Further evidence that (+/-)-carteolol-induced relaxation is mediated by beta2-adrenoceptors but not by beta3-adrenoceptors in the guinea pig taenia caecum.
The properties of the beta1- and beta2-adrenoceptor partial agonist (+/-)-carteolol were investigated against the beta2- and beta3-adrenoceptors of the taenia caecum of the guinea pig. (--)-Isoprenaline and (+/-)-carteolol induced concentration-dependent relaxation in this tissue. The non-selective beta1- and beta2-adrenoceptor antagonist (+/-)-propranolol (10-100 nM), the selective beta2-adrenoceptor antagonist ICI 118,551 (10-100 nM) and the non-selective beta1-, beta2- and beta3-adrenoceptor antagonist (+/-)-bupranolol (10-100nM), caused a concentration-dependent rightward shift of the concentration-response curves for (--)-isoprenaline and (+/-)-carteolol. Schild regression plot analyses carried out for (+/-)-propranolol against (--)-isoprenaline and (+/-)-carteolol gave pA2 values of 8.35 and 8.24, respectively. Schild plot analyses of ICI 118,551 against (--)-isoprenaline and (+/-)-carteolol gave pA2 values of 8.47 and 8.41, respectively. Schild plot analyses of (+/-)-bupranolol against (--)-isoprenaline and (+/-)-carteolol gave pA2 values of 8.47 and 8.53, respectively. Slopes of the Schild plots were not significantly different from unity. These results suggest that the relaxant effects of (+/-)-carteolol in the guinea pig taenia caecum are mediated by beta2-adrenoceptors but not by beta3-adrenoceptors.
Horinouchi
T
T
Department of Chemical Pharmacology, Toho University School of Pharmaceutical Sciences, Funabashi, Chiba, Japan.
Koike
K
K
D058672:Adrenergic beta-2 Receptor Antagonists; D058673:Adrenergic beta-3 Receptor Antagonists; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D002046:Bupranolol / Q000494:pharmacology; D002354:Carteolol / Q000494:pharmacology*; D002432:Cecum / Q000187:drug effects / Q000502:physiology*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D011412:Propanolamines / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D018343:Receptors, Adrenergic, beta-2 / Q000502:physiology*; D022702:Receptors, Adrenergic, beta-3 / Q000502:physiology*; D013237:Stereoisomerism
D058672:Adrenergic beta-2 Receptor Antagonists; D058673:Adrenergic beta-3 Receptor Antagonists; D000319:Adrenergic beta-Antagonists; D011412:Propanolamines; D018343:Receptors, Adrenergic, beta-2; D022702:Receptors, Adrenergic, beta-3; C026777:ICI 118551; D002046:Bupranolol; D002354:Carteolol; D011433:Propranolol; D007545:Isoproterenol