The relationship between alterations in alpha 1-adrenoceptor reserve by phenoxybenzamine and benextramine and the sensitivity of cirazoline-induced pressor responses to inhibition by nifedipine.
Nifedipine does not inhibit the alpha 1-adrenoceptor-mediated pressor response of cirazoline at a dose that significantly antagonizes the alpha 2-adrenoceptor-mediated pressor response of B-HT 933. After elimination of the alpha 1-adrenoceptor reserve with either phenoxybenzamine or benextramine, the response to cirazoline was rendered highly sensitive to antagonism by nifedipine. These results support the hypothesis that the resistance of alpha 1-adrenoceptor-mediated pressor responses to inhibition by calcium channel antagonists may be caused by a large alpha 1-adrenoceptor reserve.
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003538:Cystamine / Q000031:analogs & derivatives / Q000494:pharmacology; D003714:Denervation; D007093:Imidazoles / Q000494:pharmacology*; D008297:Male; D009543:Nifedipine / Q000494:pharmacology*; D010643:Phenoxybenzamine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects* / Q000502:physiology
D000317:Adrenergic alpha-Antagonists; D007093:Imidazoles; D011942:Receptors, Adrenergic, alpha; D010643:Phenoxybenzamine; C029998:benextramine; D009543:Nifedipine; C014282:cirazoline; D003538:Cystamine