Fig. 4. High magnification of cyclooxygenase-1 (COX-1) immunoreactivity over time in the ipsilateral spinal dorsal horn of rats that underwent L5–L6 spinal nerve ligation. (A, B ) Superficial and deep laminae of the ipsilateral spinal dorsal horn 4 h after surgery. (C, D ) Superficial and deep laminae of the ipsilateral spinal dorsal horn 4 days after surgery. (E, F ) Superficial and deep laminae of the ipsilateral spinal dorsal horn 2 weeks after surgery. Scale bar , 20 μm.