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Activity Changes of the Hypothalamus-Pituitary Hormonal Axis in Peripubertal Female Rats
1Department of Biotechnology, Sangmyung University, Seoul 03016, Korea.
Insights
Gene expression in the hypothalamus-pituitary (HP) axis changes dynamically during puberty onset. Key reproductive genes show increased expression after vaginal opening (VO), but patterns remain unstable, unlike adult hormonal surges.
Area of Science:
- Reproductive Biology
- Endocrinology
- Neuroscience
Background:
- Regulation of the hypothalamus-pituitary (HP) axis during normal puberty onset is poorly understood.
- Understanding peripubertal gene expression is crucial for identifying normal and abnormal pubertal development.
Purpose of the Study:
- To investigate gene expression profiles in the HP axis during the transition to puberty.
- To correlate gene expression changes with reproductive organ maturation and hormone levels.
Main Methods:
- Examined gene expression in the hypothalamus and pituitary every other day from postnatal day (PND) 29 to PND 43 using polymerase chain reactions (PCR).
- Monitored reproductive organ weight, vaginal opening (VO) timing, and serum steroid hormone levels.
Main Results:
- Significant increases in reproductive organ weight and serum steroid hormones were observed around PND 37-39.
- Most hypothalamus and pituitary gene expression increased after VO, but patterns were unstable and lacked adult LH surge characteristics.
- mRNA levels of gonadotropin-inhibitory hormone (GnIH), GPR147, neurokinin B (Tac), TacR3, and gonadotropin subunits (Cgα, LH-β, FSH-β) increased in the later experimental period.
Conclusions:
- Confirmed rapid reproductive organ maturation and dynamic gene expression changes in the HP axis post-VO.
- Peripubertal gene expression patterns are incomplete and unstable, differing from adult preovulatory surges.
- Provides a foundation for understanding normal and pathological pubertal development.
Abstract:
Little is known about the regulation of gene expression related to the hypothalamus-pituitary (HP) axis around the onset of normal puberty. In the present study, we examined the expression profiles of genes in HP hormone circuit on every other day from postnatal day (PND) 29 to PND 43. Average vaginal opening (VO) date was PND 37 (66%), and the weight of reproductive organs increased significantly from PND 37. Serum steroid hormone levels significantly increased on PND 39. The appearance of a number of Graafian follicles and corpora lutea on PND 37. Generally, our polymerase chain reactions (PCR) results showed that most of the expression of hypothalamus and pituitary factors tended to increase after VO, and the patterns were rather unstable and no significant peak pattern such as LH surge shown in proestrus adults. The mRNA levels of gonadotropin-inhibitory hormone (GnIH)-GPR147 and neurokinin B(Tac)-TacR3 mostly reached a peak in the last period of the experimental schedule. In pituitary, mRNA level of gonadotropin subunits (Cgα, LH-β and FSH-β) also significantly increased on later experimental period. In conclusion, we could confirm the rapid growth and maturation of reproductive organs immediately after VO, and dynamic changes in gene expression of the HP axis factors. The gene expression patterns at peripubertal period were incomplete and unstable without showing the preovulatory LH surge-related gene expression pattern in adults. The present study on neuroendocrine control of peripubertal sexual maturation may offer a basis for understanding normo- and/or patho-physiological status of puberty.
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