The beta3-adrenoceptor-mediated relaxation induced by epinephrine in guinea pig taenia caecum.
The mechanisms of the beta-adrenoceptor mediated relaxation induced by epinephrine in guinea pig taenia caecum were examined. The relaxant response to epinephrine was unaffected by propranolol (approximately 10(-5) M) or phentolamine (approximately 10(-5) M). The response to epinephrine was antagonized in a concentration dependent manner by bupranolol, and Schild plot of the data revealed the pA2 value of 5.87. Epinephrine significantly increased cyclic AMP level in this preparation. Bupranolol (10(-4) M) significantly decreased the cyclic AMP level that was elicited by epinephrine, whereas propranolol (10(-5) M) produced no effect. These results suggest that the relaxant response to epinephrine in the guinea pig taenai caecum is mainly mediated by beta3-adrenoceptors.
Koike
K
K
Department of Chemical Pharmacology, Toho University School of Pharmaceutical Sciences, Funabashi, Chiba, Japan.
Horinouchi
T
T
Yamamoto
Y
Y
D000818:Animals; D002046:Bupranolol / Q000494:pharmacology; D002432:Cecum / Q000187:drug effects / Q000502:physiology; D000242:Cyclic AMP / Q000032:analysis; D004837:Epinephrine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D010646:Phentolamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology*
D011943:Receptors, Adrenergic, beta; D002046:Bupranolol; D011433:Propranolol; D000242:Cyclic AMP; D004837:Epinephrine; D010646:Phentolamine