N-methyl-D-aspartate receptors (NMDAR) in cerebral cortexes of rat brain injury induced by Bordetella pertussis (Bp) were measured by methods of Northern blot analysis and [3H] MK-801 radioligand-receptor binding to study changes and effects of NMDAR1 of gene expression in the infection brain injury. The affinity (Kd) of NMDAR in Bp group was significantly decreased [30.5 +/- 3.0 nmol.L-1 (Bp), 43.1 +/- 4.2 nmol.L-1 (NS), P < 0.05], but expression of NMDAR1 mRNA and binding site density (Bmax) of NMDAR observed no significant differences between the experimental and the control group (P > 0.05), respectively. The results suggest that NMDAR1 was activated with high affinity functionally, but no changes in binding site density and transcriptional expression of NMDAR1 occured in the infection brain injury.