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Ethanol attenuation of long-term depression in the nucleus accumbens can be overcome by activation of TRPV1 receptors.

ABSTRACT: Altered expression of synaptic plasticity within the nucleus accumbens (NAc) constitutes a critical neuroadaptive response to ethanol (EtOH) and other drugs of abuse. We have previously reported that N-methyl-D-aspartate receptor (NMDAR)-dependent long-term depression (LTD) is markedly affected by chronic intermittent ethanol exposure in vivo; however, endocannabinoid (eCB)-dependent synaptic depression, despite being very well-documented in the dorsal striatum, is much less well understood in the NAc.Whole cell patch clamp electrophysiology was used to investigate interactions between these different plasticity-induction systems. Excitatory postsynaptic currents (EPSCs) were measured in the NAc shell and NMDAR-LTD was induced by a pairing protocol (500 stimuli at 1 Hz stimulation [low-frequency stimulation (LFS)] paired with postsynaptic depolarization to -50 mV). AM251, a CB1 receptor antagonist, was used to determine whether this form of LTD is modulated by eCBs. To determine the effect of EtOH on a purely eCB-dependent response in the NAc, depolarization-induced suppression of excitation (DSE) was used in the presence of 40 mM EtOH. Finally, we determined whether the enhancement of eCB signaling with URB597, a fatty acid amide hydrolase inhibitor, and AM404, an anandamide re-uptake inhibitor would also modulate LFS LTD in the presence of NMDAR blockade or EtOH.In the presence of AM251, the LFS pairing protocol resulted in NMDAR-dependent long-term potentiation that was blocked with either EtOH or DL-APV. We also found that DSE in the NAc shell was blocked by AM251 and suppressed by EtOH. Enhanced eCB signaling rescued NAc-LTD expression in the presence of EtOH through a distinct mechanism requiring activation of TRPV1 receptors.EtOH modulation of synaptic plasticity in the NAc is dependent upon a complex interplay between NMDARs, eCBs, and TRPV1 receptors. These findings demonstrate a novel form of TRPV1-dependent LTD in the NAc shell that may be critical for EtOH dependence.

SUBMITTER: Renteria R

PROVIDER: S-EPMC4244656 | biostudies-literature | 2014 Nov

REPOSITORIES: biostudies-literature

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Ethanol attenuation of long-term depression in the nucleus accumbens can be overcome by activation of TRPV1 receptors.

Renteria Rafael R Jeanes Zachary M ZM Morrisett Richard A RA

Alcoholism, clinical and experimental research 20141101 11

<h4>Background</h4>Altered expression of synaptic plasticity within the nucleus accumbens (NAc) constitutes a critical neuroadaptive response to ethanol (EtOH) and other drugs of abuse. We have previously reported that N-methyl-D-aspartate receptor (NMDAR)-dependent long-term depression (LTD) is markedly affected by chronic intermittent ethanol exposure in vivo; however, endocannabinoid (eCB)-dependent synaptic depression, despite being very well-documented in the dorsal striatum, is much less w ...[more]

PMID: 25421513

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Project description:BackgroundChronic ethanol exposure reduces dopamine transmission in the nucleus accumbens, which may contribute to the negative affective symptoms associated with ethanol withdrawal. Kappa opioid receptors have been implicated in withdrawal-induced excessive drinking and anxiety-like behaviors and are known to inhibit dopamine release in the nucleus accumbens. The effects of chronic ethanol exposure on kappa opioid receptor-mediated changes in dopamine transmission at the level of the dopamine terminal and withdrawal-related behaviors were examined.MethodsFive weeks of chronic intermittent ethanol exposure in male C57BL/6 mice were used to examine the role of kappa opioid receptors in chronic ethanol-induced increases in ethanol intake and marble burying, a measure of anxiety/compulsive-like behavior. Drinking and marble burying were evaluated before and after chronic intermittent ethanol exposure, with and without kappa opioid receptor blockade by nor-binaltorphimine (10mg/kg i.p.). Functional alterations in kappa opioid receptors were assessed using fast scan cyclic voltammetry in brain slices containing the nucleus accumbens.ResultsChronic intermittent ethanol-exposed mice showed increased ethanol drinking and marble burying compared with controls, which was attenuated with kappa opioid receptor blockade. Chronic intermittent ethanol-induced increases in behavior were replicated with kappa opioid receptor activation in naïve mice. Fast scan cyclic voltammetry revealed that chronic intermittent ethanol reduced accumbal dopamine release and increased uptake rates, promoting a hypodopaminergic state of this region. Kappa opioid receptor activation with U50,488H concentration-dependently decreased dopamine release in both groups; however, this effect was greater in chronic intermittent ethanol-treated mice, indicating kappa opioid receptor supersensitivity in this group.ConclusionsThese data suggest that the chronic intermittent ethanol-induced increase in ethanol intake and anxiety/compulsive-like behaviors may be driven by greater kappa opioid receptor sensitivity and a hypodopaminergic state of the nucleus accumbens.

Dataset Information

Ethanol attenuation of long-term depression in the nucleus accumbens can be overcome by activation of TRPV1 receptors.

Publications

Ethanol attenuation of long-term depression in the nucleus accumbens can be overcome by activation of TRPV1 receptors.

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