Lisuride-induced mounting and its modification by drugs active on adrenergic and dopaminergic receptors.

Imidazole (IMID), (9.37-75 mg/Kg) and yohimbine (YOH), (0.5-2.5 mg/Kg), strongly potentiated lisuride-induced mounting, scored as a percentage of animals affected and mean number of mounts per animal, while clonidine (150 micrograms/Kg) significantly antagonized the phenomenon. A high (2 mg/Kg) but not a low (50 micrograms/Kg) dose of B-HT 920 and DPI (100 and 500 micrograms/Kg) also inhibited lisuride-induce mounting. While, at present, IMID specific activity on monaminergic system is not yet conclusive, it is demonstrated that, at the doses used, YOH and clonidine are selective alpha 2 antagonist and agonist, respectively; B-HT 920 preferentially stimulates D2 receptors at 50 micrograms/Kg and alpha 2 receptors at 2 mg/Kg; finally DPI, proposed as DAI agonist, also activates alpha 2 receptors. Therefore, in view of the dose-related receptorial selectivity of action of the drugs tested, neurochemical mechanisms on specific receptors involved for modulation of this form of sexual behaviour are briefly discussed.