Studies into the dual effects of serotonergic pharmacological agents on female sexual behaviour in the rat: preliminary evidence that endogenous 5HT is stimulatory.

The potential stimulatory and inhibitory effects on female sexual behaviour of five 5HT antagonists and five agents that increase 5HT activity, were noted in ovariectomised rats primed with various steroid regimes such that they were either "receptive" (LQ greater than 50%) or "non-receptive" (LQ less than 50%). The 5HT antagonists cinanserin, mianserin, ketanserin and metergoline all inhibited behaviour in receptive rats. Methysergide and cinanserin stimulated behaviour in non-receptive rats. All the drugs which increased 5HTP activity, i.e., 5HTP, zimelidine, alaproclate, WY 26002 and quipazine stimulated sex behaviour in non-receptive rats. In rats that had been ovariectomised only, part of this effect was probably due to stimulation of adrenal progesterone, but a significant stimulatory effect could still be observed in ovariectomised-adrenalectomised rats. 5HT also had a significant inhibitory effect on receptive rats, and the other agonists showed a similar but non-significant tendency. In view of the fact that 4 out of 5 of the 5HT antagonists inhibited sexual behaviour, we hypothesise that 5HT has a stimulatory role in the control of female sexual behaviour. The possible mechanisms mediating the dual action of 5HTP on female sexual behaviour are discussed.