Stimulated release of [3H]beta-alanine from the rabbit retina

The efflux of [3H]beta-alanine from rabbit retina after intravitreal injection has been studied. The site of uptake of [3H]beta-alanine into retina was checked by autoradiography and was found mainly in the inner plexiform layer and in cells with the position of amacrines and in some ganglion cells. When the preloaded retina was stimulated by light flashes and release of radioactivity increased significantly. Chromatography of the superfusate demonstrated a single radioactive spot which cochromatographed with authentic beta-alanine. The efflux of [3H]beta-alanine was affected by raising the K+ concentration. The rate of efflux was also immediately increased when unlabelled beta-alanine or GABA was added to the superfusion medium. Glycine was much less effective. The present study shows that light stimulation releases [3H]beta-alanine from the retina and that beta-alanine may use the same transport system as GABA. This further supports the suggestion that beta-alanine may act as a "false transmitter" replacing GABA in the retina.