Microinjections of dopamine agonists in the nucleus accumbens increase ethanol-reinforced responding.
Long-Evans rats (N = 3) were trained to lever press on a fixed-ratio 4 (FR 4) schedule with ethanol (10% v/v) presented as the reinforcer. Each rat received a total of six bilateral nucleus accumbens microinjections, one per week. They were tested with one physiological saline control, three 20.0-microgram/brain d-amphetamine, and two 6.0-microgram/brain quinpirole injections given 10 min prior to operant sessions. Ethanol-reinforced responding terminated after approximately 10 min during control sessions. Microinjections of the D2 agonist quinpirole and the nonspecific dopamine (DA) agonist d-amphetamine increased total responding but produced slowed response rates that continued for 45-60 min. The slowed response rate produced by d-amphetamine resulted in a peak increase in interresponse times (IRTs) between 8-10 s, whereas quinpirole increased IRTs in the 14- to 16-s range, indicating that nonspecific DA activation resulted in higher rates of ethanol-reinforced responding than specific D2 activation although both drugs decreased local response rates. These data indicate that the amount and temporal extent of ethanol-reinforced responding are increased by microinjections of DA agonists in the nucleus accumbens and support the hypothesis that DA activity in this region is involved in the regulation of ethanol-reinforced responding.
Alcohol and Drug Abuse Institute, University of Washington, Seattle 98195.
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Hodge
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Samson
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Haraguchi
D000818:Animals; D003216:Conditioning, Operant / Q000187:drug effects*; D003913:Dextroamphetamine / Q000494:pharmacology; D015259:Dopamine Agents / Q000008:administration & dosage / Q000494:pharmacology*; D004873:Ergolines / Q000494:pharmacology; D000431:Ethanol / Q000494:pharmacology*; D008297:Male; D008845:Microinjections; D009714:Nucleus Accumbens; D019257:Quinpirole; D051381:Rats; D012054:Reinforcement, Psychology
D015259:Dopamine Agents; D004873:Ergolines; D019257:Quinpirole; D000431:Ethanol; D003913:Dextroamphetamine