Actions of cholinergic agonist and antagonists on the adrenocortical response of basal, hypoxic, and hypercapnic rats.

Cholinergic neuronal influences on the function of male rat's hypothalamo-hypophyseal-adrenocortical (HHA) system both during basal and stressful situations (hypoxia and hypercapnia) were investigated using a cholinergic agonist (eserine) and antagonists (atropine, methyl atropine, mecamylamine and 4-(1-naphthylvinyl) pyridine). The results indicate that the transmitter, acetylcholine (ACh), plays a partial role in the regulation of the HHA system. The muscarinic (m) effects of ACh were stimulatory peripherally and inhibitory centrally. The nicotinic (n) effects were stimulatory and possibly affected the HHA system by inhibiting the central m-inputs. The cholinergic regulation of the HHA system for both non-stressed and hypercapnic animals is probably mediated via a common nm-cholinergic pathway.