Effects of buprenorphine on candy and sweetened fluid self-administration by rhesus monkeys

Rationale: Previous studies have shown that buprenorphine differentially suppresses the reinforcing effects of different drugs (cocaine, alfentanil), drug versus nondrug reinforcers (food, drug), and the same reinforcer (food) maintained under different schedules of reinforcement. Objectives: The purpose of the present study was to determine whether buprenorphine (0.03, 0.1, 0.3 mg/kg) differentially affects candy versus sweetened fluid self-administration. The hypotheses were that (1) candy would maintain higher rates of responding and would be chosen on more occasions than sweetened fluid, and (2) buprenorphine would produce smaller disruptions in responding for the more-preferred reinforcer. Methods: During separate sessions, rhesus monkeys self-administered candy alone, sweetened fluid alone, or had the opportunity to choose between candy and sweetened fluid. Monkeys responded under a second order, two-chain schedule of reinforcement. Results: Candy was a more-preferred reinforcer than sweetened fluid. Buprenorphine significantly decreased rates of responding for fluid, but increased rates of responding for candy. Although buprenorphine significantly decreased both candy and fluid intake, it produced a more robust, and longer-lasting suppression of sweetened-fluid intake than candy. Choice to self-administer candy or fluid was not affected by buprenorphine. Conclusions: These results demonstrate that behavior maintained by a less-preferred reinforcer is more easily disrupted by buprenorphine than is behavior maintained by a more-preferred reinforcer.