c-Fos basal immunoreactivity decreases in rat spinal cord during normal ageing.

The pattern of distribution in rat spinal cord and changing pattern during normal ageing of c-Fos expression were investigated by immunohistochemical staining in male Sprague-Dawley rats at the age of 1 week, 5 months and 2 years. c-Fos immunoreactivity was observed diffusely in gray matters in neonatal rats, preferentially located in deep dorsal horn and around central canal. Compared with those of neonatal rats, these cells decreased prominently in adult rats. In aged rats, immunoreactive cells were not seen in any segments. c-Fos immunoreactivity in spinal cord may be related to stress response, functional differentiation, and in part, neuronal death with target dependence. In conclusion, we demonstrated for the first time that c-Fos expression patterns change during normal ageing.