ANDROGENIC REGULATION OF ANDROGEN RECEPTOR IMMUNOREACTIVITY IN MOTONEURONS OF THE SPINAL NUCLEUS OF THE BULBOCAVERNOSUS OF MALE-RATS

Androgenic regulation of androgen receptor (AR) immunoreactivity was e xamined in androgen-sensitive motoneurons of the spinal nucleus of the bulbocavernosus (SNB) in adult male rats by immunohistochemistry usin g the polyclonal antibody, PG21. In intact controls, intense AR immuno reactivity was confined to the cell nucleus, but not in the nucleolus of SNB motoneurons, whereas cytoplasmic AR immunoreactivity was weak. Androgen withdrawal significantly reduced both the intensity of AR imm unoreactivity in the nuclei and number of AR immunoreactive nuclei of the SNB motoneurons within 1 day of castration. AR immunostaining in t he nucleus and cytoplasm was completely eliminated 5 or 10 days follow ing castration. These changes were prevented by replacement of testost erone propionate (TP). The number of AR immunoreactive nuclei recovere d to about half of the control levels within 20 min or 1 hr of TP admi nistration to males 5 days after castration, although the intensity of AR immunoreactivity was almost the same as that of males 1 day follow ing castration. Both the intensity of nuclear and cytoplasmic AR immun oreactivity and number of AR immunoreactive nuclei recovered to the co ntrol levels 2 or 6 hr after TP injection. These results suggest that androgen causes a significant up-regulation in AR expression of SNB mo toneurons.