In vitro effects of serotonin and prostaglandins on release of eggs from the ovary of the scallop, Patinopecten yessoensis.

When ovarian pieces of the scallop, Patinopecten yessoensis, were incubated in media containing serotonin (5-HT), the number of released eggs increased significantly. These eggs developed normally after fertilization. The threshold of the 5-HT effect reached a maximum at a concentration of 10(-6) M, and decreased sharply with increasing concentrations. Methysergide, a 5-HT antagonist, completely inhibited the 5-HT-induced egg release. Addition of aspirin or indomethacin to the incubation media also inhibited the 5-HT effect. However, neither aspirin nor indomethacin inhibited the 5-HT-induced egg release when 10(-6) M prostaglandin E2 (PGE2) was also present. PGE2 did not induce egg release, but enhanced the 5-HT effect. In contrast to PGE2, PGF2 alpha significantly inhibited the 5-HT effect. These results show that 5-HT induces spawning of female P. yessoensis via specific 5-HT receptors in the ovary, and that the effect of 5-HT may be regulated by PGE2 (progressive) and PGF2 alpha (suppressive).