Rapid glutamatergic alterations in the neural retina induced by retinal detachment

PURPOSE. Retinal detachment induces neurochemical changes in the neural ret ina over a span of days to weeks. However, little information is available on the acute response in the retina to detachment. METHODS. Distribution of the neurotransmitters glutamate, glycine, and gamm a-aminobutyric acid (GABA) and the metabolic amino acids aspartate and glut amine was examined immunocytochemically from 5 to 30 minutes and at 3 hours after retinal detachment in a salamander eyecup preparation. RESULTS. Glutamate showed a rapid depletion from neuronal cell bodies in de tached retina, whereas Muller cells, which normally sequester and metaboliz e glutamate, showed increased immunolabeling for glutamine. Changes occurre d exclusively in detached retinal regions of the eyecup. Aspartate, a precu rsor for glutamate synthesis, also showed decreased labeling in neuronal ce ll bodies in detached retinal regions, although these changes were not as s triking as those observed for glutamate. In contrast, the distributions of the inhibitory amino acid neurotransmitters glycine and GABA were not affec ted appreciably by acute retinal detachment. CONCLUSIONS. These results indicate that retinal detachment induces rapid, localized alterations in the glutamatergic system of the neural retina that are consistent with a massive efflux of neuronal glutamate and concomitant alterations in glutamate metabolism. An acute efflux of neuronal glutamate in detached retina could contribute to excitotoxicity and to the initiatio n of structural alterations and changes in gene expression; it is also cons istent with reported neurochemical changes associated with longer term reti nal detachment.