Schroeder JP, Overstreet DH, Hodge CW. The mGluR5 antagonist MPEP decreases operant ethanol self-administration during maintenance and after repeated alcohol deprivations in alcohol-preferring (P) rats.
Psychopharmacology (Berl) 2005;
179:262-70. [PMID:
15717208 PMCID:
PMC11583314 DOI:
10.1007/s00213-005-2175-9]
[Citation(s) in RCA: 134] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2004] [Accepted: 01/13/2005] [Indexed: 11/29/2022]
Abstract
RATIONALE
Recent research indicates that blockade of mGluR5 modifies the reinforcing properties of ethanol.
OBJECTIVES
The present studies examined the effects of mGluR5 receptor blockade in a genetic model of high ethanol intake, the alcohol-preferring (P) rat, on the maintenance of operant ethanol self-administration. In addition, we determined the effect of 2-methyl-6-(phenylethyl)-pyridine (MPEP) on the repeated alcohol deprivation effect.
METHODS
Twelve male (P) rats were trained in experimental sessions to self-administer 10% w/v ethanol via a sucrose-fading procedure. After the establishment of operant ethanol self-administration, subjects were treated with various metabotropic glutamate receptor (mGluR) subtype antagonists immediately prior to experimental sessions: the mGluR5 antagonist MPEP (1, 3, and 10 mg/kg); the mGluR2--3 antagonist LY-341495 (1, 3, and 10 mg/kg); and the mGluR1 antagonist CPCCOEt (1, 3, and 10 mg/kg). After determining the role of mGluR5 in the maintenance of operant ethanol self-administration, we examined the role of this receptor in relapse following repeated periods of alcohol deprivation by depriving subjects of ethanol exposure for three 2-week deprivation periods.
RESULTS
The mGluR5 antagonist MPEP dose-dependently decreased operant ethanol self-administration. In addition, rats that received saline immediately prior to repeated alcohol deprivation sessions self-administered ethanol at increasing levels that were above those achieved in the last operant-conditioning session prior to the initial 2-week deprivation period. This repeated alcohol deprivation effect was prevented in subjects pretreated with MPEP (10 mg/kg).
CONCLUSIONS
These findings suggest that mGluR5 receptors may modulate both the maintenance of operant ethanol self-administration and abstinence-induced increases in ethanol intake.
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