Beta3-adrenoceptor mechanisms in guinea-pig taenia caecum.
Beta-adrenoceptor-mediated relaxation of guinea-pig taenia caecum was investigated by studying the effects of BRL37344, CGP12177 and norepinephrine. These drugs caused graded relaxation of the guinea-pig taenia caecum. The concentration-response curves for these drugs were unaffected by propranolol, atenolol, butoxamine, prazosin, yohimbine and phentolamine. Bupranolol produced shifts of the concentration-response curves for these drugs. Schild regression analyses carried out for bupranolol against BRL37344, CGP12177 and norepinephrine gave pA2 values of 5.79, 5.61 and 5.53, respectively. CGP12177 and norepinephrine significantly increased cyclic AMP levels in this preparation. Bupranolol significantly decreased cyclic AMP levels elicited by CGP12177 and norepinephrine, whereas propranolol produced no effect. These results suggest that the relaxant responses to BRL37344, CGP12177 and norepinephrine in the guinea-pig taenia caecum are mediated by beta3-adrenoceptors.
Koike
K
K
Department of Chemical Pharmacology, Toho University School of Pharmaceutical Sciences, Funabashi, Chiba, Japan.
Takayanagi
I
I
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D002432:Cecum / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure*; D004983:Ethanolamines / Q000494:pharmacology; D006168:Guinea Pigs; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D009638:Norepinephrine / Q000494:pharmacology; D011412:Propanolamines / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology*; D022702:Receptors, Adrenergic, beta-3; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D004983:Ethanolamines; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; D022702:Receptors, Adrenergic, beta-3; D014662:Vasoconstrictor Agents; C057368:BRL 37344; C033394:CGP 12177; D009638:Norepinephrine