AMPHETAMINE FACILITATION OF WIN SHIFT RADIAL-ARM MAZE RETENTION - THEINVOLVEMENT OF PERIPHERAL ADRENERGIC AND CENTRAL DOPAMINERGIC SYSTEMS

In these experiments we examined the role of peripheral and central ca techolamine systems in mediating the memory-improving effects of 4-OH amphetamine and d-amphetamine in an eight-arm radial maze task. Sotalo l (a peripherally acting beta-adrenergic antagonist), propranolol (a p eripherally and centrally acting beta-adrenergic antagonist), or halop eridol (a dopaminergic antagonist) was administered prior to injection of amphetamine. Rats were first allowed to obtain food pellets placed in four of the eight maze arms and then were returned to their home c ages. After a delay, food pellets were placed only in the four arms th at were blocked prior to the delay, and each rat was returned to the m aze and given access to all eight arms. Entries into the baited arms w ere scored as correct responses. On the experimental day, the animals received intraperitoneal injections of 0.9% saline, sotalol (5.0 mg/kg ), propranolol (2.0 mg/kg), haloperidol (0.5 or 1.0 mg/kg), or a combi nation of propranolol (2.0 mg/kg) and haloperidol (0.5 mg/kg) 10 min b efore training, and subcutaneous injections of either saline, d-amphet amine (1.0 mg/kg), or 4-OH amphetamine (2.0 mg/kg) immediately after t hey completed four alley entrances. Retention was tested 18 h later. P osttraining administration of 4-OH amphetamine or d-amphetamine produc ed a significant improvement in retention relative to saline controls( p < .01). Sotalol and propranolol significantly blocked the improvemen t in retention produced by 4-OH amphetamine (p < .05), but not that pr oduced by d-amphetamine. However, the effect of d-amphetamine on reten tion was completely blocked by 1.0 mg/kg of haloperidol (p < .01). The combined administration of propranolol (2.0 mg/kg) and the lower dose of haloperidol (0.5 mg/kg) did not attenuate the retention-enhancing effects of d-amphetamine. These findings suggest that the memory-impro ving effects of posttraining amphetamine are mediated by influences in volving peripheral adrenergic and central dopaminergic systems.