EFFECTS OF HIGH-SALT INTAKE ON CONTROL OF HINDLIMB VASCULAR-RESISTANCE BY ARTERIAL BAROREFLEX AND VAGAL AFFERENTS IN SPONTANEOUSLY HYPERTENSIVE RATS

1. This study aimed to examine whether a high salt diet alters control of vascular resistance by arterial baroreflex and vagal afferents in spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). 2. SHR and WKY aged 8 weeks were fed either high (8%) or normal salt (0.4 %) diet for 4 weeks. Arterial baroreflex control of hindlimb vascular resistance was assessed by examining reflex-induced vasodilation and v asoconstriction in response to phenylephrine and nitroprusside, respec tively, in the constant-flow perfused hindlimb of urethane-anesthetize d rats. 3. Tonic influence of the cardiopulmonary vagal afferents was evaluated by examining the effects of vagotomy on hindlimb vascular re sistance and on the gain of arterial baroreflex control of hindlimb va scular resistance. 4. The gain of the arterial baroreflex control of h indlimb vascular resistance in response to both phenylephrine and nitr oprusside were not significantly different between SHR receiving high and normal salt diets, and between WKY receiving high and normal salt diets. 5. Vagotomy increased hindlimb vascular resistance in all four groups of rats. However the magnitude of the increase in hindlimb vasc ular resistance was less in SHR on a high salt diet than those in SHR on a normal salt diet but similar between the two groups of WKY. Vagot omy increased the slope of arterial baroreflex control of hindlimb vas cular resistance in SHR receiving a normal salt diet and the two group s of WKY but not in SHR receiving a high salt diet. 6. These results s uggest that a high salt diet attenuates the inhibitory influence of va gal afferents on the control of vascular resistance in SHR but not in WKY, while the arterial baroreflex control of vascular resistance is p reserved during high salt diet in both SHR and WKY.