FOS and inflammatory response: For example, the injection of formalin in the rat colonic wall induced c-Fos expression in the myenteric plexus, the spinal cord and the brainstem, in a retrograde way24, similarly, in a model of intestinal inflammation associated with the post-operative ileus, the increased expression of cycloxigenase-2 leads to cFos activation in the spinal cord via the ascending nerve pathways25.