ENHANCEMENT OF WIN SHIFT RADIAL MAZE RETENTION BY PERIPHERAL POSTTRAINING ADMINISTRATION OF D-AMPHETAMINE AND 4-OH AMPHETAMINE
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We examined the effect of posttraining subcutaneous injections of d-amphetamine and 4-OH amphetamine on acquisition of a win-shift task in an eight-arm radial maze. On each day, rats were allowed to obtain food from four randomly selected maze arms and were then removed from the maze. After a delay, the rats were returned to the maze for a retention test in which all eight arms were open and only the four arms that were not visited (i.e., win-shift) prior to the delay contained food. On the experimental day, rats were injected with drug or vehicle after completion of the first four choices, and a retention test was given after a delay of 18 h. Posttraining injections of 1.0-mg/kg d-amphetamine enhanced win-shift retention relative to the performance of saline-injected controls, while doses of 0.5 mg/kg and 2.0 mg/kg were ineffective. Posttraining injections of 4-OH amphetamine (2.0 mg/kg), an analogue that does not readily cross the blood-brain barrier, also enhanced win-shift retention, while doses of 0.5, 1.0, and 4.0 mg/kg had no effect. Injections of memory-enhancing doses of d-amphetamine and 4-OH amphetamine administered 2 h posttraining were ineffective. The memory enhancement observed following administration of 4-OH amphetamine suggests that peripheral actions of amphetamine may be sufficient for improving retention. However, the difference in effective doses of the two amphetamines suggests that d-amphetamine may enhance win-shift retention by either a direct central action or a dual action on the brain and periphery. 1992, Psychonomic Society, Inc.. All rights reserved.