Light-microscopic studies on the development of the interrelationship between the neurosecretory pathway and the portal system in rats

Therapeutic effects of melatonin in female mice with central precocious puberty by regulating the hypothalamic Kiss-1/Kiss1R system

In recent years, central precocious puberty (CPP) in children is becoming more common, which seriously affects their physical and psychological health and requires finding a safe and effective treatment method. The aim of this study was to investigate the therapeutic effect of melatonin on CPP. A CPP model was established by subcutaneous injection of 300 micrograms of danazol into 5-day-old female mice, followed by treatment with melatonin and leuprolide. The vaginal opening was checked daily. Mice were weighed, gonads were weighed, gonadal index was calculated, and gonadal development was observed by hematoxylin and eosin (HE) staining. Serum follicle stimulating hormone (FSH), luteinizing hormone (LH) and estradiol (E2) levels were measured by ELISA. By using RT-PCR and Western blotting, the mRNA and protein expression of the hypothalamus Kiss-1, Kiss-1 receptor (Kiss1R), gonadotropin-releasing hormone (GnRH), and pituitary GnRH receptor (GnRHR) were identified. The results showed that melatonin delayed vaginal opening time and reduced body weight, gonadal weight and indices in female CPP mice. Melatonin treatment prevents uterine wall thickening and ovarian luteinization in female CPP mice. Melatonin treatment reduces serum concentrations of FSH, LH, and E2 in female CPP mice. Melatonin suppressed the expressions of Kiss-1, Kiss1R and GnRH in the hypothalamus, and the expression of GnRHR in the pituitary of the female CPP mice. Our results suggest that melatonin can inhibit the hypothalamic-pituitary-gonadal (HPG) axis by down-regulating the Kiss-1/Kiss1R system, thereby treating CPP in female mice.

Study on the Mechanism of Sarsasapogenin in Treating Precocious Puberty by Regulating the HPG Axis

The present study aims to investigate the effects and mechanisms of sarsasapogenin resistance to precocious puberty. Female Sprague Dawley rats were divided into a normal (N) group, model (M) group, leuprolide (L) group, and sarsasapogenin (Sar) group. Rats at 5 days of age were given a single subcutaneous injection of 300 micrograms of danazol to establish the precocious puberty model. After 10 days of modeling, drug intervention was started. The development of the uterus and ovary was observed by hematoxylin and eosin (HE) staining. The levels of the serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), and estradiol (E2) were determined by radioimmunoassay. Also, the expressions of the hypothalamic gonadotropin releasing hormone (GnRH), Kiss-1, G protein-coupled receptor 54 (GPR54), and pituitary gonadotropin releasing hormone receptor (GnRH-R) were detected by RT-PCR. The results showed that compared with the model group, sarsasapogenin could significantly delay the opening time of vaginal, decreased uterine and ovarian coefficients, and reduced uterine wall thickness. Moreover, it can significantly downregulate the levels of serum hormones and reduce the expression of GnRH, GnRH-R, and kiss-1. In summary, our results indicate that sarsasapogenin can regulate the HPG axis through the kiss-1/GPR54 system for therapeutic precocious puberty.

Neuroendocrine control of the onset of puberty

This chapter is based on the Geoffrey Harris Memorial Lecture presented at the 8th International Congress of Neuroendocrinology, which was held in Sydney, August 2014. It provides the development of our understanding of the neuroendocrine control of puberty since Harris proposed in his 1955 monograph (Harris, 1955) that "a major factor responsible for puberty is an increased rate of release of pituitary gonadotrophin" and posited "that a neural (hypothalamic) stimulus, via the hypophysial portal vessels, may be involved." Emphasis is placed on the neurobiological mechanisms governing puberty in highly evolved primates, although an attempt is made to reverse translate a model for the timing of puberty in man and monkey to non-primate species.

Induction of true precocious puberty by neonatal treatment with danazol in female rats

Female rats at 5 days of age were given a single subcutaneous injection of varying doses of danazol or vehicle. Rats treated with 300 micrograms of danazol showed significant (P < 0.01, respectively) advancement in the day of vaginal opening (37.50 +/- 0.49 days vs. 25.20 +/- 0.19 days; mean +/- S.E.M.), first estrus (38.19 +/- 0.62 days vs. 29.10 +/- 0.26 days) and onset of estrous cycle (49.63 +/- 1.30 days vs. 37.07 +/- 1.50 days). All rats treated with danazol showed 4- or 5-day estrous cycle in the adulthood. Rats treated with 300 micrograms of danazol at 5 days of age discharged luteinizing hormone in the late stage of first proestrus. These results demonstrate that neonatally administered danazol produces the true precocious puberty in female rats, and this sexual precocity rat represents a unique model for analysis of the onset of puberty.

Ontogeny of proopiomelanocortin (POMC) gene expression in the intermediate lobe of the rat pituitary gland

The ontogeny of proopiomelanocortin (POMC) gene expression in the intermediate lobe of the pituitary was studied in rats of both sexes using quantitative in situ hybridization performed on fixed pituitary sections. Electron microscopic studies revealed in the adult animal the hybridization signal was found in all the secretory cells of the intermediate lobe and only in the POMC cells in the anterior lobe, thus indicating the specificity of the technique used. Hybridization signal was first detected on day 15 of gestation and progressively increased during foetal life. After birth, POMC and mRNA levels markedly increased so that, in one-day old animals, they were 4.5-fold higher than at the end of gestation. Thereafter, mRNA concentrations steadily increased to reach a plateau at 60 days of age in both sexes. No sexual dimorphism was observed at any ages. The results indicate that the development of intermediate lobe cells occurs mostly after birth. They are consistent with previous results indicating a 200-fold increase in the levels of POMC-derived peptides from birth to adulthood.

Post-natal development of the median eminence of the guinea pig

The ultrastructure of the median eminence of neonatal (newborn) 1-, 3-, 5-, and 10-day old) and adult guinea pigs was studied to determine the dynamic changes occurring in this structure during early life. At birth the portal vasculature consists of the Mantelplexus and a few, non-fenestrated capillary loops. The number of ansae and the degree of fenestration increase rapidly after birth. The abundance of cytoplasmic and ciliary projections into the ventricular recess and the large numbers of organelles indicate that the ependymal cells are more active in the neonatal period than in the adult male. Moreover, the ependymal endfeet cover most of the surface area of the primary portal plexus during this time. The neuronal layers of the median eminence are difficult to distinguish at birth due to the lack of myelinated fibers in the zona interna. Significant myelination appears on day 3 but is not complete until day 10. There is a progressive increase in the numbers of Herring bodies and large neuro-secretory granules (1,500-1,700 A) during this same time period. In the zona externa, few nerve terminals abut on the perivascular space until day 3. Increases in numbers of granules per axon profile were noted for each day after birth. Despite the relatively long gestation period of the guinea pig (68-72 days), the morphologic appearance of the median eminence at birth suggests that the neurovascular link controlling anterior pituitary function is not yet complete.