Male and female rats with hippocampal lesions and controls were compared with respect to activity, body weight, performance on a DRL schedule, and extinction. Normal females acquired the DRL schedule faster than normal males. For both sexes, hippocampal lesions resulted in poor DRL performance and more responses during extinction. Male rats with hippocampal lesions were further below their target deprived weight each day than their controls; the lightest animals had the worst DRL performance. Sex-lesion interactions were found for activity in the operant chamber during Dlt L performance and for DRL extinction: females with hippocampal lesions were more active and made more responses during extinction than males with hippocampal lesions. Corticosterone levels were manipulated prior to DRL sessions, and resting and stress levels of corticosterone were measured at the end of the experiment. While females had higher corticosterone levels than males, brain lesions did not affect corticosterone levels, nor did hormone manipulations affect DRL performance for either sex.
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