BAROREFLEX CONTROL OF ARTERIAL AND VENOUS COMPLIANCES AND VASCULAR CAPACITY IN HYPERTENSIVE DOGS

The ability of the carotid sinus baroreflex to elicit reflex changes i n vascular capacity was studied in chronically hypertensive (one-kidne y, one-clip) and sham-operated normotensive dogs under pentobarbital s odium anesthesia. Vascular compliances and reflex-induced changes in e xternal reservoir volume were measured in response to changes in isola ted carotid sinus pressure (CSP). The mean arterial pressure-CSP refle x characteristic curve was shifted to a higher arterial pressure with hypertension with no change in maximum reflex gains. Arterial complian ce in both groups increased significantly (P < 0.01) when CSP was incr eased from 50 to 200 mmHg. Total, arterial, and venous vascular compli ances were not different in normotensive and hypertensive groups. Chan ges in CSP caused no significant changes in either total systemic vasc ular or calculated venous compliances. A decrease in CSP from 250 to 5 0 mmHg resulted in an increase in external reservoir volume of 8.02 +/ - 1.03 and 7.44 +/- 1.33 ml/kg in normotensive and hypertensive groups , respectively, with changes in venous volume of 11.99 +/- 1.39 and 12 .58 +/- 1.52 ml/kg (NS). We conclude that despite the increase in arte rial resistance, Goldblatt hypertensive dogs retain the ability to mak e short-term reflex adjustments in both arterial pressure and venous b lood volume.