5 years ago

Selective Enhancement of Domoic Acid Toxicity in Primary Cultures of Cerebellar Granule Cells by Lowering Extracellular Na+ Concentration.

Novelli, Salas Puig, Fernández-Sánchez, Marini, Cabrera-García, Warm, Pérez-Gómez
Domoic acid (DOM) is an excitatory amino acid analog of kainic acid (KA) that acts through glutamic acid (GLU) receptors, inducing a fast and potent neurotoxic response. Here we present evidence for an enhancement of excitotoxicity following exposure of cultured cerebellar granule cells to DOM in the presence of lower than physiological Na+ concentrations. The concentration of DOM that reduced by 50% neuronal survival was ̴ 3 µM in Na+-free conditions and 16 µM in presence of a physiological concentration of extracellular Na+. The enhanced neurotoxic effect of DOM was fully prevented by AMPA/KA receptor antagonist, while NMDA-receptor-mediated neurotoxicity did not seem to be involved, as the absence of extracellular Na+ failed to potentiate GLU excitotoxicity under the same experimental conditions. Lowering of extracellular Na+ concentration to 60 mM eliminated extracellular recording of spontaneous electrophysiological activity from cultured neurons grown on a multi electrode array (MEA), and prevented DOM stimulation of the electrical activity. While changes in the extracellular Na+ concentration did not alter the magnitude of the rapid increase in intracellular Ca2+ levels associated to DOM exposure, they did change significantly the contribution of voltage-sensitive calcium channel (VSCaC) and the recovery time to baseline. The prevention of Ca2+ influx via VSCaC by nifedipine failed to prevent DOM toxicity at any extracellular Na+ concentration, while the reduction of extracellular Ca2+ concentration ameliorated DOM toxicity only in the absence of extracellular Na+, enhancing it in physiological conditions. Our data suggest a crucial role for extracellular Na+ concentration in determining excitotoxicity by DOM.

Publisher URL: http://doi.org/10.1093/toxsci/kfx201

DOI: 10.1093/toxsci/kfx201

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