AMPA, but not NMDA, receptor antagonism is neuroprotective in gerbil global ischaemia, even when delayed 24 h

The selective alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) antagonist 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(f)quinoxaline (NBQX) and the selective N-methyl-D-aspartate (NMDA) receptor antagonists MK 801 and ifenprodil were administered to Mongolian gerbils following a 5 min period of bilateral carotid artery occlusion. NBQX when given 4, 6 or 24 h after ischaemia gave a reduced loss of hippocampal CA1 neurones compared to control animals receiving vehicle only. Dizocilipine (MK 801) (1-10 mg/kg i.p.) and ifenprodil (a total of 45 mg/kg i.p.) gave no protection. The peak levels of NBQX obtained in the cerebrospinal fluid of gerbils receiving the neuroprotective dose (3 x 30 mg/kg i.p.) was 1 microM. In gerbil cortex slices, this concentration had no effect on NMDA-evoked depolarization, but had a moderate effect on kainate and gave a total blockade of AMPA depolarizations. It is concluded that antagonists of non-NMDA glutamate receptor subtypes, possibly AMPA, may be a useful therapeutic approach for cerebral ischaemia-related brain damage following global ischaemia.