Effect of L-glutamic acid on [14C]GABA release from isolated rat retina.

The effect of various putative neurotransmitters on the release of [14C]GABA taken up by isolated rat retina was investigated by a perfusion technique. L-Glutamic acid initially enhanced the GABA release and subsequently reduced it to a level below the baseline rate. This enhancing effect of L-glutamic acid was Ca2+-dependent and tetrodotoxin-sensitive. L-Aspartic acid only reduced the GABA release, whereas kainic acid exhibited only a marked enhancement of its release. Acetylcholine, norepinephrine, dopamine, glycine and taurine did not have any significant effects on GABA release.