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Carotid baroreflex responsiveness in normotensive African Americans is attenuated at rest and during dynamic leg

Seth W Holwerda1, Mitchel R Samels, David M Keller

  • 1Department of Medical Pharmacology and Physiology, University of Missouri Columbia, SC, USA.

Frontiers in Physiology
|March 14, 2013
PubMed

Insights

African Americans (AAs) show reduced carotid baroreflex (CBR) control of heart rate and blood pressure during exercise compared to Caucasian Americans (CAs). This impairment affects their ability to manage hypertensive challenges.

Area of Science:

  • Cardiovascular Physiology
  • Exercise Physiology
  • Racial Health Disparities

Background:

  • Differences in cardiovascular responses to stressors exist between African Americans (AAs) and Caucasian Americans (CAs).
  • The carotid baroreflex (CBR) is crucial for regulating heart rate (HR) and blood pressure (MAP) during physiological challenges.

Purpose of the Study:

  • To test if CBR control of HR and MAP is reduced in AAs compared to CAs during exercise.
  • To investigate potential racial differences in autonomic cardiovascular regulation.

Main Methods:

  • 23 healthy young males (12 AA, 11 CA) underwent rest and exercise (leg cycling) protocols.
  • Carotid baroreflex (CBR) function was assessed using neck pressure (simulated hypotension) and neck suction (simulated hypertension).
  • Continuous recording of mean arterial pressure (MAP) and heart rate (HR) was performed.

Main Results:

  • At rest, AAs exhibited attenuated CBR-mediated reductions in HR and MAP in response to neck suction (hypertensive stimulus) compared to CAs.
  • During exercise, AAs continued to show attenuated CBR responses for HR and MAP to neck suction, despite similar reflex gain.
  • No significant differences in CBR responses to neck pressure (hypotensive stimulus) were observed between groups at rest or during exercise.

Conclusions:

  • African Americans demonstrate an impaired ability to counteract hypertensive challenges via the carotid baroreflex during steady-state exercise compared to Caucasian Americans.
  • These findings suggest a racial disparity in autonomic cardiovascular regulation during physical exertion.
  • Further research is warranted to understand the mechanisms underlying these observed differences.

Keywords:
blood pressureexerciseheart ratehypertensionracial differences

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