Developmental changes of neuromedin U and galanin-like peptide gene expressions in the rat pituitary : an analysis by in situ hybridization histochemistry

GALP在PP中的表达本研究首次证实了PP中GALP的表达自出生之日起就开始表达，并在新生儿期升至成体水平，而在ARC中GALP的表达从出生后期开始表达，并在断奶至青春期期间显著增加。在出生后发育过程中，PP和ARC中GALP的调节机制可能不同。PP中的GALP系统发育相对成熟，而ARC中的GALP系统在新生期仍不成熟，PP中的GALP在成年动物的血浆渗透压和神经垂体激素的调节中起重要作用。PP中GALP的形成可能与体液渗透调节机制的形成有关，即使在新生儿早期，体液渗透调节机制的发育也相对成熟。分娩伴随着婴儿HPA轴的激活，以应对从宫内环境向宫外环境的过渡。出生时这种高水平的NMU表达可能在HPA轴的激活中起作用，以适应环境的变化。在发育过程中，HPA轴通常在出生后4天到14天之间被抑制，这就是所谓的应激-低反应期(SHRP)。生后第8天NMU基因表达的降低可能与SHRP时HPA轴活动受到抑制有关。出生后14d，AP内NMU mRNA在整个出生后发育过程中逐渐增加。结论：NMU和GALP在垂体各叶的发育模式不同，可能与各肽在出生后发育过程中的特定功能意义有关。

Development of GALP in the PPThe present study first demonstrated that the GALP mRNA in the PP exhibited from the day of birth and rose to adult level during neonatal period, while that in the ARC was expressed from late neonatal period and markedly increased between weaning and pubertal period. The regulatory mechanism of the GALP in the PP might be different from that in the ARC during postnatal development. The GALP system in the PP develops in a relatively mature, although that in the ARC is still immature in the neonatal period.The GALP in the PP is important in the regulation of plasma osmolality and neurohypophysial hormones in the adult animals. Development of GALP in the PP may be associated with development of the osmoregulatory mechanism of the body fluid, which develops in a relatively mature even in the early neonates.Development of NMU in the APWe also first demonstrated that the NMU mRNA in the AP was detected at relatively high level at the day of birth. Birth is accompanied with the infant's HPA axis activation in response to stresses with the transition from intra-uterine to extra-uterine environment. This high level of NMU expression at the time of birth may have a role in the HPA axis activation to adapt the environmental changes.During development, the HPA axis is normally suppressed between postnatal day 4 and 14, which is so-called “ stress-hyporesponsive" period (SHRP). The decrease in the NMU mRNA expression at postnatal day 8 might be responsible to the inhibition of the HPA axis activity during SHRP. After postnatal day 14, the NMU mRNA in the AP gradually increased throughout postnatal development. It might be related with the maturation of HPA axis during postnatal development.In conclusion, development of the NMU and GALP, which showed different patterns in each lobe in pituitary, may be associated with the specific functional significance in each peptide during postnatal development.