Reduced arterial baroreflex control of muscle sympathetic nerve activity in young borderline hypertensives

: Mean arterial pressure (MAP), heart interval (HI) and muscle sympathetic nerve activity (MSNA) were measured before and after a bolus injection of phenylephrine in 11 normotensives (NT) and 12 borderline hypertensives (BHT). (1) Basal MSNA was elevated in BHT compared to NT. (2) Both baroreflex slope for HI and that for MSNA were significantly less in BHT. (3) There was an inverse correlation between the slope for MSNA and the basal MSNA (r = -0.63). Thus, arterial baroreflex control of sympathetic activity may be reduced in BHT and the reduction may be involved in the elevated sympathetic nerve activity in these subjects.