Effects of imidazole and some imidazole-derivatives on lisuride-induced mounting and aggressiveness.

Adult male rats were treated intraperitoneally (IP) with imidazole (IMID), distilled water or saline prior to administration of lisuride either IP or intracerebroventricularly (ICV) at doses too low by themselves to elicit the behavioural signs of mounting and aggressiveness, typically induced by higher doses of this drug. Pretreatment with distilled water or saline, or the procedure of injection alone, stimulated mounting in some of the animals. At a certain range of doses IMID induced a marked increase in both mounting and aggressive posturing in the same animals, while at higher doses mounting ceased, violent aggressive behaviour appeared and some of the rats died. Seven IMID derivatives were used on the lisuride-test: N-methylimidazole, 2-methylimidazole, 4-methylimidazole, N-acetylimidazole, 4-imidaaoleacetic acid, clonidine and cimetidine. Only 4-imidazoleacetic acid was completely ineffective with respect to controls. All the other drugs enhanced aggressive behaviour to varying degrees but proved to be less potent than IMID in inducing mounting, and clonidine reduced mounting at all the doses tested.