Changes Of Expression Of Vesicular And Plasma Membrane Glutamate Transporters In The Glutamate-induced Mouse Retina

ObjectivesTo investigate the changes of expression and possible functions of different types of vesicular and plasma membrane glutamate transporters in the mouse retina following glutamate excitotoxicity.MethodsSeventy-eight C57BL/6 mice were divided into 3 groups randomly: Normal control group had 6 mice; Experimental control group included 36 mice that were treated with saline by intravitreal injection; Experimental group had 36 mice that were treated with glutamate by intravitreal injection. Six mice of each group were sacrificed at 0.5 h,3 h,6 h,12 h,24 h,72 h respectively. Changes of expression of vesicular glutamate transporter 1 and 2 (VGluT1 and VGluT2) and plasma membrane glutamate transporters: glutamate/aspartate transporter (GLAST), glutamate transporter-1 (GLT-1) and excitatory amino acid transporter-1 (EAAC-1) were determined by immunocytochemistry. Semi-quantitative RT-PCR was also used to detect the changes of mRNA of these transporters.ResultsIn comparison with experimental control group, the expressional levels and distribution patterns of VGluT1 and VGluT2 were unaltered until 12 h after glutamate excitotoxicity. During 24 h -72 h, VGluT1 expression was still unchanged while VGluT2 immunoreactivity significantly reduced likely due to delayed retinal ganglion cell death. GLAST, GLT-1 and EAAC-1 immunoreactivities were enhanced during 3 h -12 h after glutamate injection. However, their expression began to reduce at 24 h after glutamate excitatory injury. The results of semi-quantitative RT-PCR were consistent with those of immunocytochemistry.Conclusions Expression of vesicular glutamate transporters is unchanged, but that of plasma membrane glutamate transporters is significantly enhanced within 12 h in the mouse retina following glutamate excitotoxicity. Thus, it is plasma membrane glutamate transporters, not vesicular glutamate transporters that are responsible for glutamate homeostasis in the synaptic cleft after acute retinal insult.