Role of norepinephrine in mediating stress hormone regulation of long-termmemory storage: A critical involvement of the amygdala

There is extensive evidence indicating that the noradrenergic system of the amygdala, particularly the basolateral nucleus of the amygdala (BLA), is i nvolved in memory consolidation. Infusions of norepinephrine or beta-adreno ceptor agonists into the BLA enhance memory for inhibitory avoidance as wel l as water maze training. Other findings show that alpha(1)-adrenoceptor ac tivation also enhances memory for inhibitory avoidance training through an interaction with beta-adrenergic mechanisms. The central hypothesis guiding the research reviewed in this chapter is that stress hormones released dur ing emotionally arousing experiences activate noradrenergic mechanisms in t he BLA, resulting in enhanced memory for those Events. Findings from experi ments using rats have shown that the memory-modulatory effects of the adren ocortical stress hormones epinephrine and glucocorticoids are mediated by i nfluences involving activation of beta-adrenoceptors in the BLA. In additio n, bath behavioral and microdialysis studies have shown that the noradrener gic system of the BLA also mediates the influences of other neuromodulatory systems such as opioid peptidergic and GABAergic systems on memory storage . Other findings indicate that this stress hormone-induced activation of no radrenergic mechanisms in the BLA regulates explicit/declarative memory sto rage in other brain regions. (C) 1999 Society of Biological Psychiatry.