1999 Curt P. Richter award. Glucocorticoids and the regulation of memory consolidation.

This paper summarizes recent findings on the amygdala's role in mediating acute effects of glucocorticoids on memory consolidation in rats. Posttraining activation of glucocorticoid-sensitive pathways involving glucocorticoid receptors (GRs or type II) enhances memory consolidation in a dose-dependent inverted-U fashion. Selective lesions of the basolateral nucleus of the amygdala (BLA) or infusions of beta-adrenoceptor antagonists into the BLA block the memory-modulatory effects of systemic injections of glucocorticoids. Additionally, posttraining infusions of a specific GR agonist administered directly into the BLA enhance memory consolidation, whereas those of a GR antagonist impair. These findings indicate that glucocorticoid effects on memory consolidation are mediated, in part, by an activation of GRs in the BLA and that the effects require beta-adrenergic activity in the BLA. Other findings indicate that the BLA interacts with the hippocampus in mediating glucocorticoid-induced modulatory influences on memory consolidation. Lesions of the BLA or inactivation of beta-adrenoceptors within the BLA also block the memory-modulatory effects of intrahippocampal administration of a GR agonist or antagonist. These findings are in agreement with the general hypothesis that the BLA integrates hormonal and neuromodulatory influences on memory consolidation. However, the BLA is not a permanent locus of storage for this information, but modulates consolidation processes for explicit/associative memories in other brain regions, including the hippocampus.