Arterial baroreflex alters strength and mechanisms of muscle metaboreflex during dynamic exercise

• Published in: American journal of physiology. Heart and circulatory physiology Vol. 288; no. 3; pp. H1374 - H1380
• Main Authors: Kim, Jong-Kyung, Sala-Mercado, Javier A, Rodriguez, Jaime, Scislo, Tadeusz J, O'Leary, Donal S
• Format: Journal Article
• Language: English
• Published: United States 01.03.2005
• Subjects: Animals; Aorta - innervation; Aorta - physiology; Baroreflex - physiology; Blood Pressure - physiology; Cardiac Output - physiology; Denervation; Dogs; Female; Male; Physical Exertion - physiology; Vasoconstriction - physiology
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.01040.2004

Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan Submitted 12 October 2004 ; accepted in final form 7 November 2004 Previous studies showed that the arterial baroreflex opposes the pressor response mediated by muscle metaboreflex activation during mild dynamic exercise. However, no studies have investigated the mechanisms contributing to metaboreflex-mediated pressor responses during dynamic exercise after arterial baroreceptor denervation. Therefore, we investigated the contribution of cardiac output (CO) and peripheral vasoconstriction in mediating the pressor response to graded reductions in hindlimb perfusion in conscious, chronically instrumented dogs before and after sinoaortic denervation (SAD) during mild and moderate exercise. In control experiments, the metaboreflex pressor responses were mediated via increases in CO. After SAD, the metaboreflex pressor responses were significantly greater and significantly smaller increases in CO occurred. During control experiments, nonischemic vascular conductance (NIVC) did not change with muscle metaboreflex activation, whereas after SAD NIVC significantly decreased with metaboreflex activation; thus SAD shifted the mechanisms of the muscle metaboreflex from mainly increases in CO to combined cardiac and peripheral vasoconstrictor responses. We conclude that the major mechanism by which the arterial baroreflex buffers the muscle metaboreflex is inhibition of metaboreflex-mediated peripheral vasoconstriction. sinoaortic denervation; cardiac output; pressor response Address for reprint requests and other correspondence: D. S. O'Leary, Dept. of Physiology, Wayne State Univ. School of Medicine, 540 East Canfield Ave., Detroit, MI 48201 (E-mail: doleary{at}med.wayne.edu )