ELECTRICALLY-EVOKED [H-3]GABA RELEASE FROM CEREBRAL CORTICAL CULTURES- AN IN-VITRO APPROACH FOR STUDYING GLUTAMATE-INDUCED NEUROTOXICITY

In the present study the [H-3]GABA release in the rat cerebral cortex primary cultures, kept at rest or electrically stimulated, was measure d. In addition, the development of excitotoxic cell damage caused by p retreating the cells for 10 min with increasing glutamate concentratio ns (10-300 mu M) was examined 2 and 24 h after the insult. Cellular in jury was quantitatively assessed by measuring the electrically-evoked [H-3] GABA release, the [H-3] GABA uptake, and (4,5-dimethylthiazol-2- yl)-2,5-diphenyltetrazolium bromide staining. Trains of electrical pul ses at different frequencies (2, 5, 10, and 20 Hz) applied to the cult ures elicited a [H-3] GABA release which was frequency related, Ca++-d ependent, and tetrodotoxin sensitive. Either 2 or 24 h after glutamate exposure, the electrically evoked [H-3]GABA release was reduced by gl utamate in a concentration dependent manner, while [H-3]GABA uptake an d (4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide staining appeared less sensitive. The N-methyl-D-aspartate, lpha-amino-3-hydrox y-5-methyl-4-isoxazolepropionic acid and metabotropic receptor antagon ists were tested on 100 mu M glutamate-exposed cells and a prominent N -methyl-D-aspartate receptor-mediated component was observed. The pres ent findings indicate that the electrically-evoked [H-3]GABA release f rom cerebral cortical cells could represent a useful approach not only to study the spike-triggered neurosecretion but also to the neuronal damage caused by glutamate, as well as to test potential neuroprotecti ve compounds. Synapse 30:247-254, 1998. (C) 1998 Wiley-Liss, Inc.