Estradiol reduces seizure-induced hippocampal injury in ovariectomized female but not in male rats.

Estrogens protect ovariectomized rats from hippocampal injury induced by kainic acid-induced status epilepticus (SE). We compared the effects of 17beta-estradiol in adult male and ovariectomized female rats subjected to lithium-pilocarpine-induced SE. Rats received subcutaneous injections of 17beta-estradiol (2 microg/rat) or oil once daily for four consecutive days. SE was induced 20 h following the second injection and terminated 3 h later. The extent of silver-stained CA3 and CA1 hippocampal neurons was evaluated 2 days after SE. 17beta-Estradiol did not alter the onset of first clonus in ovariectomized rats but accelerated it in males. 17beta-Estradiol reduced the argyrophilic neurons in the CA1 and CA3-C sectors of ovariectomized rats. In males, estradiol increased the total damage score. These findings suggest that the effects of estradiol on seizure threshold and damage may be altered by sex-related differences in the hormonal environment.