Objeetlve To investigate the expression of synaptophysin (SYN) in rat retina following acute high intraocular pressure (HIOP).Methods The intraocular pressure of all left eyes was increased until b wave of flash electroretinogragh (fERG) disappeared and such pressure maintained for 60 min.All right eyes served as normal control.Animals were sacrificed at 1,3,7 or 14 d following operation respectively.Immunohistochemistry and in situ hybridization were used to detecting the expression of SYN.Results In normal condition,SYN was mainly located in the outer plexiform layer (OPL) and the inner plexiform layer (IPL).SYN expression was extended to the inner part of the outer nuclear layer (ONL) after HIOP.There was the widest distribution of SYN in the OPL and ONL on the 7th after HIOP.To the 14th day,the distribution of SYN was similar to that of the normal control.