Circulation research
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Circulation research · Apr 1985
Differential effects of central angiotensin II and substance P on sympathetic nerve activity in conscious rats. Implications for cardiovascular adaptation to behavioral responses.
The centrally induced effects of angiotensin II and substance P on the cardiovascular system and on neuronal efferent activity of the splanchnic, renal, and adrenal nerves were investigated in chronically instrumented conscious rats. The pressor responses to substance P injected into the lateral brain ventricle were accompanied by marked and short latency increases in heart rate, cardiac output, splanchnic, renal, and adrenal nerve activity, and a rise in plasma noradrenaline and adrenaline. Behaviorally, an arousal-type reaction was observed. ⋯ When rats were allowed to drink in response to angiotensin II, a further sharp rise in blood pressure occurred, together with increases in heart rate and splanchnic nerve activity. The results demonstrate fundamental differences in the mechanisms by which central pressor peptides can influence cardiovascular and autonomic function. It is conceivable that the distinct sympathetic response patterns to central angiotensin II and substance P receptor stimulation form part of a specific cardiovascular adjustment to the individual behavioral reactions, such as drinking, as in the case of angiotensin II, or arousal within the central processing of pain, as in the case of substance P.