Fig. 4. Spinal cord cyclooxygenase 1 (COX-1) immunoreactivity after surgery in 4-week-old animals. COX-1 immunoreactivity in the spinal cord if 4-week-old animals after surgery. There was no difference between left and right COX-1 positive cells in the spinal cord before left paw surgery. However, there was a significant increase in COX-1 positive cells on the left (surgery side) compared with the right (nonsurgery side) at both 5 and 24 h after surgery (* P < 0.05; n = 6). Ten to 15 spinal cord slices were counted from each animal and were averaged to give the number of positive cells per slice for each animal.