Hippocampal cholinergic blockade enhances hypothalamic-pituitary-adrenal responses to stress.

We examined the role of the hippocampal cholinergic system, which is known to mediate processes related to fear and anxiety, in the regulation of stress-induced hypothalamic-pituitary-adrenal (HPA) activity. Bilateral intra-hippocampal injections (30 microg per side) of the muscarinic antagonist Scopolamine augmented adrenocorticotropin and corticosterone responses to restraint without altering basal HPA activity compared to vehicle-treated animals. These results suggest that the hippocampal cholinergic system regulates stress-induced HPA activity and may serve to coordinate behavioral and neuroendocrine responses to stress.