title: Influence of calcium entry blockade on alpha 1- and alpha 2-adrenoceptor mediated vasoconstriction in the forearm of hypertensive patients.
abstract: The influence of treatment with the calcium entry blockers PY 108-068 (PY) and PN 200-110 (PN) on alpha 1- and alpha 2-adrenoceptor mediated vasoconstriction has been investigated in the forearms of hypertensive patients. Changes in forearm vascular resistance (FVR) in response to the intra-arterial infusion of drugs were determined at the end of a placebo period and after 2-4 weeks of treatment with PY or PN. The drugs used were the selective agonists methoxamine (alpha 1) and B-HT 933 (alpha 2). During placebo, basal FVR was dose-dependently increased by methoxamine and B-HT 933. Basal blood pressure was lowered during PN but not during PY. Treatment with the calcium entry blockers did not influence the effect of methoxamine, but the vasoconstriction induced by B-HT 933 was attenuated by both of the calcium entry blockers. These results confirm the findings in animal studies that calcium entry blockers preferentially inhibit the alpha 2-adrenoceptor mediated vasoconstriction induced by selective agonists.
mesh_terms: D000328:Adult; D001381:Azepines / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D005260:Female; D005542:Forearm / Q000098:blood supply*; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D017275:Isradipine; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D008875:Middle Aged; D009543:Nifedipine / Q000031:analogs & derivatives / Q000494:pharmacology; D010069:Oxadiazoles / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D012039:Regional Blood Flow / Q000187:drug effects; D014655:Vascular Resistance / Q000187:drug effects; D014661:Vasoconstriction / Q000187:drug effects*
chemical_list: D001381:Azepines; D002121:Calcium Channel Blockers; D010069:Oxadiazoles; D011942:Receptors, Adrenergic, alpha; C015603:azepexole; D008729:Methoxamine; D009543:Nifedipine; C034600:darodipine; D017275:Isradipine