The levels of free taurine, glutamate, glycine and γ-amino butyric acid during the postnatal development of the normal and dystrophic retina of the mouse

Abstract

The levels of free taurine, glutamate, glycine and γ-amino butyric acid (GABA) were measured in normal and dystrophic retinas of congenic mice of the rdle, C57 Bl (6) strain and C57 Bl (6) controls during the first postnatal month, starting at 2 days. While the taurine level began a progressive increase in the normal retinas on about the eighth day, this increase continuing until the 30th day, the dystrophic retinas failed to show this increase and their taurine concentration began to decline after the 15th day. No differences were seen in the glutamate concentrations of the two varieties of retina, the glutamate concentration in both increasing during the first 15 days of development and then leveling off. In normal retinas the concentration of GABA increased progressively during the entirety of the first postnatal month, but the glycine concentration, after a sharp rise during the first week, then began to decline. In the dystrophic retinas the GABA concentration rose more sharply to higher levels than that of the controls, starting at the 10th day, and the glycine concentration of the dystrophic retinas exhibited a delayed rise but then remained at the 10-day level, i.e. it did not show the fall seen in the controls. The data seem consistent with the hypothesis that photoreceptors are considerably richer in taurine than the remaining retina, have similar glutamate concentrations, but are considerably poorer in their levels of free glycine and GABA. Accordingly, the chemical differences seen in the dystrophic retina largely reflect the maturation failure and eventual absence of receptor material from the assay. However, later assays of normal and dystrophic retinas probably exhibit complex deviations which include the effects of transneuronal degeneration and functional differences.