Mydriasis model in rats as a simple system to evaluate α2-adrenergic activity of the imidazol(in)e compounds

Imidazol(in)e compounds show the diversity of pharmacological effects including mydriasis, hypotension, sedation, bradycardia and hypothermia. At first it was postulated that these effects are mediated via α2-adrenoceptors exclusively. Clonidine is well known as a model agent to produce pupillary dilation in rats. However, it became obvious later that clonidine-like imidazol(in)e adrenoceptor agonists which produced mydriasis in rats, exhibit also a high affinity for imidazoline I1-receptors. That short report attempts to review the present status of studies to confirm that the mydriasis model in rats can be a selective system to evaluate the α2-adrenergic activity of potential pharmacologically active compounds of imidazol(in)e structure.