Potentiation of reward-related responding by psychostimulant infusion into nucleus accumbens: Role of dopamine receptor subtypes

Abstract

The conditioned-reinforcement paradigm measures the ability of a conditioned stimulus to act as a reinforcer for newly learned operant behavior. The following experiments had two objectives. First, the effects of cocaine and pipradrol infused directly into the nucleus accumbens were assessed for their ability to potentiate responding for a conditioned reinforcer. Second, the role of D1 and D2 dopamine receptor subtypes in potentiated conditioned-reinforcement responding was examined. Cocaine (1–60 µg), pipradrol (2–20 µg), and amphetamine (2–20 µg) all significantly enhanced conditioned-reinforcement responding when injected into the nucleus accumbens. A control experiment showed this potentiation to be dependent on the contingency between lever-pressing and the conditioned reinforcer. Pretreatment with either a D1 (SCH 23390, 0.1-mg/kg) or a D2 (raclopride, 1.0-mg/kg) dopamine antagonist selectively reduced stimulant-potentiated responding. Direct infusion of haloperidol (1–2.5 µg) into the nucleus accumbens also reduced the potentiation effect of pipradrol given systemically. Infusion of a D1 agonist (CY 208–243, 0.1–10 µg) or a D2 agonist (quinpirole, 0.2–20 µg) into the nucleus accumbens did not enhance responding; however, when a combined infusion was carried out, a significant increase was noted. It is concluded that the potentiation of reward-related responding observed following dopaminergic activation of the nucleus accumbens is dependent on concurrent stimulation of both D1 and D2 receptor subtypes. © 1992, Psychonomic Society, Inc.. All rights reserved.