Beta-adrenergic control of motility in the rat colon. I. Evidence for functional separation of the beta 1- and beta 2-adrenoceptor-mediated inhibition of colon activity

B EkB Lundgren


The beta-adrenoceptor-mediated inhibitory response in isolated rat colon strips of beta-adrenoceptor agonists (isoproterenol, terbutaline, prenalterol) in the absence and presence of the selective beta-adrenoceptor antagonists metoprolol (beta 1) and IPS 339 (beta 2) demonstrates that both beta 1- and beta 2-adrenoceptors are involved in the inhibition of colonic motility. Neuronal blockade induced by tetrodotoxin suppressed the relatively high (68%) maximal response of prenalterol (partial beta-adrenoceptor agonist) to 23%. The concentration-response curves for terbutaline (beta 2-selective agonist) and isoproterenol (nonselective agonist) were not influenced by tetrodotoxin. The results thus indicate that the beta-adrenergic inhibition of spontaneous activity in the rat colon strip may be mediated at two functional levels within the colon wall: either by beta 2-adrenoceptors in the smooth muscle layer or by beta 1-adrenoceptors in the intramural ganglionic plexuses, which by neuronal elements are coupled to the effector smooth muscle.


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Related Concepts

IPS 339, monohydrochloride, (+-)-isomer
Adrenergic beta-Agonists
Adrenergic beta-Antagonists
Taenia Coli
Intestinal Motility
Smooth Muscle

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