Resistance to blockade of vasodepressor responses to tolazoline by chlorpheniramine and metiamide in rabbit hindlimb vasculature.
In perfused hindquarters of anesthetized rabbits, metiamide alone and a combination of metiamide and chlorpheniramine failed to modify tolazoline-induced depressor responses, indicating a lack of histamine H1 and H2-receptor involvement. Failure of atropine and propranolol to alter tolazoline responses precludes cholinergic and beta-adrenergic mechanisms. On the other hand, graded pressor responses to histamine were reversed to depressor responses by chlorpheniramine, whereas a combination of chlorpheniramine and metiamide completely abolished the effects of histamine. The latter results confirm that in the rabbit hindlimb vasculature histamine H1 and H2-receptors mediate pressor and depressor responses, respectively.
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D002744:Chlorpheniramine / Q000494:pharmacology*; D004347:Drug Interactions; D006614:Hindlimb / Q000098:blood supply; D006632:Histamine / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D008785:Metiamide / Q000494:pharmacology*; D011433:Propranolol / Q000494:pharmacology; D011817:Rabbits; D012039:Regional Blood Flow / Q000187:drug effects; D013890:Thiourea / Q000031:analogs & derivatives*; D014043:Tolazoline / Q000494:pharmacology*; D014666:Vasomotor System / Q000187:drug effects*
D008785:Metiamide; D002744:Chlorpheniramine; D001285:Atropine; D006632:Histamine; D011433:Propranolol; D014043:Tolazoline; D013890:Thiourea; D007545:Isoproterenol; D000109:Acetylcholine