ORAL CAFFEINE PRETREATMENT PRODUCED MODEST INCREASES IN SMOKED COCAINE SELF-ADMINISTRATION IN RHESUS-MONKEYS

Several recent studies have shown that caffeine potentiates the reinfo rcing, discriminative stimulus, and motor activating effects of cocain e in rats. The present study was designed to determine whether oral ca ffeine pretreatment would enhance the reinforcing effects of cocaine i n rhesus monkeys trained to self-administer smoked cocaine base. The e ffects of oral caffeine pretreatment (0, 100, or 200 mg) and fixed-rat io (FR) value on cocaine-base smoking were evaluated in four male rhes us monkeys. Monkeys responded on a lever under a fixed-ratio (FR) sche dule (FR 128, 256, 512, 1024, 2048, or 4096) and then made five inhala tions on a smoking sprout to gain access to volatilized cocaine base ( 0.25 or 1.0 mg/kg per delivery) during daily experimental sessions. Tw enty pellets [20 non-caffeinated (0 mg caffeine), or 20 caffeinated (2 00 mg caffeine) pellets] were administered 30 min prior to experimenta l sessions. The lever FR value was held constant within each experimen tal session, but was increased after 3 consecutive days of stable resp onding. Although the number of smoke deliveries that was self-administ ered significantly decreased from FR 128 to FR 4096, it did not change as a function of cocaine dose across the range of FR values tested. H owever, the interaction between cocaine dose and caffeine pretreatment was statistically significant. Compared to 0 mg caffeine, three of fo ur monkeys pretreated with 200 mg caffeine responded for a greater num ber of smoke deliveries when they were maintained on a cocaine dose of 1.0 mg/kg per delivery, but not 0.25 mg/kg per delivery. Thus, caffei ne pretreatment can produce small, but statistically significant incre ases in smoked cocaine self-administration in rhesus monkeys.