Location preference related to smoked heroin self-administration by rhesusmonkeys

Rationale: Although common in humans, little is known about the reinforcing efficacy of smoked heroin in laboratory animals. Objectives: To evaluate t he reinforcing efficacy of smoked heroin in non-opioid dependent, non-human primates. Methods: Self-administration and location-preference measures we re obtained by having monkeys live in two chambers with heroin self-adminis tration (0, 0.3, 0.6 mg/kg; eight dosings available per day) specific to on e chamber and no commodity available in the other chamber. Operant respondi ng reinforced by smoked heroin provided a self-administration measure of re inforcement, and the length of time monkeys spent in the heroin-associated chamber provided a location preference estimate of reinforcing efficacy. Re sults: Four of six monkeys acquired heroin self-administration: these monke ys completed six to eight smoking trials each day when either of the active heroin doses was available. Urine toxicology confirmed that monkeys were a bsorbing the smoked heroin. The number of completed smoking trials rapidly decreased under extinction conditions, indicating that smoked heroin was an efficacious reinforcer using the self-administration measure. Monkeys deve loped a location preference for the chamber where heroin was self-administe red, indicating that smoked heroin was an efficacious reinforcer using the location-preference measure. Conclusions. Smoked heroin is an efficacious r einforcer in non-opioid dependent rhesus monkeys as measured using a self-a dministration procedure and estimated using a location-preference procedure . Keywords Second-order