TOXIC EFFECT OF SODIUM GLUTAMATE ON RAT RETINA - CHANGES IN PUTATIVE TRANSMITTERS AND THEIR CORRESPONDING ENZYMES

S.c. administration of high doses of sodium glutamate to rats during their 1st wk after birth produced an almost total loss of choline acetyltransferase, [EC 2.3.16] a 90% reduction in glutamate decarboxylase [EC 4.1.1.15] and 70% reductions in acetylcholinesterase and dopa decarboxylase [EC 4.1.1.26] activities in the adult retina. In addition there was a 70% decrease in GABA and 35-55% decrease in asparate, glutamate, glycine, alamine and glutamine. No reduction in taurine was observed. The enzymes are probably mainly localized in the interneurons of the retina and taurine is present in the photoreceptor cells. Glutamate treatment was also followed by a small reduction in choline acetyltransferase and glutamate decarboxylase of the superior colliculus and in choline acetyltransferase of hippocampus, whereas no changes could be detected in the lateral geniculate body of the adult rat. Unilateral enucleation performed on 1 day old animals did not alter choline acetyltransferase, acetylcholinesterase, glutamate decarboxylase and dopa decarboxylase activities in the superior colliculus and in the lateral geniculate body of the adult rat.