TAURINE AND GABA IN THE RAT RETINA DURING POSTNATAL-DEVELOPMENT

The content of taurine and the immunocytochemical localization of taur ine and gamma-aminobutyric acid (GABA) in the rat retina during postna tal development are described. The rat retina is immature at birth; ab out two-thirds of the cells are undifferentiated neuroblasts, and the taurine content per retina is approximately one-seventh of the adult v alue. Shortly after weaning the adult morphology and taurine content a re attained. Expression of taurine immunoreactivity (taurine-IR) accom panies differentiation; in some cell types (ganglion and horizontal ce lls) this expression is transient, while in others (photoreceptors, bi polar, and a subpopulation of amacrine cells) it persists into the adu lt state. At birth, taurine-IR is localized mainly in cells in the pos ition of ganglion cells, especially in their axons within the nerve fi ber layer. This reactivity is soon lost from the somata, and disappear s from the axons by 10 days of age. At 2 days of age, taurine-IR appea red additionally in somata of amacrine cells flanking the forerunner o f the inner plexiform layer, and in growth cone-like processes of phot oreceptors. At day 6, taurine-IR was marked in photoreceptor cell inne r and outer segments, and in horizontal cells and their lateral proces ses. Taurine-IR was lost from horizontal cells and most amacrine cells around day 10, and appeared in bipolar cells, where it remained, with that in photoreceptors, into adulthood. Particularly striking was tau rine-IR in large synaptic terminal-like processes close to the ganglio n cell layer which were first seen around day 16. GABA immunoreactivit y was never seen in photoreceptor or bipolar cells, was expressed tran siently in horizontal cells at the same time as taurine-IR, but persis ted in a subpopulation of amacrine cells and synaptic lamina in the in ner plexiform layer and in some fine glial processes in the adult.