Serotonergic Mechanisms of Oocyte Germinal Vesicle Breakdown in the Mud Crab, .

The mechanism of serotonin (5-HT)-induced oocyte germinal vesicle breakdown (GVBD) in the mud crab, , was investigated in this study. Histological staining showed that there were two meiotic arrests in oocyte, appearing at prophase I and metaphase I. This result indicated that meiosis I arrest at prophase I in was similar to that of vertebrates, but meiosis II arrest at metaphase I was different from that of vertebrates. Resumption of oocytes arrest at meiosis prophase I could be induced by 5-HT rapidly within 5 min in . We obtained the sequence of the 5-HT receptor type 1A ( ) from the NCBI database, and found that was expressed in oocytes and follicle cells. In addition, we found that an agonist 8-OH-DPAT which binds induced GVBD and an antagonist WAY100635 which inhibited 5-HT induced GVBD in . This result showed that mediated the regulation of oocyte GVBD by 5-HT. To explore the functional mechanism of 5-HT in inducing oocyte GVBD, forskolin, a cAMP agonist was used. Results showed that, forskolin significantly blocked 5-HT-induced GVBD, and there was a negative correlation between GVBD rate and cAMP level. Our data indicate that there are two meiotic arrests in , and the resumption of prophase I arrest can be induced by 5-HT, which binds to , and this process is mediated by cAMP, which acts as negative regulator via cAMP signaling pathway.