EFFECTS OF CONCURRENT SACCHARIN AVAILABILITY AND BUPRENORPHINE PRETREATMENT ON DEMAND FOR SMOKED COCAINE BASE IN RHESUS-MONKEYS

The effects of saccharin and the opioid partial agonist buprenorphine on cocaine base smoking were evaluated in five male rhesus monkeys. Mo nkeys completed a sequence of responding consisting of lever-press res ponses maintained under a fixed-ratio (FR) schedule followed by inhala tion responses (FR5) on a smoking spout to gain access to a single del ivery of volatilized cocaine base (1.0 mg/kg per delivery). Monkeys co uld receive a maximum of ten smoke deliveries per session. In the firs t experiment, either saccharin (0.03% wt/vol) or water was concurrentl y available under an FR1 schedule through a lip-operated drinking devi ce. As lever FR values increased from 128 to 256, 512, 1024 and 2048, the number of cocaine smoke deliveries decreased. Cocaine intake was n ot statistically different when water versus saccharin was concurrentl y available. However, as cocaine consumption decreased, saccharin inta ke increased demonstrating that under these conditions, saccharin was substituting for cocaine as a reinforcer. On the first day that lidoca ine replaced cocaine, all of the monkeys received the maximum number o f smoke deliveries (ten) and saccharin intake increased. Lever-press r esponding gradually extinguished over days when lidocaine (1.0 mg/kg p er delivery) was available with concurrent saccharin. In the second ex periment, water was concurrently available with cocaine and buprenorph ine (0.01 or 0.1 mg/kg) was administered intramuscularly (IM) 30 min b efore the start of the session. Although pretreatment with the lower d ose of buprenorphine (0.01 mg/kg) had little effect on cocaine intake overall, individual differences in cocaine intake occurred. The higher dose of buprenorphine (0.1 mg/kg) decreased the amount of cocaine con sumed at all lever FR values tested.