STEROID REGULATION OF CALCITONIN GENE-RELATED PEPTIDE MESSENGER-RNA EXPRESSION IN MOTONEURONS OF THE SPINAL NUCLEUS OF THE BULBOCAVERNOSUS

Motoneurons express calcitonin gene-related peptide (CGRP). Previous studies have shown that CGRP immunoreactivity is regulated by testosterone in the androgen-sensitive motoneurons of the spinal nucleus of the bulbocavernosus (SNB). In this research the effect of plasma levels of testosterone on the expression of αCGRP mRNA in the SNB motoneurons of adult male rats was studied with in situ hybridization. The number of motoneurons expressing αCGRP mRNA and the level of αCGRP mRNA expression was significantly higher in the SNB of castrated male rats than in the SNB of gonadally intact rats. Using a 5× background labeling criterion in castrated rats 88.1 ± 4.5% while in intact rats 75.3 ± 6.4% of SNB motoneurons expressed αCGRP mRNA. Testosterone replacement at the time of castration prevented the effect of castration on the expression of αCGRP mRNA in SNB motoneurons. In castrated rats, the increase in the number of SNB cells expressing CGRP was the result of increased steady state levels of αCGRP mRNA in all SNB neurons. © 1990.