Effects of repeated low dose administration and withdrawal of haloperidol on sexual behaviour of male rats

Neuroleptics are known to cause anhedonia and attenuate sexual behaviour at therapeutic doses in humans. These effects are assumed to result from the dopamine antagonism of the drugs. It has been observed that a mixed dopamin e D-1/D-2 antagonist, haloperidol, may cause a reduction in the number of i ntromissions required to achieve ejaculation. On the other hand, dopamine a ntagonists are considered unable to modify sexual behaviour once the copula tory sequence is initiated. In this study, male rats received low doses of haloperidol (30 or 60 mu g/kg) before the investigation of sexual behaviour in five consecutive days and the mating test was repeated after withdrawal periods of four and five days. Haloperidol dose-dependently reduced introm ission frequency, and this effect was maintained for four days after withdr awal. Ejaculation latency was reduced in all groups, including controls. Th e results indicate that at low doses haloperidol dose-dependently reduces i ntromission frequency, and the effect of a repeated dosage may persist seve ral days after cessation of medication.