We thank the Deutsche Forschungsgemeinschaft (DFG), KFO 247, for funding our study.

Experimental procedures were conducted in accordance with the German Animal Welfare Act (last revised in 2014) and European regulations (2010/63/EU). Experiments were approved by the local animal welfare authority (LaGeSo, Berlin), and conformed to local department and international guidelines.
NOTE: In the presented method two models of electrodes are used to record from the hyperdirect cortico-basal ganglia pathway that connects the primary motor cortex (M1) with the subthalamic nucleus (STN...

<ol>
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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=Increased+efficacy+of+the+6-hydroxydopamine+lesion+of+the+median+forebrain+bundle+in+small+rats,+by+modification+of+the+stereotaxic+coordinates.">Increased efficacy of the 6-hydroxydopamine lesion of the median forebrain bundle in small rats, by modification of the stereotaxic coordinates.</a> J Neurosci Methods. 200 (1), 29-35 (2011).</li><li>Hadar, 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=Rats+overexpressing+the+dopamine+transporter+display+behavioral+and+neurobiological+abnormalities+with+relevance+to+repetitive+disorders.">Rats overexpressing the dopamine transporter display behavioral and neurobiological abnormalities with relevance to repetitive disorders.</a> Sci Rep. 6, 39145 (2016).</li><li>Parr-Brownlie, L. C., Poloskey, S. L., Bergstrom, D. A., Walters, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Parafascicular+thalamic+nucleus+activity+in+a+rat+model+of+Parkinson's+disease.">Parafascicular thalamic nucleus activity in a rat model of Parkinson's disease.</a> Exp Neurol. 217 (2), 269-281 (2009).</li><li>Steriade, M., Nunez, A., Amzica, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+slow+(&lt;+1+Hz)+oscillation+of+neocortical+neurons+in+vivo:+depolarizing+and+hyperpolarizing+components.">A novel slow (&lt; 1 Hz) oscillation of neocortical neurons in vivo: depolarizing and hyperpolarizing components.</a> J Neurosci. 13 (8), 3252-3265 (1993).</li><li>Maggi, C. A., Meli, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Suitability+of+urethane+anesthesia+for+physiopharmacological+investigations+in+various+systems.+Part+1:+General+considerations.">Suitability of urethane anesthesia for physiopharmacological investigations in various systems. Part 1: General considerations.</a> Experientia. 42 (2), 109-114 (1986).</li><li>Goldberg, J. A., Kats, S. S., Jaeger, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Globus+pallidus+discharge+is+coincident+with+striatal+activity+during+global+slow+wave+activity+in+the+rat.">Globus pallidus discharge is coincident with striatal activity during global slow wave activity in the rat.</a> J Neurosci. 23 (31), 10058-10063 (2003).</li><li>Karain, B., Xu, D., Bellone, J. A., Hartman, R. E., Shi, W. X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rat+globus+pallidus+neurons:+functional+classification+and+effects+of+dopamine+depletion.">Rat globus pallidus neurons: functional classification and effects of dopamine depletion.</a> Synapse. 69 (1), 41-51 (2015).</li><li>Paasonen, 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=Comparison+of+seven+different+anesthesia+protocols+for+nicotine+pharmacologic+magnetic+resonance+imaging+in+rat.">Comparison of seven different anesthesia protocols for nicotine pharmacologic magnetic resonance imaging in rat.</a> Eur Neuropsychopharmacol. 26 (3), 518-531 (2016).</li><li>Mahmud, M., Vassanelli, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Processing+and+Analysis+of+Multichannel+Extracellular+Neuronal+Signals:+State-of-the-Art+and+Challenges.">Processing and Analysis of Multichannel Extracellular Neuronal Signals: State-of-the-Art and Challenges.</a> Front Neurosci. 10, 248 (2016).</li><li>Hadar, 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=Altered+neural+oscillations+and+elevated+dopamine+levels+in+the+reward+pathway+during+alcohol+relapse.">Altered neural oscillations and elevated dopamine levels in the reward pathway during alcohol relapse.</a> Behav Brain Res. 316, 131-135 (2017).</li><li>Voget, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Altered+local+field+potential+activity+and+serotonergic+neurotransmission+are+further+characteristics+of+the+Flinders+sensitive+line+rat+model+of+depression.">Altered local field potential activity and serotonergic neurotransmission are further characteristics of the Flinders sensitive line rat model of depression.</a> Behav Brain Res. 291, 299-305 (2015).</li></ol>

In the present study, the method is demonstrated how to record extracellular electrophysiological signals simultaneously from multiple sites of a given network using the example of the hyperdirect cortico-basal ganglia pathway that connects the M1 with the STN and SNr in rodents.
A critical step in the recording of small subcortical structures such as the STN is the precisely guided insertion of the recording electrodes into the target. In the presented method, taking care of two crucial steps...

Recent cumulative evidence on different neuropsychiatric disorders such as Parkinson&#180;s disease (PD) and schizophrenia strongly suggests that their pathophysiology is based on a critical dysfunction of extended neuronal circuits that often involve cortical and subcortical structures1,2,3. According to this theory, the clinical manifestations of the diseases arise as a consequence of an impaired information processing capacity of a network of cells instead of single cells or specific neuronal elements1,2,3. In order to enhance the understanding of this complex group of neuropsychiatric diseases and to find new treatment options, it is mandatory to characterize the neuronal dynamics of those disordered networks in human patients and in animal models in great detail. An excellent method to study large-scale networks in living subjects is multi-site electrophysiological recordings of extracellular potentials4. Using this method, it is possible to simultaneously assess local field potentials (LFPs), that primarily represent the temporal summation of excitatory and inhibitory postsynaptic currents and multi-unit activity (MUA), that is generated by presynaptic potentials5. The recording of extracellular potentials has several advantages over alternative methods to study networks, e.g., functional magnetic resonance imaging and calcium imaging, because it provides a higher temporal and spatial resolution and because it is not dependent on genetically engineered organisms5. However, the use of extracellular in vivo recordings is limited since it is an invasive technique that cannot be universally applied.
In vivo electrophysiological recordings can be performed in awake as well as in anesthetized animals6. Both methods are accompanied by specific pros and cons. Studies in awake animals allow the recording of brain signals during the performance of defined behavioral tasks, but are prone to movement related and other artifacts7,8. Recordings in anesthetized animals on the other hand offer the opportunity to assess LFPs and MUA with a minimum of artifacts at highly defined cortical synchronization states, but the results also differ to some extent to what can be found in awake subjects9,10,11.
In recent years, it has been demonstrated that the sampling of LFPs is especially useful to delineate pathological changes of network activity. A prominent example of this is research on the pathophysiology of PD in human patients and animal models of the disease, where it could be shown that enhanced beta oscillations in the cortico-basal ganglia loop are linked to parkinsonian motor symptoms12,13. As a consequence of this line of research, it is currently investigated if beta oscillations could be used as an online feedback biomarker for closed-loop deep brain stimulation14,15.
In the present study, a detailed description of acute multi-site in vivo electrophysiological recordings of LFPs and MUA in rats anesthetized with urethane is provided. It is demonstrated how a complete network, such as the hyperdirect cortico-basal ganglia pathway can be characterized electrophysiologically using standard and customized electrodes and how those electrodes can be build. It is especially emphasized how a precise targeting of basal ganglia nuclei can be achieved by combining stereotactic surgery together with the online registration of MUAs.

<table>
	<tbody>
		<tr>
			<td>Ag/AgCl custom epidural electrodes</td>
			<td>Goodfellow GmbH 
			D-61213 Bad Nauheim, Germany 
			info@goodfellow.com</td>
			<td>Product-ID AG005127 for 99.99% silver wire</td>
			<td>Ag/AgCl electrodes will allow for better signal quality, but may only be used in acute experiments. Possible replacement: Stainless steel electrodes</td>
		</tr>
		<tr>
			<td>Stereotaxic holder with acrylic block</td>
			<td>David Kopf Instruments, 
			7324 Elmo Street, Tujunga, CA 91042, USA</td>
			<td>Product ID Model 1770 Standard Electrode Holder</td>
			<td>Make sure the acrylic block has recesses which suit the electrode setup for the desired target. Acrylic blocks can easily be modified with a file to obtain the desired configuration. Possible replacement: Self-constructed electrode holders</td>
		</tr>
		<tr>
			<td>Tungsten microwire electrodes 1.5 M&#937; impedance</td>
			<td>Microprobes.com 
			18247-D Flower Hill Way&#160; Gaithersburg, Maryland, 20879 USA</td>
			<td>Product-ID WE3ST31.5A5-250um</td>
			<td>The 1.5 M&#937; is necessary to record MUA and LFP at the same time. Possible replacement: Microelectrodes of different materials can be used. The electrodes have to be straight, robust and as thin as possible.</td>
		</tr>
		<tr>
			<td>Rat alignment tool</td>
			<td>David Kopf Instruments, 
			7324 Elmo Street, Tujunga, CA 91042, USA</td>
			<td>Product ID Model 944 Rat Alignment Tool</td>
			<td>Allows the exact orientation of the brain to match stereotaxic atlases. Possible replacement: Stereotaxic holder with a cannula</td>
		</tr>
		<tr>
			<td>Two-component dental acrylic</td>
			<td>Associated Dental Products Ltd. 
			Kemdent Works, Purton, Swindon 
			Wiltshire, SN5 4HT, United Kingdom</td>
			<td>Simplex Rapid Powder Clear 225g, Product code: ACR803; Simplex Rapid Liquid 150ml, Product code: ACR920</td>
			<td>Depending in the electrodes used, superglue might be an easy alternative, if the electrodes are small and lightweight. Possible replacement: Superglue (Cyanacrylate-based)</td>
		</tr>
		<tr>
			<td>Faraday cage</td>
			<td>Self-construction</td>
			<td></td>
			<td>A proper Faraday cage will be the best protection from electromagnetic artifacts, but everything which can be formed into a box shape or applied to a frame and is made of conductive material may help. Possible replacement: Aluminum foil or copper mesh</td>
		</tr>
		<tr>
			<td>Electrophysiological setup with recording software and online spike-sorting capabilities</td>
			<td>OmniPlex&#174; Neural Data Acquisition System 
			Plexon Inc 
			6500 Greenville Avenue, Suite 700 
			Dallas, Texas 75206 
			USA</td>
			<td></td>
			<td>Offline sorting software is a potential alternative, multiple scripts and softwares can be found for free in the open source community.</td>
		</tr>
	</tbody>
</table>

acute in vivo electrophysiological recordings of local field potentials and multi-unit activity from the hyperdirect pathway in anesthetized rats

Converging evidence shows that many neuropsychiatric diseases should be understood as disorders of large-scale neuronal networks. To better understand the pathophysiological basis of these diseases, it is necessary to precisely characterize in which way the processing of information is disturbed between the different neuronal parts of the circuit. Using extracellular in vivo electrophysiological recordings, it is possible to accurately delineate neuronal activity within a neuronal network. The application of this method has several advantages over alternative techniques, e.g., functional magnetic resonance imaging and calcium imaging, as it allows a unique temporal and spatial resolution and does not rely on genetically engineered organisms. However, the use of extracellular in vivo recordings is limited since it is an invasive technique that cannot be universally applied. In this article, a simple and easy to use method is presented with which it is possible to simultaneously record extracellular potentials such as local field potentials and multiunit activity at multiple sites of a network. It is detailed how a precise targeting of subcortical nuclei can be achieved using a combination of stereotactic surgery and online analysis of multi-unit recordings. Thus, it is demonstrated, how a complete network such as the hyperdirect cortico-basal ganglia loop can be studied in anesthetized animals in vivo.

With the herein used recording electrodes, it is possible to sample LFPs from the primary motor cortex, the subthalamic nucleus and the substantia nigra pars reticulata and MUA from the STN and SNr. Initially, LFPs and multi-unit activity are recorded together in a broad-band signal. Thereafter, LFPs and MUAs are separated by bandpass filters (0.05-250 Hz for LFPs and 300-4,000 Hz for MUA).
For the correct targeting of subcortic...

Watch this Scientific Journal Video about Acute In Vivo Electrophysiological Recordings of Local Field Potentials and Multi-unit Activity from the Hyperdirect Pathway in Anesthetized Rats at JoVE.com

Acute In Vivo Electrophysiological Recordings of Local Field Potentials and Multi-unit Activity from the Hyperdirect Pathway in Anesthetized Rats

In this study, the methodology is presented on how to perform multi-site in vivo electrophysiological recordings from the hyperdirect pathway under urethane anesthesia.

Acute In Vivo Electrophysiological Recordings of Local Field Potentials and Multi-unit Activity from the Hyperdirect Pathway in Anesthetized Rats

Converging evidence shows that many neuropsychiatric diseases should be understood as disorders of large-scale neuronal networks. To better understand the ...

The overall goal of this experiment is to demonstrate how to perform acute in vivo electrophysiological recordings of local field potentials and multi-unit activity from the cortico-basal ganglia loop of anesthetized rats. This method can help answer key questions in the neuroscience field such as how pathological oscillations contribute to the complex pathophysiology in neuropsychiatric diseases. The main advantage of this technique is that it can be used to record extracellular potentials from various cortical and subcortical targets of the brain simultaneously.The implications of this technique extend toward therapy of different neuropsychiatric diseases because local field potentials can be potentially used as a biomarker for treatments such as closed-loop stimulation. Though this method can provide insight into the pathophysiology of the basal ganglia, it can also be applied to other brain areas. To begin this procedure, prepare a five centimeter length of silver wire with a diameter of 200 micrometers and remove any coating if necessary.Next, hold the wire tip downwards in a flame until the tip starts to melt and forms a ball with a diameter of one millimeter. Then cut off the electrode to a total length of 15 millimeters from the beginning of the ball-shaped tip to the wire end. Solder a precision connector to the end of the wire which fits the electrophysiological recording system.Then cover the soldering point from the wire end to the connector with conductive silver varnish to improve conductivity. After the conductive varnish has dried, cover the soldering point with a one to three millimeter heat shrinking tube. Carefully flatten the ball-shaped tip to half the thickness using a watchmaker's hammer.Subsequently, put on examination gloves and use a lint-free cleaning cloth with 100%ethanol to remove any dirt and grease. Then place the electrodes in a 15 milliliter centrifuge tube or a cell culture tube and fill it up with household chlorine bleach until the ball-shaped tip is fully covered. After 23 minutes, take the electrodes out and flush them generously with distilled water.The electrode surface should appear homogeneously dark purple in the successful application of silver chloride. Following that, leave the electrodes to dry in air. Take the electrodes with fine tweezers after they have been fully dried.Then use a fine paintbrush to apply liquid electrical insulation onto the electrodes. Start from the wire directly behind the electrode tip and cover everything up to heat shrinking tube. Afterward, let the insulation dry for at least two hours.In this step, loosely fix the first pair of electrodes to the acrylic block of the holder with pieces of adhesive tape. The electrodes should protrude from the acrylic block by approximately 12 millimeters. Next, carefully fix the second bipolar electrode next to the first electrode.For targeting the structures of the hyper direct pathway, the distance between the electrode pairs should be two millimeters. Under the microscope, adjust the second bipolar electrode by sliding it carefully to a position in which the most ventral tip is approximately 200 micrometers recessed compared to the first electrode. Press on the adhesive tape and then secure the electrodes with the holder's metal clamp.After anesthetizing the animal, shave its head to achieve a clean surgical field. Fix the animal in the stereotaxic frame and then disinfect the incision site and the surrounding area with appropriate surgical disinfectant. Subsequently, perform a two centimeter long incision on the scalp in the sagittal direction with a scalpel.Use the scalpel to slightly scrape off the skull aponeurosis and disinfect the skull with 3%hydrogen peroxide. Then use cotton buds soaked in 3%hydrogen peroxide to remove any remaining tissue. Next, adjust the incisor bar until the top of the skull is leveled which means the bregma and lambda as stereotaxic reference points are in the same plane.Under the microscope, use a standard stereotaxic rat alignment tool to calibrate the designated tip to the bregma and adjust the incisor bar until the designated points for the bregma and lambda on the tool touch the skull at the same time. Using a stereotaxic holder with cannula, calibrate it to the bregma and then calculate the position of all drill holes on the skull. Then mark the positions of the holes to be drilled either by carefully scratching the skull or by using a surgical color marker.Then using a micro drill, carefully drill all the holes with a diameter of about one millimeter. For the STN and SNr, drill a common hole approximately two millimeters by three millimeters. Take one fine cannula and bend the tip to form two hooks.Then use the hooks to remove any debris from the drill holes and carefully cut and remove the dura mater in the common STN/SNr hole. After that, flush the drill holes with physiological saline. Apply a drop of physiological saline every 15 minutes to the drill holes to prevent the brain and dura from drying out.Then take a micro drill and matching stainless steel micro screw, drill a hole and screw in a micro screw between the drill holes of the reference epidural electrodes above the cerebellum. Next, guide the electrode tips with fine tweezers and slide them directly below the skull bone into the drill holes. Fix all epidural electrodes with two components stencil acrylic.Make sure not to cover the bregma point nor affect the common STN/SNr hole. Then insert the prepared holder with the tungsten micro wire electrodes into the stereotaxic frame. Calibrate the most ventral electrode to the bregma which is intended to target the STN.Adjust to the calculated position above the common STN/SNr hole and lower the electrodes down to the brain. Make sure that the tungsten micro wire electrodes go inside the brain smoothly. In this procedure, set up the recording software such as band-pass filter and amplify the raw data signal.Then use an online LFP and spike filter with appropriate settings. For all filters, use a Butterworth-type filter. Set up a spike threshold for online spike sorting.Most recording software allows for the setting up of a spike threshold which is an amplitude value above the threshold that a signal is marked as a spike by the software. Next, slowly lower the tungsten micro wire electrodes to one millimeter above the STN and wait for the signal to stabilize if necessary. For the electrophysiological mapping, advance the electrodes ventrally in the steps of 100 micrometers.At each step, evaluate the firing pattern, firing rate and shape of spikes by comparing those with the typical examples given in figure two of the accompanying manuscript. Once the electrodes are in the desired structures, set up online filtering and spike sorting and then start the recording of the data. Here is a representative 600-second LFP recording of the primary motor cortex.Time periods with high frequency low amplitude activity corresponding to the activated state and the time periods with the slower rhythm and higher amplitude corresponding to the slow wave activity state can be differentiated. And this is the corresponding time frequency plot over an interval of 600 seconds illustrating the zero to 20 Hertz relative power of the LFPs. Once mastered, this technique can be done in two hours if it's performed properly.After watching this video, you should have a good understanding of how to perform extracellular in vivo electrophysiological recordings from the cortico-basal ganglia loop of anesthetized rats.

acute-vivo-electrophysiological-recordings-local-field-potentials

Research

JoVE Journal

Neuroscience

15.4K visualizações.  Charité University Medicine Berlin. The overall goal of this experiment is to demonstrate how to perform acute in vivo electrophysiological recordings of local field potentials and multi-unit activity from the cortico-basal ganglia loop of anesthetized rats. This method can help answer key questions in the neuroscience field such as how pathological oscillations contribute to the complex pathophysiology in neuropsychiatric diseases. The main advantage of this technique is that it can be used to record extracellular potentials f...

Vídeo: Acute In Vivo Electrophysiological Recordings of Local Field Potentials and Multi-unit Activity from the Hyperdirect Pathway in Anesthetized Rats