Prevention of salt-induced hypertension in the Dahl strain by 6-hydroxydopamine.

Salt-induced hypertension in Dahl's genetically hypertensive rat has been attributed to humoral or renal factors. However, a recent study from our laboratory suggested that neurogenic mechanisms contribute to salt-induced increased in hindquarters vascular resistance in Dahl salt-sensitive (S) rats. In the present study, we examined the hypothesis that "chemical sympathectomy" with 6-hydroxydopamine (6-OHDA) prevents salt-induced hypertension and increased vascular resistance in S rats. Hypertension did not develop during high-salt diet (8% NaCl) in S rats treated with 6-OHDA, (75--100 mg/kg ip), whereas in rats treated with vehicle, hypertension developed after 4 wk of high salt diet. Chow consumption, sodium excretion, and weight gain were not altered by 6-OHDA. Hindquarters vascular resistance and neurogenic vasoconstrictor tone were significantly lower in S rats treated with 6-OHDA than in S rats treated with vehicle. 6-OHDA also significantly reduced responses to direct sympathetic nerve stimulation and tyramine. These results suggest that an intact sympathetic nervous system plays an essential role in the development of salt-induced increase in blood pressure in Dahl S rats.