Excess Glutamate May Cause Dilation of Retinal Blood Vessels in Glutamate/Aspartate Transporter-Deficient Mice

PURPOSE: To investigate the longitudinal findings of fundus features and spectral-domain optical coherence tomography (SD-OCT) to characterize the morphologic features in a mouse model of defective glutamate/aspartate transporter (GLAST(−/−) mice). MATERIALS AND METHODS: The fundus findings and SD-OCT images were longitudinally recorded at five time points from postnatal (P) 22 to P156 in GLAST(−/−) mice. As a control wild type, age-matched C57BL/6J mice were employed. The mouse retina was subdivided into five layers, and the thickness of each layer was longitudinally measured by InSight® using SD-OCT pictures. The SD-OCT findings were compared with the histologic appearances. The diameter of the retinal blood vessels was measured by the ImageJ® software program using SD-OCT images. The data were statistically compared between both age-matched mouse groups. RESULTS: The retinal blood vessels appeared more dilated in GLAST(−/−) mice than in wild-type mice. This tendency was statistically significant at all time points after P44 by analyses using SD-OCT images. The ganglion cell complex (GCC) and outer nuclear layer (ONL) were significantly thinner in GLAST(−/−) mice at all time points after P80 than in the wild-type mice. This tendency was more clearly indicated by SD-OCT than histologic sections. DISCUSSION: In the present study, we found for the first time the dilation of the retinal blood vessels and the thinning of the ONL in GLAST(−/−) mice, in addition to the thinning of the GCC.