Effects of N-methyl-D-aspartate receptor antagonists on carbon monoxide-induced brain damage in mice.

The mechanism of neurodegeneration and the possible therapeutic amelioration were investigated in a model induced by successive carbon monoxide (CO) exposures. Successive CO exposures resulted in a consistent pattern of degeneration of hippocampal CA1 pyramidal cells, which was quantified using an image analyzer. Competitive and noncompetitive antagonists of N-methyl-D-aspartate (NMDA) receptors, cyclopentenophenanthrene, (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten,5,10-imine maleate and an antagonist of glycine binding sites, 7-chlorokynurenic acid, significantly reduced the CO-induced neurodegeneration. Ifenprodil (a antagonist of polyamine binding sites) and glycine had no effect. From these results, it is clear that NMDA receptor/ion channel complex is involved in the mechanism of CO-induced neurodegeneration, and that glycine binding site antagonist as well as NMDA competitive and noncompetitive antagonists may have neuroprotective properties in neurological disorders associated with overactivation of NMDA receptors.