Support for a bimodal role for type II adrenal steroid receptors in spatial memory.

We investigated the effects of acute adrenal steroid treatment on spatial memory using the Y-maze and employing adrenal steroid receptor antagonists and agonists. For receptor activation, adrenalectomized rats were injected 2 h prior to their first Y-maze trial with sesame oil (adrenalectomy or SHAM), stress levels of corticosterone, a Type I receptor agonist (aldosterone), or a Type II receptor agonist (RU362). For receptor inactivation, unoperated rats were injected with a Type I receptor antagonist (RU318), a Type II receptor antagonist (RU555), sesame oil, or not injected at all. The findings indicated that spatial memory was impaired when the Type II receptors were blocked (RU555) or highly occupied (corticosterone or RU362) and normal for the other treatment conditions. These data suggest that the Type II receptors may be responsible for the inverted U-shaped relationship between spatial memory and corticosterone levels reported by others.