Effects of Oral and Intravenous Administration of Buspirone on Food–Cocaine Choice in Socially Housed Male Cynomolgus Monkeys

Drugs acting at D3 dopamine receptors have been suggested as medications for cocaine dependence. These experiments examined the effects of intravenously and orally administered buspirone, a D2-like receptor antagonist with high affinity for D3 and D4 receptors, on the relative reinforcing strength of cocaine in group-housed male cynomolgus monkeys. Use of socially housed monkeys permitted the assessment of whether social status, known to influence D2-like receptor availability, modulates the behavioral effects of buspirone. Buspirone was administered acutely to monkeys self-administering cocaine under a food–drug choice procedure in which a cocaine self-administration dose–effect curve was determined daily. When administered by either route, buspirone significantly decreased cocaine choice in dominant-ranked monkeys. In subordinate monkeys, however, i.v. buspirone was ineffective on average, and oral buspirone increased choice of lower cocaine doses. The effects of buspirone only differed according to route of administration in subordinate monkeys. Moreover, it is noteworthy that the effects of buspirone were similar to those of the D3 receptor-selective antagonist PG01037 and qualitatively different than those of less selective drugs that act at D2-like or serotonin (5-HT)1A receptors, suggesting a D3 and possibly D4 receptor mechanism of action for buspirone. Taken together, the data support the utility of drugs targeting D3/D4 receptors as potential treatments for cocaine addiction, particularly in combination with enriching environmental manipulations.