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CNS mechanisms of alcohol self-administration.

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  • 1Department of Psychiatry, Indiana University, School of Medicine, Indianapolis, USA.

Abstract

Neurochemical and neuropharmacological studies were undertaken to examine the possible involvement of the ventral tegmental area (VTA) dopamine (DA) system and the dorsal raphe nucleus (DRN) serotonin (5-HT) system in regulating oral alcohol self-administration. In vivo microdialysis studies demonstrated that either i.p. ethanol administration (1.0-2.0 g/kg) or local perfusion with ethanol (100 mM) could enhance the extracellular concentrations of both DA and 5-HT in the nucleus accumbens (ACB). Furthermore, the effects of local perfusion with ethanol on DA release in the ACB could be blocked by co-perfusion with a 5-HT3 antagonist. In the selectively-bred alcohol preferring P line of rats, there appears to be abnormal 5-HT and/or DA systems in certain limbic structures, i.e., ACB, olfactory tubercles (OTU) and medial prefrontal cortex (MPF). This is indicated by (a) lower contents of DA and 5-HT; (b) fewer 5-HT immunostained fibers; (c) lower densities of 5-HT1B, 5-HT2 and D2 receptors; and (d) higher densities of 5-HT1A receptors in the CNS of P rats compared to the alcohol-nonpreferring NP line of rats. Neuropharmacological studies demonstrated that local microinfusion of the D2 antagonist, sulpiride, or, at low doses, the DA releaser, d-amphetamine, could increase alcohol drinking by P rats. Intracranial self-administration (ICSA) studies showed that the P line of rats, but not the NP line, will self-administer 50-150 mg% ethanol directly into the VTA. Overall, these results suggest an innate abnormal functioning of the VTA DA and DRN 5-HT systems may be key factors facilitating the rewarding actions of ethanol in the CNS of P rats.

PMID:
7748340
[PubMed - indexed for MEDLINE]
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