The beta3-adrenoceptor-mediated relaxation induced by dopamine in guinea pig taenia caecum.
The mechanisms of the beta-adrenoceptor-mediated relaxation induced by dopamine in guinea pig taenia caecum were examined. The relaxant response to dopamine was unaffected by propranolol (10(-8)-10(-5) M) or phentolamine (10(-8)-10(-5) M). Atenolol (3 x 10(-7)-3 x 10(-4) M), butoxamine (10(-7)-10(-4) M), prazosin (10(-8)-10(-5) M), yohimbine (10(-8)-10(-5) M), SCH 23390 (10(-8)-10(-5) M) and haloperidol (10(-8)-10(-5) M) had no effect on the potency of dopamine. The response to dopamine was antagonized in a concentration-dependent manner by bupranolol (3 x 10(-6)-3 x 10(-5) M), and Schild plot of the data revealed the pA2 value of 5.55 and the slope of the regression line was 1.13. These results suggest that the relaxant response to dopamine in the guinea pig taenia caecum is mainly mediated by the beta3-adrenoceptors.
Department of Chemical Pharmacology, Toho University School of Pharmaceutical Sciences, 2-2-1, Miyama, Funabashi, Chiba 274-8510, Japan. yurie@phar.toho-u.ac.jp
Yurie
Y
Akimoto
Takahiro
T
Horinouchi
Yoshio
Y
Tanaka
Katsuo
K
Koike
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001262:Atenolol / Q000494:pharmacology; D001552:Benzazepines / Q000494:pharmacology; D002078:Butoxamine / Q000494:pharmacology; D002432:Cecum / Q000187:drug effects / Q000502:physiology*; D004298:Dopamine / Q000494:pharmacology*; D018492:Dopamine Antagonists / Q000494:pharmacology; D006168:Guinea Pigs; D006220:Haloperidol / Q000494:pharmacology; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects* / Q000502:physiology*; D010646:Phentolamine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D022702:Receptors, Adrenergic, beta-3 / Q000502:physiology*; D015016:Yohimbine / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D001552:Benzazepines; D018492:Dopamine Antagonists; D022702:Receptors, Adrenergic, beta-3; D002078:Butoxamine; D015016:Yohimbine; D001262:Atenolol; D011433:Propranolol; D006220:Haloperidol; D004298:Dopamine; D011224:Prazosin; D010646:Phentolamine