Objective To study the effects of the selective inhibitor of PDE5 on mouse oocyte maturation in vitro.Methods Mouse cumulus-oocyte complexes(COCs) or denuded oocytes(DOs) were collected and cultured in the medium supplemented with the selective inhibitor of PDE5 and the rates of germinal vesical breakdown(GVBD) and first polar body(PB1) extrusion were observed at the end of the culture.In addition,a mouse follicle culture model was also used.Results In isolated oocytes,PDE5 inhibitor zaprinast prevented significantly both spontaneous oocyte meiotic maturation and FSH-induced HX-arrested meiotic maturation.In addition,treated the follicles with the type 5 inhibitor significantly inhibited the follicle-enclosed oocyte maturation induced by FSH.Conclusion Collectively,these results suggest that PDE5 induces mouse oocyte maturation.