A functional role glial cells in the retina

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The glutamate analogue,alpha-aminoadipate(<alpha>AAA) was administered in the D-,DL-, and L-forms to carp (Cyprinus carpio) retina in vivo.For assessment of its gliotoxic action,the activity of a glial marker enzyme,glutamine synthetase(GS)whose locarization was identified with retinal Muller cells by immunohistochemical technique,was examined at various intervals over one month.A reduction in GS activity was present within 4 hrs of intravitreal injection of umol<alpha>AAAs and was maximal by 24 hrs. The minimum effective dose of the L-and DL-from was about 0.8 and 1.2 umol per eye, respectively.At 3-4days after <alpha>-AAAs injection,SDS gel electrophoresis suggested that some soluble proteins of the retina including GS were significatly reduced,whilst others were increased.These changes were fully recovered by 1-2 weeks for D- or DL-from, but they were long-lasting more than l month for L-from.The electroretinographic (ERG) bwave, another glial marker,was completely blocked by 8 umol of <alpha>-AAAs within 2-4 hrs. The ERG b-wave recovered first in the case of D-and than of DL-from in 1-2 weeks,but in the case of L-from it was blocked over a long period (more than l month).Morphological observation might explain such a difference in recovery time after DL-from and L-from treatment.DL-<alpha>-AAAs caused relatively selective swelling of glial Muller cells,while L-from caused severe glial as well as neuronal lesions in the retina.