Estradiol suppresses NMU mRNA expression during sexual maturation in the female rat pituitary

Neuromedin U (NMU) suppresses food intake and gonadotropin secretion. However, the developmental transition of NMU expression in the pituitary gland and the regulation of NMU expression are unclear. The objective of this study was to examine the transition of the expression of NMU mRNA in the pituitary glands of female rats from the juvenile period to the mature period of development. Furthermore, factors such as estradiol, insulin, leptin, and inhibin A, whose expressions change throughout puberty and which affect gonadotropin secretion in pituitary cell culture, were examined. In the pituitary gland, the expression of NMU mRNA was significantly lower in 8-week-old rats than in 4- and 6-week-old rats. In the pituitary cell culture, the expressions of NMU mRNA in the estradiol- and insulin-treated groups were significantly lower than in the control group. These results suggest that the expression of NMU mRNA in the female rat pituitary is reduced as the rats develop from the pubertal to the mature period. Additionally, the reduction of NMU expression in the pituitary may be related to the increases in serum estradiol and insulin levels that occur during the pubertal period, which may negate NMU suppression of gonadotropin secretion.