[Imidazoline receptors. Historic review and current status of knowledge]

After the initial demonstration, by Ruffolo in 1977, that imidazolines and phenethylamines do not interact in the same manner with adrenoceptors, a different class of receptors (imidazoline-preferring receptors) was identified. They are present in the brain stem and in several tissues at the periphery. This imidazoline-preferring receptor is believed to be the target of the anti-hypertensive effect of clonidine and the newly developed clonidine-related substances, rilmenidine and moxonidine. This review summarises the current knowledge and latest developments in this field, including the consensus on the nomenclature proposed by Ernsberger to classify the imidazoline receptors in I1 (clonidine and idazoxan sensitive) and I2 (idazoxan sensitive but clonidine insensitive) types.