In keeping with this possibility is the observation that the decrease in blood pressure in response to antihypertensive drugs acting through adrenergic mechanisms is smaller in blacks. 3–5 This finding suggests that ethnic differences exist, either in regulation of sympathetic activity or in vascular response to the same degree of sympathetic activation. 2 Many investigators have observed that blood pressure responses to stress are higher in normotensive black than white subjects. 1 Several environmental and genetic factors have been suggested to contribute. Hypertension is more prevalent and more severe in black Americans and is associated with greater morbidity and mortality rates. The response to dexmedetomidine provides a model that will allow further study of the regulation of α 2-adrenergic receptor–mediated vascular responses

These findings do not support the hypothesis that altered α 2-adrenergic receptor sensitivity is the explanation for the decreased blood pressure response to systemic administration of clonidine in blacks. Our data indicate that α 2-adrenergic receptor–induced venoconstriction is similar in blacks and whites. There was substantial intersubject variability in the sensitivity to dexmedetomidine the dose resulting in 50% (ED 50) of maximum vasoconstriction ranged from 0.08 ng/min to 256 ng/min. Dexmedetomidine caused pronounced venoconstriction, with an average (±SD) maximum response of 74.5☑7.72% but with no difference between blacks and whites. Increasing doses of dexmedetomidine (0.001 to 1000 ng/min) were infused into a dorsal hand vein, and the local response was measured with a linear variable differential transformer. Therefore, to determine the role of altered α 2-adrenergic receptor vascular sensitivity in ethnic differences in vascular response, we compared local vascular responses with the highly selective α 2-adrenergic receptor agonist dexmedetomidine in healthy black (n=18) and white (n=19) subjects. However, clonidine has a low α 2/α 1 selectivity ratio.

This reduced hypotensive response might be explained by greater postsynaptic vascular α 2-adrenergic receptor vasoconstrictive response.

Customer Service and Ordering Informationīlack Americans have a reduced hypotensive response to the α 2-adrenergic receptor agonist clonidine compared with whites, despite similar central sympathoinhibition.Stroke: Vascular and Interventional Neurology.Journal of the American Heart Association (JAHA).Circ: Cardiovascular Quality & Outcomes.Arteriosclerosis, Thrombosis, and Vascular Biology (ATVB).

Alpha 2 adrenergic agonist