Name: combined infusion and stimulation with fast-scan cyclic voltammetry (cis-fscv) to assess ventral tegmental area receptor regulation of phasic dopamine
Uploaded: 2020-04-23T14:00:00
Description: Watch this Scientific Journal Video about Combined Infusion and Stimulation with Fast-Scan Cyclic Voltammetry CIS-FSCV to Assess Ventral Tegmental Area Receptor Regulation of Phasic Dopamine at JoVE.c

Work was supported by Elizabethtown College (R.J.W, M.L., and L.M.), by a NSF Graduate Fellowship (R.J.W.) and by the Yale School of Medicine (N.A.).

All experiments were conducted according to the National Institutes of Health (NIH) Guide for the Care and Use of Laboratory Animals and were approved by both Elizabethtown College and Yale University Institutional Animal Care and Use Committee (IACUC). This protocol is specific to the anesthetized rat preparation of utilizing CIS-FSCV.
1. Presurgical preparations
<ol>
	<li>Electrode solution preparation
	<ol>
		<li>To make the electrode backfill solution, prepare a solution of 4 M potassium...

<ol>
	<li>Grace, A. A., Bunney, B. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+control+of+firing+pattern+in+nigral+dopamine+neurons:+burst+firing.">The control of firing pattern in nigral dopamine neurons: burst firing.</a> Journal of Neuroscience. 4 (11), 2877-2890 (1984).</li><li>Lester, D. B., 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=Midbrain+acetylcholine+and+glutamate+receptors+modulate+accumbal+dopamine+release.">Midbrain acetylcholine and glutamate receptors modulate accumbal dopamine release.</a> Neuroreport. 19 (9), 991-995 (2008).</li><li>Lodge, D. J., Grace, A. 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Y., 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=Expression+of+functional+cannabinoid+CB2+receptor+in+VTA+dopamine+neurons+in+rats.">Expression of functional cannabinoid CB2 receptor in VTA dopamine neurons in rats.</a> Addiction Biology. 22 (3), 752-765 (2017).</li><li>Wickham, R. 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=Advances+in+studying+phasic+dopamine+signaling+in+brain+reward+mechanisms.">Advances in studying phasic dopamine signaling in brain reward mechanisms.</a> Frontiers in Bioscience. 5, 982-999 (2013).</li><li>Wightman, R. 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=Monitoring+of+transmitter+metabolites+by+voltammetry+in+cerebrospinal+fluid+following+neural+pathway+stimulation.">Monitoring of transmitter metabolites by voltammetry in cerebrospinal fluid following neural pathway stimulation.</a> Nature. 262 (5564), 145-146 (1976).</li><li>Grace, A. A., Bunney, B. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+control+of+firing+pattern+in+nigral+dopamine+neurons:+single+spike+firing.">The control of firing pattern in nigral dopamine neurons: single spike firing.</a> Journal of Neuroscience. 4 (11), 2866-2876 (1984).</li><li>Mameli-Engvall, 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=Hierarchical+control+of+dopamine+neuron-firing+patterns+by+nicotinic+receptors.">Hierarchical control of dopamine neuron-firing patterns by nicotinic receptors.</a> Neuron. 50 (6), 911-921 (2006).</li><li>Wickham, 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=Ventral+tegmental+area+alpha6beta2+nicotinic+acetylcholine+receptors+modulate+phasic+dopamine+release+in+the+nucleus+accumbens+core.">Ventral tegmental area alpha6beta2 nicotinic acetylcholine receptors modulate phasic dopamine release in the nucleus accumbens core.</a> Psychopharmacology. 229 (1), 73-82 (2013).</li><li>Solecki, W., 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+role+of+ventral+tegmental+area+acetylcholine+and+N-methyl-D-aspartate+receptors+in+cocaine-seeking.">Differential role of ventral tegmental area acetylcholine and N-methyl-D-aspartate receptors in cocaine-seeking.</a> Neuropharmacology. 75, 9-18 (2013).</li><li>John, C. E., Jones, S. R., Michael, A. C., Borland, L. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fast+Scan+Cyclic+Voltammetry+of+Dopamine+and+Serotonin+in+Mouse+Brain+Slices.">Fast Scan Cyclic Voltammetry of Dopamine and Serotonin in Mouse Brain Slices.</a> Electrochemical Methods for Neuroscience. , (2007).</li><li>Rice, M. E., Cragg, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nicotine+amplifies+reward-related+dopamine+signals+in+striatum.">Nicotine amplifies reward-related dopamine signals in striatum.</a> Nature Neuroscience. 7 (6), 583-584 (2004).</li><li>Espana, R. 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=Hypocretin+1/orexin+A+in+the+ventral+tegmental+area+enhances+dopamine+responses+to+cocaine+and+promotes+cocaine+self-administration.">Hypocretin 1/orexin A in the ventral tegmental area enhances dopamine responses to cocaine and promotes cocaine self-administration.</a> Psychopharmacology. 214 (2), 415-426 (2011).</li><li>Addy, N. 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=The+L-type+calcium+channel+blocker,+isradipine,+attenuates+cue-induced+cocaine-seeking+by+enhancing+dopaminergic+activity+in+the+ventral+tegmental+area+to+nucleus+accumbens+pathway.">The L-type calcium channel blocker, isradipine, attenuates cue-induced cocaine-seeking by enhancing dopaminergic activity in the ventral tegmental area to nucleus accumbens pathway.</a> Neuropsychopharmacology. 43 (12), 2361-2372 (2018).</li><li>Hermans, A., Wightman, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Conical+tungsten+tips+as+substrates+for+the+preparation+of+ultramicroelectrodes.">Conical tungsten tips as substrates for the preparation of ultramicroelectrodes.</a> Langmuir. 22 (25), 10348-10353 (2006).</li><li>Borland, L. M., Michael, A. C., Borland, L. M., Michael, A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+Introduction+to+Electrochemical+Methods+in+Neuroscience.">An Introduction to Electrochemical Methods in Neuroscience.</a> Electrochemical Methods for Neuroscience. , (2007).</li><li>Mundroff, M. L., Wightman, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Amperometry+and+cyclic+voltammetry+with+carbon+fiber+microelectrodes+at+single+cells.">Amperometry and cyclic voltammetry with carbon fiber microelectrodes at single cells.</a> Current Protocols in Neuroscience. 6 (6), 14 (2002).</li><li>Rodeberg, N. T., 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=Hitchhiker's+Guide+to+Voltammetry:+Acute+and+Chronic+Electrodes+for+in+vivo+Fast-Scan+Cyclic+Voltammetry.">Hitchhiker's Guide to Voltammetry: Acute and Chronic Electrodes for in vivo Fast-Scan Cyclic Voltammetry.</a> ACS Chemical Neuroscience. 8 (2), 221-234 (2017).</li><li>Sabeti, J., Gerhardt, G. A., Zahniser, N. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chloral+hydrate+and+ethanol,+but+not+urethane,+alter+the+clearance+of+exogenous+dopamine+recorded+by+chronoamperometry+in+striatum+of+unrestrained+rats.">Chloral hydrate and ethanol, but not urethane, alter the clearance of exogenous dopamine recorded by chronoamperometry in striatum of unrestrained rats.</a> Neuroscience Letters. 343 (1), 9-12 (2003).</li><li>Masuzawa, 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=Pentobarbital+inhibits+ketamine-induced+dopamine+release+in+the+rat+nucleus+accumbens:+a+microdialysis+study.">Pentobarbital inhibits ketamine-induced dopamine release in the rat nucleus accumbens: a microdialysis study.</a> Anesthesia &amp; Analgesia. 96 (1), 148-152 (2003).</li><li>Montague, P. 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=Dynamic+gain+control+of+dopamine+delivery+in+freely+moving+animals.">Dynamic gain control of dopamine delivery in freely moving animals.</a> Journal of Neuroscience. 24 (7), 1754-1759 (2004).</li><li>Keithley, R. B., 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=Higher+sensitivity+dopamine+measurements+with+faster-scan+cyclic+voltammetry.">Higher sensitivity dopamine measurements with faster-scan cyclic voltammetry.</a> Analytical Chemistry. 83 (9), 3563-3571 (2011).</li><li>Jackson, B. P., Dietz, S. M., Wightman, R. 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CIS-FSCV provides a unique opportunity to investigate VTA receptor mechanisms underlying phasic DA release. There are two critical steps in order to ensure a proper recording. First, a stable baseline recording must be achieved, with little drift in the evoked DA signal. An important way to increase the likelihood of establishing a stable recording is to ensure that the electrode has had plenty of time to cycle at both 60 Hz and 10 Hz (typically 15 min at 60 Hz, and 10 min at 10 Hz). As the carbon fiber is being cycled, ...

Phasic dopamine (DA) release from the ventral tegmental area (VTA) to the nucleus accumbens (NAc) plays a vital role in reward-related behaviors. VTA DA neurons switch from a tonic-like firing (3-8 Hz) to a burst-like firing (&#62;14 Hz)1, which produces phasic DA release in the NAc. The VTA expresses a variety of somatodendritic receptors that are well-positioned to control the switch from tonic to burst-firing2,3,4,5. Identifying which of these receptors, and their respective inputs, control phasic DA release will deepen our understanding of how the reward-related circuitry is organized. The purpose of the methodology described here, combined infusion and stimulation with fast-scan cyclic voltammetry (CIS-FSCV), is to quickly and robustly assess the functionality of VTA receptors in driving phasic DA release.
The term combined infusion and stimulation (CIS) refers to pharmacologically manipulating receptors on a group of neurons (here the VTA) and stimulating those neurons to study the receptor&#39;s function. In the anesthetized rat, we electrically stimulate the VTA to evoke a large phasic DA signal (1-2 &#181;M) in the NAc core, as measured by fast-scan cyclic voltammetry (FSCV). Infusions of pharmacological drugs (i.e., receptor agonists/antagonists) at the stimulation site can be used to measure the function of VTA receptors by observing the subsequent change in evoked phasic DA release. FSCV is an electrochemical approach that enjoys both high spatial (50-100 &#181;m) and temporal (10 Hz) resolution, and is well-suited to measure reward-related, phasic DA events6,7. This resolution is finer than other in vivo neurochemical measurements, such as microdialysis. Thus, together, CIS-FSCV is well-suited to assess VTA receptor regulation of phasic dopamine release.
One common way to investigate VTA receptor function is by using a combination of electrophysiological approaches that address how those receptors alter the firing rate of neurons1,8. These studies are highly valuable in understanding what receptors are involved in driving DA firing upon activation. However, these studies can only suggest what might happen downstream at the axon terminal (i.e., release of a neurotransmitter). CIS-FSCV builds on these electrophysiological studies by answering how the output of VTA burst-firing, phasic DA release, is regulated by receptors located on VTA dendrites and cell bodies. Thus, CIS-FSCV is well-suited to build on these electrophysiology studies. As an example, nicotinic receptor activation can induce burst-firing in the VTA9, and CIS-FSCV in the anesthetized rat was used to show that nicotinic acetylcholine receptor (nAChR) activation in the VTA also controls phasic DA release in the NAc10,11.
Mechanistic examination of phasic DA regulation is also commonly studied using slice preparations alongside with bath application of drugs. These studies often focus on the presynaptic regulation of phasic DA release from dopamine terminals, as the cell bodies are often removed from the slice12. These preparations are valuable for studying presynaptic receptor effects on dopamine terminals, whereas CIS-FSCV is better suited to study somatodendritic receptor effects on dopamine neurons, as well as presynaptic inputs to the VTA. This distinction is important, because somatodendritic receptor activation in the VTA may have a different effect than NAc presynaptic receptor activation. Indeed, blocking dopaminergic presynaptic nAChRs in the NAc can elevate phasic dopamine release during burst-firing13, whereas the opposite is true at VTA somatodendritc nAChRs10,11.
CIS-FSCV is an ideal approach for studying the ability of VTA receptors to regulate phasic DA release. Importantly, this approach can be performed in an intact rat, either anesthetized or free moving. This approach is suitable for acute studies, to study receptor function in its baseline state10,14 as well as long-term studies that can assess functional changes in a receptor after drug exposure or behavioral manipulation11,15.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Electrode Filling Solution/Supplies</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Micropipette</td>
			<td>World Precision Instruments</td>
			<td>MF286-5 (28 gauge)</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium Acetate</td>
			<td>Sigma</td>
			<td>236497-100G</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium Chloride</td>
			<td>Sigma</td>
			<td>P3911-25G</td>
			<td></td>
		</tr>
		<tr>
			<td>Electrode Supplies</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Carbon fiber</td>
			<td>Thornel</td>
			<td>T650</td>
			<td></td>
		</tr>
		<tr>
			<td>Electrode puller</td>
			<td>Narishige International</td>
			<td>PE-22</td>
			<td>Note: horizontal pullers can be used as well</td>
		</tr>
		<tr>
			<td>Glass capillary</td>
			<td>A-M systems</td>
			<td>626000</td>
			<td></td>
		</tr>
		<tr>
			<td>Insulated wires for electrodes</td>
			<td>Weico Wire and Cable Incorporated</td>
			<td>UL 1423</td>
			<td>Length; 10 cm; diameter,0.4mm; must get custom made; insulated material should cover 5 cm of the wire</td>
		</tr>
		<tr>
			<td>Light Microscope (for viewing and cutting electrode)</td>
			<td>Fischer Scientific</td>
			<td>M3700</td>
			<td></td>
		</tr>
		<tr>
			<td>Pin</td>
			<td>Phoenix Enterprises</td>
			<td>HWS1646</td>
			<td>To be soldered onto the insuled electrode wire and reference electrode; connects to headstage</td>
		</tr>
		<tr>
			<td>Putty</td>
			<td>Alcolin</td>
			<td><a target="_blank" href="https://www.dickblick.com/items/23922-1003/">23922-1003</a></td>
			<td>Used to place electrode on while cutting the carbon fiber</td>
		</tr>
		<tr>
			<td>Scalpal Blade</td>
			<td>World Precision Instruments</td>
			<td>500239</td>
			<td>For cutting carbon fiber to the apprpriate length</td>
		</tr>
		<tr>
			<td>Silver Wire</td>
			<td>Sigma</td>
			<td>327026-4G</td>
			<td></td>
		</tr>
		<tr>
			<td>FSCV Hardware/Software</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Faraday Cage</td>
			<td>U-Line</td>
			<td>H-3618 (36&#34; x 24&#34; x 42&#34;)</td>
			<td></td>
		</tr>
		<tr>
			<td>Potentiostat</td>
			<td>Univ. of N. Carolina, Electronics Facility</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Stimulating electrode</td>
			<td>PlasticsOne</td>
			<td>MS303/2-A/SPC</td>
			<td>when ordering, request a 22 mm cut below pedestal</td>
		</tr>
		<tr>
			<td>TarHeel HDCV Software</td>
			<td>University of North Carolina-Chapel Hill</td>
			<td>-</td>
			<td><a href="https://chem.unc.edu/critcl-main/criticl-electronics/criticl-electronics-hardware/" target="_blank">https://chem.unc.edu/critcl-main/criticl-electronics/criticl-electronics-hardware/</a> for ordering information</td>
		</tr>
		<tr>
			<td>UEI breakout box</td>
			<td>Univ. of N. Carolina, Electronics Facility</td>
			<td></td>
			<td><a href="https://chem.unc.edu/critcl-main/criticl-electronics/criticl-electronics-hardware/" target="_blank">https://chem.unc.edu/critcl-main/criticl-electronics/criticl-electronics-hardware/</a> for ordering information</td>
		</tr>
		<tr>
			<td>UEI power supply</td>
			<td>Univ. of N. Carolina, Electronics Facility</td>
			<td></td>
			<td><a href="https://chem.unc.edu/critcl-main/criticl-electronics/criticl-electronics-hardware/" target="_blank">https://chem.unc.edu/critcl-main/criticl-electronics/criticl-electronics-hardware/</a> for ordering information</td>
		</tr>
		<tr>
			<td>Stimulator Hardware</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Neurolog stimulus isolator</td>
			<td>Digitimer Ltd.</td>
			<td>DS4</td>
			<td>Neurolog 800A</td>
		</tr>
		<tr>
			<td>Infusion/Stimulation Supplies</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Infusion Pump</td>
			<td>New Era Syringe Pump</td>
			<td>NE-300</td>
			<td></td>
		</tr>
		<tr>
			<td>Internal Cannula</td>
			<td>PlasticsOne</td>
			<td>C315I/SPC INTERNAL 33GA</td>
			<td></td>
		</tr>
		<tr>
			<td>Microliter Syringe</td>
			<td>Hamilton</td>
			<td>80308</td>
			<td></td>
		</tr>
		<tr>
			<td>Tubing</td>
			<td>PlasticsOne</td>
			<td>C313CT/ PKG TUBING 023 X 050 PE50</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical Supplies</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Cannula Holder</td>
			<td>Kopf Instruments</td>
			<td>1776 P-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Cotton Tip Applicators</td>
			<td>Vitality Medical</td>
			<td>806</td>
			<td></td>
		</tr>
		<tr>
			<td>Electrode Holder</td>
			<td>Kopf Instruments</td>
			<td>1770</td>
			<td></td>
		</tr>
		<tr>
			<td>Heating Pad</td>
			<td>Kent Scientific</td>
			<td>RT-0501</td>
			<td></td>
		</tr>
		<tr>
			<td>Povidone Iodine</td>
			<td>Vitality Medical</td>
			<td>29906-004</td>
			<td></td>
		</tr>
		<tr>
			<td>Screws</td>
			<td>Stoelting</td>
			<td>Bone Anchor Screws/Pkg.of 100</td>
			<td>1.59 mm O.D., 3.2 mm long</td>
		</tr>
		<tr>
			<td>Silver wire reference with AgCl</td>
			<td>InVivo Metric</td>
			<td>E255A</td>
			<td></td>
		</tr>
		<tr>
			<td>Square Gauze</td>
			<td>Vitality Medical</td>
			<td>441408</td>
			<td></td>
		</tr>
		<tr>
			<td>Stereotax</td>
			<td>Kopf Instruments</td>
			<td>Model 902 (Dual Arm Bar)</td>
			<td></td>
		</tr>
		<tr>
			<td>Histological Supplies</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Formulin</td>
			<td>Sigma</td>
			<td>1004960700</td>
			<td></td>
		</tr>
		<tr>
			<td>Power supply</td>
			<td>BK Precision</td>
			<td>9110</td>
			<td></td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Sigma</td>
			<td>80497</td>
			<td></td>
		</tr>
		<tr>
			<td>Tungsten microelectrode</td>
			<td>MicroProbes</td>
			<td>WE30030.5A3</td>
			<td></td>
		</tr>
		<tr>
			<td>Drugs for infusions</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>((2R)-amino-5-phosphonovaleric acid</td>
			<td>Sigma Aldrich</td>
			<td>A5282</td>
			<td></td>
		</tr>
		<tr>
			<td>N-methyl-D-aspartate</td>
			<td>Sigma Aldrich</td>
			<td>M3262</td>
			<td></td>
		</tr>
		<tr>
			<td>Mecamylamine hydrochloride (M9020-5mg)</td>
			<td>Sigma Aldrich</td>
			<td>M9020</td>
			<td></td>
		</tr>
		<tr>
			<td>Scopolamine hydrobromide (S0929-1g)</td>
			<td>Sigma Aldrich</td>
			<td>S0929</td>
			<td></td>
		</tr>
	</tbody>
</table>

combined infusion and stimulation with fast-scan cyclic voltammetry (cis-fscv) to assess ventral tegmental area receptor regulation of phasic dopamine

Phasic dopamine (DA) release from the ventral tegmental area (VTA) to the nucleus accumbens plays a pivotal role in reward processing and reinforcement learning. Understanding how the diverse neuronal inputs into the VTA control phasic DA release can provide a better picture of the circuitry that controls reward processing and reinforcement learning. Here, we describe a method that combines intra-VTA cannula infusions of pharmacological agonists and antagonists with stimulation-evoked phasic DA release (combined infusion and stimulation, or CIS) as measured by in vivo fast-scan cyclic voltammetry (FSCV). Using CIS-FSCV in anesthetized rats, a phasic DA response can be evoked by electrically stimulating the VTA with a bipolar electrode fitted with a cannula while recording in the nucleus accumbens core. Pharmacological agonists or antagonists can be infused directly at the stimulation site to investigate specific VTA receptors&#39; roles in driving phasic DA release. A major benefit of CIS-FSCV is that VTA receptor function can be studied in vivo, building on in vitro studies.

CIS-FSCV was used to study the function of VTA N-methyl-D-aspartate receptors (NMDAR), nicotinic acetylcholine receptors (nAChRs), and muscarinic acetylcholine receptors (mAChRs) in driving phasic DA release in the NAc core. Figure 2 shows representative data for a negative control, infusion of 0.9% saline, before (baseline) and 9 min postinfusion (saline). Figure 2 shows a color plot with potential on the y-axis, time on the x-a...

Watch this Scientific Journal Video about Combined Infusion and Stimulation with Fast-Scan Cyclic Voltammetry CIS-FSCV to Assess Ventral Tegmental Area Receptor Regulation of Phasic Dopamine at JoVE.c

Combined Infusion and Stimulation with Fast-Scan Cyclic Voltammetry CIS-FSCV to Assess Ventral Tegmental Area Receptor Regulation of Phasic Dopamine

The goal of this protocol is to directly manipulate ventral tegmental area receptors to study their contribution to subsecond dopamine release.

Combined Infusion and Stimulation with Fast-Scan Cyclic Voltammetry (CIS-FSCV) to Assess Ventral Tegmental Area Receptor Regulation of Phasic Dopamine

Phasic dopamine (DA) release from the ventral tegmental area (VTA) to the nucleus accumbens plays a pivotal role in reward processing and reinforcement ...

This approach can help elucidate the role of specific ventral tegmental area, somatodendritic receptors and phasic dopamine release in the nucleus accumbens. The main advantage of this approach is that questions about receptor function control over phasic dopamine release can be addressed in the intact brain. Optimizing the carbon fiber microelectrode and bipolar stimulator location can be challenging, and some advice for beginners is starting recording in the dorsal striatum.Due to the use and manipulation of multiple types of electrodes, including recording, reference, and stimulating electrodes, a visual guide of when and where these electrodes are implanted will be useful. After confirming a lack of response to pedal reflex, clean the scalp of an anesthetized rat with three sequential iodopovidone and 70%ethanol scrubs. After the last scrub, use sterilized needle nose tweezers and surgical scissors to cut away enough scalp tissue to make room for the implanted electrodes.Gently clean the exposed skull surface with sterilized cotton tip applicators before applying two to three drops of 3%hydrogen peroxide to help identify lambda and bregma. Next, use a one millimeter drill bit set to approximately 20, 000 revolutions per minute to make a 1.5 millimeter diameter hole, 2.5 millimeters anterior and 3.5 millimeters lateral to the bregma. Implant a 1.59 millimeter outer diameter, 3.2 millimeter long screw about halfway into the hole until the screw is firmly in place.Next, drill a one millimeter diameter reference electrode hole in the left hemisphere, 1.5 millimeters anterior, and 3.5 millimeters lateral to the bregma. Insert approximately two millimeters of reference wire into the hole while wrapping the wire around and under the head of the implanted screw. Then fully implant the screw, pinning the reference electrode in place.In the right hemisphere, drill a 1.5 millimeter diameter hole, 1.2 millimeters anterior, and 1.4 millimeters lateral to the bregma, and use tweezers to carefully remove the dura. For the stimulating electrode, drill a square hole two millimeters anterior-posterior and five millimeters medial-lateral centered at 5.2 millimeters posterior and one millimeter lateral to the bregma. Using stereotactic arm bars, lower the bipolar stimulating electrode guide cannula five millimeters below the dura.Using the stereotactic arm bars, lower the carbon fiber microelectrode four millimeters below the dura at the most dorsal portion of the striatum and connect the reference wire and carbon fiber to a potentiostat. Then apply a minus 0.4 to 1.4 volt, 400 volt per second triangular waveform for 15 minutes at 60 Hertz, followed by a 10-minute stimulus at 10 Hertz. To optimize the stimulating electrode location, set the stimulator to produce a bipolar electrical waveform with a 60 Hertz frequency, 24 pulses, 300 microamp current, and two millisecond per phase pulse width.Gently lower the stimulator in 0.2 millimeter increments from 5 to 7.8 millimeters below the dura, stimulating the VTA at each increment. Continue to lower the bipolar-stimulating electrode guide cannula until a stimulation produces phasic dopamine release at the carbon fiber microelectrode within the dorsal striatum. Once a dopamine release has been observed, lower the carbon fiber microelectrode until it is at least six millimeters below the dura into the most dorsal part of the nucleus accumbens core.When the electrode is in position, stimulate the VTA and record the peak amplitude of the dopamine peak, then lower or raise the carbon fiber microelectrode to the site that produces the greatest dopamine release, making sure that the peak of the dopamine response is represented as a clear oxidation peak at 0.6 volts and a reduction peak at minus 0.2 volts. Once the carbon fiber and stimulating electrode guide cannula location has been optimized, stimulate the animal every three minutes for 20 to 30 minutes. After achieving a stable baseline, gently lower the internal cannula by hand into the guide cannula pre-fitted into the bipolar stimulator and obtain an additional two to three baseline recordings to confirm that the cannula insertion did not cause a change in the evoked signal.Once a baseline response has been established, use a syringe pump and a microsyringe to infuse 0.5 microliters of the drug solution of interest into the VTA over a two-minute period. After the infusion, leave the internal cannula in place for at least one minute prior to removal, continuing to record the response every three minutes to measure the post-infusion effects. As demonstrated in these representative color plots, saline infusion does not alter the stimulated phasic dopamine release.The infusion of NMDA produces a robust increase in stimulated phasic dopamine release, while the NMDA receptor competitive antagonist, AP5, produces a robust decrease. Both the non-competitive nicotinic acetylcholine receptor antagonist mecamylamine and the non-selective competitive muscarinic acetylcholine receptor antagonist scopolamine produce a robust decrease in the stimulated phasic dopamine release. In this graph, a summary of the effects of the tested drugs over time can be observed.The infusion cannula must be carefully inserted into the bipolar stimulating electrode. Otherwise, excessive damage can occur, leading to artifactual changes in phasic dopamine release. This approach has allowed investigators to more finely address the specific receptor mechanisms by which phasic dopamine release is regulated in vivo.

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