Prolactin secretion and its dopamine inhibitory control in rat fetuses

Area of Science:

• Reproductive Endocrinology
• Neuroendocrinology
• Developmental Biology

Background:

• The regulation of prolactin (PRL) secretion is crucial for reproductive functions.
• Dopamine (DA) is known to inhibit PRL release, but its ontogeny is not fully understood.
• Understanding the developmental timeline of PRL regulation is essential for comprehending reproductive health.

Purpose of the Study:

• To determine the onset of pituitary prolactin (PRL) synthesis and release in developing rats.
• To elucidate the establishment of dopamine (DA) inhibitory control over PRL secretion during fetal development.
• To investigate sex differences in the ontogeny of PRL regulation.

Main Methods:

• Radioimmunoassay (RIA) was used to quantify PRL levels in pituitary and plasma.
• Surgical decapitation of fetuses was performed to assess PRL release.
• Pharmacological inhibition of DA receptors on lactotropes was employed to study DAergic control.
• Encephalectomy was used to investigate the role of the central nervous system in DAergic inhibition.

Main Results:

• PRL traces were detected in the pituitary by embryonic day 18 (E18), with significant synthesis onset around E20.
• Pituitary PRL levels increased by E22, with higher levels observed in females than males.
• DA receptor inhibition increased plasma PRL at E20 and E22, indicating developing DAergic control.
• DAergic inhibition of PRL release was established between E20-E22, completely inhibiting release in males but not females.

Conclusions:

• Rat pituitary prolactin (PRL) synthesis begins around embryonic day 20.
• Dopamine (DA) exerts inhibitory control over PRL release starting between embryonic days 20 and 22.
• The establishment of DAergic inhibition shows sex-specific differences, with complete arrest in males but not females.