Estradiol tends to improve inhibitory avoidance performance in adrenalectomized male rats and reduces pyknotic cells in the dentate gyrus of adrenalectomized male and female rats.

Estradiol or vehicle was administered daily to gonadectomized, adrenalectomized (ADX) male (experiment 1) and female (experiment 2) Long-Evans rats. Four and 5 days after ADX, respectively, animals were trained and tested in an inhibitory avoidance task. Male and female ADX rats had shorter cross over latencies on the test day than did nonADX rats. In males, estradiol administration to ADX rats improved inhibitory avoidance performance to levels that were comparable to nonADX, estradiol-administered male rats. No effects of estradiol were seen on inhibitory avoidance performance of female rats. In both males and females, ADX increased the number of pyknotic cells in the dentate gyrus compared to nonADX rats; estradiol also reduced pyknotic cell number compared to vehicle administration. These findings suggest that estradiol's effects on inhibitory avoidance and pyknosis in the dentate gyrus may be independent of each other.