Effect of Taurine on Neurotransmitter Release from Insect Synaptosomes

The effect of taurine on the release of 3H]acetylcholine (3H]ACH) and 3H]gamma-aminobutyric acid (3H]GABA) from preloaded locust synaptosomes has been studied. Veratridine (100 microM) and K+ (100 mM) both evoked 3H]ACh release and this was reduced in a concentration-dependent manner by taurine (5, 10, and 20 mM). In contrast to this, veratridine induced no observable release of 3H]GABA, and the response to K+ was slight. In the presence of taurine, however, a concentration-dependent enhancement of 3H]GABA release was observed. Since nipecotic acid (1 mM), an inhibitor of neuronal GABA uptake, also revealed 3H]GABA release induced by veratridine, it is suggested that both this effect and that of taurine are due to prevention of GABA reuptake. These results suggest that taurine may act as a neuromodulator in insects.