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

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.