ACTIVATION OF VOLTAGE-DEPENDENT SODIUM-CHANNELS IN CULTURED CEREBELLAR GRANULE CELLS INDUCES NEUROTOXICITY THAT IS NOT MEDIATED BY GLUTAMATE RELEASE

Exposure of rat cerebellar granule cell cultures to neurotoxins that s pecifically enhance the open state probability of voltage-dependent Na + channels, resulted in neuronal death as estimated by a cell viabilit y assay based on fluorescent staining and Cr-51-uptake. Toxicity was d etected within 1 h after addition of 100 mu M veratridine and was comp lete within 10-18 h; it was dose-dependent and was found to be complet ely abolished by tetrodotoxin, an Na+ channel blocker. When veratridin e was replaced by an alpha-scorpion toxin, similar observations were d one. In contrast, when cultured neurons prepared from the cerebral hem isphere of fetal rat brain were exposed to either veratridine or alpha -scorpion toxin for 18 h or even for a longer time of incubation, no n euronal death was observed. DNA fragmentation analysis showed that the toxicity was not mediated by apoptosis. Neuronal death was neither pr evented by glutamate receptor antagonists, nor by depletion of endogen ous glutamate, nor by voltage sensitive calcium channel antagonists su ch as omega-Conotoxin-GVIA (N-type channels), omega-Agatoxin-IVA (P-ty pe channels), nimodipine and nitrendipine (L-type channels). Our study indicates that prolonged opening of Na+ channels induced neuronal dea th of cerebellar granule cells which is not mediated by glutamate and reveals novel neurotoxic mechanism in addition to the well-established excitatory amino acid receptor pathway. (C) 1996 IBRO. Published by E lsevier Science Ltd.