EFFECTS OF DIETARY-SODIUM AND CALCIUM ON BLOOD-PRESSURE REACTIVITY IN THE SHR AND WKY

Salt-sensitive spontaneously hypertensive rats (SHR) and their normotensive control strain, Wistar-Kyoto rats (WKY) were fed four diets varying in sodium chloride and calcium content in order to assess the effects of diet on learned blood pressure responses. The animals were exposed to a classical conditioning paradigm in which one tone was always followed by a brief electric shock and a second tone was never followed by shock. Sodium chloride loading raised baseline blood pressure in both strains, while supplemental calcium attenuated blood pressure. Sodium chloride potentiated blood pressure orienting responses to initial presentations of the tones among calcium deficient, but not calcium replete SHR. Increased sodium chloride intake also potentiated the learned pressor responses to the tone paired with shock in the SHR, but not the WKY. Calcium intake had no apparent effect on the learned blood pressure responses to the two tones.