Rostral medullary cholinergic mechanisms and chronic stress-induced hypertension.

This work was designed to study the relationship between the cholinergic mechanisms in the rostral ventrolateral medulla (rVLM) and the incidence of hypertension induced by chronic stress. Under anaesthetized conditions, bilateral microinjection of scopolamine (1.18 nmol/site) into the rVLM produced a much greater depressor response in chronic stress-induced hypertensive rats than in normotensive rats. Similar bradycardic effects were observed in both the normotensive and the hypertensive rats when scopolamine was injected into the rVLM. Acetylcholine (Ach) content and choline acetyltransferase (ChAT) activity in rostral medulla were determined by radioimmunoassay both in the normotensive and the hypertensive rats. Ach content and ChAT activity increased significantly in the hypertensive rats, and such increase mainly occurred within the ventral part of the rostral medulla. These results suggest that the cholinergic mechanisms in the rVLM may be activated during chronic stress and such activation may be involved in the pathogenesis of the hypertension induced by chronic stress.