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 acetate with 140 mM potassium chloride16.</li>
	</ol>
	</li>
	<li>Electrode preparation
	<ol>
		<li>Using vacuum suction, insert a T-650 carbon fiber (7 &#181;m in diameter) into a borosilicate glass capillary (length = 100 mm, diameter = 1.0 mm, inside diameter = 0.5 mm).</li>
		<li>Once the carbon fiber has been placed inside the glass capillary, place the glass capillary into a vertical electrode puller, with the heat element roughly in the middle of the capillary. Set the heater to 55 with the magnet turned off.</li>
		<li>After the capillary is pulled, carefully raise the upper capillary holder so that the tip of the electrode is not surrounded by the heating element.</li>
		<li>Using sharp scissors, cut the carbon fiber that is still connecting the two pieces of the capillary. This will result in two separate carbon fiber microelectrodes.</li>
		<li>Under a light microscope, carefully cut the exposed carbon fiber with a sharp scalpel, so that the carbon fiber extends approximately 75-100 &#181;m beyond the end of the glass.</li>
		<li>Using a light microscope, ensure that the electrode is free of cracks along the capillary. Also ensure that the seal, where the carbon fiber exits the capillary, is difficult to notice and free from cracks. 
		NOTE: A good seal will help reduce noise during recordings. See published studies17,18,19 for a more detailed protocol.</li>
	</ol>
	</li>
	<li>Reference electrode fabrication
	<ol>
		<li>Solder a gold pin to a 5 cm silver wire.</li>
		<li>Attach the anode to a metal paper clip or other conductor, the cathode to a pin, and apply a voltage (~2 V) while the paper clip and silver wire is submerged in 0.1 M HCl.</li>
		<li>Cease the voltage once a white coating (AgCl) appears on the silver wire.</li>
	</ol>
	</li>
	<li>Preparing electrode for implantation
	<ol>
		<li>Solder a gold pin to a thin insulated wire (~10 cm in length, &#60;0.50 mm diameter).</li>
		<li>Remove ~5 cm of insulation from the wire opposite to the gold pin.</li>
		<li>Fill the electrode approximately halfway with electrode solution.</li>
		<li>Insert insulated wire into the electrode. 
		NOTE: The wire should make contact with the carbon fiber inside the electrode.</li>
	</ol>
	</li>
</ol>
2. Electrode implantations
<ol>
	<li>Give adult, male, Sprague Dawley rats (250&#8722;450 g) an intraperitoneal injection (1.5 g/kg or 1 mL/kg volume) of 0.5 g/mL urethane dissolved in sterile saline. Start with an initial urethane dose of 1.0&#8722;1.2 g/kg. If the animal is still responsive to the noxious stimulus test (tail pinch) 20 min after urethane administration, administer an additional 0.3&#8722;0.5 g/kg urethane for a 1.5 g/kg total dose. 
	NOTE: For preparation of the 0.5 g/mL urethane solution, add 10 g of urethane to 10 g (~10 mL) of saline. Urethane is a carcinogen and must be handled with care. Urethane is an important anesthetic, as it does not alter levels of dopamine, as do other anesthetics such as ketamine/ xylazine and chloral hydrate20,21.</li>
	<li>Once the animal is deeply anesthetized and is not responsive to noxious stimuli (e.g., toe pinch), place it in the stereotaxic frame.&#160;Apply ophthalmic lubricant to each eye of the rat. 
	NOTE: This is a non-survival surgery, but good aseptic technique is encouraged.</li>
	<li>Clean the rat&#39;s scalp using a two-stage scrub (i.e., an iodopovidone scrub followed by a 70% ethanol scrub; perform with a 3 cycle repetition).</li>
	<li>Cut away the scalp tissue using sterilized needle nose tweezers and surgical scissors. Remove a significant amount of tissue to make room for the various implantations outlined below.</li>
	<li>Gently clean the skull surface using sterilized cotton tip applicators. Then apply 2&#8722;3 drops of 3% hydrogen peroxide to help identify the lambda and bregma.</li>
	<li>Using a stereotaxic or hand drill (1.0 mm, ~20,000 rpm), drill a 1.5 mm diameter hole 2.5 mm anterior to the bregma and 3.5 mm lateral to the bregma. Partially (about halfway, until it is firmly in place) implant a screw (1.59 mm O.D., 3.2 mm long) in this hole. It is recommended to use sterile saline to irrigate while drilling to prevent thermal injury.</li>
	<li>For the reference electrode, drill a 1.0 mm diameter hole 1.5 mm anterior and 3.5 mm lateral to the bregma, in the left hemisphere.</li>
	<li>By hand, insert ~2 mm of reference wire into this hole, while wrapping the reference wire around and under the head of the implanted screw.</li>
	<li>Fully implant the screw, pinning down the reference electrode in place.</li>
	<li>In the right hemisphere, drill a 1.5 mm diameter hole 1.2 mm anterior and 1.4 mm lateral to the bregma.</li>
	<li>Gently remove the dura using tweezers.</li>
	<li>For the stimulating electrode, drill a square hole (2 mm anterior-posterior, 5 mm medial-lateral) centered at 5.2 mm posterior and 1.0 mm lateral to the bregma.</li>
	<li>Using the stereotactic arm bars, lower the bipolar stimulating electrode/guide cannula 5 mm below the dura. In case of bleeding during the implantation of the electrode, use sterile cotton swabs and gauze to minimize bleeding. 
	NOTE: The bipolar stimulating electrode used in this method is prefitted with a guide cannula (Table of Materials). The internal cannula used with this item should be flushed with the prongs on the bipolar stimulating electrode when fully inserted into the guide cannula. This will allow the internal cannula to sit directly in between the two prongs of the stimulator, which sit about 1 mm apart. A similar protocol is described elsewhere14.</li>
	<li>Using the stereotactic arm bars, lower the carbon fiber microelectrode 4 mm below the dura. This location is at the most dorsal portion of the striatum.</li>
	<li>Connect the reference wire and carbon fiber to a potentiostat.</li>
	<li>Apply a triangular wave form (-0.4&#8722;1.3 V, 400 V/s) for 15 min at 60 Hz, and again for 10 min at 10 Hz. 
	NOTE: Typically, when applying waveforms to carbon fiber microelectrodes in the brain, oxide groups are added to the surface of the carbon fiber. Equilibrium of this reaction must be reached prior to recording; otherwise significant drift will occur19. Cycling the electrode at higher frequencies (60 Hz) allows the carbon fiber to achieve equilibrium faster.</li>
</ol>
3. Optimizing carbon fiber and stimulating electrode/guide cannula locations
<ol>
	<li>Set the stimulator to produce a bipolar electrical waveform, with a frequency of 60 Hz, 24 pulses, 300 &#181;A current, and pulse width of 2 ms/phase.</li>
	<li>Gently lower the stimulator in increments of 0.2 mm from 5 mm to 7.8 mm below the dura. At each increment, stimulate the VTA. 
	NOTE: At more dorsal depths (5&#8722;6 mm), stimulation of the brain will typically (~80% of the time) cause the whiskers of the rat to twitch. At further depths, the whiskers will cease twitching, which occurs between 7.5&#8722;8.2 mm below the dura. When the whiskers cease twitching, the stimulating electrode will be near or at the VTA. This will not occur in every rat, and lack of whisker twitching should not be taken as a sign that the bipolar stimulating electrode/infusion cannula is misplaced. Whisker twitching may not occur for all anesthetics (e.g., isoflurane).</li>
	<li>Continue to lower the bipolar stimulating electrode/guide cannula until a stimulation produces phasic DA release at the carbon fiber microelectrode (currently in the dorsal striatum). 
	NOTE: DA release in the dorsal striatum will not always occur if the bipolar electrode is implanted in the VTA, but observation of DA release in the dorsal striatum upon VTA stimulation is usually a good sign that a good signal will be observed in the NAc core.</li>
	<li>Lower the carbon fiber microelectrode until it is at least 6.0 mm below the dura. This is the most dorsal part of the NAc core.</li>
	<li>Stimulate the VTA and record the peak amplitude of the DA peak.</li>
	<li>Lower or raise the carbon fiber microelectrode at the site that produces the greatest DA release.</li>
	<li>Ensure that the peak of the DA response is a clear oxidation peak at 0.6 V and a reduction peak at -0.2 V. These peaks are indicative of DA.</li>
</ol>
4. Combination infusion and stimulation FSCV recording
NOTE: Figure 1 shows the timeline for recording before and after VTA microinfusion.
<ol>
	<li>Once the carbon fiber and stimulating electrode/guide cannula location has been optimized, stimulate for ~20&#8722;30 min. 
	NOTE: Under the current stimulation parameters, do not stimulate any more than once every 3 min, to allow for vesicular reloading22.</li>
	<li>After achieving a stable baseline (&#60;20% variation over five stimulations), gently lower the internal cannula by hand into the guide cannula that is prefitted into the bipolar stimulator.</li>
	<li>Take an additional 2&#8722;3 baseline recordings to ensure that the cannula insertion itself did not cause a change in the evoked signal. In some cases, insertion and removal of the internal cannula can cause damage to the VTA. If the signal drastically changes over this baseline period (&#62;20%), then take an additional 3&#8722;4 recordings until the baseline restabilizes.</li>
	<li>Using a syringe pump and microsyringe, infuse 0.5 &#181;L of solution (e.g., 0.9% saline, N-methyl-D-aspartate [NMDA], (2R)-amino-5-phosphonovaleric acid [AP5]) into the VTA over a 2 min period.</li>
	<li>Postinfusion, leave the internal cannula for at least 1 min prior to removal. 
	NOTE: Some drugs may require leaving the internal cannula for a longer time based on the drug kinetics, and removal of the internal cannula may cause the drug to travel back up through the internal cannula. If there is concern, one could leave the internal cannula in the guide cannula during the entirety of the recording. Otherwise, recording can begin after this 1 min interval.</li>
	<li>Continue recording every 3 min to measure postinfusion effects. 
	NOTE: If infusing a control solution, and no effect is observed, it is possible to infuse a second time10. If there is altered DA release caused by inserting the internal cannula or saline infusion, the signal typically recovers to baseline within 30 min.</li>
</ol>
5. Histological verification of electrode placement
<ol>
	<li>At the end of the experiment, create a small lesion at the recording site using the carbon fiber microelectrode.
	<ol>
		<li>If the electrode must be preserved for postexperiment calibration, then use a tungsten wire placed in a glass capillary protruding ~100 &#181;m beyond the capillary tip. In this case, raise the electrode from the brain, replace the recording electrode with the tungsten electrode, and lower it to the same dorsoventral coordinate. 
		NOTE: The carbon fiber may be used to lesion the brain as well and will provide a more accurate representation of the location of the recording site; however, the experimenter will lose the ability to calibrate these electrodes.</li>
	</ol>
	</li>
	<li>To lesion the recording site, apply voltage using a power supply. Start at 1 V and increase by 1 V every 10 s until 10 V is reached.</li>
	<li>Euthanize the animal using a lethal intraperitoneal injection of pentobarbital (150 mg/kg).</li>
	<li>Perfuse the rat using a 4% formalin solution.</li>
	<li>Remove the head from the rat using a sharpened guillotine.</li>
	<li>Using rongeurs, remove the connective tissue and skull surrounding the brain, and gently dislodge the brain from any remaining tissue.</li>
	<li>Store the brain in 4% formalin for 1 day and then transfer it to 30% sucrose. 
	NOTE: Perfusion with 4% formalin is not necessary to see the lesion site, although as a best practice it will improve the reconstruction of the lesion site.</li>
	<li>Create 30 &#181;m slices of the brain using a cryostat.</li>
	<li>Mount the slices on slides and cover with a cover slip.</li>
	<li>Denote the location of the carbon fiber microelectrode lesion and bipolar stimulator/infusion cannula location using a light microscope.</li>
</ol>

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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=Monitoring+rapid+chemical+communication+in+the+brain.">Monitoring rapid chemical communication in the brain.</a> Chemical Reviews. 108 (7), 2554-2584 (2008).</li><li>Park, 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=Heterogeneous+extracellular+dopamine+regulation+in+the+subregions+of+the+olfactory+tubercle.">Heterogeneous extracellular dopamine regulation in the subregions of the olfactory tubercle.</a> Journal of Neurochemistry. 142 (3), 365-377 (2017).</li><li>Ganesana, M., Venton, B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Early+changes+in+transient+adenosine+during+cerebral+ischemia+and+reperfusion+injury.">Early changes in transient adenosine during cerebral ischemia and reperfusion injury.</a> PLoS One. 13 (5), e0196932 (2018).</li></ol>

The authors have nothing to disclose.

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 ...

combined-infusion-stimulation-with-fast-scan-cyclic-voltammetry-cis

Research

JoVE Journal

Neuroscience

3.0K Views.  Elizabethtown College. The goal of this protocol is to directly manipulate ventral tegmental area receptors to study their contribution to subsecond dopamine release.

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

Combining Transcranial Magnetic Stimulation and fMRI to Examine the Default Mode Network

The default mode network is a group of brain regions that are active when an individual is not focused on the outside world and the brain is at "wakeful rest."1,2,3 It is thought the default mode network corresponds to self-referential or "internal mentation".2,3
It has been hypothesized that, in humans, activity within the default mode network is correlated with certain pathologies (for instance, hyper-activation has been linked to schizophrenia 4,5,6 and autism spectrum disorders 7 whilst hypo-activation of the network has been linked to Alzheimer's and other neurodegenerative diseases 8). As such, noninvasive modulation of this network may represent a potential therapeutic intervention for a number of neurological and psychiatric pathologies linked to abnormal network activation. One possible tool to effect this modulation is Transcranial Magnetic Stimulation: a non-invasive neurostimulatory and neuromodulatory technique that can transiently or lastingly modulate cortical excitability (either increasing or decreasing it) via the application of localized magnetic field pulses.9
In order to explore the default mode network's propensity towards and tolerance of modulation, we will be combining TMS (to the left inferior parietal lobe) with functional magnetic resonance imaging (fMRI). Through this article, we will examine the protocol and considerations necessary to successfully combine these two neuroscientific tools.

In this article, we examine the methodology and considerations relevant to the combination of TMS and fMRI to examine the effects of brain stimulation on the default network.

The default mode network is a group of brain regions that are active when an individual is not focused on the outside world and the brain is at "wakeful ...

TMS: Using the Theta-Burst Protocol to Explore Mechanism of Plasticity in Individuals with Fragile X Syndrome and Autism

Fragile X Syndrome (FXS), also known as Martin-Bell Syndrome, is a genetic abnormality found on the X chromosome.1,2 Individuals suffering from FXS display abnormalities in the expression of FMR1 - a protein required for typical, healthy neural development.3 Recent data has suggested that the loss of this protein can cause the cortex to be hyperexcitable thereby affecting overall patterns of neural plasticity.4,5
In addition, Fragile X shows a strong comorbidity with autism: in fact, 30% of children with FXS are diagnosed with autism, and 2 - 5% of autistic children suffer from FXS.6
Transcranial Magnetic Stimulation (a non-invasive neurostimulatory and neuromodulatory technique that can transiently or lastingly modulate cortical excitability via the application of localized magnetic field pulses 7,8) represents a unique method of exploring plasticity and the manifestations of FXS within affected individuals. More specifically, Theta-Burst Stimulation (TBS), a specific stimulatory protocol shown to modulate cortical plasticity for a duration up to 30 minutes after stimulation cessation in healthy populations, has already proven an efficacious tool in the exploration of abnormal plasticity.9,10 
Recent studies have shown the effects of TBS last considerably longer in individuals on the autistic spectrum - up to 90 minutes.11 This extended effect-duration suggests an underlying abnormality in the brain's natural plasticity state in autistic individuals - similar to the hyperexcitability induced by Fragile X Syndrome.
In this experiment, utilizing single-pulse motor-evoked potentials (MEPs) as our benchmark, we will explore the effects of both intermittent and continuous TBS on cortical plasticity in individuals suffering from FXS and individuals on the Autistic Spectrum.

In this article, we examine the effects of Theta-Burst TMS stimulation on cortical plasticity in individuals suffering from Fragile X syndrome and individuals on the autistic spectrum.

Fragile X Syndrome (FXS), also known as Martin-Bell Syndrome, is a genetic abnormality found on the X chromosome.1,2 Individuals suffering from FXS ...

Presynaptic Dopamine Dynamics in Striatal Brain Slices with Fast-scan Cyclic Voltammetry

Extensive research has focused on the neurotransmitter dopamine because of its importance in the mechanism of action of drugs of abuse (e.g. cocaine and amphetamine), the role it plays in psychiatric illnesses (e.g. schizophrenia and Attention Deficit Hyperactivity Disorder), and its involvement in degenerative disorders like Parkinson's and Huntington's disease. Under normal physiological conditions, dopamine is known to regulate locomotor activity, cognition, learning, emotional affect, and neuroendocrine hormone secretion. One of the largest densities of dopamine neurons is within the striatum, which can be divided in two distinct neuroanatomical regions known as the nucleus accumbens and the caudate-putamen. The objective is to illustrate a general protocol for slice fast-scan cyclic voltammetry (FSCV) within the mouse striatum. FSCV is a well-defined electrochemical technique providing the opportunity to measure dopamine release and uptake in real time in discrete brain regions. Carbon fiber microelectrodes (diameter of ~ 7 &mu;m) are used in FSCV to detect dopamine oxidation. The analytical advantage of using FSCV to detect dopamine is its enhanced temporal resolution of 100 milliseconds and spatial resolution of less than ten microns, providing complementary information to in vivo microdialysis.

Using fast-scan cyclic voltammetry to measure electrically evoked presynaptic dopamine dynamics in striatal brain slices.

Extensive research has focused on the neurotransmitter dopamine because of its importance in the mechanism of action of drugs of abuse (e.g. cocaine and ...

Voltage Biasing, Cyclic Voltammetry, &amp; Electrical Impedance Spectroscopy for Neural Interfaces

Electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measure properties of the electrode-tissue interface without additional invasive procedures, and can be used to monitor electrode performance over the long term. EIS measures electrical impedance at multiple frequencies, and increases in impedance indicate increased glial scar formation around the device, while cyclic voltammetry measures the charge carrying capacity of the electrode, and indicates how charge is transferred at different voltage levels. As implanted electrodes age, EIS and CV data change, and electrode sites that previously recorded spiking neurons often exhibit significantly lower efficacy for neural recording. The application of a brief voltage pulse to implanted electrode arrays, known as rejuvenation, can bring back spiking activity on otherwise silent electrode sites for a period of time. Rejuvenation alters EIS and CV, and can be monitored by these complementary methods. Typically, EIS is measured daily as an indication of the tissue response at the electrode site. If spikes are absent in a channel that previously had spikes, then CV is used to determine the charge carrying capacity of the electrode site, and rejuvenation can be applied to improve the interface efficacy. CV and EIS are then repeated to check the changes at the electrode-tissue interface, and neural recordings are collected. The overall goal of rejuvenation is to extend the functional lifetime of implanted arrays.

The electrode-tissue interface of neural recording electrodes can be characterized with electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Application of voltage biasing changes the electrochemical properties of the electrode-tissue interface and can improve recording capability. Voltage biasing, EIS, CV, and neural recordings are complementary.

Electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measure properties of the electrode-tissue interface without additional invasive ...

Single Cell Measurement of Dopamine Release with Simultaneous Voltage-clamp and Amperometry

After its release into the synaptic cleft, dopamine exerts its biological properties via its pre- and post-synaptic targets1. The dopamine signal is terminated by diffusion2-3, extracellular enzymes4, and membrane transporters5. The dopamine transporter, located in the peri-synaptic cleft of dopamine neurons clears the released amines through an inward dopamine flux (uptake). The dopamine transporter can also work in reverse direction to release amines from inside to outside in a process called outward transport or efflux of dopamine5. More than 20 years ago Sulzer et al. reported the dopamine transporter can operate in two modes of activity: forward (uptake) and reverse (efflux)5. The neurotransmitter released via efflux through the transporter can move a large amount of dopamine to the extracellular space, and has been shown to play a major regulatory role in extracellular dopamine homeostasis6. Here we describe how simultaneous patch clamp and amperometry recording can be used to measure released dopamine via the efflux mechanism with millisecond time resolution when the membrane potential is controlled. For this, whole-cell current and oxidative (amperometric) signals are measured simultaneously using an Axopatch 200B amplifier (Molecular Devices, with a low-pass Bessel filter set at 1,000 Hz for whole-cell current recording). For amperometry recording a carbon fiber electrode is connected to a second amplifier (Axopatch 200B) and is placed adjacent to the plasma membrane and held at +700 mV. The whole-cell and oxidative (amperometric) currents can be recorded and the current-voltage relationship can be generated using a voltage step protocol. Unlike the usual amperometric calibration, which requires conversion to concentration, the current is reported directly without considering the effective volume7. Thus, the resulting data represent a lower limit to dopamine efflux because some transmitter is lost to the bulk solution.

The amperometric technique measures dopamine release from a single cell by detecting the oxidative current produced by spontaneous dopamine oxidization. Simultaneous voltage clamp and amperometry methodology reveal the mechanistic relationship between the overall "activity" of dopamine transporter and the regulatory role of this activity on the reverse transport of dopamine.

After its release into the synaptic cleft, dopamine exerts its biological properties via its pre- and post-synaptic targets1. The dopamine signal is ...

Comprehensive Profiling of Dopamine Regulation in Substantia Nigra and Ventral Tegmental Area

Dopamine is a vigorously studied neurotransmitter in the CNS. Indeed, its involvement in locomotor activity and reward-related behaviour has fostered five decades of inquiry into the molecular deficiencies associated with dopamine regulation. The majority of these inquiries of dopamine regulation in the brain focus upon the molecular basis for its regulation in the terminal field regions of the nigrostriatal and mesoaccumbens pathways; striatum and nucleus accumbens. Furthermore, such studies have concentrated on analysis of dopamine tissue content with normalization to only wet tissue weight. Investigation of the proteins that regulate dopamine, such as tyrosine hydroxylase (TH) protein, TH phosphorylation, dopamine transporter (DAT), and vesicular monoamine transporter 2 (VMAT2) protein often do not include analysis of dopamine tissue content in the same sample. The ability to analyze both dopamine tissue content and its regulating proteins (including post-translational modifications) not only gives inherent power to interpreting the relationship of dopamine with the protein level and function of TH, DAT, or VMAT2, but also extends sample economy. This translates into less cost, and yet produces insights into the molecular regulation of dopamine in virtually any paradigm of the investigators' choice.
We focus the analyses in the midbrain. Although the SN and VTA are typically neglected in most studies of dopamine regulation, these nuclei are easily dissected with practice. A comprehensive readout of dopamine tissue content and TH, DAT, or VMAT2 can be conducted. There is burgeoning literature on the impact of dopamine function in the SN and VTA on behavior, and the impingements of exogenous substances or disease processes therein 1-5. Furthermore, compounds such as growth factors have a profound effect on dopamine and dopamine-regulating proteins, to a comparatively greater extent in the SN or VTA 6-8. Therefore, this methodology is presented for reference to laboratories that want to extend their inquiries on how specific treatments modulate behaviour and dopamine regulation. Here, a multi-step method is presented for the analyses of dopamine tissue content, the protein levels of TH, DAT, or VMAT2, and TH phosphorylation from the substantia nigra and VTA from rodent midbrain. The analysis of TH phosphorylation can yield significant insights into not only how TH activity is regulated, but also the signaling cascades affected in the somatodendritic nuclei in a given paradigm.
We will illustrate the dissection technique to segregate these two nuclei and the sample processing of dissected tissue that produces a profile revealing molecular mechanisms of dopamine regulation in vivo, specific for each nuclei (Figure 1).

Dopamine is distinctly regulated in the midbrain nuclei, which contain the cell bodies and dendrites of the dopamine neurons. Here we describe a dissection and sample-handling approach to maximize results, and thus conclusions and insights, on dopamine regulation in the midbrain nuclei of the substantia nigra (SN) and ventral tegmental area (VTA) in rodents.

Dopamine is a vigorously studied neurotransmitter in the CNS. Indeed, its involvement in locomotor activity and reward-related behaviour has fostered five ...

Laser Capture Microdissection - A Demonstration of the Isolation of Individual Dopamine Neurons and the Entire Ventral Tegmental Area

Laser capture microdissection (LCM) is used to isolate a concentrated population of individual cells or precise anatomical regions of tissue from tissue sections on a microscope slide. When combined with immunohistochemistry, LCM can be used to isolate individual cells types based on a specific protein marker. Here, the LCM technique is described for collecting a specific population of dopamine neurons directly labeled with&#160;tyrosine hydroxylase immunohistochemistry and for isolation of the dopamine neuron containing region of the ventral tegmental area using indirect tyrosine hydroxylase immunohistochemistry on a section adjacent to those used for LCM. An infrared (IR) capture laser is used to both dissect individual neurons as well as the ventral tegmental area off glass slides and onto an LCM cap for analysis. Complete dehydration of the tissue with 100% ethanol and xylene is critical. The combination of the IR capture laser and the ultraviolet (UV) cutting laser is used to isolate individual dopamine neurons or the ventral tegmental area when using PEN membrane slides. A PEN membrane slide has significant advantages over a glass slide as it offers better consistency in capturing and collecting cells, is faster collecting large pieces of tissue, is less reliant on dehydration and results in complete removal of the tissue from the slide. Although removal of large areas of tissue from a glass slide is feasible, it is considerably more time consuming and frequently leaves some residual tissue behind. Data shown here demonstrate that RNA of sufficient quantity and quality can be obtained using these procedures for quantitative PCR measurements. Although RNA and DNA are the most commonly isolated molecules from tissue and cells collected with LCM, isolation and measurement of microRNA, protein and epigenetic changes in DNA can also benefit from the enhanced anatomical and cellular resolution obtained using LCM.

The isolation of individual dopamine neurons or the ventral tegmental area with direct or indirect immunohistochemistry is demonstrated using laser capture microdissection. Parameters for isolation of tissue from a glass slide using an infrared laser and from membrane slides using the combination of an infrared and ultraviolet laser are discussed.

Laser capture microdissection (LCM) is used to isolate a concentrated population of individual cells or precise anatomical regions of tissue from tissue ...

The Preparation of Oblique Spinal Cord Slices for Ventral Root Stimulation

Electrophysiological recordings from spinal cord slices have proven to be a valuable technique to investigate a wide range of questions, from cellular to network properties. We show how to prepare viable oblique slices of the spinal cord of young mice (P2 - P11). In this preparation, the motoneurons retain&#160;their axons coming out from the ventral roots of the&#160;spinal cord. Stimulation of these axons elicits back-propagating action potentials invading the motoneuron&#160;somas and exciting the motoneuron&#160;collaterals within the spinal cord. Recording of antidromic action potentials is an immediate, definitive and elegant way to characterize motoneuron identity, which surpasses&#160;other identification methods. Furthermore, stimulating the motoneuron collaterals is a simple and reliable way to excite the collateral targets of the motoneurons within the spinal cord, such as other motoneurons or Renshaw cells. In this protocol, we present antidromic recordings from the motoneuron somas as well as Renshaw cell excitation, resulting from ventral root stimulation.

We show how to prepare oblique slices of the spinal cord in young mice. This preparation allows for the stimulation of the ventral roots.

Electrophysiological recordings from spinal cord slices have proven to be a valuable technique to investigate a wide range of questions, from cellular to ...

Using Enzyme-based Biosensors to Measure Tonic and Phasic Glutamate in Alzheimer's Mouse Models

Neurotransmitter disruption is often a key component of diseases of the central nervous system (CNS), playing a role in the pathology underlying Alzheimer's disease, Parkinson's disease, depression, and anxiety. Traditionally, microdialysis has been the most common (lauded) technique to examine neurotransmitter changes that occur in these disorders. But because microdialysis has the ability to measure slow 1-20 minute changes across large areas of tissue, it has the disadvantage of invasiveness, potentially destroying intrinsic connections within the brain and a slow sampling capability. A relatively newer technique, the microelectrode array (MEA), has numerous advantages for measuring specific neurotransmitter changes within discrete brain regions as they occur, making for a spatially and temporally precise approach. In addition, using MEAs is minimally invasive, allowing for measurement of neurotransmitter alterations in vivo. In our laboratory, we have been specifically interested in changes in the neurotransmitter, glutamate, related to Alzheimer's disease pathology. As such, the method described here has been used to assess potential hippocampal disruptions in glutamate in a transgenic mouse model of Alzheimer's disease. Briefly, the method used involves coating a multi-site microelectrode with an enzyme very selective for the neurotransmitter of interest and using self-referencing sites to subtract out background noise and interferents. After plating and calibration, the MEA can be constructed with a micropipette and lowered into the brain region of interest using a stereotaxic device. Here, the method described involves anesthetizing rTg(TauP301L)4510 mice and using a stereotaxic device to precisely target sub-regions (DG, CA1, and CA3) of the hippocampus.

Using Enzyme-based Biosensors to Measure Tonic and Phasic Glutamate in Alzheimer&#039;s Mouse Models

Here, we describe the setup, software navigation, and data analysis for a spatially and temporally precise method of measuring tonic and phasic extracellular glutamate changes in vivo using enzyme-linked microelectrode arrays (MEA).

Neurotransmitter disruption is often a key component of diseases of the central nervous system (CNS), playing a role in the pathology underlying ...

Modeling Fast-scan Cyclic Voltammetry Data from Electrically Stimulated Dopamine Neurotransmission Data Using QNsim1.0

Central dopaminergic (DAergic) pathways have an important role in a wide range of functions, such as attention, motivation, and movement. Dopamine (DA) is implicated in diseases and disorders including attention deficit hyperactivity disorder, Parkinson's disease, and traumatic brain injury. Thus, DA neurotransmission and the methods to study it are of intense scientific interest. In vivo fast-scan cyclic voltammetry (FSCV) is a method that allows for selectively monitoring DA concentration changes with fine temporal and spatial resolution. This technique is commonly used in conjunction with electrical stimulations of ascending DAergic pathways to control the impulse flow of dopamine neurotransmission. Although the stimulated DA neurotransmission paradigm can produce robust DA responses with clear morphologies, making them amenable for kinetic analysis, there is still much debate on how to interpret the responses in terms of their DA release and clearance components. To address this concern, a quantitative neurobiological (QN) framework of stimulated DA neurotransmission was recently developed to realistically model the dynamics of DA release and reuptake over the course of a stimulated DA response. The foundations of this model are based on experimental data from stimulated DA neurotransmission and on principles of neurotransmission adopted from various lines of research. The QN model implements 12 parameters related to stimulated DA release and reuptake dynamics to model DA responses. This work describes how to simulate DA responses using QNsim1.0 and also details principles that have been implemented to systematically discern alterations in the stimulated dopamine release and reuptake dynamics.

Fast-scan cyclic voltammetry can monitor in vivo dopamine neurotransmission in the context of drugs, disease, and other experimental manipulations. This work describes the implementation of QNsim1.0, a software to model electrically stimulated dopamine responses according to the quantitative neurobiological model to quantify estimates of dopamine release and reuptake dynamics.

Central dopaminergic (DAergic) pathways have an important role in a wide range of functions, such as attention, motivation, and movement. Dopamine (DA) is ...