Modulation of the discriminative-stimulus effects of cocaine by buprenorphine.

Modulation of the discriminative-stimulus effects of cocaine by the mixed-action opioid buprenorsphine was studied in squirrel monkeys trained to discriminate cocaine from saline, using a two-lever drug discrimination procedure. Lever pressing was maintained under a fixed-ratio 10 schedule of food presentation. During test sessions, monkeys received cumulative doses of cocaine after presession treatment with either saline or buprenorphine (0.001-0.01mg/kg). After pretreatment with saline, cocaine engendered dose-related increases in the percentage of cocaine-appropriate responses, reaching a maximum of 99-100 percent at doses of 0.3 or 1.0mg/kg. Pretreatment with buprenorphine shifted the cocaine dose-response function to the left, resulting in 98-100 percent cocaine-appropriate responding at doses of cocaine that previously engendered only saline-appropriate responding. When tested alone, buprenorphine did not occasion cocaine-appropriate responding at any dose. The results show that although buprenorphine does not itself have cocaine-like discriminative-stimulus effects, it can potentiate the discriminative-stimulus effects of cocaine.