beta 1-Adrenoceptors mediating relaxation of the guinea-pig trachea: experiments with prenalterol, a beta 1-selective adrenoceptor agonist.
In the presence of 17 beta-oestradiol, prenalterol, a beta-selective adrenoceptor agonist, caused a dose-dependent relaxation of the isolated, pilocarpine-contracted guinea-pig trachea. This effect was blocked by the antagonists propranolol (non-selective) and practolol (beta 1-selective) but not by IPS 339 [(t-butylamino-3-ol-2-propyl)oximino-9-fluorene HCl] (beta 2-selective). The relaxing effect of terbutaline, a beta 2-selective adrenoceptor agonist, was more efficiently blocked by IPS 339 than by practolol. These data support the hypothesis that the guinea-pig trachea contains both beta 1- and beta 2-adrenoceptors mediating relaxation and that the beta 1-adrenoceptors are selectively stimulated by prenalterol. The efficacy of prenalterol was less than that of terbutaline, thus confirming its partial agonistic activity. In the absence of 17 beta-oestradiol, the ability of prenalterol to relax the pilocarpine-contracted trachea was lost. It is suggested that 17 beta-oestradiol may act as a functional antagonist to pilocarpine as it caused a partial relaxation itself.
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D004958:Estradiol / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009126:Muscle Relaxation / Q000187:drug effects*; D010862:Pilocarpine / Q000494:pharmacology; D011217:Practolol / Q000031:analogs & derivatives* / Q000494:pharmacology; D011294:Prenalterol; D011941:Receptors, Adrenergic / Q000502:physiology*; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D013256:Steroids / Q000494:pharmacology; D014132:Trachea / Q000187:drug effects* / Q000502:physiology
D000318:Adrenergic beta-Agonists; D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D013256:Steroids; D010862:Pilocarpine; D004958:Estradiol; D011294:Prenalterol; D011217:Practolol