A diminished aortic-cardiac reflex during hypotension in aerobically fit young men

Xiangrong Shi, Craig G. Crandall, Jeffrey T. Potts, Jon W. Williamson, Brian H. Foresman, Peter B. Raven

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

We compared the aortic-cardiac baroreflex sensitivity in eight average fit (AF: VO2max = 44.7 ± 1.3 ml•kg-1•min-1) and seven high fit (HF: VO2max = 64.1 ± 1.7 ml • min-1 • kg-1) healthy young men during hypotension elicited by steady state sodium nitroprusside (SN) infusion. During SN mean arterial pressure (MAP) was similarly decreased in AF (-12.6 ± 1.0 mm Hg) and HF (-12.1 ± 1.1 mm Hg). However, the increases in heart rate (HR) were less (P< 0.023) in HF (15 ± 3 bpm) than AF (25 ± 1 bpm). When sustained neck suction (NS, -22 ± 1 torr in AF and -20 ± 1 torr in HF, P > 0.05) was applied to counteract the decreased carotid sinus transmural pressure during SN, thereby isolating the aortic baroreceptors, the increased HR remained less (P < 0.021) in HF (8 ± 2 bpm) than AF (16 ± 2 bpm). During both SN infusion and SN+NS, the calculated gains (i.e., AHR/AMAP) were significantly greater in AF (2.1 ± 0.3 and 1.3 ± 0.2 bpm•mm Hg-1) than HF (1.2 ± 0.2 and 0.6 ± 0.2 bpm•mm Hg-1). However, the estimated carotid-cardiac baroreflex sensitivity (i.e., the gain difference between the stage SN and SN+NS) was not different between AF (0.7 ± 0.2 bpm•mm Hg-1) and HF (0.6 ± 0.1 bpm•mm Hg-1). These data indicated that the aortic-cardiac baroreflex sensitivity during hypotension was significantly diminished with endurance exercise training.

Original languageEnglish
Pages (from-to)1024-1030
Number of pages7
JournalMedicine and Science in Sports and Exercise
Volume25
Issue number9
DOIs
StatePublished - Sep 1993

Keywords

  • Adaptation
  • Baroreceptor sensitivity
  • Exercise training
  • Neck suction
  • Nitroprusside

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