Effects of MK801 on COX-2 expression. COX-2 expression was evaluated by immunoistochemical analysis in the spinal cord section 24 h after SCI. Spinal cord section from sham-operated mice did not stain for COX-2 (a), whereas spinal cord section obtained from SCI-operated mice exhibited positive staining for COX-2 (b) mainly localized in various inflammatory cells of white and gray matter of spinal cord. MK801 treatment (2 mg/kg 30 min and 6 h after SCI induction) reduced the degree for positive staining for COX-2 in the spinal cord tissue (c). Densitometry analysis of immunocytochemistry photographs (n = 5 photos from each sample collected from all mice in each experimental group) for COX-2 (d) from spinal cord tissues was assessed. The assay was carried out by using Optilab Graftek software on a Macintosh personal computer (CPU G3-266). Data are expressed as % of total tissue area. This figure is representative of at least 3 experiments performed on different experimental days. *p < 0.01 vs. Sham; °p < 0.01 vs. SCI. Moreover spinal cord sections were processed at 24 h after SCI to determine also the COX-2 levels by western blot analysis. COX-2 was significantly increased in the spinal cord from SCI mice (e and e1). On the contrary, MK801 treatment (2 mg/kg 30 min and 6 h after SCI induction) significantly reduced the expression of COX-2 induced by SCI (e and e1). The relative expression of the protein band was standardized for densitometry analysis to α-tubulin levels and reported in h1, and expressed as mean ± s.e.m. from n = 5/6 spinal cord for each group. **p < 0.01 vs. Sham; ###p < 0.001 vs. SCI.