Reflex cardiovascular response to exercise is modulated by circulating vasopressin

Charles L Stebbins

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Abstract

Peripheral vasopressin (AVP) can act centrally to sensitize the arterial baroreflex and/or peripherally to attenuate regional blood flow by a direct vascular effect. Because plasma concentrations of AVP increase during exercise, this study examined the possibility that AVP is capable of modulating the reflex cardiovascular response to static muscle contraction. Thus, in anesthetized cats, the pressor [mean arterial pressure (MAP)], myocardial contractile (dP/dt), and heart rate responses to 30-45 s of electrically induced static contraction of the hindlimb muscles were compared before and after intravenous injection of the V1 receptor antagonist d[(CH2)5Tyr(Me)]-AVP (V(1-x), n = 7), V(1-x) plus the V2 receptor antagonist [d(CH2)5,D-Phe2,Ile4,Arg8,Ala9]vasopressin (V(2-x), n = 5), or the ganglionic blocker hexamethonium chloride (n = 5). In three additional cats, the contraction-induced cardiovascular response was monitored before and after injection of V(1-x) + V(2-x) and after hexamethonium. Subsequent to treatment with V(1-x), the MAP and dP/dt responses to contraction were augmented by 18 ± 5 and 22 ± 10%, respectively (P < 0.05). After injection of V(1-x) + V(2-x), the MAP and dP/dt responses were augmented to a similar extent (32 ± 6 and 40 ± 17%, respectively; P < 0.05). However, there was no difference in the magnitude of augmentation of these responses between the two conditions. The heart rate response was not altered by either treatment. Ganglionic blockade eliminated the cardiovascular responses to contraction. Last, when the pressor and contractile response to contraction were initially augmented by administration of V(1-x) + V(2-x), subsequent ganglionic blockade abolished the entire cardiovascular response. These results suggest that AVP modulates the sympathetic response to brief muscle contraction when vascular effects of this peptide are not apparent. Thus it is likely that the modulating action of AVP is the result of its effect on the arterial baroreflex.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume263
Issue number5 32-5
StatePublished - 1992

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Keywords

  • cats
  • exercise pressor response
  • ganglionic blockade
  • static muscle contraction
  • V and V antagonists
  • V and V receptors

ASJC Scopus subject areas

  • Physiology

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