The metabotropic glutamate receptor subtype 5 antagonist MPEP and the Na+ channel blocker riluzole show different neuroprotective profiles in reversing behavioral deficits induced by excitotoxic prefrontal cortex lesions
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Overactivation of excitatory amino acid receptors has been involved in several neurodegenerative diseases. The present study aims at investigating the potential neuroprotective action of 2-methyl-6-(phenylethylnyl)-pyridine (MPEP), a selective non-competitive antagonist of metabotropic glutamate receptor subtype 5, and 2-amino-6-trifluoro methoxy-benzothiole (riluzole), a Na+ channel blocker exhibiting anti-glutamatergic properties, on the ibotenate-induced damage to the rat medial prefrontal cortex. The neuroprotective efficacy of these compounds was assessed on the recovery from behavioral deficits induced by prefrontal cortical excitotoxic lesions in a reaction time task. MPEP (3, 10 or 30mg/kg) or riluzole (2, 4 or 8mg/kg) was administered i.p. 30 min before and after medial prefrontal cortex lesions. As previously found, lesions to the medial prefrontal cortex significantly altered the motor preparatory processes involved in the reaction time task. These deficits were prevented by MPEP 3mg/kg and riluzole 2mg/kg while higher doses of either compound were ineffective. Furthermore, the neuron-specific nuclear protein immunostaining of the lesioned cortical area in animals treated with the efficient dose of either compound revealed that MPEP reduced the volume of the lesion whereas riluzole reversed the decrease of neuronal density within the lesioned area. Altogether, these results suggest a neuroprotective action of MPEP as well as riluzole at both behavioral and cellular levels on excitatory amino acid-induced toxicity.
