The pressor response mediated by group III muscle afferent mechanoreflex is altered in prehypertensive women

Abstract

Group III muscle afferent mechanoreflex evokes excessive blood pressure response in hypertensive rats. However, hemodynamic responses to the mechanoreflex are not well understood in prehypertensive women. Therefore, we investigated the effect of mechanoreceptors to physiological responses during passive ankle dorsiflexion in both normotension and prehypertension. Thirty healthy women (10 prehypertension and 10 normotension) were recruited for this study. Subjects were continuously instrumented to measure stroke volume (SV), heart rate (HR), cardiac output (CO), mean arterial pressure (MAP) throughout the experiment. To stimulate group III mechanoreceptors, passive ankle dorsiflexion was performed by a Cybex Norm for one minute. The results indicate that MAP was significantly increased during ankle dorsiflexion in both groups; however, this pressor response was significantly higher in prehypertensive women (9.8±1.7 vs. 13.7±1.5 mmHg). SV and CO were significantly increased in normotensive women, while no differences in prehyperentsive women. There was no difference in HR in both groups. Total vascular conductance was significantly decreased in prehypertensive women. It is concluded that excessive pressor response mediated by ankle dorsiflexion is occurred by overactivity of group III mechanorecptors and the mechanism is produced via peripheral vasoconstriction in prehypertensive women.