Effects of chronic exercise on blood pressure in Dahl salt-sensitive rats.

ABSTRACT

We tested the hypothesis that daily exercise would reduce directly measured arterial blood pressure (BP) and sympathetic nervous system support of BP in conscious, unrestrained, female Dahl salt-sensitive rats consuming 4.0% NaCl. Dahl S/Jr inbred rats were assigned to daily exercise (EX) or sedentary (SED) treatment conditions (n = 12/group) at 4 weeks of age. Rats in the EX group were housed in cages with attached running wheels. After 5 weeks of exercise, rats were running 10.3 +/- 1.7 km/day. After at least 5 wks of treatment, all rats in both groups were placed on a 4.0% NaCl diet for 2 weeks to produce sodium-induced hypertension. Rats continued to either exercise daily or remain sedentary for an additional 2 weeks while consuming the high sodium diet. Carotid and jugular catheters were then implanted for measurements in conscious, resting, unrestrained rats on two separate days. Daily wheel running exercise for 7 to 9 weeks did not alter BP or HR in Dahl S/Jr rats consuming a 4.0% NaCl diet. However, acute arterial depressor responses to ganglionic blockade were less in EX rats. Furthermore, greater alpha-adrenergic (phenylephrine-induced) pressor responses were observed in the EX group while under ganglionic blockade. The findings suggest that overall resting sympathetic neural activity or cardiac beta-adrenergic responsiveness to sympathetic activity is reduced in this model of hypertension by daily wheel running exercise.