Lobeline Attenuates D-methamphetamine Self-administration in Rats

alpha-Lobeline inhibits d-amphetamine-evoked dopamine release from striatal slices in vitro, appearing to reduce the cytosolic pool of dopamine available for reverse transport by the dopamine transporter. Based on this neurochemical mechanism of action, the present study determined if lobeline decreases d-methamphetamine self-administration. Rats were surgically implanted with jugular catheters and were trained to lever press on a fixed ratio 5 schedule for intravenous d-methamphetamine (0.05 mg/kg/infusion). To assess the specificity of the effect of lobeline, another group of rats was trained to lever press on a fixed ratio 5 schedule for sucrose reinforcement. Pretreatment of rats with lobeline (0.3-3.0 mg/kg, 15 min prior to the session) decreased responding for both d-methamphetamine and sucrose reinforcement. Following repeated lobeline (3.0 mg/kg) administration, tolerance developed to the decrease in responding for sucrose; however, the lobeline-induced decrease in responding for d-methamphetamine persisted. Furthermore, the lobeline-induced decrease in responding for d-methamphetamine was not surmounted by increasing the unit dose of d-methamphetamine. These results suggest that lobeline produces a nonspecific rate suppressant effect following acute administration, to which tolerance develops following repeated administration. Importantly, the results also suggest that repeated administration of lobeline specifically decreases responding for d-methamphetamine in a noncompetitive manner. Thus, lobeline may be an effective, novel pharmacotherapy for d-methamphetamine abuse.