Alterations in Hemodynamic Response Variability Following Acute Stressors in Dahl salt‐sensitive‐mcw and Brown Norway‐mcw Rats on a High Salt Diet.

We have described differences in hemodynamic response patterns to acute stressors in two unrelated rat strains, Dahl salt‐sensitive‐mcw (SS/Mcw) and Brown Norway‐mcw (BN/Mcw), maintained on a low salt (0.10% NaCl) diet. Stress evokes a pressor response due to a large increase in systemic vascular resistance (SVR) in BN/Mcw rats but due to both an increase in cardiac output (CO) and a smaller increase in SVR in SS/Mcw rats. We reported that rats with greater vascular responses to stressors have an increased risk of developing hypertension. Therefore, we tested hemodynamic responses to cocaine (5 mg/kg, i.v.) or startle with cold water, elicited by sudden exposure to ice cold water (1 cm deep), in SS/Mcw and BN/Mcw after 4 weeks of a high salt (4% NaCl) diet. SS/Mcw on high salt diets had elevated arterial pressure (172 ± 9 mmHg, n = 8) compared to BN/Mcw (109 ± 5 mmHg, n = 10). High salt diet enhanced the increase in SVR in both strains and prevented the increase in CO in SS/Mcw following cocaine. High salt diet blunted the increase in CO in SS/Mcw, but attenuated the initial large increase in SVR in BN/Mcw following startle with cold water. Taken together, these results suggest that the vascular response to stress is not correlated with salt‐sensitivity, since SS/Mcw on high salt diets became hypertensive but did not become vascular responders to stress. Supported by DA13256 and GM008306, and a grant from the AHA, Heartland Affiliate.