title: Effect of alpha2B-adrenoceptor polymorphism on peripheral vasoconstriction in healthy volunteers.
abstract: BACKGROUND
  Alpha-2B adrenoceptor is the vasoconstrictive subtype in the mouse. Human alpha2B-AR deletion (D) allele has been associated with loss of short-term agonist-promoted receptor desensitization, which may lead to increased vasoconstriction on alpha2 activation. The goal of this study was to test the hypothesis that alpha2B-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 alpha2B 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 alpha2 agonist induced vasomotor and hemodynamic effects in peripheral vasculature. However, the results do not support the hypothesis that alpha2B-adrenoceptor polymorphism has an effect on peripheral vasoconstriction in humans.
authors.affiliation: Department of Anesthesia and Perioperative Medicine, University of California, San Francisco 94143-0648, USA. talkep@anesthesia.ucsf.edu
authors.forename: Pekka
authors.initials: P
authors.lastname: Talke
authors.forename: Claudia
authors.initials: C
authors.lastname: Stapelfeldt
authors.forename: Errol
authors.initials: E
authors.lastname: Lobo
authors.forename: Ronald
authors.initials: R
authors.lastname: Brown
authors.forename: Mika
authors.initials: M
authors.lastname: Scheinin
authors.forename: Amir
authors.initials: A
authors.lastname: Snapir
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D020927:Dexmedetomidine / Q000494:pharmacology; D005260:Female; D005838:Genotype; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D011110:Polymorphism, Genetic; D018341:Receptors, Adrenergic, alpha-2 / Q000235:genetics*; D014661:Vasoconstriction / Q000187:drug effects*
chemical_list: D000316:Adrenergic alpha-Agonists; D018341:Receptors, Adrenergic, alpha-2; D020927:Dexmedetomidine