BAROREFLEX FUNCTION IN STREPTOZOTOCIN (STZ) INDUCED DIABETIC RATS

To determine whether the renal sympatho-inhibition and bradycardia in responses to acute increases in arterial pressure are altered in the d iabetic state, the renal nerve discharge and heart rate were measured in streptozotocin (STZ) induced diabetic (DIA) rats. Integrated renal sympathetic nerve activity and heart rate were measured before and dur ing an acute increase in blood pressure in anesthetized (Inactin 0.1 g /kg, i.p.) control (vehicle) and DIA rats (Sprague Dawley rats injecte d with STZ 65 mg/kg i.p.). Blood glucose Levels were significantly ele vated in the DIA group compared with the control group. Baroreflex cha nges in renal nerve activity and heart rate were not significantly dif ferent in the DIA rats compared with control rats at a time when the r enal sympatho-inhibition in response to acute volume expansion was blu nted in the diabetic rats. In addition, blocking the effect of elevate d angiotensin II in diabetic rats with the converting enzyme inhibitor enalapril did not change the baroreflex function in DIA rats compared with control rats. However, administration of vasopressin failed to p otentiate the baroreflex in diabetic rats as it did in normal control rats. This study demonstrates that (1) the baroreflex function is norm al in STZ induced diabetic rats unlike the volume reflex during the ea rly phase of the disease, (2) blockade of the AII system does not alte r baroreflex function in diabetic rats and (3) vasopressin fails to po tentiate the baroreflex in diabetic rats as it does in the euglycemic normal rats.