Is serotonin involved in the ovulatory process of the rat ovary perfused in vitro?

The presence of 5-HT (serotonin) in ovarian tissue and its varying concentrations during the oestrous cycle suggests that it takes part in ovarian function and in the ovulatory process as one of several mediators of the inflammatory-type reaction preceding follicular rupture. With the aid of a recirculating perfusion model, in which the central stimulatory action of 5-HT was avoided, its direct ovarian effect on ovulation was studied using immature, pregnant, mare serum gonadotrophin (PMSG)-treated rats. Four out of five ovaries ovulated after the addition of 5-HT to the perfusion medium, though the ovulation rate (0.8 per ovary) did not reach the order of magnitude seen after luteinizing hormone (LH) stimulation (5.4 per ovary). The selective 5-HT2 receptor antagonist, ketanserin, did not significantly reduce the 5-HT induced ovulations, and moreover, reduced the LH-stimulated ovulations. The calcium entry blocker, nifedipine, had no effect on either 5-HT or LH induction ovulations.