[Functional interaction between alpha- and beta-adrenoreceptors of the small intestine]

Effect of desensitization of alpha-adrenoreceptors on the functional state of beta-receptors and vice versa was studied in isolated sections of the rat small intestine. Neither blockade, nor desensitization of alpha-receptors produced any effect on the sensitivity of beta-receptors to isopropyl-noradrenaline (IPN) whereas desensitization of beta-receptors to IPN resulted in the increase of alpha-receptors sensitivity to phenylephrine with a decreased maximal reaction. In the presence of GTP (0.02 mM) and propranolol (2.00 x 10(-7) M) IPN acts as a competitive reversible auto-inhibitor, GTP fully removing the inhibitory effect of IPN on both alpha- and beta-adrenoreceptors. Existence of functional interrelationship between alpha- and beta-adrenoreceptors is suggested.