Effect of low-intensity exercise training on aortic baroreceptors gain-sensitivity, arterial and cardiopulmonary baroreflexes in spontaneously hypertensive rats

Author(s)

Gustavo José Justo da Silva

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Escola de Educação Física e Esportes (EEFE/BT)
• Defense date: 1999-06-16

Examining board members

Patricia Chakur Brum; Eduardo Moacyr Krieger; Lisete Compagno Michelini

• Advisor: Patricia Chakur Brum

Abstract

The effect of low-intensity exercise training on arterial and cardiopulmonary baroreceptors sensitivity and aortic baroreceptors gain-sensitivity were studied in spontaneously hypertensive rats (SHR). Exercise training (ET) was performed on a motor treadmill, at 50% VO2max, 12 weeks, 5 days/wk during 60 min. Arterial and cardiopulmonary baroreflexes were evaluated by phenylephrine and sodium nitroprusside injections and serotonin injections (cardiopulmonary baroreflex). Aortic baroreceptor gain-sensitivity was evaluated by a multifiber preparation. Baseline levels of blood pressure and heart rate were decreased in exercise-trained SHR. Baroreflex bradycardia and tachycardia, analyzed by baroreceptor sensitivity index, linear regression equation and sigmoid logistic equation were increased in exercise-trained SHR. ET increased cardiopulmonary baroreceptor bradycardia and hypotension responses in SHR. Baroreceptor gain-sensitivity nerve discharge, analyzed by a sigmoid logistic equation was increased after ET. These data suggest that low-intensity ET in SHR: a) decreases resting arterial pressure and heart rate; b) improve arterial baroreflex sensitivity to bradycardia and tachycardia; c) improves cardiopulmonary baroreflex sensitivity; and d) increases aortic baroreceptor gain-sensitivity (AU)