MEDETOMIDINE STEREOISOMERS DELINEATE 2 CLOSELY RELATED SUBTYPES OF IDAZOXAN (IMIDAZOLINE) I-RECEPTORS IN THE GUINEA-PIG

A number of imidazoline, imidazole and guanidinium compounds and other drugs were compared for their ability to bind to non-adrenergic idazoxan (imidazoline) I-receptors in particulate guinea pig cerebral cortex and ileum smooth muscle fractions. Radioligand binding with [H-3]idazoxan was used for the experiments. Computer modelling of the binding data gave dissociation constants for drug binding to both I-receptors and alpha-2-adrenoceptors. Most drugs showed similar affinities for I-receptors in cortex and ileum. However, medetomidine stereoisomers as well as a few other drugs clearly delineated the I-receptors in cortex and ileum as different.