Influence of sino-aortic baroreceptor denervation on catecholamines, catecholamine-synthesizing enzymes and choline acetyltransferase activity in the brainstem nuclei of the rat.

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Abstract
At 1 wk after sino-aortic baroreceptor denervation in the rat, aortic blood pressure and plasma contents of epinephrine [E] and dopamine .beta.-hydroxylase (DBH) activity were elevated during resting and conscious states. Stress-induced elevation of blood pressure and plasma E were pronounced. These changes disappeared at 4 wk 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 [NE] levels, phenylethanolamine N-methyltransferase (PNMT) activity and E levels in the LC, accompanied with a reduction of DBH activity and NE contents in the nucleus hypothalamicus posterior. These alterations were confirmed 1 wk after denervation but did not persist for a period of 4 wk. At 4 wk 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. Sino-aortic denervation transiently decreased ChAc activity in the NTS and LC, and enhanced synthesis and accumulation of NE and E in the LC accompanied with a decrease in NE contents and DBH activity in the nucleus hypothalamicus posterior, causally resulting in short-lasting labile hypertension and activation of the adrenal medulla.