The effect of an AMPA antagonist (NBQX) on postischemic neuron loss and protein synthesis in the rat brain.

Two groups of rats were subjected to 12 min of global cerebral ischemia and 6 days recirculation using the four-vessel occlusion model with hypotension and then treated with the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) antagonist NBQX [2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo (F) quinoxalinedione (Honoré et al. 1988]. One group was used for routine and quantitative histology and immunostaining for glial fibrillary acidic protein (GFAP). The second group was subjected to autoradiographic studies of regional cerebral protein synthesis, with special emphasis on the hippocampus, the frontal cortex, and the thalamus. It was found that neuroprotective treatment with NBQX normalized cerebral protein synthesis rate (CPSR) in all investigated regions 6 days after ischemia. In untreated ischemic animals CPSR was normalized in all regions except for the CA3 and thalamus, where it had increased by 29% and 41%, respectively. Treatment of controls with NBQX had no effect on CPSR after 6 days. The histological investigations revealed that NBQX did not protect vulnerable cells in the dentate hilus and the reticular thalamic nucleus (RTN). In these regions reactive astrocytosis visualized by GFAP immunostaining was equally pronounced in both ischemic and NBQX-treated animals, and most neurons in the RTN were eosinophilic. The 80-100% pyramidal neuron loss in CA1 was accompanied by a high degree of reactive astrocytosis, whereas the NBQX-treated animals showed no signs of astrocytosis in this region. The ischemic CA1 pyramidal layer was also massively invaded by microglia.(ABSTRACT TRUNCATED AT 250 WORDS)