INFLUENCE OF SINO-AORTIC BARORECEPTOR DENERVATION ON CATECHOLAMINES, CATECHOLAMINE-SYNTHESIZING ENZYMES AND CHOLINE ACETYLTRANSFERASE ACTIVITY IN THE BRAINSTEM NUCLEI OF THE RAT

Abstract

AbstractAt one week after sino-aortic baroreceptor denervation in the rat, aortic blood pressure and plasma contents of epinephrine and dopamine β-hydroxylase (DBH) activity were elevated during resting and conscious states. Stress-induced elevation of blood pressure and plasma epinephrine were markedly pronounced. These changes disappeared at four weeks after denervation. Sino-aortic deafferentation decreased choline acetyltransferase (ChAc) activity in the nucleus tractus solitarii (NTS) and locus coeruleus (LC) and increased DBH activity, norepinephrine levels, phenylethanolamine N-methyltransferase (PNMT) activity and epinephrine levels in the LC, accompanied with a reduction of DBH activity and norepinephrine contents in the nucleus hypothalamicus posterior. These alterations were confirmed one week after denervation but did not persist for a period of four weeks. At four weeks after denervation, ChAc activity was significantly decreased in the nucleus dorsalis nerve of the vagi but not in the nucleus ambiguus. During the transient hypertensive phase, sino-aortic deafferentation did not alter DBH and PNMT activities in the NTS, A2 cell and A1 cell areas, and both catecholamine levels in the NTS. In conclusion, sino-aortic denervation transiently decreased ChAc activity in the NTS and LC, and enhanced synthesis and accumulation of norepinephrine and epinephrine in the LC accompanied with a decrease in norepinephrine contents and DBH activity in the nucleus hypothalamicus posterior, causally resulting in short-lasting labile hypertension and activation of the adrenal medulla.