Effect of α2B-Adrenoceptor Polymorphism on Peripheral Vasoconstriction in Healthy Volunteers

Background: Alpha-2B adrenoceptor is the vasoconstrictive subtype in the mouse. Human α 2B -AR deletion (D) allele has been associated with loss of short-term agonist-promoted receptor desensitization, which may lead to increased vasoconstriction on α 2 activation. The goal of this study was to test the hypothesis that α 2B -adrenoceptor activation induces enhanced vasoconstriction in carriers of the DD genotype, compared with carriers of the insertion/insertion (II) genotype. Methods: The authors administered increasing doses of dexmedetomidine (targeting plasma concentrations of 0.15, 0.3, 0.6, and 1.2 ng/ml) to 16 healthy young volunteers (8 carrying the α 2B DD genotype, 8 carrying the II genotype) in whom sympatholytic effects of the drug were attenuated by general anesthesia. Measurements were made of finger blood volume (an indicator of vasoconstriction) by photoplethysmographic determination of light transmitted through a finger, finger blood flow by venous occlusion plethysmography, and hemodynamic variables. Results: All concentration of dexmedetomidine increased light transmitted through the finger (vasoconstriction) and systolic blood pressure and decreased heart rate in both groups (P < 0.001 for all). Dexmedetomidine reduced finger arterial inflow only in the DD group (P < 0.001). Dexmedetomidine had no effect on finger venous outflow or venous capacitance. There were no significant differences between the II and DD groups in any of the variables. Conclusions: The results of this study confirm the α 2 agonist induced vasomotor and hemodynamic effects in peripheral vasculature. However, the results do not support the hypothesis that α 2B -adrenoceptor polymorphism has an effect on peripheral vasoconstriction in humans.