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NEUROHUMORAL CONTROL OF CARDIOVASCULAR FUNCTION

Central angiotensin II receptors mediate hemodynamic response variability to stressors

Department of Pharmacological and Physiological Science, St Louis University School of Medicine, St. Louis, Missouri

Submitted 23 November 2005 ; accepted in final form 18 March 2006

We examined whether ANG II receptors in the central nervous system mediate hemodynamic responses to pharmacological (cocaine) and behavioral (cold water) stressors. After administration of cocaine (5 mg/kg iv), rats were classified as vascular responders (VR) if their pressor response was due entirely to an increase in systemic vascular resistance (SVR) despite a decrease in cardiac output (CO). Cocaine elicited a pressor response in mixed responders (MR) that was dependent on small increases in both SVR and CO. ANG II (30 ng/5 µl icv, 5 min before cocaine) augmented the decrease in CO in VR and prevented the increase in CO in MR. Administration of [Sar¹,Thr⁸]ANG II (20 µg/5 µl icv; sarthran) before cocaine attenuated the decrease in CO and the large increase in SVR in VR so that they were no longer different from MR. Losartan (20 µg icv) or captopril (50 µg icv) preceding cocaine administration also attenuated the decrease in CO and the large increase in SVR seen in VR only. The role of angiotensin was not specific for cocaine, because ANG II (icv) pretreatment before startle with cold water (1 cm deep) enhanced the decrease in CO and the increase in SVR in both MR and VR, whereas losartan (icv) pretreatment before startle attenuated the decrease in CO and the increase in SVR in VR so that they were no longer different from MR. These data suggest that central ANG II receptors mediate the greater vascular and cardiac responsiveness in vascular responders to acute pharmacological and behavioral stressors.

renin-angiotensin system; cardiac output; systemic vascular resistance; startle; cocaine; central nervous system

This article has been cited by other articles:

				J. A. Schwartz, N. S. Reilly, and M. M. Knuepfer Angiotensin and NMDA receptors in the median preoptic nucleus mediate hemodynamic response patterns to stress Am J Physiol Regulatory Integrative Comp Physiol, July 1, 2008; 295(1): R155 - R165. [Abstract] [Full Text] [PDF]