A chronic high-salt diet fails to enhance blood pressure reactivity to a tone associated with footshock, in SHR, BHR, and WKY rats

Abstract Both the human and animal literatures suggest that reactivity to stress is enhanced in the presence of a positive family history of hypertension. There is also some suggestive evidence, though not as strong, that a high-salt diet will enhance reactivity to stress, at least in a subpopulation of individuals. In the present study, rats withzero (Wistar-Kyoto, or WKY), one (borderline hypertensive, or BHR), or two (spontaneously hypertensive, or SHR) hypertensive parents were placed on a normal or high (8% in chow)-salt diet for 8 weeks starting at 8 weeks of age. After 6 weeks on the appropriate diet, rats were stressed daily for 5 days. Each session consisted of 28 foot shock trials preceded by a tone. On the following week, animals were instrumented with femoral artery catheters. After a 2-day recovery period, they were again subjected to the experimental paradigm, during which blood pressure was continuously monitored. Differences were found with respect to blood pressure reactivity and family history: SHR were the most reactive to the tone associated with foot shock. However, no effects of salt on reactivity were observed, despite an effect of this manipulation on basal blood pressure. The effect of foot shock itself was also studied, and revealed that BHR showed a blood pressure reactivity response intermediate between SHR and WKY. Once again, no effects of the salt manipulation were seen. In conclusion, while the data support a relationship between family history of hypertension and reactivity to stress, they do not support a relationship between salt intake and reactivity to stress. Studies that do suggest such a relationship appear to have in common the use of stressors that would be expected to evoke active coping.