CHRONIC TREATMENT WITH SABELUZOLE PROTECTS CULTURED RAT-BRAIN NEURONS FROM THE NEUROTOXIC EFFECTS OF EXCITATORY AMINO-ACIDS

The neuroprotective properties of the cognitive enhancer sabeluzole were investigated in rat brain neuronal cultures derived from the hippocampal formation of 17-day-old rat embryos. Measurement of the neuronal cytoskeletal microtubule-associated protein, MAP2, was used to assess survival of neurons after exposure of neuronal cultures to glutamate. MAP2 was quantified in neuronal cell homogenates by means of an enzyme-linked immunosorbent assay (ELISA) using a mouse monoclonal MAP2 antibody, peroxidase-labeled goat anti-mouse Ig antiserum, and 2,2'-azido-di-[3-ethylbenz-thiazoline] sulphonate (ABTS) as substrate. Exposure of 7-day-old neuronal cultures to 1 mM glutamate for 16 hours led to a three-fold increase in released lactate dehydrogenase (LDH) and a 40% decrease in cellular MAP2 content. Acute treatment of neuronal cultures with 10 muM sabeluzole yielded a 40% drop in released LDH induced by glutamate. Cultures treated chronically with 0.1 muM sabeluzole on days 1 and 4 in culture showed, after 1 week in culture, a MAP2 content and total LDH activity that was not different from control cultures. A 16-hour exposure to 1 mM glutamate did not induce LDH release or changes in MAP2 levels in sabeluzole-treated cultures. A single treatment with 0.1 muM sabeluzole between day 1 to 5 induced a 70-80% drop in glutamate-induced released LDH in 7-day-old neuronal cultures. Full and partial neuronal protection after chronic sabeluzole treatment at 0.1 muM was also observed for neurotoxicity induced by 5 mM N-methyl-D-aspartate (NMDA) and 1 mM kainic acid or 30 muM veratridine, respectively. Within a series of compounds such as Ca++ and Na+ channel antagonists, glutamate receptor antagonists and various neurotransmitter receptor antagonists, sabeluzole, chronically given, were the most potent for inhibition of released LDH induced by 1 mM glutamate (IC50-value: 34 +/- 13 nM). In conclusion, chronic sabeluzole treatment protects cultured rat brain neurons from excitotoxic aggression.