Figure 3: Photomicrographs showing FLI in spinal cord sections at level L4/L5 of non-stressed groups in different laminae (ipsilateral side). (a) saline; (b) morphine; (c) ketamine. I–II: superficial lamina; III–IV: nucleus proprius; V–VI: neck of dorsal horn. Arrow indicates the dark staining Fos positive neurons (FLI) ( magnification X 50 ).