Memory in male and female Wistar rats: effects of gonadectomy, and stimulus presentations during the delay interval.

The present experiment was designed to investigate the effects of gonadectomy on the response accuracy of male and female Wistar rats in an operant delayed spatial response alternation procedure. Subjects were exposed to 3 randomly presented delay intervals during each experimental session (15, 30 and 60 s). Response accuracy decreased as a function of the duration of the delay interval. Prolonged exposure to the experimental procedure differentially affected the behavior of intact and gonadectomized males and females. Intact males showed a more rapid increase in response accuracy as compared to any of the other groups of subjects, but differences in steady-state behavior were not observed. The effect of stimulus presentations during the delay interval on the alternation accuracy of intact and gonadectomized male and female Wistar rats was studied in a second experimental condition. The presentation of stimuli during the delay interval equally affected response accuracy of intact and gonadectomized subjects at all delay interval durations. Differences between the sexes, or between intact and gonadectomized subjects were not observed in the second experimental condition. The results of the present experiments thus suggest that intact and gonadectomized male and female Wistar rats do not differ with respect to memory as measured in operant delayed spatial alternation tasks, since both males and females were equally susceptible to the presentation of stimuli meant to disrupt ongoing memory processes.