PROTECTIVE EFFECT OF RILUZOLE ON EXCITATORY AMINO ACID-MEDIATED NEUROTOXICITY IN MOTONEURON-ENRICHED CULTURES

Excitatory amino acid-mediated neurotoxicity was investigated in moton euron-enriched cultures from fetal rats at 12-14 days of gestation. Th e cultures were mainly composed of differentiated motoneurons identifi ed by choline acetyl transferase and calcitonin gene-related peptide ( CGRP) immunoreactivity. Addition of glutamate (600 mu M) to the condit ioned medium induced no acute neuronal swelling. However, it was follo wed by a widespread neuronal degeneration over the next 24 h, accounti ng for 77% of the total cell number. Glutamate toxicity was dose depen dent, with an EC(50) around 300 mu M. Treatment for 24 h with the agon ists, N-methyl-D-aspartate (NMDA, 100 mu M), kainate (500 mu M) or alp ha-amino-3-hydroxy-5-methyl-4-isoxalopropionate (AMPA, 10 mu M), also induced a significant cell loss. Riluzole (2-amino 6-trifluoromethoxyb enzothiazole), a compound known to interfere with glutamatergic transm ission pre- and postsynaptically, significantly reduced glutamate and NMDA neurotoxicity in a dose-dependent manner. These results suggest t hat a prolonged activation of one or more subtypes of ionotropic excit atory amino acid receptors can lead to motoneuron degeneration in vitr o, and provide direct experimental evidence supporting the neuroprotec tive effect of riluzole in cultured motoneurons.