Figure 5.

The κ-opioid system blocks neuron activation, as indicated by c-Fos expression, after nociceptive stimulation of the spinal cord in IFD mice. A, Photomicrographs and immunohistochemical analyses of the expression patterns of c-Fos protein in the dorsal lumbar spinal cord of AL (i, ii) and IFD (iii, iv) mice 90 min after nociceptive treatment (ii, iv) or nontreatment (i, iii). The graph represents the number of positive neurons in each group. In the graph, filled bars represent nociceptive treatment, and open bars represent nontreated animals. B, Effect of nor-BNI on the c-fos mRNA transcription in thoracic and lumbar spinal cord after acetic acid injection in AL and IFD mice. gapdh mRNA served as control. We used six animals for each experimental group. These animals were obtained from three independent experiments. The statistical analysis was performed by two-tailed Student's t test. ⁺ indicates statistical significance of the same treatments in groups AL and IFD; ^* indicates statistical significance of the different treatments with respect to vehicle in the same group; ⁺⁺⁺,^***p ≤ 0.001.