CAROTID BAROREFLEX SENSITIVITY AT REST AND DURING PSYCHOLOGICAL STRESS IN OFFSPRING OF HYPERTENSIVES AND NONTWIN SIBLING PAIRS

The baroreceptor reflexes of 38 young adult males were mechanically stimulated by negative external cervical pressure during a mental arithmetic task and pre-stress and post-stress relaxation periods. The subjects comprised 19 pairs of non-twin siblings. Baroreflex sensitivity was significantly less pronounced during arithmetic. Using non-invasive techniques, this finding replicates several others indicating a damping of the baroreceptor reflex during stress. More importantly, analyses of sibling similarities also revealed significant familiality of baroreflex sensitivity, independent of age, body mass, pressure applied and baseline heart rate. To examine the relationship between baroreflex sensitivity and parental history of hypertension, 21 young adult males with a parental history and 25 without participated in a second experiment. The two groups were not significantly different in resting baroreflex sensitivity. However, sensitivity was damped to a significantly greater degree during mental arithmetic in offspring of hypertensives, offering one possible explanation for their greater blood pressure reactivity to stress. These results suggest that familial influences may effect baroreflex sensitivity and, possibly as a result, blood pressure reactivity and risk for hypertension.