Pharmacological observations on the mechanism of spawning in the scallop Patinopecten yessoensis.

Abstract

1) In the scallop Patinopecten yessoensis, the induction of female spawning by serotonin (5-HT) injections was prevented by methysergide (5-HT antagonist), lanthanum chloride and aspirin (inhibitor of prostaglandin synthesis), but was not affected by LY 53857 (5-HT antagonist), sulphide (dopamine antagonist), nor γ-hydroxybutyric acid (depressor in firing of dopamine neurons). 2) The induction of female spawning by UV ray-irradiated seawater was prevented by methysergide and γ-hydroxybutyric acid. 3) Neither thermal stimulations nor fluoxetine (inhibitor of 5-HT uptake) injections induced spawning, but the thermal stimulations could induce spawning in the scallops which had been injected with fluoxetine. The induction of female spawning by this combined stimulation was prevented by methysergide and sulpiride. 4) Neither the induction of male spawning by 5-HT injections nor that by thermal stimulations following fluoxetine injections was affected by any of the chemicals used. 5) These results support the notion that serotonergic mechanisms mediate the spawning in at least the female scallops, and suggest that prostaglandins and dopaminergic mechanisms may also be implicated in the female spawning.