Baroreceptor reflex function in young normotensive men with a family history of hypertension

Abstract

The purpose of this study is to evaluate the baroreflex function using lower body negative pressure (LBNP) and neck suction in young normotensive men with or without a family history of hypertension. Twenty-two young normotensive men with a family history of hypertension (FH+) and eight young normotensive men who had no family history of hypertension (FH-) were studied. FH(+) consisted of men who had a family history of hypertension within second degree relatives. We studied cardiopulmonary baroreflex function using LBNP and carotid sinus baroreflex function using neck suction and evaluated the reflex function under stimulated conditions using both LBNP and neck suction at the same time. Systolic arterial pressure (SAP)(F = 5.42, p < 0.0001) and pulse pressure (PP)(F = 15.57, p < 0.0001) decreased similarly in both groups in response to LBNP. SAP and PP responses to LBNP were not significantly affected by the family history of hypertension. Diastolic arterial pressure (DAP) increased (F = 2.89, p < 0.005) in both groups. There was a relationship between the LBNP level and family history of hypertension (F = 2.53, p < 0.013), and the increment in DAP during LBNP-30, -40 mmHg was larger in the FH(+) group. Though mean arterial pressure (MAP) was not effected by LBNP, there LBNP level was related to the family history of hypertension (F = 2.23, p < 0.02). Heart rate increased progressively (F = 25.7, p < 0.0001) with increasing levels of LBNP; however, these changes did not differ significantly in either group. The hemodynamic responses to neck suction and both LBNP and neck suction were not affected by the family history of hypertension. Forearm vascular resistance increased considerably just after starting LBNP and the increment was slightly greater in FH(+) than FH(-)(p = 0.08). Plasma epinephrine and norepinephrine concentrations increased in response to LBNP, LBNP and neck suction, decreased in response to neck suction in both groups. These results suggest that cardiopulmonary baroreflex restraint on sympathetic vasomotor outflow is augmented in normotensive young men with a family history of hypertension, while carotid sinus baroreflex function is not different between the two groups.