SELF-ADMINISTRATION OF GBR-12909 ON A FIXED-RATIO AND PROGRESSIVE RATIO SCHEDULE IN RATS

Intravenous self-administration of GBR 12909, an indirect dopamine ago nist, was examined on a Fixed Ratio (FR 1) and a Progressive Ratio (PR ) schedule of reinforcement in rats. Subjects were first trained to se lf-administer cocaine (1.5 mg/kg/inj) during daily 5 h sessions, after which GBR 12909 (0.187-1.5 mg/kg/inj) was substituted. On the FR 1 sc hedule, the inter-infusion interval for GBR 12909 self-administration was directly related to dose and was approximately three times longer than that established for equivalent doses of cocaine. Breaking points on the PR schedule were comparable for GBR 12909 and cocaine self-adm inistration. The data indicate that, compared to cocaine, GBR 12909 ha s a longer duration of action and a similar reinforcing efficacy.