Cyclooxygenase Expression in Canines Following Peripheral Nerve Injury

In order to investigate the mechanism of neurogenic pain, this study used a median nerve compression model in dogs. The nerve was compressed with a clip for three weeks. Immunohistochemistry was done by the avidin-biotin-peroxidase complex method to observe the changes of T cells (CD45) and macrophages (Mac-1) after compression. Antibodies against cyclooxygenase (COX)-1 and 2 were used to examine the localization and changes of these mediators caused by nerve compression. In control animals, resident T cells were detected, but there were no macrophages. COX-2 was positive in the Schwann cells and vascular endothelial cells, while COX-1 was detected in the vascular endothelial cells. After nerve compression, numerous T cells and macrophages appeared among the demyelinized nerve fibers. The macrophages were positive for COX-2. COX-2 may be deeply involved in neuritis arising from mechanical compression, and this mediator seems to be important in the manifestation of neurogenic pain.