Pharmacological characterisation of melatonin mt1 receptor-mediated stimulation of [35S]-GTPγs binding∗∗The nomenclature and classification of melatonin receptors used here was recently approved by the Nomenclature Committee of the International Union of Pharmacology [1]. The denomination ‘mt1’ corresponds to that of the recombinant receptor previously termed Mel1a. MT2 refers to native functional receptors with pharmacological characteristics similar to that of the recombinant receptor mt2, previously termed Mel1b. MT3 corresponds to the pharmacologically defined melatonin receptor subtype, with unknown molecular structure, previously referred to as ML2.