Sexual behaviour of morphine-dependent and abstinent male rats.

Abstract

Morphine HCl (5–20 mg/kg) impaired the sexual behaviour of non-tolerant male rats in a doserelated way. Mounting responses and the amount of time spent in social and sexual interaction with a receptive female were reduced, while the frequency of contacts remained unchanged. Tolerant male rats which had been maintained on large daily doses of morphine HCl (100 mg/kg) also showed marked variations in sexual behaviour, depending upon whether they were tested in the drugged or the abstinent state. When tested 2.5 h after their usual dose of morphine, sexual behaviour was almost completely suppressed although the rats were active and, in one test, made bodily contact more frequently with the females than did the controls. The time spent in social and sexual interaction was markedly reduced and the drugged males appeared to respond inappropriately to the females. When tested after 23-h withdrawal or 1 h after the precipitation of abstinence by naloxone, the sexual behaviour of tolerant rats was indistinguishable from that of controls. Thus, disturbances of sexual behaviour appear to differ from patterns of change in eating and drinking in drugged and morphine-abstinent rats. Post-dependent rats, tested after 2 weeks of withdrawal, did not differ from controls, unless they were challenged with morphine (30 mg/kg), when their sexual responses and locomotor behaviour were less affected.