Cardiovascular response to stress: Baroreflex resetting and hemodynamics

Daniel C. Hatton, Virginia Brooks, Yue Qi, David A. McCarron

Research output: Contribution to journalArticle

44 Scopus citations

Abstract

Borderline hypertensive rats (BHR) were used to test the hypothesis that baroreflex resetting prevents a fall in blood pressure (BP) when cardiac output (CO) is reduced during air-jet stress. Eight-week-old BHR were instrumented with flow probes around the ascending aorta for measuring CO, femoral and jugular catheters were inserted for measurement of arterial pressure and infusion of drugs, and sinoaortic baroreceptors were either denervated (SAD) or left intact. Alternating bolus injections of phenylephrine and sodium nitroprusside were given at baseline and during air- jet stress to assess the baroreflex. Air-jet stress immediately shifted the midpoint of the baroreflex curve for heart rate (HR) to a higher BP level. When metoprolol was administered during air-jet stress, HR was reduced and CO reverted to prestress levels, but the stress-induced pressor response was not changed. In SAD BHR, air-jet stress caused an elevation of BP that was not different from intact rats. Administration of metoprolol to SAD rats during air-jet stress resulted in a further elevation rather than a reduction in BP. We conclude that the sinoaortic cardiac baroreflex is reset during air-jet stress and that it integrates reflex changes in BP during stress. The arterial baroreflex is not, however, necessary for the initiation or maintenance of the pressor response during stress, nor does it prevent a fall in BP when CO is compromised during stress.

Original languageEnglish (US)
Pages (from-to)R1588-R1594
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume272
Issue number5 41-5
DOIs
StatePublished - Jan 1 1997

Keywords

  • Baroreceptor denervation
  • Beta blocker
  • Blood pressure
  • Borderline hypertensive rat
  • Cardiac output

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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