Fig. 2. Time course of 75% nitrous oxide (N2O)–induced c-Fos expression in the spinal cord at the lumbar level (L5). Each closed circle represents the mean number of c-Fos–positive cells from five randomly selected sections from one animal. Each horizontal bar indicates the mean of three animals at each time point. *P < 0.05 compared with basal c-Fos expression (0 min, control).
