Effects of salt intake on blood pressure and heart rate responses to footshock stress in SHR, BHR, and WKY rats

Abstract

The SHR shows chronic elevations in blood pressure in response to stress or a high salt diet, at least in some studies. Stress and salt have also been combined in studies in the SHR. Tonic levels of blood pressure are not clearly elevated by superimposing acute stress on top of a chronic high salt diet. The BHR is a new model with lower resting blood pressure and marked sensitivity to environmental stressors such as stress and dietary salt intake. In the present study, SHR, BHR, or WKY were placed on a normal or high salt (8% in chow) diet. During the 8th week of the appropriate diet, blood pressure and heart rate were monitored during rest and footshock stress. Salt elevated the resting blood pressure in all three strains, but only marginally in the WKY. Stress did not further elevate the effect seen with salt, although it had a differential effect on heart rate in the three strains. In SHR, the salt group had a higher heart rate, although in BHR it was no different, and in WKY it was lower, than that seen in same-strain normal diet groups. The results are discussed in terms of the ability of the combination of stress and chronic high salt intake to alter baroreflex function in SHR, although only marginally affecting it in BHR. WKY, on the other hand, do not show evidence of altered baroreflex function when an acute stressor is superimposed on a high-salt diet.