Developmental correlation between hypothalamic gonadotropin-releasing hormone and hypophysial luteinizing hormone

Area of Science:

• Neuroendocrinology
• Developmental Biology
• Reproductive Science

Background:

• The pituitary-gonadal axis is active in fetal development.
• The precise timing of gonadotropin-releasing hormone (GnRH) and gonadotropin secretion during fetal development is largely unknown.

Purpose of the Study:

• To correlate the appearance of GnRH in the fetal mouse brain with the differentiation of LH-gonadotropes in the pituitary.
• To establish the developmental timeline for the initiation of the hypothalamic-pituitary-gonadal axis in mice.

Main Methods:

• Immunocytochemistry using the peroxidase-antiperoxidase (PAP) method.
• Analysis of fetal mouse brain and pituitary tissue at 15, 16, 17, and 19 days of gestation.

Main Results:

• GnRH was first detected at 17 days of gestation in the median eminence and organum vasculosum of the lamina terminalis (OVLT).
• LH-gonadotropes also first appeared at 17 days of gestation in the ventral pars distalis.
• Both GnRH and LH-gonadotropes increased in number and staining intensity by 19 days of gestation.

Conclusions:

• The simultaneous appearance of GnRH and LH-gonadotropes at 17 days of gestation suggests the onset of neuroendocrine control of gonadotropin secretion.
• This study provides evidence for the early establishment of the reproductive axis in fetal mice.