Axotomy-induced changes in ribosomal RNA levels in female hamster facial motoneurons: differential effects of gender and androgen exposure.

Following facial nerve injury, female hamster facial motoneurons (HFMN) regenerate faster than their male counterparts. Testosterone propionate (TP) markedly accelerates the rate of facial nerve regeneration in males, but has a relatively reduced effect in females. In the present study, we utilized in situ hybridization in conjunction with ribosomal DNA probes to test the hypothesis that in females HFMN axotomy produces a less dramatic cell body response than in males and to examine gender differences in the effects of steroids on peripheral nerve regeneration at the molecular level. The results indicate that in females axotomy alone induced moderate increases in rRNA levels, beginning 2 days postoperatively. These changes were both slower in onset and lower in magnitude than those in the males. TP augmented the effects of axotomy on rRNA levels at the later postoperative times. There were no early, rapid effects of TP, like those observed in males. These molecular data substantiate our previous findings of inherent sex differences in neuronal regeneration and the ability of gonadal steroids to augment the reparative response of peripheral neurons to injury.