Cholinergic mechanisms and sexual behavior in the male rabbit

The effects of cholinolytic as well as of cholinomimetic agents on sexual behavior in male rabbits were investigated. Castrated animals, injected with a supramaximal testosterone dose, were used. Scopolamine or methylscopolamine, 0.1 mg/kg, inhibited sexual activity. A dose of 0.02 mg had no effects. The muscarinic receptor-stimulating drug, pilocarpine, completely inhibited sexual activity at doses of 2, 10, and 50 mg/kg. A subeffective dose of methylscopolamine completely antagonized the effects of pilocarpine 2 mg/kg, partly the effect of pilocarpine 10 mg/kg, and not at all the effect of pilocarpine 50 mg/kg. Scopolamine completely antagonized the effects of pilocarpine 2 and 10 mg/kg, and not at all the effects of pilocarpine 50 mg/kg. The data indicate that the peripheral effects of both the receptor-blocking and stimulating agents is most important for the effects on sexual behavior, although a central site of action of pilocarpine cannot be ruled out.