Effect of domperidone on apomorphine inhibition of the copulatory response and exploratory behaviour in the female rat.

The effects of domperidone, a peripheral dopamine receptor blocker which poorly crosses the blood-brain barrier, on copulatory and exploratory behaviour were studied in apomorphine (oestrogen + progesterone) treated ovariectomized rats. The dose of domperidone (1.0 mg/kg) which clearly prevented the inhibitory action of apomorphine on the lordotic response did not influence the effect of apomorphine in an exploratory test situation. This finding indicates that peripherally (intraperitoneally) administered domperidone influences dopaminergic mechanisms implicated in the copulatory behaviour of the female rat, but not dopaminergic mechanisms involved in exploratory behaviour. The possibility that domperidone reaches the brain region responsible for the lordotic behaviour, e.g. the hypothalamus, is discussed.