BENZO(F)QUINOXALINE, NBQX, PREVENTS TRANSNEURONAL DEGENERATION OF NIGRAL NEURONS AFTER NEUROTOXIC STRIATAL-PALLIDAL LESION

Unilateral neurotoxin lesion of rat caudate-putamen and globus pallidus resulted in delayed, transneuronal degeneration of GABAergic substantia nigra pars reticulata neurons. To explore whether the disinhibition of endogenous glutamate excitatory input played a role in the degeneration of substantia nigra pars reticulata neurons, animals with unilateral striatal-pallidal lesions received three daily intraperitoneal injections of either dizocilpine maleate (MK-801, 1 or 10 mg/kg), an N-methyl-d-aspartate glutamate receptor blocker, or 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(f)quinoxaline (NBQX, 30 mg/ kg), an AE-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor blocker, that began 24 h after the striatal-pallidal neurotoxin lesion. Drug treatment aVected neither the volume of the initial lesion nor the volume of striatal-pallidal glial fibrillary acidic protein immunoreactivity. Neuron number in the substantia nigra pars reticulata ipsilateral to the lesioned striatopallidum was reduced on average by 37% in untreated control rats, in low dose MK-801, and NBQX-treated rats (P<0.0001). However, in animals treated with high doses of MK-801 there was no diVerence in the number of neurons in the substantia nigra pars reticulata ipsilateral or contralateral to the neurotoxin lesion. These data demonstrate that dose-related treatment with N-methyl-d-aspartate glutamate receptor blockers protects substantia nigra pars reticulata neurons, and suggests that glutamatergic mechanisms play a role in delayed transneuronal degeneration. ? 1999 IBRO. Published by Elsevier Science Ltd.