Adrenal steroid receptors in the PVN: studies with steroid antagonists in relation to macronutrient intake.

These studies tested the impact of steroid receptor antagonists on food intake induced by steroid agonists implanted into the paraventricular nucleus (PVN) and also on feeding that naturally occurs at the onset of the active (dark) period in the rat. Implants of corticosterone (CORT) or the selective type II agonist RU28362 in the PVN stimulated feeding in adrenalectomized (ADX) rats, specifically by enhancing carbohydrate ingestion. This feeding response induced by CORT or RU28362 was blocked by PVN implants of the type II antagonist RU486 but was unaffected by the type I antagonist RU28318. In contrast, the type I agonist aldosterone (ALDO) in the PVN stimulated feeding in both sham and ADX rats by preferentially enhancing fat ingestion, which could be inhibited by the type I antagonist RU28318 but not by the type II antagonist RU486. These results indicate that the feeding elicited by CORT at dark onset is dependent upon the functional integrity of type II glucocorticoid receptors within the PVN, in contrast to the feeding elicited by ALDO which is dependent upon endogenous type I steroid receptor activation within this nucleus. Test results with these antagonists alone in freely feeding animals support a functional role for these PVN steroid receptors in adrenal steroid control of natural food intake. Specifically, blockade of PVN type II receptors with RU486 in intact rats selectively suppressed spontaneous carbohydrate feeding at dark onset, while PVN implants of the type I receptor antagonist RU28318 caused a suppression of spontaneous fat intake.(ABSTRACT TRUNCATED AT 250 WORDS)