[The role of alpha2-adrenergic and I1-imidazoline receptors in the effects of clonidine and moxonidine on isolated large intestine of mice].

The ability of clonidine and moxonidine to interact with alpha2-adreno- and I1-imidazoline receptors was studied on isolated segments of large intestine of mice. Both drugs induced dose-dependent contractions in longitudinal muscles of the intestine segments. In both cases, the drug action was almost equally decreased by pretreatment with of yohimbine (alpha2-adrenoreceptor agonist with low affinity to I1-imidazoline receptors) and efaroxan (I1-imidazoline receptor agonist with low affinity to alpha2-adrenoreceptors). Analysis of the ratios of the antagonist activities (pA2) of yohimbine and efaroxan with respect to clonidine and moxonidine, as well as the relative selectivity of the two antagonists suggested that the action of both drugs on the large intestine is realized predominantly via alpha2-adrenoreceptors.