Characteristics of 3HGABA release evoked by oxygen-glucose deprivation in rat cerebral cortex slices

ABSTRACT

In present study, the mechanism for oxygen-glucose deprivation -induced [3H]gamma-aminobutyric acid (GABA) from cerebral cortex slices of the rat was examined. Deprivation of oxygen and glucose(OGD) from Mg2+-free artificial cerebrospinal fluid, induced significant release of [3H]GABA (7.4+/-0.6% of total tissue content) from cerebral cortex slices. OGD-induced release of [3H]GABA was significantly attenuated by tetrodotoxin(TTX)(1 micrometer), Mg2+(1.2 mM), MK-801(10 micrometer), ketamine(10 micrometer), N-methyl-D-aspartate(NMDA) receptor antagonists, (DNQX)(30 micrometer), and 6-cyano-7-nitroquinoxaline-2,3-dione(CNQX)(30 micrometer), kainate/AMPA receptor antagonists, or 6-nitro-7-sulphamoyl-benzo[f]quinoxaline-2, 3-dione(NBQX)(10 micrometer), a selective AMPA receptor blocker. OGD-evoked [3H]GABA release was attenuated by (NG-nitro-L-arginine methyl ester(L-NAME) and 7-nitronidazole, nitric oxide synthase inhibitors, and methylene blue, potentiated by zaprinast, a cGMP phosphodiesterase inhibitor. OGD-induced release of [3H]GABA was inhibited by nipecotic acid, a selective neuronal GABA transporter blocker, and potentiated by DL-2.4-diamino-n-butyric acid(DABA), a neuronal and glial GABA transporter blocker. Dantrolene (30 micrometer) and 1,2-bis (2-aminophenoxy)-ethane-N, N, N', N'-tetraacetic acid tetrakis (acetoxymethyl) ester(BAPTA-AM)(30 micrometer), inhibitors of intracellular Ca2+ release, verapamil(5 micrometer), omega-conotoxinGVIA(100 nM) and omega-agatoxinIVA(100 nM), inhibitors of voltage-dependent Ca2+ channels, significantly attenuated the OGD-induced release of [3H]GABA. These results suggest that glutamate is involved in OGD-evoked [3H]GABA release, and this release is achieved by Ca2+-dependent exocytosis and reversal of transporters, and can be modulated by various neuronal mechanisms.