Age-related changes in nuclear receptor coactivator immunoreactivity in motoneurons of the spinal nucleus of the bulbocavernosus of male rats.

Immunoreactivity of phosphorylated cAMP response element binding protein-binding protein/p300 (CBP/p300) and steroid receptor coactivator-1 (SRC-1) was examined in motoneurons of the spinal nucleus of the bulbocavernosus (SNB) in young and old male rats by immunohistochemistry. In young animals, intense immunoreactive CBP/p300 and SRC-1 proteins were confined to the nuclei, but not in the nucleolus of SNB motoneurons. In old animals, both the intensity of CBP/p300 and SRC-1 immunoreactivity in the nuclei and number of CBP/p300 and SRC-1 immunoreactive nuclei of the SNB motoneurons were significantly reduced. A marked decline in the expression of CBP/p300 and SRC-1 in the aged SNB motoneurons suggests down-regulation of androgen receptor coactivator-mediated gene expression in the SNB system with advancing age.