The actions of SCH 23390, a D1 receptor antagonist, on operant and avoidance behavior in rats

Previous studies have shown that dopamine antagonists such as haloperidol, pimozide and metoclopramide will produce gradually increasing decrements of operant and avoidance responding. The present study was carried out to investigate whether the dopamine D1 blocking agent, SCH 23390, would exert a similar effect. In the first experiment, SCH 23390 produced a dose-related (0.03-0.1 mg/kg) reduction in responding maintained by an FR 10 schedule of food reinforcement. However, the compound gave rise to similar reductions of response rate throughout the 15 min session. In a second experiment, higher doses of SCH 23390 (0.1-1.0 mg/kg) disrupted one-way avoidance performance in a shuttle-box. Again, there was no within-session decline in responding after administration of SCH 23390 although injection of a dose of 0.4 mg/kg of haloperidol produced a greater response deficit during the second half of the session. During 4 daily administrations of 0.3 mg/kg of SCH 23390 the degree to which avoidance responding was disrupted neither increased nor decreased. SCH 23390 disrupts operant bar pressing and one-way avoidance responding but its actions in these behavioral tests are not identical to the effects of typical neuroleptics such as haloperidol.