EFFECTS OF TAURINE ON GABA RELEASE FROM SYNAPTOSOMES OF RAT OLFACTORY-BULB

Superfusion of synaptosomes prepared from rat olfactory bulb revealed constant basal release of endogenous taurine (Tau), aspartate (Asp), g lutamate (Glu) and gamma-aminobutyrate (GABA): their release rates wer e 110.4 +/- 13.0, 30.3 +/- 6.7, 93.7 +/- 13.1, and 53.3 +/- 8.8 pmol/m in/mg protein, respectively. The depolarizing-stimulation with 30mM KC l evoked 1.17-, 2.18-, 2.55- and 1.53-fold increases, respectively. Ta u release was calcium-independent. However, the perfusion of synaptoso mes with Tau (10 mu M) inhibited the evoked increase in GABA release b y 63% without changing basal release, although it did not affect relea se of Asp and Glu. Phaclofen (10 mu M, a GABA, receptor antagonist), b ut not bicuculline (10 mu M, a GABA, receptor antagonist), counteracte d the Tau-induced reduction in GABA release. These data suggest that T au may be abundantly released from nerve endings of rat olfactory bulb and that it may regulate GABA release through the activation of presy naptic GABA(B) autoreceptors.