RAPID BARORECEPTOR RESETTING IN DAHL SALT-SENSITIVE RATS

Dahl salt-sensitive rats rapidly become hypertensive when exposed to a high salt diet, but Dahl salt-resistant rats maintain normal blood pressure on a high salt diet. A defect in baroreceptor afferents is thought to play a key role in the low sensitivity of baroreceptor reflexes in Dahl salt-sensitive rats even in the prehypertensive stage during low salt treatment. In the present study, we tested whether differences in rapid resetting ability might contribute to differences in baroreceptor function in Dahl rats. Four groups of rats were tested: salt-sensitive and salt-resistant rats on low salt and high salt diets (0.15% and 8.0% NaCl). We compared the rapidly resetting responses of baroreceptors from each group using an in vitro preparation. Rapid resetting was assessed for each aortic baroreceptor (n=46) by linear fit of the relation of pressure threshold and conditioning mean arterial pressure. Each group had a wide range of resetting ratios (the slope of the resetting relation). Despite higher initial pressure thresholds in salt-sensitive rats on a high salt diet, resetting ratios among the four groups were similar. Thus, the ability of Dahl salt-sensitive baroreceptors to rapidly reset is preserved, despite high dietary salt and a genetic predisposition to dysfunction. The present findings in Dahl rats reinforce the results of recent studies of rapid resetting during spontaneous and renal hypertension, which suggests that the rapid resetting process is remarkably resistant to factors that compromise baroreceptor function.