereby emphasize several steps that are critical for successful routine recordings.
The freshness and flatness of the retina are important for penetrating it with a recording pipette. In this regard, the firm attachment of the retina to the punched nitrocellulose membrane is paramount and is achieved by transient absorption of solution followed by time...

As an easily accessible part of the central nervous system, the retina has for decades been a useful model in neuroscience studies. Genetic marking of neurons has allowed detailed characterization of synaptic connections in the retina. With many methodologies available to examine function and morphology of retinal neurons, the patch clamp recording technique has been instrumental in our current understanding of vertically transmitted signals in the retina. These signals are originated from photon absorption in photoreceptors and sent to brain visual centers through spiking of retinal ganglion cells (RGCs). Despite a large body of knowledge accumulated thus far, neural diversity in vascularized mammalian retina remains unsolved and obstructs the full appreciation of retinal circuits that subserve normal vision. This is in part because most recordings were performed on retinal slices to trade lateral circuit integrity for access to more proximal retinal neurons1-3. To gain a comprehensive picture on how retina computes visual signals, it is thus desirable to record neurons in flat-mounts wherein lateral connections, large and small, may be better preserved.
When synaptic transmission from photoreceptors to bipolar cells is interrupted due to a defective metabotropic glutamate receptor 6 (mGluR6) signaling pathway in depolarizing bipolar cells4-6 or simply as the result of photoreceptor loss in degenerated retinas7-10, many RGCs exhibit oscillatory activities. These oscillations originate from multiple sources, however the one involving gap junction coupling between AII amacrine cells (AII-ACs) and depolarizing cone bipolar cells (DCBCs) has received the most attention and hence is best understood1,7,11. We have found another source, which persists under pharmacological blockade of the aforementioned AII-AC/DCBC network and drives oscillation of OFF-type SACs in Rho&#916;CTA and Nob mice with deafferentated retinas7,8,12. Here we detail our protocol of preparing retinal flat-mounts for INL neuron recording. This approach uses commercial mouse lines (Jax stock no. 006410 and 007905) to mark cholinergic retinal neurons by fluorescent protein (tdTomato) expression that is identifiable under a fluorescent microscope equipped with contrast enhancing optics. Some experimental results acquired through this approach have been previously reported4,5,7,13.

<table border="0" cellpadding="0" cellspacing="0" width="984">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:195px;">Fixed-stage fluorescent microscope with DIC</td>
			<td style="width:155px;">Olympus</td>
			<td style="width:219px;">BX51-WI</td>
			<td style="width:419px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Micromanipulators</td>
			<td style="width:155px;">Sutter</td>
			<td style="width:219px;">MP-225</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Patch clamp amplifier</td>
			<td style="width:155px;">A-M System</td>
			<td style="width:219px;">AM2400</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">AD converter</td>
			<td style="width:155px;">National Instrument</td>
			<td style="width:219px;">NI-USB-6221</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Heater controller</td>
			<td style="width:155px;">Warner Instrument</td>
			<td style="width:219px;">TC-324B</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Inline heater</td>
			<td style="width:155px;">Warner Instrument</td>
			<td style="width:219px;">SC-20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Peristaltic pump</td>
			<td style="width:155px;">Rainin</td>
			<td style="width:219px;">Dynamax</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">pipette puller</td>
			<td style="width:155px;">Sutter Instrument</td>
			<td style="width:219px;">P-1000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Glass tube with filament</td>
			<td style="width:155px;">King Precision Glass</td>
			<td style="width:219px;">Customized</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Stimulator</td>
			<td style="width:155px;">A.M.P.I.</td>
			<td style="width:219px;">Master-8</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Biocytin</td>
			<td style="width:155px;">Sigma</td>
			<td style="width:219px;">B4261</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">NaCl</td>
			<td style="width:155px;">Sigma</td>
			<td style="width:219px;">S6191</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">KCl</td>
			<td style="width:155px;">Sigma</td>
			<td style="width:219px;">P5405</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">NaHCO3</td>
			<td style="width:155px;">Fisher</td>
			<td style="width:219px;">BP328-1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Na2HPO4</td>
			<td style="width:155px;">Sigma</td>
			<td style="width:219px;">S0876</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">NaH2PO4</td>
			<td style="width:155px;">Sigma</td>
			<td style="width:219px;">S5011</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">CaCl2</td>
			<td style="width:155px;">Sigma</td>
			<td style="width:219px;">C5670</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">MgSO4</td>
			<td style="width:155px;">Sigma</td>
			<td style="width:219px;">M1880</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">D-glucose</td>
			<td style="width:155px;">Sigma</td>
			<td style="width:219px;">G6152</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">K-gluconate</td>
			<td style="width:155px;">Sigma</td>
			<td style="width:219px;">G4500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">ATP-Mg</td>
			<td style="width:155px;">Sigma</td>
			<td style="width:219px;">A9187</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Li-GTP</td>
			<td style="width:155px;">Sigma</td>
			<td style="width:219px;">G5884</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">EGTA</td>
			<td style="width:155px;">Sigma</td>
			<td style="width:219px;">E0396</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">HEPES</td>
			<td style="width:155px;">Sigma</td>
			<td style="width:219px;">H4034</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">KOH</td>
			<td style="width:155px;">Sigma</td>
			<td style="width:219px;">P5958</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Cs-methanesulfonate</td>
			<td style="width:155px;">Sigma</td>
			<td style="width:219px;">C1426</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">CsOH</td>
			<td style="width:155px;">Sigma</td>
			<td align="right" style="width:219px;">232041</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Syringer filter</td>
			<td style="width:155px;">Nalgene</td>
			<td align="right" style="width:219px;">171</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">1 ml syring</td>
			<td style="width:155px;">Rainin</td>
			<td align="right" style="width:219px;">17013002</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">10 ul pipette tip</td>
			<td style="width:155px;">Genesee Scientific</td>
			<td style="width:219px;">24-130RL</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Streptavidin-488</td>
			<td style="width:155px;">ThermoFisher</td>
			<td style="width:219px;">S-11223</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">10X PBS</td>
			<td style="width:155px;">Lonza</td>
			<td style="width:219px;">17-517Q</td>
			<td></td>
		</tr>
	</tbody>
</table>

patch clamp recording of starburst amacrine cells in a flat-mount preparation of deafferentated mouse retina

The mammalian retina is a layered tissue composed of multiple neuronal types. To understand how visual signals are processed within its intricate synaptic network, electrophysiological recordings are frequently used to study connections among individual neurons. We have optimized a flat-mount preparation for patch clamp recording of genetically marked neurons in both GCL (ganglion cell layer) and INL (inner nuclear layer) of mouse retinas. Recording INL neurons in flat-mounts is favored over slices because both vertical and lateral connections are preserved in the former configuration, allowing retinal circuits with large lateral components to be studied. We have used this procedure to compare responses of mirror-partnered neurons in retinas such as the cholinergic starburst amacrine cells (SACs).

Representative recordings of ON- and OFF-type SACs from a deafferentated mouse retina are shown in Figure 1. Cholinergic cells in both GCL and INL can be reliably identified by tdTomato fluorescence and targeted for whole-cell patch clamp recording under DIC (Figure 1A) to reveal oscillation of their membrane potentials (top traces) and the synaptic currents that drive it (bottom traces, Figure 1B). Inhibitory and excitatory synaptic curr...

Watch this Scientific Journal Video about Patch Clamp Recording of Starburst Amacrine Cells in a Flat-mount Preparation of Deafferentated Mouse Retina at JoVE.com

Patch Clamp Recording of Starburst Amacrine Cells in a Flat-mount Preparation of Deafferentated Mouse Retina

This protocol demonstrates how to perform whole-cell patch clamp recording on retinal neurons from a flat-mount preparation.

The mammalian retina is a layered tissue composed of multiple neuronal types. To understand how visual signals are processed within its intricate synaptic ...

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8.1K Views.  Baylor College of Medicine. This protocol demonstrates how to perform whole-cell patch clamp recording on retinal neurons from a flat-mount preparation.

Video: Patch Clamp Recording of Starburst Amacrine Cells in a Flat-mount Preparation of Deafferentated Mouse Retina

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 ...

Culturing and Electrophysiology of Cells on NRCC Patch-clamp Chips

Due to its exquisite sensitivity and the ability to monitor and control individual cells at the level of ion channels, patch-clamping is the gold standard of electrophysiology applied to disease models and pharmaceutical screens alike 1. The method traditionally involves gently contacting a cell with a glass pipette filled by a physiological solution in order to isolate a patch of the membrane under its apex 2. An electrode inserted in the pipette captures ion-channel activity within the membrane patch or, when ruptured, for the whole cell. In the last decade, patch-clamp chips have been proposed as an alternative 3, 4: a suspended film separates the physiological medium from the culture medium, and an aperture microfabricated in the film replaces the apex of the pipette. Patch-clamp chips have been integrated in automated systems and commercialized for high-throughput screening 5. To increase throughput, they include the fluidic delivery of cells from suspension, their positioning on the aperture by suction, and automated routines to detect cell-to-probe seals and enter into whole cell mode. We have reported on the fabrication of a silicon patch-clamp chip with optimized impedance and orifice shape that permits the high-quality recording of action potentials in cultured snail neurons 6; recently, we have also reported progress towards interrogating mammalian neurons 7. Our patch-clamp chips are fabricated at the Canadian Photonics Fabrication Centre 8, a commercial foundry, and are available in large series. We are eager to engage in collaborations with electrophysiologists to validate the use of the NRCC technology in different models. The chips are used according to the general scheme represented in Figure 1: the silicon chip is at the bottom of a Plexiglas culture vial and the back of the aperture is connected to a subterranean channel fitted with tubes at either end of the package. Cells are cultured in the vial and the cell on top of the probe is monitored by a measuring electrode inserted in the channel.The two outside fluidic ports facilitate solution exchange with minimal disturbance to the cell; this is an advantage compared to glass pipettes for intracellular perfusion.
<img alt="Figure 1" src="/files/ftp_upload/3288/3288fig1.jpg" />
Figure 1. Principle of measurement using the NRCC patch-clamp chip
We detail here the protocols to sterilize and prime the chips, load them with medium, plate them with cells, and finally use them for electrophysiological recordings.

We show how planar patch-clamp chips fabricated at the National Research Council of Canada are sterilized, primed, loaded with medium, plated with cells, and used for electrophysiological recordings.

Due to its exquisite sensitivity and the ability to monitor and control individual cells at the level of ion channels, patch-clamping is the gold standard ...

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  ...

F1FO ATPase Vesicle Preparation and Technique for Performing Patch Clamp Recordings of Submitochondrial Vesicle Membranes

Mitochondria are involved in many important cellular functions including metabolism, survival1, development and, calcium signaling2. Two of the most important mitochondrial functions are related to the efficient production of ATP, the energy currency of the cell, by oxidative phosphorylation, and the mediation of signals for programmed cell death3.
The enzyme primarily responsible for the production of ATP is the F1FO-ATP synthase, also called ATP synthase4-5. In recent years, the role of mitochondria in apoptotic and necrotic cell death has received considerable attention. In apoptotic cell death, BCL-2 family proteins such as Bax enter the mitochondrial outer membrane, oligomerize and permeabilize the outer membrane, releasing pro-apoptotic factors into the cytosol6. In classic necrotic cell death, such as that produced by ischemia or excitotoxicity in neurons, a large, poorly regulated increase in matrix calcium contributes to the opening of an inner membrane pore, the mitochondrial permeability transition pore or mPTP. This depolarizes the inner membrane and causes osmotic shifts, contributing to outer membrane rupture, release of pro-apoptotic factors, and metabolic dysfunction. Many proteins including Bcl-xL7 interact with F1FO ATP synthase, modulating its function. Bcl-xL interacts directly with the beta subunit of F1FO ATP synthase, and this interaction decreases a leak conductance within the F1FOATPasecomplex, increasing the net transport of H+ by F1FO during F1FO ATPase activity8 and thereby increasing mitochondrial efficiency. To study the activity and modulation of the ATP synthase, we isolated from rodent brain submitochondrial vesicles (SMVs) containing F1FO ATPase. The SMVs retain the structural and functional integrity of the F1FO ATPase as shown in Alavian et al. Here, we describe a method that we have used successfully for the isolation of SMVs from rat brain and we delineate the patch clamp technique to analyze channel activity (ion leak conductance) of the SMVs.

F1FO ATPase Vesicle Preparation and Technique for Performing Patch Clamp Recordings of Submitochondrial Vesicle Membranes

A method to isolate submitochondrial vesicles enriched in F1FO ATP synthase complexes from rat brain is described. These vesicles allow the study of the activity of F1FO ATPase complex and its modulation using the technique of patch clamp recording.

Mitochondria are involved in many important cellular  functions including metabolism, survival1, development and, calcium signaling2. Two of the most ...

Whole Cell Patch Clamp for Investigating the Mechanisms of Infrared Neural Stimulation

It has been demonstrated in recent years that pulsed, infrared laser light can be used to elicit electrical responses in neural tissue, independent of any further modification of the target tissue. Infrared neural stimulation has been reported in a variety of peripheral and sensory neural tissue in vivo, with particular interest shown in stimulation of neurons in the auditory nerve. However, while INS has been shown to work in these settings, the mechanism (or mechanisms) by which infrared light causes neural excitation is currently not well understood. The protocol presented here describes a whole cell patch clamp method designed to facilitate the investigation of infrared neural stimulation in cultured primary auditory neurons. By thoroughly characterizing the response of these cells to infrared laser illumination in vitro under controlled conditions, it may be possible to gain an improved understanding of the fundamental physical and biochemical processes underlying infrared neural stimulation.

Infrared nerve stimulation has been proposed as an alternative to electrical stimulation in a range of nerve types, including those associated with the auditory system. This protocol describes a patch clamp method for studying the mechanism of infrared nerve stimulation in a culture of primary auditory neurons.

It has been  demonstrated in recent years that pulsed, infrared laser light can be used to  elicit electrical responses in neural tissue, independent of ...

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 ...

Recording Light-evoked Postsynaptic Responses in Neurons in Dark-adapted, Mouse Retinal Slice Preparations Using Patch Clamp Techniques

The retina is the gateway to the visual system. To understand visual signal processing mechanisms, we investigate retinal neural network functions. Retinal neurons in the network comprise of numerous subtypes. More than 10 subtypes of bipolar cells, ganglion cells, and amacrine cells have been identified by morphological studies. Multiple subtypes of retinal neurons are thought to encode distinct features of visual signaling, such as motion and color, and form multiple neural pathways. However, the functional roles of each neuron in visual signal processing are not fully understood. The patch clamp method is useful to address this fundamental question. Here, a protocol to record light-evoked synaptic responses in mouse retinal neurons using patch clamp recordings in dark-adapted conditions is provided. The mouse eyes are dark-adapted O/N, and retinal slice preparations are dissected in a dark room using infrared illumination and viewers. Infrared light does not activate mouse photoreceptors and thus preserves their light responsiveness. Patch clamp is used to record light-evoked responses in retinal neurons. A fluorescent dye is injected during recordings to characterize neuronal morphological subtypes. This procedure enables us to determine the physiological functions of each neuron in the mouse retina.

We will demonstrate how to prepare retinal slices from the mouse eye and record light responses in retinal neurons. The entire procedure is conducted in dark-adapted conditions.

The retina is the gateway to the visual system. To understand visual signal processing mechanisms, we investigate retinal neural network functions. ...

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 ...

Preparation of Horizontal Slices of Adult Mouse Retina for Electrophysiological Studies

Vertical slice preparations are well established to study circuitry and signal transmission in the adult mammalian retina. The plane of sectioning in these preparations is perpendicular to the retinal surface, making it ideal for the study of radially oriented neurons like photoreceptors and bipolar cells. However, the large dendritic arbors of horizontal cells, wide-field amacrine cells, and ganglion cells are mostly truncated, leaving markedly reduced synaptic activity in these cells. Whereas ganglion cells and displaced amacrine cells can be studied in a whole-mounted preparation of the retina, horizontal cells and amacrine cells located in the inner nuclear layer are only poorly accessible for electrodes in whole retina tissue.
To achieve maximum accessibility and synaptic integrity, we developed a horizontal slice preparation of the mouse retina, and studied signal transmission at the synapse between photoreceptors and horizontal cells. Horizontal sectioning allows&#160;(1) easy and unambiguous visual identification of horizontal cell bodies for electrode targeting, and (2) preservation of the extended horizontal cell dendritic fields, as a prerequisite for intact and functional cone synaptic input to horizontal cell dendrites.
Horizontal cells from horizontal slices exhibited tonic synaptic activity in the dark, and they responded to brief flashes of light with a reduction of inward current and diminished synaptic activity. Immunocytochemical evidence indicates that almost all cones within the dendritic field of a horizontal cell establish synapses with its peripheral dendrites. The horizontal slice preparation is therefore well suited to study the physiological properties of horizontally extended retinal neurons as well as sensory signal transmission and integration across selected synapses.

We developed a horizontal slice preparation of the adult mammalian retina with the plane of sectioning parallel to the retinal surface. Dendritic fields of nonradially oriented retinal neurons were not truncated, allowing the study of signal processing with patch-clamp and imaging techniques.

Vertical slice preparations are well established to study circuitry and signal transmission in the adult mammalian retina. The plane of sectioning in ...