The authors wish to thank Ina Wolter for her excellent technical assistance. VGAT-Venus transgenic rats were generated by Drs. Y. Yanagawa, M. Hirabayashi and Y. Kawaguchi in National Institute for Physiological Sciences, Okazaki, Japan, using pCS2-Venus provided by Dr. A. Miyawaki.

Ethics Statement: All procedures and animal maintenance were performed in accordance with Institutional guidelines, the German Animal Welfare Act, the European Council Directive 86/609/EEC regarding the protection of animals, and guidelines from local authorities (Berlin, T-0215/11)
1. Preparation of Acute-hippocampal Slices
<ol>
	<li>Take a transgenic rat (17 to 24 day old), expressing the fluorescent Venus/YFP protein under the vGAT promoter, which labels the majority of cortical inhibitory interneurons13. Decapitate the rat. Rapidly dissect the brain (&#60;40 sec) into semifrozen, carbogenated (95% O2/5% CO2) sucrose-based artificial cerebrospinal fluid (sucrose-ACSF, Figure 1A).</li>
	<li>Assess the dissected rat brain for Venus/YFP fluorescence with a 505 nm LED lamp and 515 emission filter, mounted on a pair of goggles.</li>
	<li>Remove the frontal third of the cortex and cerebellum; then separate the hemispheres, all with a scalpel. Remove the dorsal surface of the cortex to provide a flat surface to glue the brain down, as previously described14.</li>
	<li>Cut transverse slices (300&#160;&#956;m) of the hippocampal formation on a vibratome, the hemispheres should be surrounded with semifrozen, carbogenated sucrose-ACSF (Figure 1B)14. Remove additional regions of rostral cortex, midbrain and brainstem. Transfer each slice to a submerged holding chamber containing sucrose-ACSF, which is carbogenated and warmed to 35 &#186;C.</li>
	<li>Leave the slices to recover at 35 &#186;C for 30 min from the time of the last slice entering the warmed ACSF. Do this in order to reactivate metabolic processes and facilitate the resealing of cut neuronal processes. Then transfer to room temperature for storage (Figure 1C).</li>
</ol>
2. Fabrication and Filling of Recording Pipettes
<ol>
	<li>Pull patch pipettes from glass capillaries, so that a pipette resistance of 2-4&#160;M&#937; is achieved when filled with filtered (syringe filter, pore size: 0.2&#160;&#956;m) intracellular solution containing 0.1% biocytin (for intracellular labeling). Keep the intracellular solution chilled on ice to prevent degradation of its constituents.</li>
	<li>Fill patch pipettes for identification of postsynaptic currents with a solution containing a physiologically relevant low Cl- concentration (ER(Cl-)= -61&#160;mV; see solution list).</li>
	<li>For paired recordings to identify the presynaptic receptor mediated responses, fill patch pipettes with intracellular solution with low Ca2+ buffer capacity to prevent interference with transmitter release presynaptically, as well as 4-fold higher Cl- concentration (ER(Cl-)= -20&#160;mV) to improve signal-to-noise of observed IPSCs5 allowing accurate assessment of pharmacological responsiveness. Note that changing Cl- concentration can alter IPSC kinetics15.</li>
</ol>
3. Whole Cell Patch-clamp Recording from FS-INs
<ol>
	<li>Carbogenate the ACSF and feed through the perfusion system to the recording chamber, by means of a peristaltic pump (which also removes ACSF from the recording chamber through a suction line, Figure 2A). Turn on all equipment on the setup in preparation for recording.</li>
	<li>Transfer a slice to the recording chamber and hold in place with a platinum ring strung with single fibers of silk. Position the slice so that the stratum (str.) pyramidale of CA1 runs vertically through the field of view, allowing access with 2 pipettes to both the str. radiatum and str. oriens simultaneously (Figures 2C and 4A).</li>
	<li>Place the chamber into the setup and start perfusion of carbogenated and warmed (32-34 &#186;C) recording ACSF at a flow rate of 5-10&#160;ml/min.</li>
	<li>Assess slice quality under IR-DIC optics at 40X objective magnification, and visualize with a CCD camera viewed on a display. Assume good slice quality if a large number of round, moderately contrasted CA1 pyramidal cells (CA1 PC) can be seen in str. pyramidale at depths of 20-30&#160;&#956;m below a smooth and lightly cratered surface (Figure 2C). Poor quality slices contain large numbers of highly contrasted, shrunken or swollen cells, with an uneven slice surface.</li>
	<li>Identify putative FS interneurons under epifluorescence illumination as those expressing Venus/YFP (Figure 2B), with large multipolar somata in or near the str. pyramidale. Select cells reasonably deep within the slice (50-100&#160;&#956;m, Figure 2C) in order to better preserve their morphological integrity.</li>
	<li>Mount the recording electrode in the pipette holder on the headstage; then apply a low, positive pressure (20-30&#160;mBar) through the tube line. Lower the pipette to the surface of the slice, slightly offset to the center of the selected neuron.</li>
	<li>Obtain whole-cell recording configuration as described previously14,16 and see also Figures 2D and 2E:
	<ol>
		<li>Target a cell: Increase the pressure to 70-80&#160;mBar and rapidly lower the pipette through the slice to just above the soma of the selected cell (Figure 2D, top).</li>
		<li>Approach the cell: Press the pipette against the cell membrane to produce a &#8220;dimple&#8221; on it (Figure 2D, top). Perform this step swiftly, in order to prevent biocytin labeling of neighboring cells.</li>
		<li>Create a giga-ohm seal: Release the pressure and simultaneously apply a 20&#160;mV voltage command to the pipette. A giga-ohm seal (1-50&#160;G&#937;; Figure 2D, bottom and Figure 2E middle) typically develops rapidly. Once sealed, apply the expected resting membrane potential (typically between -70 and -60 mV) as a voltage command.</li>
		<li>Break through the patch: Once sealed, rupture the membrane patch with a short pulse of negative pressure; thereby achieving the whole-cell configuration (Figure 2E, bottom).</li>
	</ol>
	</li>
	<li>Compensate whole-cell capacitance and series resistance (RS). Rs is normally 5-20&#160;M&#937; and stable for up to 120&#160;min. Abandon cells if membrane potential (VM) on break-through is more depolarized than -50&#160;mV; RS is initially greater than 30&#160;M&#937;; or RS changes by more than 20% over the course of the recording.</li>
	<li>Identify FS-INs by their response (in current-clamp mode) to a family of hyper- to depolarizing current pulses (-250 to +250&#160;pA, Figure 2F, top). FS-INs have relatively depolarized VM (typically -50 to -60&#160;mV), short membrane time-constant (&#60;20&#160;msec) and respond to a 500&#160;pA depolarizing current injection with a train of action potentials (APs) at frequencies &#62;100&#160;Hz 11 (Figure 2F, bottom), which are markedly different from those in CA1 PCs (Figure 2F, middle).</li>
</ol>
4. Extracellular Electrical Stimulation to Evoke GABABR-mediated Responses
<ol>
	<li>To observe synaptically evoked responses, position an extracellular stimulation electrode (a patch pipette filled with 2&#160;M NaCl; Resistance: 0.1-0.3&#160;M&#937;) in the slice at the border of str. radiatum and str. lacunosum-moleculare. Position the electrode 200-300&#160;&#956;m lateral to the soma to prevent direct electrical stimulation of the cell and minimize stimulation artifacts (Figure 3A).</li>
	<li>Once the stimulation electrode is positioned, obtain whole-cell recording of the chosen cell and assess the physiological phenotype in current-clamp mode as in section 3.9 (Figure 3B).</li>
	<li>With the neuron recorded in voltage-clamp (VM -65&#160;mV), deliver electrical stimulation of presynaptic axons at 50&#160;V (~500&#160;&#956;A effective stimulus) every 20&#160;sec, using an isolated constant-voltage stimulator. Use single stimuli (100&#160;&#956;sec duration, Figure 3C, top) to observe GABABR mediated IPSCs, and interleave with trains of multiple stimuli (at 200&#160;Hz) to produce greater transmitter release.</li>
	<li>Bath apply ionotropic glutamate receptor antagonists (AMPA receptor: DNQX [10&#160;&#956;M]; NMDA receptor: d-AP5 [50&#160;&#956;M]) to reveal the isolated monosynaptic IPSC (Figure 3C, middle upper). Further isolate the GABABR-mediated IPSC with application of a GABAAR blocker (gabazine [10&#160;&#956;M]; Figure 3C middle lower).</li>
	<li>Confirm the resultant slow-outward current (Figure 3C lower, expanded) as being GABABR-mediated by the subsequent application of CGP-55,845 [5 &#956;M] (Figure 3C lower, underlain in grey)</li>
</ol>
5. Paired Recordings of Synaptically Coupled FS-IN and CA1 PCs
<ol>
	<li>Assess GABABR-mediated presynaptic control of inhibitory synaptic transmission with simultaneous recordings, performed between synaptically-coupled IN and PC pairs as described below.</li>
	<li>First, establish a whole-cell recording of a presynaptic interneuron (as in section 3) and confirm the FS phenotype (Figure 4A).</li>
	<li>Then patch a neighboring CA1 PC (20-100&#160;&#956;m distance, Figure 4A) and apply brief suprathreshold depolarizing current pulses (1&#160;msec duration, 1-5&#160;nA amplitude) to the presynaptic IN (held in current-clamp mode) to elicit APs. If a synaptic connection is present, APs in the IN result in IPSCs in the CA1 PC, held in voltage-clamp (compensate RS to about 80%).</li>
	<li>If necessary, fill a new recording electrode and record from further CA1 PCs until a connection is found.</li>
	<li>Once a connection is established, elicit pairs of APs in the presynaptic FS-IN to assess both the unitary synaptic response and dynamic behavior. Use a typical paired-pulse protocol of 2 depolarizing stimuli with a 50&#160;msec interval (Figure 4B).</li>
	<li>Collect control traces in baseline conditions. Then, apply the selective GABABR agonist baclofen (10&#160;&#956;M) to the perfusing ACSF, thus activating GABABRs, followed by the antagonist CGP-55,845 (5 &#956;M), to fully block the receptor mediated effects. Collect ~50 traces during steady state of each drug condition (Figure 4B and C).</li>
	<li>Once the recording is complete, seal the somatic membrane by forming an outside-out patch: Slowly withdraw the pipette from the cell body in V-clamp and as the RS increases, reduce the VM to -40&#160;mV. Do this to facilitate the formation of the outside-out patch; then remove the pipette from the bath.</li>
</ol>
6. Analysis of Electrophysiological Properties
<ol>
	<li>NOTE: A multitude of different software packages are available for the acquisition of electrophysiological data. Here, WinWCP, a Windows program in the free Strathclyde Electrophysiology Software package is used, which allows recording of up to 16 analog input channels and output of 10 digital signals.</li>
	<li>Low-pass filter all data at 5-10&#160;kHz and sample at 20&#160;kHz.</li>
	<li>Analyze physiological data with an off-line analysis suite. 
	NOTE: Stimfit, an open source software package which includes a Python shell, is used in this instance; however other alternatives can easily be used instead.
	<ol>
		<li>Analyze passive membrane properties of recorded neurons, acquired in current clamp, from resting membrane potential.</li>
		<li>Measure the mean resting membrane potential from the baseline of recorded responses from the beginning of the recording.</li>
		<li>Calculate input resistance, using Ohm&#8217;s law, from the voltage response to the smallest hyperpolarizing current pulses (&#8804; -50&#160;pA). To improve signal to noise ratio, average multiple traces. Note: our examples are typically averages of 10-50 individual sweeps.</li>
	</ol>
	</li>
	<li>Estimate the apparent membrane time constant by fitting a monoexponential curve to the decay of the responses to the smallest hyperpolarizing current pulses.</li>
	<li>Analyze action potential waveform to determine threshold, amplitude (threshold to peak) and duration (width measured at half height) elicited by threshold level depolarizing current pulses.</li>
	<li>Analyze GABABR mediated IPSCs from voltage clamp recordings. Filter traces off-line at 500&#160;Hz (Gaussian filter) and assess the peak amplitude and latency of the GABABR mediated response (in averages of at least 10 traces).</li>
	<li>Detect the effect of GABABRs on the inhibitory output of INs as a change in peak amplitude of the GABAAR-mediated IPSCs measured between peak and preceding baseline. Calculate the mean amplitude from &#8805;50 traces for the control period and the steady-state of all pharmacological epochs.</li>
</ol>
7. Visualization and Immunocytochemistry of FS-Ins
<ol>
	<li>Following the recordings, fix the slices by immersion in 4% paraformaldehyde with 0.1&#160;M phosphate buffer (PB, pH=7.35) O/N at 4 &#176;C.</li>
	<li>If necessary slices can be transferred to PB and stored for up to ~1 week before processing.</li>
	<li>Wash slices liberally in fresh PB and subsequently in 0.025&#160;M PB with 0.9% NaCl (PBS, pH=7.35).</li>
	<li>To reduce non-specific antibody binding, block the slices for 1 hr at RT in a solution containing 10% normal goat serum (NGS), 0.3% Triton-X100 (a detergent to permeabilize membranes) and 0.05% NaN3, made up in PBS.</li>
	<li>To label for PV expression, use an anti-PV monoclonal mouse antibody diluted in a solution containing 5% NGS, 0.3% Triton-X100, 0.05% NaN3, in PBS. Incubate primary antibodies for 2-3&#160;days at 4 &#176;C12. Rinse slices thoroughly in PBS.</li>
	<li>Apply fluorescent anti-mouse secondary antibodies (e.g. Alexafluor-546) along with the biotin binding-protein streptavidin, conjugated to a fluorochrome (e.g., Alexafluor-647); and incubate in a solution containing 3% NGS, 0.1% Triton-X100, 0.05% NaN3, diluted in PBS and incubate O/N at 4 &#176;C.</li>
	<li>Liberally rinse slices 2-3x&#160;with PBS followed by 2-3 rinses in PB. Mount the slices on glass slides. Use a 300&#160;&#956;m agar spacer to prevent the slice from collapsing. Cover-slip slices with a fluorescent mounting medium and seal with nail-varnish.</li>
</ol>
8. Imaging and Reconstruction of Visualized FS-Ins
<ol>
	<li>Visualize the slices using a scanning confocal microscope, with the fluorochome reporter excited with the appropriate laser line (diode laser 635&#160;nm for Alexafluor-647; Helium-Neon 543&#160;nm for Alexafluor-546 labeling for PV and Argon 488 or 515&#160;nm for Venus/YFP).</li>
	<li>Take images at an appropriate Z-resolution (typically 0.5-1&#160;&#956;m steps, using a 20X objective) to produce a Z-stack of the whole cell. Multiple stacks are normally required to image the whole cell, which can be digitally stitched off-line using FIJI/ImageJ software (Figure 5A).</li>
	<li>Reconstruct the cell from the stitched image stack using a semi-automatic tracing method (Simple Neurite Tracer plugin in FIJI/ImageJ software package17, Figure C).</li>
	<li>Finally, assess the PV-immunoreactivity of the interneuron with a high numerical aperture objective lens (60X silicon-immersion, N.A.=1.3). Make images of the soma, proximal dendrites and proximal axon, or alternatively of axon terminals if somatic washout of PV is too strong. Cells are deemed immunoreactive for PV if immuno-labelling is seen to align with the biocytin-labeled structures (Figure 5B).</li>
</ol>

<ol>
	<li>Freund, T. F., Buzs&#225;ki, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interneurons+of+the+hippocampus.">Interneurons of the hippocampus.</a> Hippocampus. 6 (4), 347-470 (1996).</li><li>Meyer, A. H., Katona, I., Blatow, M., Rozov, A., Monyer, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+labeling+of+parvalbumin-positive+interneurons+and+analysis+of+electrical+coupling+in+identified+neurons.">In vivo labeling of parvalbumin-positive interneurons and analysis of electrical coupling in identified neurons.</a> Journal of Neuroscience. 22, 7055-7064 (2002).</li><li>Vida, I., Halasy, K., Szinyei, C., Somogyi, P., Buhl, E. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unitary+IPSPs+evoked+by+interneurons+at+the+stratum+radiatum-stratum+lacunosum-moleculare+border+in+the+CA1+area+of+the+rat+hippocampus+in+vitro.">Unitary IPSPs evoked by interneurons at the stratum radiatum-stratum lacunosum-moleculare border in the CA1 area of the rat hippocampus in vitro.</a> Journal of Physiolology. 506, 755-773 (1998).</li><li>Mody, I., De Koninck, Y., Otis, T. S., Soltesz, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bridging+the+cleft+at+GABA+synapses+in+the+brain.">Bridging the cleft at GABA synapses in the brain.</a> Trends Neurosci. 17 (12), 517-525 (1994).</li><li>Bartos, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fast+synaptic+inhibition+promotes+synchronized+gamma+oscillations+in+hippocampal+interneuron+networks.">Fast synaptic inhibition promotes synchronized gamma oscillations in hippocampal interneuron networks.</a> PNAS. 99, 13222-13227 (2002).</li><li>Cobb, S. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synaptic+effects+of+identified+interneurons+innervating+both+interneurons+and+pyramidal+cells+in+the+rat+hippocampus.">Synaptic effects of identified interneurons innervating both interneurons and pyramidal cells in the rat hippocampus.</a> Neuroscience. 79 (3), 629-648 (1997).</li><li>Bartos, M., Vida, I., Jonas, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synaptic+mechanisms+of+synchronized+gamma+oscillations+in+inhibitory+interneuron+networks.">Synaptic mechanisms of synchronized gamma oscillations in inhibitory interneuron networks.</a> Nature Review Neurosci. 8, 45-56 (2007).</li><li>Ascoli, G. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Petilla+terminology+nomenclature+of+features+of+GABAergic+interneurons+of+the+cerebral+cortex.">Petilla terminology nomenclature of features of GABAergic interneurons of the cerebral cortex.</a> Nature Review Neurosci. 9, 557-568 (2008).</li><li>Klausberger, T., Somogyi, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuronal+diversity+and+temporal+dynamics+the+unity+of+hippocampal+circuit+operations.">Neuronal diversity and temporal dynamics the unity of hippocampal circuit operations.</a> Science. 321, 53-57 (2008).</li><li>Buhl, E. H., Szil&#225;gyi, T., Halasy, K., Somogyi, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physiological+properties+of+anatomically+identified+basket+and+bistratified+cells+in+the+CA1+areas+of+the+rat+hippocampus+in+vitro.">Physiological properties of anatomically identified basket and bistratified cells in the CA1 areas of the rat hippocampus in vitro.</a> Hippocampus. 6, 294-305 (1996).</li><li>Kawaguchi, Y., Katsumara, H., Kosaka, T., Heizmann, C. W., Hama, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fast+spiking+cells+in+rat+hippocampus+(CA1+region)+contain+the+calcium-+binding+protein+parvalbumin.">Fast spiking cells in rat hippocampus (CA1 region) contain the calcium- binding protein parvalbumin.</a> Brain Res. 416 (2), 369-374 (1987).</li><li>Booker, S. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differential+GABAB-Receptor-Mediated+Effects+in+Perisomatic-+and+Dendrite-Targeting+Parvalbumin+Interneurons.">Differential GABAB-Receptor-Mediated Effects in Perisomatic- and Dendrite-Targeting Parvalbumin Interneurons.</a> Journal of Neuroscience. 33 (18), 7961-7974 (2013).</li><li>Uematsu, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+chemical+composition+of+cortical+GABAergic+neurons+revealed+in+transgenic+Venus-expressing+rats.">Quantitative chemical composition of cortical GABAergic neurons revealed in transgenic Venus-expressing rats.</a> Cerebral Cortex. 18, 315-330 (2008).</li><li>Bischofberger, J., Engel, D., Li, L., Geiger, J. R. P., Jonas, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Patch-clamp+recording+from+mossy+fiber+terminals+in+hippocampal+slices.">Patch-clamp recording from mossy fiber terminals in hippocampal slices.</a> Nature Protocols. 1, 2075-2081 (2006).</li><li>Houston, C. M., Bright, D. P., Sivilotti, L. G., Beato, M., Smart, T. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intracellular+Chloride+Ions+Regulate+the+Time+Course+of+GABA-Mediated+Inhibitory+Synaptic+Transmission.">Intracellular Chloride Ions Regulate the Time Course of GABA-Mediated Inhibitory Synaptic Transmission.</a> Journal of Neuroscience. 29 (33), 10416-10423 (2009).</li><li>Sakmann, B., Neher, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Patch+clamp+techniques+for+studying+ionic+channels+in+excitable+membranes.">Patch clamp techniques for studying ionic channels in excitable membranes.</a> Annual Review Physiology. 46, 455-472 (1984).</li><li>Schindelin, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fiji+an+open-source+platform+for+biological-image+analysis.">Fiji an open-source platform for biological-image analysis.</a> Nature Methods. 9, 676-682 (2012).</li><li>Geiger, J. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Patch-clamp+recording+in+brain+slices+with+improved+slicer+technology.">Patch-clamp recording in brain slices with improved slicer technology.</a> Pflugers Archives. 443, 491-501 (2002).</li><li>Malinow, R., Tsien, R. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Presynaptic+enhancement+shown+by+whole-cell+recordings+of+long-term+potentiation+in+hippocampal+slices.">Presynaptic enhancement shown by whole-cell recordings of long-term potentiation in hippocampal slices.</a> Nature. 346, 177-180 (1990).</li><li>Vida, I., Bartos, M., Jonas, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Shunting+inhibition+improves+robustness+of+gamma+oscillations+in+hippocampal+interneuron+networks+by+homogenizing+firing+rates.">Shunting inhibition improves robustness of gamma oscillations in hippocampal interneuron networks by homogenizing firing rates.</a> Neuron. 49 (1), 107-117 (2006).</li><li>Neu, A., F&#246;ldy, C., Soltesz, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Postsynaptic+origin+of+CB1-dependent+tonic+inhibition+of+GABA+release+at+cholecystokinin-positive+basket+cell+to+pyramidal+cell+synapses+in+the+CA1+region+of+the+rat+hippocampus.">Postsynaptic origin of CB1-dependent tonic inhibition of GABA release at cholecystokinin-positive basket cell to pyramidal cell synapses in the CA1 region of the rat hippocampus.</a> Journal of Physiology. 578 (1), 233-247 (2007).</li><li>Baude, A., Bleasdale, C., Dalezios, Y., Somogyi, P., Klausberger, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immunoreactivity+for+the+GABAA+receptor+alpha1+subunit,+somatostatin+and+Connexin36+distinguishes+axoaxonic,+basket,+and+bistratified+interneurons+of+the+rat+hippocampus.">Immunoreactivity for the GABAA receptor alpha1 subunit, somatostatin and Connexin36 distinguishes axoaxonic, basket, and bistratified interneurons of the rat hippocampus.</a> Cerebral Cortex. 17, 2094-2107 (2007).</li></ol>

The authors declare that they have no competing financial interests.

We describe a method which combines electrophysiological and neuroanatomical techniques to functionally characterize morphologically- and neurochemically-identified neurons in vitro; in particular the diverse types of cortical inhibitory INs. Key aspects of the procedure are: (1) pre-selection of potential INs; (2) intracellular recording and neuron visualization; and finally (3) morphological and immunocytochemical analysis of recorded INs. Although this study has addressed PV-INs in particular, the described protocol c...

Hippocampal neuronal circuits have long been the subject of intense scrutiny, with respect to both anatomy and physiology, due to their essential role in learning and memory as well as spatial navigation in both humans and rodents. Equally, the prominent, but simple laminar organization of the hippocampus makes this region a favored subject of studies addressing structural and functional properties of cortical networks.
Hippocampal circuits are comprised of excitatory principal cells (&#62;80%) and a smaller (10-20%), but highly diverse cohort of inhibitory interneurons1-3. Interneurons release &#947;-aminobutyric acid (GABA) from their axon terminals which acts at fast ionotropic GABAA receptors (GABAARs) and slow metabotropic GABAB receptors (GABABRs)4. These inhibitory mechanisms counterbalance excitation and regulate the excitability of principal cells, and thus their timing and pattern of discharge. However, GABA released from interneurons acts not only on principal cells, but also on the interneurons themselves5,6. Pre and postsynaptic receptors mediate feedback regulation and inhibitory mutual interactions among the various types of interneuron. These inhibitory mechanisms in interneuron networks are believed to be central to the generation and shaping of population activity patterns, in particular oscillations at different frequencies7.
Whole-cell patch-clamp recording is a well-established method for the examination of intrinsic properties and synaptic interactions of neurons. However, due to the high diversity of interneuron types, investigation of inhibitory interneurons requires rigorous identification of the recorded cells. As hippocampal interneuron types are characterized by distinct morphological features and neurochemical marker expression, combined anatomical and immunocytochemical examination can provide a means to determine precise interneuron identity6,8,9.
In the present paper we describe an experimental approach in which whole-cell patch-clamp recordings from single neurons or synaptically-coupled pairs are combined with intracellular labeling, followed by post-hoc morphological and immunocytochemical analysis, allowing for the characterization of slow GABAB receptor mediated inhibitory effects in identified interneurons. As an example, we focus on one major type of interneuron, a subset of the so called &#8220;basket cells&#8221; (BC), which innervates the soma and proximal dendrites of its postsynaptic targets and is characterized by a &#8220;fast spiking&#8221; (FS) discharge pattern, an axon densely covering the cell body layer, and expression of the calcium-binding protein parvalbumin (PV)10,11. These interneurons display large postsynaptic inhibitory currents, as well as prominent presynaptic modulation of their synaptic output, in response to GABABR activation12. The combination of techniques described here can be applied equally well to investigate intrinsic or synaptic mechanisms in a variety of other identified neuron types.

<table border="0" cellpadding="0" cellspacing="0" width="725">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:175px;">Name</td>
			<td style="width:148px;">Company</td>
			<td style="width:152px;">Catalog Number</td>
			<td style="width:251px;">Comments</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:175px;">Transgenic vGAT-venus rats</td>
			<td style="width:148px;">-</td>
			<td style="width:152px;">-</td>
			<td style="width:251px;">see Uematsu et al., 2008</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:175px;">Venus (515&#160;nm) goggles</td>
			<td style="width:148px;">BLS Ltd., Hungary</td>
			<td style="width:152px;">-</td>
			<td style="width:251px;">-</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:175px;">Dissection tools</td>
			<td style="width:148px;">i.e. FST</td>
			<td style="width:152px;">-</td>
			<td style="width:251px;">For brain removal</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:175px;">Vibratome</td>
			<td style="width:148px;">Leica</td>
			<td style="width:152px;">VT1200S</td>
			<td style="width:251px;">Or other high end vibratome with minimal vertical oscillation</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:175px;">Slice holding chambers</td>
			<td style="width:148px;">-</td>
			<td style="width:152px;">-</td>
			<td style="width:251px;">Custom-made in lab</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:175px;">Upright IR-DIC microscope</td>
			<td style="width:148px;">Olympus, Japan</td>
			<td style="width:152px;">BX50WI</td>
			<td style="width:251px;">With micromanipulator system; i.e. Luigs and Neumann, Kleindiek etc.</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:175px;">CCD camera</td>
			<td style="width:148px;">Till Photonics</td>
			<td style="width:152px;">VX55</td>
			<td style="width:251px;"></td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:175px;">505 nm LED system</td>
			<td style="width:148px;">Cairn Research</td>
			<td style="width:152px;">OptiLED system</td>
			<td style="width:251px;">Or mercury lamp or other LED system i.e. CooLED.&#160;</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:175px;">Multiclamp 700B&#160;</td>
			<td style="width:148px;">Axon Instruments</td>
			<td style="width:152px;"></td>
			<td style="width:251px;">Alternatively 2x Axopatch 200B amplifiers&#160;</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:175px;">WinWCP acquisition software</td>
			<td style="width:148px;">John Dempster, Strathclyde University</td>
			<td style="width:152px;">-</td>
			<td style="width:251px;">Any quality acquisition software could be used, i.e. EPHUS, pClamp, Igor etc.&#160;</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:175px;">Electrode Puller</td>
			<td style="width:148px;">Sutter</td>
			<td style="width:152px;">P-97</td>
			<td style="width:251px;">Used with box-filament</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:175px;">Borosilicate pipette glass</td>
			<td style="width:148px;">Hilgenberg, Germany</td>
			<td style="width:152px;">1405020</td>
			<td style="width:251px;">2&#160;mm outer, 1&#160;mm inner diameter, no filament</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:175px;">Peristaltic pump</td>
			<td style="width:148px;">Gilson</td>
			<td style="width:152px;">Minipuls</td>
			<td style="width:251px;">Other pumps or gravity feed could be used instead</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:175px;">Digital Thermometer</td>
			<td style="width:148px;">-</td>
			<td style="width:152px;">-</td>
			<td style="width:251px;">Custom made</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:175px;">Digital Manometer</td>
			<td style="width:148px;">Supertech, Hungary</td>
			<td style="width:152px;">-</td>
			<td style="width:251px;"></td>
		</tr>
		<tr height="17">
			<td height="34" rowspan="2" style="height:34px;width:175px;">Isolated constant voltage stimulator</td>
			<td rowspan="2" style="width:148px;">Digitimer, Cambridge</td>
			<td rowspan="2" style="width:152px;">DS-2A</td>
			<td rowspan="2" style="width:251px;">-</td>
		</tr>
		<tr height="17">
		</tr>
		<tr height="17">
			<td height="34" rowspan="2" style="height:34px;width:175px;"><a name="RANGE!A19:D34">Biocytin</a></td>
			<td rowspan="2" style="width:148px;">Invitrogen</td>
			<td rowspan="2" style="width:152px;">B1592</td>
			<td rowspan="2">Otherwise known as &#949;-Biotinoyl-L-Lysine&#160;</td>
		</tr>
		<tr height="17">
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:175px;">DL-AP5(V) disodium salt</td>
			<td style="width:148px;">Abcam Biochemicals</td>
			<td style="width:152px;">ab120271</td>
			<td style="width:251px;"></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:175px;">DNQX disodium salt</td>
			<td style="width:148px;">Abcam Biochemicals</td>
			<td style="width:152px;">ab120169</td>
			<td style="width:251px;">Alternatively NBQX or CNQX</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:175px;">Gabazine (SR95531)</td>
			<td style="width:148px;">Abcam Biochemicals</td>
			<td style="width:152px;">ab120042</td>
			<td style="width:251px;">Alternatively bicuculline methiodide</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:175px;">R-Baclofen</td>
			<td style="width:148px;">Abcam Biochemicals</td>
			<td style="width:152px;">ab120325</td>
			<td style="width:251px;"></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:175px;">CGP-55,845 hydrochloride</td>
			<td style="width:148px;">Tocris</td>
			<td style="width:152px;">1248</td>
			<td style="width:251px;"></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:175px;">Streptavidin 647</td>
			<td style="width:148px;">Invitrogen</td>
			<td style="width:152px;">S32357</td>
			<td style="width:251px;"></td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:175px;">anti-PV mouse monoclonal antibody</td>
			<td style="width:148px;">Swant, Switzerland</td>
			<td style="width:152px;">235</td>
			<td style="width:251px;">Working concentration 1:5000-1:10,000</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:175px;">anti-mouse secondary antibody&#160;</td>
			<td style="width:148px;">Invitrogen</td>
			<td style="width:152px;">A11030</td>
			<td style="width:251px;">If using Venus or GFP rodent using a red-channel (i.e. 546 nm) is advisable.</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:175px;">Normal Goat Serum</td>
			<td style="width:148px;">Vector Labs</td>
			<td style="width:152px;">S-1000</td>
			<td style="width:251px;"></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:175px;">Microscopy slides</td>
			<td style="width:148px;">-</td>
			<td style="width:152px;">-</td>
			<td style="width:251px;">Any high quality brand&#160;</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:175px;">Glass coverslips</td>
			<td style="width:148px;">-</td>
			<td style="width:152px;">-</td>
			<td style="width:251px;">Usually 22 x 22 mm</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:175px;">Agar spacers</td>
			<td style="width:148px;">-</td>
			<td style="width:152px;">-</td>
			<td style="width:251px;">Agar block, cut on vibratome to 300 &#956;m</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:175px;">Laser scanning confocal microscope</td>
			<td style="width:148px;">Olympus, Japan</td>
			<td style="width:152px;">Fluoview FV1000</td>
			<td style="width:251px;">Or other comparable system</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:175px;">Fiji (Fiji is just ImageJ)</td>
			<td>http://fiji.sc/Fiji</td>
			<td style="width:152px;">-</td>
			<td style="width:251px;">See Schindelin et al., 2012</td>
		</tr>
	</tbody>
</table>

whole-cell patch-clamp recordings from morphologically- and neurochemically-identified hippocampal interneurons

GABAergic inhibitory interneurons play a central role within neuronal circuits of the brain. Interneurons comprise a small subset of the neuronal population (10-20%), but show a high level of physiological, morphological, and neurochemical heterogeneity, reflecting their diverse functions. Therefore, investigation of interneurons provides important insights into the organization principles and function of neuronal circuits. This, however, requires an integrated physiological and neuroanatomical approach for the selection and identification of individual interneuron types. Whole-cell patch-clamp recording from acute brain slices of transgenic animals, expressing fluorescent proteins under the promoters of interneuron-specific markers, provides an efficient method to target and electrophysiologically characterize intrinsic and synaptic properties of specific interneuron types. Combined with intracellular dye labeling, this approach can be extended with post-hoc morphological and immunocytochemical analysis, enabling systematic identification of recorded neurons. These methods can be tailored to suit a broad range of scientific questions regarding functional properties of diverse types of cortical neurons.

Provided that slice quality is appreciably good, recording from both CA1 PCs and FS-INs can be achieved with minimal difficulty. The transgenic rat line expressing Venus / YFP under the vGAT promoter13 does not unequivocally identify FS-INs, or indeed BCs. However recordings from INs in and around str. pyramidale, where the density of FS-INs is typically high1, results in a high probability of selecting FS-INs (Figure 2B). FS-INs can be distinguished by their characteristic...

Watch this Scientific Journal Video about Whole-cell Patch-clamp Recordings from Morphologically- and Neurochemically-identified Hippocampal Interneurons at JoVE.com

Whole-cell Patch-clamp Recordings from Morphologically- and Neurochemically-identified Hippocampal Interneurons

Cortical networks are controlled by a small, but diverse set of inhibitory interneurons. Functional investigation of interneurons therefore requires targeted recording and rigorous identification. Described here is a combined approach involving whole-cell recordings from single or synaptically-coupled pairs of neurons with intracellular labeling, post-hoc morphological and immunocytochemical analysis.

GABAergic inhibitory interneurons play a central role within neuronal circuits of the brain. Interneurons comprise a small subset of the neuronal ...

whole-cell-patch-clamp-recordings-from-morphologically

Research

JoVE Journal

Neuroscience

24.3K Views.  Charité Universitätmedizin. Cortical networks are controlled by a small, but diverse set of inhibitory interneurons. Functional investigation of interneurons therefore requires targeted recording and rigorous identification. Described here is a combined approach involving whole-cell recordings from single or synaptically-coupled pairs of neurons with intracellular labeling, post-hoc morphological and immunocytochemical analysis.

Video: Whole-cell Patch-clamp Recordings from Morphologically- and Neurochemically-identified Hippocampal Interneurons

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 ...

Paired Patch Clamp Recordings from Motor-neuron and Target Skeletal Muscle in Zebrafish

Larval zebrafish represent the first vertebrate model system to allow simultaneous patch clamp recording from a spinal motor-neuron and target muscle. This is a direct consequence of the accessibility to both cell types and ability to visually distinguish the single segmental CaP motor-neuron on the basis of morphology and location. This video demonstrates the microscopic methods used to identify a CaP motor-neuron and target muscle cells as well as the methodologies for recording from each cell type. Identification of the CaP motor-neuron type is confirmed by either dye filling or by the biophysical features such as action potential waveform and cell input resistance. Motor-neuron recordings routinely last for one hour permitting long-term recordings from multiple different target muscle cells. Control over the motor-neuron firing pattern enables measurements of the frequency-dependence of synaptic transmission at the neuromuscular junction. Owing to a large quantal size and the low noise provided by whole cell voltage clamp, all of the unitary events can be resolved in muscle. This feature permits study of basic synaptic properties such as release properties, vesicle recycling, as well as synaptic depression and facilitation. The advantages offered by this in vivo preparation eclipse previous neuromuscular model systems studied wherein the motor-neurons are usually stimulated by extracellular electrodes and the muscles are too large for whole cell patch clamp. The zebrafish preparation is amenable to combining electrophysiological analysis with a wide range of approaches including transgenic lines, morpholino knockdown, pharmacological intervention and in vivo imaging. These approaches, coupled with the growing number of neuromuscular disease models provided by mutant lines of zebrafish, open the door for new understanding of human neuromuscular disorders.

Larval zebrafish represent the first vertebrate model system to allow simultaneous patch clamp recording from a spinal motor-neuron and target skeletal muscle. This video demonstrates the microscopic methods used to identify a segmental CaP motor-neuron and target muscle cells as well as the methodologies for recording from each cell type.

Larval zebrafish represent the first vertebrate model system to allow simultaneous patch clamp recording from a spinal motor-neuron and target muscle.  ...

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  ...

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 ...

Paired Whole Cell Recordings in Organotypic Hippocampal Slices

Pair recordings involve simultaneous whole cell patch clamp recordings from two synaptically connected neurons, enabling not only direct electrophysiological characterization of the synaptic connections between individual neurons, but also pharmacological manipulation of either the presynaptic or the postsynaptic neuron. When carried out in organotypic hippocampal slice cultures, the probability that two neurons are synaptically connected is significantly increased. This preparation readily enables identification of cell types, and the neurons maintain their morphology and properties of synaptic function similar to that in native brain tissue. A major advantage of paired whole cell recordings is the highly precise information it can provide on the properties of synaptic transmission and plasticity that are not possible with other more crude techniques utilizing extracellular axonal stimulation. Paired whole cell recordings are often perceived as too challenging to perform. While there are challenging aspects to this technique, paired recordings can be performed by anyone trained in whole cell patch clamping provided specific hardware and methodological criteria are followed. The probability of attaining synaptically connected paired recordings significantly increases with healthy organotypic slices and stable micromanipulation allowing independent attainment of pre- and postsynaptic whole cell recordings. While CA3-CA3 pyramidal cell pairs are most widely used in the organotypic slice hippocampal preparation, this technique has also been successful in CA3-CA1 pairs and can be adapted to any neurons that are synaptically connected in the same slice preparation. In this manuscript we provide the detailed methodology and requirements for establishing this technique in any laboratory equipped for electrophysiology.

Pair recordings are simultaneous whole cell patch clamp recordings from two synaptically connected neurons, enabling precise electrophysiological and pharmacological characterization of the synapses between individual neurons. Here we describe the detailed methodology and requirements for establishing this technique in organotypic hippocampal slice cultures in any laboratory equipped for electrophysiology.

Pair recordings involve simultaneous whole cell patch clamp recordings from two synaptically connected neurons, enabling not only direct ...

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.

Over the past decade, channelrhodopsins became indispensable in neuroscientific research where they are used as tools to non-invasively manipulate ...

Auditory Brainstem Response and Outer Hair Cell Whole-cell Patch Clamp Recording in Postnatal Rats

The outer hair cell is one of the two types of sensory hair cells in the mammalian cochlea. They alter their cell length with the receptor potential to amplify the weak vibration of low-level sound signal. The morphology and electrophysiological property of outer hair cells (OHCs) develop in early postnatal ages. The maturation of outer hair cell may contribute to the development of the auditory system. However, the process of OHCs development is not well studied. This is partly because of the difficulty to measure their function by an electrophysiological approach. With the purpose of developing a simple method to address the above issue, here we describe a step-by-step protocol to study the function of OHCs in acutely dissociated cochlea from postnatal rats. With this method, we can evaluate the cochlear response to pure tone stimuli and examine the expression level and function of the motor protein prestin in OHCs. This method can also be used to investigate the inner hair cells (IHCs).

This protocol describes methods to record the auditory brainstem response from postnatal rat pups. To examine the functional development of outer hair cells, the experimental procedure of whole-cell patch clamp recording in isolated outer hair cells is described step-by-step.

The outer hair cell is one of the two types of sensory hair cells in the mammalian cochlea. They alter their cell length with the receptor potential to ...