No abstract

The mechanisms responsible for the higher incidence of essential hypertension in blacks than in whites are the object of much research attention. One hypothesis is that the development of hypertension in blacks is associated with exaggerated blood pressure reactivity, particularly those responses mediated by vasoconstriction. Racial differences in blood pressure responses to cold stimulation of the forehead, a known alpha-adrenergic vasoconstrictive stimulus, were examined in health, college-age males. Compared to white subjects, black subjects exhibited significantly greater increases in systolic and diastolic blood pressure, as well as increases in forearm vascular resistance, in response to cold stimulation. This preliminary evidence of increased peripheral vascular reactivity in blacks suggests that known racial differences in hypertension prevalence might derive in part from physiological differences in sympathetic nervous system reactivity.

Background. Prior research has suggested a weaker parasympathetic antagonism of sympathetic effects on the heart in type A (coronary-prone) men. To confirm this phenomenon and extend our understanding of it, we investigated the effects of prior muscarinic blockade on the electrocardiogram T wave and other cardiovascular and neuroendocrine responses to isoproterenol in type A and type B (non-coronary-prone)