Enhanced cholinergic activity in the medulla oblongata of DOCA-salt hypertensive and renal hypertensive rats.

We previously demonstrated that cholinergic activity in the medulla oblongata is enhanced in adult spontaneously hypertensive rats (SHR), a genetically hypertensive rat model. In this study, we examined possible alterations of medulla oblongata cholinergic mechanisms in nongenetic forms of hypertension, using deoxycorticosterone acetate (DOCA)-salt hypertensive and renal hypertensive rats. At a fully developed stage of hypertension in DOCA-salt hypertensive and renal hypertensive rats, choline acetyl-transferase (CAT) activity in the rostro-ventral medulla oblongata was enhanced, whereas there was no change in the activity of CAT in other parts of the medulla oblongata. There was no alteration of the medulla CAT activity in prehypertensive SHR or at an early stage of renal hypertension. Increases in blood pressure and plasma catecholamine levels induced by physostigmine (0.5 mg/kg, i.p.) were enhanced in DOCA-salt hypertensive and renal hypertensive rats. These findings suggest that cholinergic activities in the medulla oblongata are enhanced and that such activities are involved in enhancement of the sympathetic nervous system in non-genetically hypertensive rats. It seems unlikely that the altered cholinergic activity in the rostral ventrolateral medulla of adult SHR occurs genetically.