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, adrenalectom ized (ADX) male (experiment 1) and female (experiment 2) Long-Evans rats. F our and 5 days after ADX, respectively, animals were trained and tested in an inhibitory avoidance task. Male and female ADX rats had shorter cross ov er latencies on the test day than did nonADX rats. In males, estradiol admi nistration to ADX rats improved inhibitory avoidance performance to levels that were comparable to nonADX, estradiol-administered male rats. No effect s 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 tha t estradiol's effects on inhibitory avoidance and pyknosis in the dentate g yms may be independent of each other. (C) 2001 Elsevier Science B.V. All ri ghts reserved.