Amphetamine facilitation of win-shift radial-arm maze retention: The involvement of peripheral adrenergic and central dopaminergic systems
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In these experiments we examined the role of peripheral and central catecholamine systems in mediating the memory-improving effects of 4-OH amphetamine and d-amphetamine in an eight-arm radial maze task. Sotalol (a peripherally acting -adrenergic antagonist), propranolol (a peripherally and centrally acting -adrenergic antagonist), or haloperidol (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 cages. After a delay, food pellets were placed only in the four arms that were blocked prior to the delay, and each rat was returned to the maze and given access to all eight arms. Entries into the baited arms were 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 combination of propranolol (2.0 mg/kg) and haloperidol (0.5 mg/kg) 10 min before training, and subcutaneous injections of either saline, d-amphetamine (1.0 mg/kg), or 4-OH amphetamine (2.0 mg/kg) immediately after they completed four alley entrances. Retention was tested 18 h later. Posttraining administration of 4-OH amphetamine or d-amphetamine produced a significant improvement in retention relative to saline controls (p < .01). Sotalol and propranolol significantly blocked the improvement in retention produced by 4-OH amphetamine (p < .05), but not that produced by d-amphetamine. However, the effect of d-amphetamine on retention 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-improving effects of posttraining amphetamine are mediated by influences involving peripheral adrenergic and central dopaminergic systems. 1994, Psychonomic Society, Inc.. All rights reserved.
