Financial support from the Flanders Research Foundation FWO (contract n. 12C9112N to DL), the 7th Framework Programme of the European Commission (Marie Curie Network &#8220;C7&#8221;, contract n. 238214; ICT Future Emerging Technology &#8220;ENLIGHTENMENT&#8221; project, contract n. 306502), the Interuniversity Attraction Poles Program initiated by the Belgian Science Policy Office (contract n. IUAP-VII/20), and the University of Antwerp is kindly acknowledged.

The protocol described here complies with the recommendations and guidelines of the Ethics Committee of the Department of Biomedical Sciences of the University of Antwerp. This protocol requires the preparation of non-sentient material from the explanted brain of juvenile Wistar rats, obtained by approved humane euthanasia techniques.
1. Equipment Preparation
<ol>
	<li>Install and configure the data acquisition and stimulation system.
	<ol>
		<li>Use a personal computer (PC) equipped with a ...

<ol>
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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=Closed-loop+optogenetic+control+of+thalamus+as+a+tool+for+interrupting+seizures+after+cortical+injury.">Closed-loop optogenetic control of thalamus as a tool for interrupting seizures after cortical injury.</a> Nature neuroscience. 16 (1), 64-70 (2013).</li><li>Wallach, A., Eytan, D., Gal, A., Zrenner, C., Marom, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuronal+response+clamp.">Neuronal response clamp.</a> Frontiers in neuroengineering. 3 (April), 3 (2011).</li><li>Linaro, D., Couto, J., Giugliano, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Command-line+cellular+electrophysiology+for+conventional+and+real-time+closed-loop+experiments.">Command-line cellular electrophysiology for conventional and real-time closed-loop experiments.</a> Journal of neuroscience. 230, 5-19 (2014).</li><li>Sharp, A., O&#8217;Neil, M., Abbott, L. 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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluctuating+synaptic+conductances+recreate+in+vivo-like+activity+in+neocortical+neurons.">Fluctuating synaptic conductances recreate in vivo-like activity in neocortical neurons.</a> Neuroscience. 107 (1), 13-24 (2001).</li><li>Fellous, J. -. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+Persistent+Activity+by+Background+Inhibition+in+an+In+Vitro+Model+of+a+Cortical+Microcircuit.">Regulation of Persistent Activity by Background Inhibition in an In Vitro Model of a Cortical Microcircuit.</a> Cerebral Cortex. 13 (11), 1232-1241 (2003).</li><li>Gal, A., Eytan, D., Wallach, A., Sandler, M., Schiller, J., Marom, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamics+of+excitability+over+extended+timescales+in+cultured+cortical+neurons.+The+Journal+of+neuroscience.">Dynamics of excitability over extended timescales in cultured cortical neurons. The Journal of neuroscience.</a> the official journal of the Society for Neuroscience. 30 (48), 16332-16342 (2010).</li><li>Wang, Y., Toledo-Rodriguez, 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=Anatomical,+physiological+and+molecular+properties+of+Martinotti+cells+in+the+somatosensory+cortex+of+the+juvenile+rat.">Anatomical, physiological and molecular properties of Martinotti cells in the somatosensory cortex of the juvenile rat.</a> The Journal of physiology. 561 (Pt 1), 65-90 (2004).</li><li>Wang, Y., Gupta, A., Toledo-Rodriguez, M., Wu, C. Z., Markram, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anatomical,+physiological,+molecular+and+circuit+properties+of+nest+basket+cells+in+the+developing+somatosensory+cortex).">Anatomical, physiological, molecular and circuit properties of nest basket cells in the developing somatosensory cortex).</a> Cerebral cortex (New York, N.Y). 12 (4), 395-410 (1991).</li><li>Brette, R., Piwkowska, Z., 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=High-resolution+intracellular+recordings+using+a+real-time+computational+model+of+the+electrode.">High-resolution intracellular recordings using a real-time computational model of the electrode.</a> Neuron. 59 (3), 379-391 (2008).</li><li>Rutishauser, U., Kotowicz, A., Laurent, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+method+for+closed-loop+presentation+of+sensory+stimuli+conditional+on+the+internal+brain-state+of+awake+animals.">A method for closed-loop presentation of sensory stimuli conditional on the internal brain-state of awake animals.</a> Journal of neuroscience. 215 (1), 139-155 (2013).</li><li>Margrie, T., Brecht, M., Sakmann, B. <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,+low-resistance,+whole-cell+recordings+from+neurons+in+the+anaesthetized+and+awake+mammalian+brain.">In vivo, low-resistance, whole-cell recordings from neurons in the anaesthetized and awake mammalian brain.</a> Pflugers Archiv European Journal of Physiology. 444 (4), 491-498 (2002).</li><li>Graham, L., Schramm, A. <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+Dynamic-Clamp+Manipulation+of+Extrinsic+and+Intrinsic+Conductances:+Functional+Roles+of+Shunting+Inhibition+and+I+BK+in+Rat+and+Cat+Cortex.">In Vivo Dynamic-Clamp Manipulation of Extrinsic and Intrinsic Conductances: Functional Roles of Shunting Inhibition and I BK in Rat and Cat Cortex.</a> Dynamic Clamp: From Principles to Applications. , (2008).</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=.">.</a> Single-channel recording. , (1995).</li><li>Molleman, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Patch Clamping. , (2002).</li><li>Davie, J. 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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reliability+of+spike+timing+in+neocortical+neurons.">Reliability of spike timing in neocortical neurons.</a> Science. 268 (5216), 1503-1506 (1995).</li><li>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=Action+potential+threshold+of+hippocampal+pyramidal+cells+in+vivo+is+increased+by+recent+spiking+activity.">Action potential threshold of hippocampal pyramidal cells in vivo is increased by recent spiking activity.</a> Neuroscience. 105 (1), 121-130 (2001).</li><li>Koch, C., Segev, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Methods in Neuronal Modeling: From Synapses to Networks. , (1988).</li><li>Silberberg, G., Markram, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Disynaptic+inhibition+between+neocortical+pyramidal+cells+mediated+by+Martinotti+cells.">Disynaptic inhibition between neocortical pyramidal cells mediated by Martinotti cells.</a> Neuron. 53 (5), 735-746 (2007).</li><li>Berger, T. K., Silberberg, G., Perin, R., Markram, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Brief+bursts+self-inhibit+and+correlate+the+pyramidal+network.">Brief bursts self-inhibit and correlate the pyramidal network.</a> PLoS biology. 8 (9), (2010).</li><li>Tsodyks, M., Pawelzik, K., Markram, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neural+networks+with+dynamic+synapses.">Neural networks with dynamic synapses.</a> Neural computation. 10 (4), 821-835 (1998).</li><li>Kapfer, C., Glickfeld, L. 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In this text a full protocol for the implementation of real-time, closed-loop single cell electrophysiological experiments was described, using the patch clamp technique and a recently developed software toolbox called LCG. To optimize the quality of the recordings it is crucial that the recording setup be properly grounded, shielded and vibration free: this ensures stable and lasting whole-cell access to the cell, which, together with the possibility of automating entire sections of the stimulation protocols, allows for...

In recent years, cellular electrophysiology has evolved from the traditional open-loop paradigm employed in voltage and current clamp experiments to modern closed-loop protocols. The best known closed-loop technique is perhaps the dynamic clamp6,7, which enabled the synthetic injection of artificial voltage-gated ion channels to determine the neuronal membrane voltage8, the in-depth study of the effects of non-deterministic flickering on ion channels on neuronal response dynamics9, as well as the recreation in vitro of realistic in vivo-like synaptic background activity10.
Other closed-loop paradigms that have been proposed include the reactive clamp11, to study in vitro the generation of self-sustained persistent activity, and the response clamp4,12, to investigate the cellular mechanisms underlying neuronal excitability.
Here we describe a powerful framework that allows applying a variety of closed-loop electrophysiological protocols in the context of whole-cell patch clamp recordings performed in acute brain slices. We show how to record somatic membrane voltage by means of patch clamp recordings in pyramidal neurons from the somatosensory cortex of juvenile rats and apply three different closed-loop protocols using LCG, a command-line-based software toolbox developed in the laboratory of Theoretical Neurobiology and Neuroengineering.
Briefly, the described protocols are, first&#160;the automated injection of a series of current clamp stimulus waveforms, relevant for the characterization of a large set of active and passive membrane properties. These have been suggested to capture the electrophysiological phenotype of a cell in terms of its response properties to a stereotyped series of stimulus waveforms. Known as the e-code of a cell (e.g., see&#160;13,14), such a collection of electrical responses is used by several laboratories to objectively classify neurons on the basis of their electrical properties. This includes the analysis of the stationary input-output transfer relationship (f-I curve), by an innovative technique that involves the closed-loop, real-time control of the rate of firing by means of a proportional-integral-derivative (PID) controller, second the recreation of realistic in vivo-like&#160;background synaptic activity in in vitro preparations10 and , third the artificial connection in real-time of two simultaneously recorded pyramidal neurons by means of a virtual GABAergic interneuron, which is simulated by the computer.
Additionally, LCG implements the technique known as Active Electrode Compensation (AEC)15, which allows implementing dynamic clamp protocols using a single electrode. This allows compensating undesired effects (artifacts) of the recording electrode that arise when it is used for delivering intracellular stimuli. The method is based on a non-parametric estimate of the equivalent electrical properties of the recording circuit.
The techniques and experimental protocols described in this paper can be readily applied in conventional open-loop voltage and current clamp experiments and can be extended to other preparations, such as extracellular4,16 or intracellular recordings in vivo17,18. The careful assembly of the setup for whole cell patch clamp electrophysiology is a very important step for stable, high quality recordings. In the following we assume that such an experimental setup is already available to the experimenter, and focus our attention on describing the usage of LCG. The reader is pointed to 19&#8211;22 for additional tips about optimization and debugging.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Tissue slicer</td>
			<td>Leica</td>
			<td>VT-1000S</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipette puller</td>
			<td>Sutter</td>
			<td>P-97</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipettes</td>
			<td>WPI</td>
			<td>1B150F-4</td>
			<td>1.5/0.84 mm OD/ID, with filament</td>
		</tr>
		<tr>
			<td>Vibration isolation table</td>
			<td>TMC</td>
			<td>20 Series</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope</td>
			<td>Leica</td>
			<td>DMLFS</td>
			<td>40X Immersion Objective</td>
		</tr>
		<tr>
			<td>Manipulators</td>
			<td>Scientifica</td>
			<td>PatchStar</td>
			<td></td>
		</tr>
		<tr>
			<td>Amplifiers</td>
			<td>Axon Instruments</td>
			<td>MultiClamp 700B</td>
			<td>Computer controlled</td>
		</tr>
		<tr>
			<td>Data acquisition card</td>
			<td>National Instruments</td>
			<td>PCI-6229</td>
			<td>Supported by Comedi Linux Drivers</td>
		</tr>
		<tr>
			<td>Desktop computer</td>
			<td>Dell</td>
			<td>Optiplex 7010 Tower</td>
			<td>OS: real-time Linux</td>
		</tr>
		<tr>
			<td>Oscilloscopes</td>
			<td>Tektronix</td>
			<td>TDS-1002</td>
			<td></td>
		</tr>
		<tr>
			<td>Perfusion Pump</td>
			<td>Gibson</td>
			<td>MINIPULS3</td>
			<td>Used with R4 Pump head (F117606)</td>
		</tr>
		<tr>
			<td>Temperature controller</td>
			<td>Multichannel Systems</td>
			<td>TC02</td>
			<td>PH01 Perfusion Cannula</td>
		</tr>
		<tr>
			<td>Manometer</td>
			<td>Testo</td>
			<td>510</td>
			<td>Optional</td>
		</tr>
		<tr>
			<td>Incubator</td>
			<td>Memmert</td>
			<td>WB14</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sigma</td>
			<td>71376</td>
			<td>ACSF</td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Sigma</td>
			<td>P9541</td>
			<td>ACSF, ICS</td>
		</tr>
		<tr>
			<td>NaH2PO4</td>
			<td>Sigma</td>
			<td>S3139</td>
			<td>ACSF</td>
		</tr>
		<tr>
			<td>NaHCO3</td>
			<td>Sigma</td>
			<td>S6014</td>
			<td>ACSF</td>
		</tr>
		<tr>
			<td>CaCl2</td>
			<td>Sigma</td>
			<td>C1016</td>
			<td>ACSF</td>
		</tr>
		<tr>
			<td>MgCl2</td>
			<td>Sigma</td>
			<td>M8266</td>
			<td>ACSF</td>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>Sigma</td>
			<td>G7528</td>
			<td>ACSF</td>
		</tr>
		<tr>
			<td>K-Gluconate</td>
			<td>Sigma</td>
			<td>G4500</td>
			<td>ICS</td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Sigma</td>
			<td>H3375</td>
			<td>ICS</td>
		</tr>
		<tr>
			<td>Mg-ATP</td>
			<td>Sigma</td>
			<td>A9187</td>
			<td>ICS</td>
		</tr>
		<tr>
			<td>Na2-GTP</td>
			<td>Sigma</td>
			<td>51120</td>
			<td>ICS</td>
		</tr>
		<tr>
			<td>Na2-Phosphocreatine</td>
			<td>Sigma</td>
			<td>P7936</td>
			<td>ICS</td>
		</tr>
	</tbody>
</table>

real-time electrophysiology: using closed-loop protocols to probe neuronal dynamics and beyond

Experimental neuroscience is witnessing an increased interest in the development and application of novel and often complex, closed-loop protocols, where the stimulus applied depends in real-time on the response of the system. Recent applications range from the implementation of virtual reality systems for studying motor responses both in mice1 and in zebrafish2, to control of seizures following cortical stroke using optogenetics3. A key advantage of closed-loop techniques resides in the capability of probing higher dimensional properties that are not directly accessible or that depend on multiple variables, such as neuronal excitability4 and reliability, while at the same time maximizing the experimental throughput. In this contribution and in the context of cellular electrophysiology, we describe how to apply a variety of closed-loop protocols to the study of the response properties of pyramidal cortical neurons, recorded intracellularly with the patch clamp technique in acute brain slices from the somatosensory cortex of juvenile rats. As no commercially available or open source software provides all the features required for efficiently performing the experiments described here, a new software toolbox called LCG5 was developed, whose modular structure maximizes reuse of computer code and facilitates the implementation of novel experimental paradigms. Stimulation waveforms are specified using a compact meta-description and full experimental protocols are described in text-based configuration files. Additionally, LCG has a command-line interface that is suited for repetition of trials and automation of experimental protocols.

In the previous sections, we have described how to use the software toolbox LCG to characterize the electrophysiological properties of L5 pyramidal cells and to recreate in vivo-like synaptic activity in a slice preparation. The use of a command-line interface and semi-automated protocol favor the reproducibility and efficiency of the experiment, which can have a large impact on the output and quality of the data produced. Additionally, since the data is saved in a consistent way, it is easy to extend the analys...

Watch this Scientific Journal Video about Real-time Electrophysiology: Using Closed-loop Protocols to Probe Neuronal Dynamics and Beyond at JoVE.com

Real-time Electrophysiology: Using Closed-loop Protocols to Probe Neuronal Dynamics and Beyond

Closed-loop protocols are becoming increasingly widespread in modern day electrophysiology. We present a simple, versatile and inexpensive way to perform complex electrophysiological protocols in cortical pyramidal neurons in vitro, using a desktop computer and a digital acquisition board.

Experimental neuroscience is witnessing an increased interest in the development and application of novel and often complex, closed-loop protocols, where ...

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11.3K vistas.  University of Antwerp. Closed-loop protocols are becoming increasingly widespread in modern day electrophysiology. We present a simple, versatile and inexpensive way to perform complex electrophysiological protocols in cortical pyramidal neurons in vitro, using a desktop computer and a digital acquisition board. 