Changes at multiple levels of the hypothalamo-pituitary adrenal axis following repeated electrically induced seizures

Seizures, including electrically induced seizures (ECS), activate the hypothalamo-pituitary-adrenal (HPA) axis in rats. The present studies were undertaken to characterize the effects of repeated ECS on hormone release and brain adrenal steroid receptors. Repeated ECS led to an increase in adrenal weight, an increase in the corticosterone response to the eighth seizure compared to the first seizure, and an increase in basal plasma corticosterone levels at the trough of the circadian rhythm. Despite increased plasma corticosterone levels at the time of sacrifice, there were no decreases in adrenal steroid receptor numbers in hypothalamus, cortex or hippocampus. In chronic ECS-treated rats which were adrenalectomized overnight to remove glucocorticoids, an increase in Type I (mineralocorticoid) steroid receptors occurred in both hippocampus and cortex. These data suggest that chronic ECS has a trophic effect on Type I receptors and that the higher levels of corticosterone resulting from chronic ECS do not induce adrenal steroid receptor down-regulation.