LEVELS OF FREE TAURINE, GLUTAMATE, GLYCINE AND GAMMA-AMINO BUTYRIC-ACID DURING POSTNATAL-DEVELOPMENT OF NORMAL AND DYSTROPHIC RETINA OF MOUSE

The levels of free taurine, glutamate, glycine and GABA were measured in normal and dystrophic retinas of congenic mice of the rdl, C57 B1 (6) strain and C57 B1 (6) controls during the 1st postnatal mo., starting at 2 days. While the taurine level began a progressive increase in the normal retinas on about the 8th 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 2 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 diring the entirety of the 1st postnatal mo., but the glycine concentration, after a sharp rise during the 1st wk, 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. Photoreceptors are probably 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. Later assays of normal and dystrophic retinas probably exhibit complex deviations which include the effects of transneuronal degeneration and functional differences.