Forearm vascular alpha 1-adrenergic blockade by verapamil

Clin Pharmacol Ther. 1990 Jun;47(6):755-9. doi: 10.1038/clpt.1990.104.

Abstract

With use of direct brachial artery infusion and measurement of forearm blood flow and vascular resistance by strain gauge plethysmography, the effect of verapamil on phenylephrine-induced vasoconstriction was determined. Seven healthy men (age range, 19 to 47 years; weight range, 68 to 108 kg; mean blood pressure, 74 to 100 mm Hg; five nonsmokers) were systemically beta-blocked with intravenous administrations of 10 mg propranolol. Each subject then received ascending doses of phenylephrine (0.191 to 7.6 micrograms/min) alone and with concurrent verapamil (19.1 micrograms/min) by brachial arterial infusion. Dose-ratio during verapamil infusion compared with control was 8.1 (p less than 0.05). No change in slope of the phenylephrine dose-response curve was noted; however, consistent with the dose ratio, verapamil shifted the curve to the right with a decrease in the y intercept determined by linear regression (60.0 versus 40.3 mm Hg ml/100 ml forearm volume/min; p less than 0.05). Verapamil-induced attenuation of forearm vasoconstriction elicited by phenylephrine indicates that, in humans, in vivo verapamil forearm vasodilating effects are, in part, a result of alpha 1-adrenergic blockade.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Blood Pressure / drug effects
  • Dose-Response Relationship, Drug
  • Forearm / blood supply*
  • Humans
  • Infusions, Intra-Arterial
  • Male
  • Middle Aged
  • Models, Biological
  • Phenylephrine / administration & dosage
  • Propranolol / administration & dosage
  • Receptors, Adrenergic, alpha / metabolism*
  • Vascular Resistance / drug effects
  • Verapamil / administration & dosage
  • Verapamil / pharmacology*

Substances

  • Receptors, Adrenergic, alpha
  • Phenylephrine
  • Propranolol
  • Verapamil