This work was supported by the National Science Center grant No. 2017/25/B/NZ7/00373. Authors would like to recognize the work of Hanna Drzyma&#322;a-Celichowska and W&#322;odzimierz Mr&#243;wczy&#324;ski, who both contributed to the data gathering and analysis of the results presented in this paper.

All procedures connected to this protocol have been accepted by the appropriate authorities (e.g., Local Ethics Committee) and follow the national and international rules on animal welfare and management.
NOTE: Each participant involved in the procedure has to be properly trained in basic surgical procedures and has to have a valid license for performing animal experiments.
1. Anesthesia and premedication
<ol>
	<li>Anesthetize a rat with intraperitoneal injections...

<ol>
	<li>Angius, L., Hopker, J., Mauger, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Ergogenic+Effects+of+Transcranial+Direct+Current+Stimulation+on+Exercise+Performance.">The Ergogenic Effects of Transcranial Direct Current Stimulation on Exercise Performance.</a> Frontiers in Physiology. 8, 90 (2017).</li><li>Berry, H. R., Tate, R. J., Conway, B. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcutaneous+spinal+direct+current+stimulation+induces+lasting+fatigue+resistance+and+enhances+explosive+vertical+jump+performance.">Transcutaneous spinal direct current stimulation induces lasting fatigue resistance and enhances explosive vertical jump performance.</a> PloS One. 12 (4), 0173846 (2017).</li><li>Lenoir, C., Jankovski, A., Mouraux, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anodal+transcutaneous+spinal+direct+current+stimulation+(tsDCS)+selectively+inhibits+the+synaptic+efficacy+of+nociceptive+transmission+at+spinal+cord+level.">Anodal transcutaneous spinal direct current stimulation (tsDCS) selectively inhibits the synaptic efficacy of nociceptive transmission at spinal cord level.</a> Neuroscience. 393, 150-163 (2018).</li><li>Parazzini, 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=Modeling+the+current+density+generated+by+transcutaneous+spinal+direct+current+stimulation+(tsDCS).">Modeling the current density generated by transcutaneous spinal direct current stimulation (tsDCS).</a> Clinical Neurophysiology: Official Journal of the International Federation of Clinical Neurophysiology. 125 (11), 2260-2270 (2014).</li><li>Choi, Y. A., Kim, Y., Shin, H. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pilot+study+of+feasibility+and+effect+of+anodal+transcutaneous+spinal+direct+current+stimulation+on+chronic+neuropathic+pain+after+spinal+cord+injury.">Pilot study of feasibility and effect of anodal transcutaneous spinal direct current stimulation on chronic neuropathic pain after spinal cord injury.</a> Spinal Cord. 57 (6), 461-470 (2019).</li><li>G&#243;mez-Soriano, J., Meg&#237;a-Garc&#237;a, A., Serrano-Mu&#241;oz, D., Osuagwu, B., Taylor, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non-invasive+spinal+direct+current+simulation+for+spasticity+therapy+following+spinal+cord+injury:+mechanistic+insights+contributing+to+long-term+treatment+effects.">Non-invasive spinal direct current simulation for spasticity therapy following spinal cord injury: mechanistic insights contributing to long-term treatment effects.</a> The Journal of Physiology. 597 (8), 2121-2122 (2019).</li><li>de Ara&#250;jo, A. V. L., 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=Effectiveness+of+anodal+transcranial+direct+current+stimulation+to+improve+muscle+strength+and+motor+functionality+after+incomplete+spinal+cord+injury:+a+systematic+review+and+meta-analysis.">Effectiveness of anodal transcranial direct current stimulation to improve muscle strength and motor functionality after incomplete spinal cord injury: a systematic review and meta-analysis.</a> Spinal Cord. , (2020).</li><li>de Paz, R. H., Serrano-Mu&#241;oz, D., P&#233;rez-Nombela, S., Bravo-Esteban, E., Avenda&#241;o-Coy, J., G&#243;mez-Soriano, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Combining+transcranial+direct-current+stimulation+with+gait+training+in+patients+with+neurological+disorders:+a+systematic+review.">Combining transcranial direct-current stimulation with gait training in patients with neurological disorders: a systematic review.</a> Journal of Neuroengineering and Rehabilitation. 16 (1), 114 (2019).</li><li>Ahmed, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modulation+of+gamma+and+alpha+spinal+motor+neurons+activity+by+trans-spinal+direct+current+stimulation:+effects+on+reflexive+actions+and+locomotor+activity.">Modulation of gamma and alpha spinal motor neurons activity by trans-spinal direct current stimulation: effects on reflexive actions and locomotor activity.</a> Physiological Reports. 4 (3), (2016).</li><li>Bolzoni, F., Jankowska, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Presynaptic+and+postsynaptic+effects+of+local+cathodal+DC+polarization+within+the+spinal+cord+in+anaesthetized+animal+preparations.">Presynaptic and postsynaptic effects of local cathodal DC polarization within the spinal cord in anaesthetized animal preparations.</a> The Journal of Physiology. 593 (4), 947-966 (2015).</li><li>Cogiamanian, F., 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=Transcutaneous+Spinal+Direct+Current+Stimulation.">Transcutaneous Spinal Direct Current Stimulation.</a> Frontiers in Psychiatry. 3, (2012).</li><li>Ahmed, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trans-spinal+direct+current+stimulation+alters+muscle+tone+in+mice+with+and+without+spinal+cord+injury+with+spasticity.">Trans-spinal direct current stimulation alters muscle tone in mice with and without spinal cord injury with spasticity.</a> The Journal of Neuroscience: The Official Journal of the Society for Neuroscience. 34 (5), 1701-1709 (2014).</li><li>Bolzoni, F., Pettersson, L. G., Jankowska, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evidence+for+long-lasting+subcortical+facilitation+by+transcranial+direct+current+stimulation+in+the+cat.">Evidence for long-lasting subcortical facilitation by transcranial direct current stimulation in the cat.</a> The Journal of Physiology. 591 (13), 3381-3399 (2013).</li><li>Manuel, M., Zytnicki, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alpha,+beta+and+gamma+motoneurons:+functional+diversity+in+the+motor+system's+final+pathway.">Alpha, beta and gamma motoneurons: functional diversity in the motor system's final pathway.</a> Journal of Integrative Neuroscience. 10 (3), 243-276 (2011).</li><li>Feiereisen, P., Duchateau, J., Hainaut, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Motor+unit+recruitment+order+during+voluntary+and+electrically+induced+contractions+in+the+tibialis+anterior.">Motor unit recruitment order during voluntary and electrically induced contractions in the tibialis anterior.</a> Experimental Brain Research. 114 (1), 117-123 (1997).</li><li>Van Cutsem, M., Feiereisen, P., Duchateau, J., Hainaut, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+properties+and+behaviour+of+motor+units+in+the+tibialis+anterior+during+voluntary+contractions.">Mechanical properties and behaviour of motor units in the tibialis anterior during voluntary contractions.</a> Canadian Journal of Applied Physiology = Revue Canadienne De Physiologie Appliquee. 22 (6), 585-597 (1997).</li><li>Gardiner, P. F. <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+motoneurons+innervating+different+muscle+unit+types+in+rat+gastrocnemius.">Physiological properties of motoneurons innervating different muscle unit types in rat gastrocnemius.</a> Journal of Neurophysiology. 69 (4), 1160-1170 (1993).</li><li>Ahmed, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trans-spinal+direct+current+stimulation+modifies+spinal+cord+excitability+through+synaptic+and+axonal+mechanisms.">Trans-spinal direct current stimulation modifies spinal cord excitability through synaptic and axonal mechanisms.</a> Physiological Reports. 2 (9), (2014).</li><li>Manuel, M., Iglesias, C., Donnet, M., Leroy, F., Heckman, C. J., Zytnicki, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fast+kinetics,+high-frequency+oscillations,+and+subprimary+firing+range+in+adult+mouse+spinal+motoneurons.">Fast kinetics, high-frequency oscillations, and subprimary firing range in adult mouse spinal motoneurons.</a> The Journal of Neuroscience: The Official Journal of the Society for Neuroscience. 29 (36), 11246-11256 (2009).</li><li>Liebetanz, D., Koch, R., Mayenfels, S., K&#246;nig, F., Paulus, W., Nitsche, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Safety+limits+of+cathodal+transcranial+direct+current+stimulation+in+rats.">Safety limits of cathodal transcranial direct current stimulation in rats.</a> Clinical Neurophysiology: Official Journal of the International Federation of Clinical Neurophysiology. 120 (6), 1161-1167 (2009).</li><li>B&#261;czyk, M., Jankowska, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-term+effects+of+direct+current+are+reproduced+by+intermittent+depolarization+of+myelinated+nerve+fibers.">Long-term effects of direct current are reproduced by intermittent depolarization of myelinated nerve fibers.</a> Journal of Neurophysiology. 120 (3), 1173-1185 (2018).</li><li>B&#261;czyk, M., Drzyma&#322;a-Celichowska, H., Mr&#243;wczy&#324;ski, W., Krutki, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Motoneuron+firing+properties+are+modified+by+trans-spinal+direct+current+stimulation+in+rats.">Motoneuron firing properties are modified by trans-spinal direct current stimulation in rats.</a> Journal of Applied Physiology. 126 (5), 1232-1241 (2019).</li><li>B&#261;czyk, M., Drzyma&#322;a-Celichowska, H., Mr&#243;wczy&#324;ski, W., Krutki, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-lasting+modifications+of+motoneuron+firing+properties+by+trans-spinal+direct+current+stimulation+in+rats.">Long-lasting modifications of motoneuron firing properties by trans-spinal direct current stimulation in rats.</a> European Journal of Neuroscience. , (2019).</li><li>Miranda, P. C., Faria, P., Hallett, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=What+does+the+ratio+of+injected+current+to+electrode+area+tell+us+about+current+density+in+the+brain+during+tDCS.">What does the ratio of injected current to electrode area tell us about current density in the brain during tDCS.</a> Clinical Neurophysiology: Official Journal of the International Federation of Clinical Neurophysiology. 120 (6), 1183-1187 (2009).</li><li>Rahman, 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=Cellular+effects+of+acute+direct+current+stimulation:+somatic+and+synaptic+terminal+effects.">Cellular effects of acute direct current stimulation: somatic and synaptic terminal effects.</a> The Journal of Physiology. 591 (10), 2563-2578 (2013).</li><li>Bikson, 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=Effects+of+uniform+extracellular+DC+electric+fields+on+excitability+in+rat+hippocampal+slices+in+vitro.">Effects of uniform extracellular DC electric fields on excitability in rat hippocampal slices in vitro.</a> The Journal of Physiology. 557, 175-190 (2004).</li><li>Jankowska, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spinal+control+of+motor+outputs+by+intrinsic+and+externally+induced+electric+field+potentials.">Spinal control of motor outputs by intrinsic and externally induced electric field potentials.</a> Journal of Neurophysiology. 118 (2), 1221-1234 (2017).</li><li>Button, D. C., Gardiner, K., Marqueste, T., Gardiner, P. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Frequency-current+relationships+of+rat+hindlimb+alpha-motoneurones.">Frequency-current relationships of rat hindlimb alpha-motoneurones.</a> The Journal of Physiology. 573, 663-677 (2006).</li></ol>

Authors have no conflict of interest to disclose.

If performed correctly, the surgical part of the described protocol should be completed within approximately three hours. One should take particular care in maintaining stable physiological conditions of an animal during the surgery, in particular body temperature and depth of anesthesia. Apart from obvious ethical considerations, a lack of proper anesthesia can result in excessive limb movements during nerve dissection or laminectomy and lead to damage to the preparation or a premature experiment termination. Upon paral...

Trans-spinal direct current stimulation (tsDCS) is gaining recognition as a potent method to modify spinal circuit excitability in health and disease1,2,3. In this technique, a constant current is passed between an active electrode located above selected spinal segments, with a reference electrode located either ventrally or more rostrally4. Several studies have already confirmed that tsDCS can be used in managing certain pathological conditions, such as neuropathic pain5, spasticity6, spinal cord injury7 or to facilitate rehabilitation8. Researchers&#160;suggest that tsDCS evokes alterations in the ion distribution between the intracellular and the extracellular space across the cell membrane, and this can either facilitate or inhibit neuronal activity depending on the current orientation9,10,11. However, until recently, a direct confirmation of this influence on motoneurons was lacking.
Here, we describe a detailed protocol to conduct in vivo intracellular recording of electrical potentials from lumbar spinal motoneurons in the anesthetized rat with simultaneous application of tsDCS, in order to observe changes in motoneuron membrane and firing properties in response to anodal or cathodal polarization of the spinal neuronal network. Intracellular recordings open several areas of investigation of neuron properties, unavailable for previously used extracellular techniques9,12. For example, it is possible to precisely measure motoneuron membrane voltage response to direct current flow induced by tsDCS, to indicate voltage threshold for spike generation, or to analyze action potential parameters. Moreover, this technique allows us to determine motoneuron passive membrane properties, such as input resistance, and to observe the relationship between intracellular stimulation current and frequency of rhythmic firing of motoneurons. Antidromic identification of recorded motoneuron, based on the stimulation of functionally identified nerves (i.e., nerves providing efferents to flexors or extensors) allows us to additionally identify types of innervated motor units (fast versus slow), which gives an opportunity to test whether polarization differently influences individual elements of the mature spinal neuronal system. Due to extensive surgery preceding the recording and high requirements on stability and reliability of recordings, this technique is highly challenging but allows direct and long-term assessment of electrophysiological characteristics of one motoneuron: before, during and after application of tsDCS, which is crucial to determine both its acute actions and persistent effects13. As a motoneuron directly activates extrafusal muscle fibers14 and takes part in feedback control of a muscle contraction and developed force15,16 any observed influence of tsDCS on the motor unit or muscle contractile properties may be linked to modulations of motoneuron excitability or firing characteristics.

<table>
	<tbody>
		<tr>
			<td>Durgs and solutions</td>
			<td>-</td>
			<td>-</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Atropinum sulfuricum</td>
			<td>Polfa Warszawa</td>
			<td>-</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>Merck</td>
			<td>346351</td>
			<td>-</td>
		</tr>
		<tr>
			<td>NaHCO3</td>
			<td>Merck</td>
			<td>106329</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Pancuronium Jelfa</td>
			<td>PharmaSwiss/Valeant</td>
			<td>-</td>
			<td>Neuromuscular blocker</td>
		</tr>
		<tr>
			<td>Pentobarbital sodium</td>
			<td>Biowet Pu&#322;awy Sp. z o.o</td>
			<td>-</td>
			<td>Main anesthetic agent</td>
		</tr>
		<tr>
			<td>Pottasium citrate</td>
			<td>Chempur</td>
			<td>6100-05-06</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Tetraspan</td>
			<td>Braun</td>
			<td>-</td>
			<td>HES solution</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical equipment</td>
			<td>-</td>
			<td>-</td>
			<td>-</td>
		</tr>
		<tr>
			<td>21 Blade</td>
			<td>FST</td>
			<td>10021-00</td>
			<td>Scalpel blade</td>
		</tr>
		<tr>
			<td>Cauterizer</td>
			<td>FST</td>
			<td>18010-00</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Chest Tubes</td>
			<td>Mila</td>
			<td>CT1215</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Dumont #4 Forceps</td>
			<td>FST</td>
			<td>11241-30</td>
			<td>Muscle forceps</td>
		</tr>
		<tr>
			<td>Dumont #5 Forceps</td>
			<td>FST</td>
			<td>11254-20</td>
			<td>Dura forceps</td>
		</tr>
		<tr>
			<td>Dumont #5F Forceps</td>
			<td>FST</td>
			<td>11255-20</td>
			<td>Nerve forceps</td>
		</tr>
		<tr>
			<td>Dumont #5SF Forceps</td>
			<td>FST</td>
			<td>11252-00</td>
			<td>Pia forceps</td>
		</tr>
		<tr>
			<td>Forceps</td>
			<td>FST</td>
			<td>11008-13</td>
			<td>Blunt forceps</td>
		</tr>
		<tr>
			<td>Forceps</td>
			<td>FST</td>
			<td>11053-10</td>
			<td>Skin forceps</td>
		</tr>
		<tr>
			<td>Hemostat</td>
			<td>FST</td>
			<td>13013-14</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Rongeur</td>
			<td>FST</td>
			<td>16021-14</td>
			<td>For laminectomy</td>
		</tr>
		<tr>
			<td>Scissors</td>
			<td>FST</td>
			<td>15000-08</td>
			<td>Vein scissors</td>
		</tr>
		<tr>
			<td>Scissors</td>
			<td>FST</td>
			<td>15002-08</td>
			<td>Dura scissors</td>
		</tr>
		<tr>
			<td>Scissors</td>
			<td>FST</td>
			<td>14184-09</td>
			<td>For trachea cut</td>
		</tr>
		<tr>
			<td>Scissors</td>
			<td>FST</td>
			<td>104075-11</td>
			<td>Muscle scissors</td>
		</tr>
		<tr>
			<td>Scissors</td>
			<td>FST</td>
			<td>14002-13</td>
			<td>Skin scissors</td>
		</tr>
		<tr>
			<td>Tracheal tube</td>
			<td>-</td>
			<td>-</td>
			<td>Custom made</td>
		</tr>
		<tr>
			<td>Vein catheter</td>
			<td>Vygon</td>
			<td>1261.201</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Vessel cannulation forceps</td>
			<td>FST</td>
			<td>18403-11</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Vessel clamp</td>
			<td>FST</td>
			<td>18320-11</td>
			<td>For vein clamping</td>
		</tr>
		<tr>
			<td>Vessel Dilating Probe</td>
			<td>FST</td>
			<td>10160-13</td>
			<td>For vein dissection</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sugrgical materials</td>
			<td>-</td>
			<td>-</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Gel foam</td>
			<td>Pfizer</td>
			<td>GTIN 00300090315085</td>
			<td>Hemostatic agent</td>
		</tr>
		<tr>
			<td>Silk suture 4.0</td>
			<td>FST</td>
			<td>18020-40</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Silk suture 6.0</td>
			<td>FST</td>
			<td>18020-60</td>
			<td>-</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Equipment</td>
			<td>-</td>
			<td>-</td>
			<td>-</td>
		</tr>
		<tr>
			<td>Axoclamp 2B</td>
			<td>Molecular devices</td>
			<td>discontinued</td>
			<td>Intracellular amplifier/ new model Axoclamp 900A</td>
		</tr>
		<tr>
			<td>CapStar-100 End-tidal CO2 Monitor</td>
			<td>CWE</td>
			<td>11-10000</td>
			<td>Gas analyzer</td>
		</tr>
		<tr>
			<td>Grass S-88</td>
			<td>A-M Systems</td>
			<td>discontinued</td>
			<td>Constant current stimulator</td>
		</tr>
		<tr>
			<td>Homeothermic Blanket Systems with Flexible Probe</td>
			<td>Harvard Apparatus</td>
			<td>507222F</td>
			<td>Heating system</td>
		</tr>
		<tr>
			<td>ISO-DAM8A</td>
			<td>WPI</td>
			<td>74020</td>
			<td>Extracellular amplifier</td>
		</tr>
		<tr>
			<td>Microdrive</td>
			<td>-</td>
			<td>-</td>
			<td>Custom made/replacement IVM/Scientifica</td>
		</tr>
		<tr>
			<td>P-1000 Microelectrode puller</td>
			<td>Sutter Instruments</td>
			<td>P-1000</td>
			<td>Microelectrode puller</td>
		</tr>
		<tr>
			<td>SAR-830/AP Small Animal Ventilator</td>
			<td>CWE</td>
			<td>12-02100</td>
			<td>Respirator</td>
		</tr>
		<tr>
			<td>Support frame</td>
			<td>-</td>
			<td>-</td>
			<td>Custom made/replacement lab standard base 51601/Stoelting</td>
		</tr>
		<tr>
			<td>Spinal clamps</td>
			<td>-</td>
			<td>-</td>
			<td>Custom made/replacement Rat spinal adaptor 51695/Stoelting</td>
		</tr>
		<tr>
			<td>TP-1 DC stimulator</td>
			<td>WiNUE</td>
			<td>-</td>
			<td>tsDCS stimulator</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Miscellaneous</td>
			<td>-</td>
			<td>-</td>
			<td>-</td>
		</tr>
		<tr>
			<td>1B150-4 glass capillaries</td>
			<td>WPI</td>
			<td>1B150-4</td>
			<td>For microelectrodes production</td>
		</tr>
		<tr>
			<td>Cotton wool</td>
			<td>-</td>
			<td>-</td>
			<td>-</td>
		</tr>
		<tr>
			<td>flexible tubing</td>
			<td>-</td>
			<td>-</td>
			<td>For respirator and CO2 analyzer connection</td>
		</tr>
		<tr>
			<td>MicroFil</td>
			<td>WPI</td>
			<td>MF28G67-5</td>
			<td>For filling micropipettes</td>
		</tr>
		<tr>
			<td>Silver wire</td>
			<td>-</td>
			<td>-</td>
			<td>For nerve electrodes</td>
		</tr>
	</tbody>
</table>

in vivo intracellular recording of type-identified rat spinal motoneurons during trans-spinal direct current stimulation

Intracellular recording of spinal motoneurons in vivo provides a &#8220;gold standard&#8221; for determining the cells&#8217; electrophysiological characteristics in the intact spinal network and holds significant advantages relative to classical in vitro or extracellular recording techniques. An advantage of in vivo intracellular recordings is that this method can be performed on adult animals with a fully mature nervous system, and therefore many observed physiological mechanisms can be translated to practical applications. In this methodological paper, we describe this procedure combined with externally applied constant current stimulation, which mimics polarization processes occurring within spinal neuronal networks. Trans-spinal direct current stimulation (tsDCS) is an innovative method increasingly used as a neuromodulatory intervention in rehabilitation after various neurological injuries as well as in sports. The influence of tsDCS on the nervous system remains poorly understood and the physiological mechanisms behind its actions are largely unknown. The application of the tsDCS simultaneously with intracellular recordings enables us to directly observe changes of motoneuron membrane properties and characteristics of rhythmic firing in response to the polarization of the spinal neuronal network, which is crucial for the understanding of tsDCS actions. Moreover, when the presented protocol includes the identification of the motoneuron with respect to an innervated muscle and its function (flexor versus extensor) as well as the physiological type (fast versus slow) it provides an opportunity to selectively investigate the influence of tsDCS on identified components of spinal circuitry, which seem to be differently affected by polarization. The presented procedure focuses on surgical preparation for intracellular recordings and stimulation with an emphasis on the steps which are necessary to achieve preparation stability and reproducibility of results. The details of the methodology of the anodal or cathodal tsDCS application are discussed while paying attention to practical and safety issues.

Parameters of action potentials and several membrane properties can be calculated on the basis of intracellular recordings when stable conditions of cell penetration are ensured. Figure 1A presents a typical orthodromic action potential evoked by intracellular stimulation, which meets all criteria for data inclusion (the resting membrane potential of at least -50 mV, and spike amplitude higher than 50 mV, with a positive overshoot). Action potential parameters, such as the spike amplitude, t...

Watch this Scientific Journal Video about In Vivo Intracellular Recording of Type-Identified Rat Spinal Motoneurons During Trans-Spinal Direct Current Stimulation at JoVE.com

In Vivo Intracellular Recording of Type-Identified Rat Spinal Motoneurons During Trans-Spinal Direct Current Stimulation

This protocol describes in vivo intracellular recording of rat lumbar motoneurons with simultaneous trans-spinal direct current stimulation. The method enables us to measure membrane properties and to record rhythmic firing of motoneurons before, during and after anodal or cathodal polarization of the spinal cord.

Intracellular recording of spinal motoneurons in vivo provides a &#8220;gold standard&#8221; for determining the cells&#8217; electrophysiological ...

This protocol uses intracellular recordings of spinal motoneurons, to directly investigate the influence of trans-spinal direct current stimulation on the function of spinal networks. The major advantage of this technique is that it allows intracellular recordings to be performed on fully mature nervous system. Facilitating translation of the experimental observations to practical applications.After confirming a lack of response to pedal reflex, an anesthetized six month old male Wistar rat, use a dissecting microscope and a number 21 blade, to make a longitudinal skin incision from the sternum to the chin. And use blunt dissection to expose the right jugular vein. Place two, 4-0 ligatures beneath the section of the vein without branching points.And make one loose knot on the proximal end of the vein segment. And one loose knot on the distal end of the segment. Clamp the vein proximal to the heart, and ligate the distal end of the vein.Use iris scissors to make an incision between the clamp and the distal ligature. And, holding a flap of the vein, introduce a pre-filled catheter to the point where the vein is blocked by the clamp. Then remove the clamp and push the catheter several millimeters into the vein.For a tracheal tube placement, use blunt forceps to separate the two mandibular glands covering the sternohyoid muscles. And separate the sternohyoid muscles at the midline, to expose the trachea. Place three, 4-0 ligatures beneath the trachea, and make two knots below the tracheal tube insertion point and one knot above.Then insert a tracheal tube into the trachea below the third tracheal cartilage. And secure the tube in place with the pre-prepared ligatures. To dissect the hind limb nerves, use a number 21 blade to make a longitudinal cut on the posterior side of the left hind limb, from the Achilles tendon to the hip.And use scissors to make a cut between the anterior and posterior regions of the popliteal fossa, at the back of the knee joint. Cut two heads of the biceps femoris, to expose the sciatic nerve. And separate the lateral head from the medial head of the gastrocnemius muscle, to expose the tibial nerve and its branches.Then use number 55 forceps, to carefully dissect the medial gastrocnemius and the lateral gastrocnemius and soleus nerves. Disconnecting them from the surrounding tissues while maintaining their connection to the respective of muscles. To perform the laminectomy, use a number 21 blade to make a longitudinal incision from the sacrum up to the thoracic vertebrae.And identify the Th13 vertebra, as a lowest thoracic segment with a rib insertion. Then use fine rongeurs to remove the spinous processes and laminae from the Th13 to the L2 vertebrae, to expose the lumbar segments of the spinal cord. To fix the vertebral column, place the rat into a custom made frame on a 37 degrees Celsius heating pad, connected to a closed loop heating system.And use the skin flaps to form a deep pool over the exposed spinal cord. Place metal clamps below the Th12 transverse processes, and at the L3 spinous processes, and fill the pool with 37 degrees Celsius mineral oil. Use the skin flaps to make a deep pool of mineral oil over the exposed tibial, medial gastrocnemius and lateral gastrocnemius and soleus nerves.And place the nerves on bipolar silver wire stimulating electrodes. Then connect the electrodes to a square pulse stimulator using separate stimulation channels for each nerve. For a surface electrode placement, under the dissecting microscope, place a silver ball electrode on the left caudal side of the exposed spinal cord.With a reference electrode inserted in the back muscles. And connect both electrodes to the differential DC amplifier. Use a constant current stimulator to stimulate the medial gastrocnemius and lateral gastrocnemius and soleus nerves, with square pulses of a 0.1 millisecond duration repeated at a three hertz frequency and observe the afferent volleys.At the end of the simulation, move the surface electrode rostrally, and repeat the stimulation to identify the spinal segments at which the amplitudes of the volleys are the highest for each nerve. After determining the location of the maximum volley, deliver a neuromuscular blocker intravenously to paralyze the rat. While an assistant connects the tracheal tube to an external ventilator in line with a rodent compatible cap nominator.To open the dura and pia mater, use number 55 forceps to gently lift the dura mater, and cut the tissue caudally from the L5 segment, rostrally up to the L4 segment. Then use a pair of ultra thin 5SF forceps, to make a small patch in the pia, covering the dorsal column between the blood vessels. Exactly at the level of the maximum afferent volley from the medial gastrocnemius and lateral gastrocnemius and soleus nerve.To place the trans-spinal direct current stimulation electrodes, place a saline soaked sponge on the dorsal side of the Th12 vertebrae. And use fine manipulation to press the sponge with an active trans-spinal direct current stimulation electrode. Then mount a custom pooled microelectrode, onto the micro manipulator, allowing a one to two micron stepping movement and stereotaxic calibration.And drive a micropipette tip into a selected patch in the pia, at a 15 to 20 degree medial lateral angle. To record the motoneuron membrane and firing properties, in the bridge mode of the intracellular amplifier, stimulate the respective nerve branches to identify the motoneuron on the basis of the all or nothing appearance, of the antidromic action potential. In the discontinuous current clamp mode of the intracellular amplifier with a current switch rate mode four to eight kilohertz, use a 0.5 millisecond intracellular depolarizing current pulses, to evoke an orthodontic action potential, in the motoneuron.To calculate the cell input resistance, stimulate a motoneuron, with 40 short 100 millisecond pulses of hyperpolarizing one nanogram current. To determine the real base value as the minimum amplitude of the depolarizing current required to elicit a single spike, stimulate a motoneuron with 50 millisecond square wave pulses at increasing amplitudes. Then inject 500 millisecond square wave pulses of depolarizing current, at increasing amplitudes.In 0.1 to two nano amp steps, to evoke rhythmic discharges of motoneurons. For a trans-spinal direct current stimulation, start the polarization procedures by trans-spinal application of direct current, while maintaining a stable penetration of the motoneuron. Here, a typical orthotropic action potential, evoked by intracellular stimulation that meets all of the criteria for data inclusion is shown.In this analysis, a cell response to a 100 millisecond hyperpolarizing current pulse of one nanogram. From which both the peak and plateau input resistance of a motoneuron, can be determined from the voltage deflection, can be observed. This expanded voltage trace of a real basic spike, exhibits a clearly marked voltage threshold of the spike.Indicating the level of membrane depolarization at which voltage gated sodium channels are activated to initiate the action potential. These graphs provide examples of intracellular voltage traces. From two motoneurons, stimulated intracellularly with 500 millisecond square pulses of depolarizing current.Before, during, and after a trans-spinal direct current stimulation application. Anodal trans-spinal direct current stimulation was found to act toward an increased motoneuron excitability and higher frequencies of rhythmic firing. While cathodal trans-spinal direct current stimulation, acted to towards firing inhibition.Moreover, the effects of both types of trans-spinal direct current stimulation, outlasted the period of polarization. Inaccurate data can be acquired, if the data inclusion criteria are compromised due to imperfect cell penetration. A failure to compensate the microelectrode resistance and capacitance or a spinal cord instability.It is imperative that no damage is done to the spinal cord during the dissection as injury can result in spinal shock, making further recordings impossible. It is possible to harvest tissue samples for further histological or immuno cyto chemical analysis. For example, the measurement of c-fos expression can be used as a proxy of neuronal activity.

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Research

JoVE Journal

Neuroscience

5.0K Views.  Poznań University of Physical Education. This protocol uses intracellular recordings of spinal motoneurons, to directly investigate the influence of trans-spinal direct current stimulation on the function of spinal networks. The major advantage of this technique is that it allows intracellular recordings to be performed on fully mature nervous system. Facilitating translation of the experimental observations to practical applications.After confirming a lack of response to pedal reflex, an anesthetized six month old male Wista...