A prolactin-releasing peptide in the brain

Area of Science:

• Endocrinology
• Neuroendocrinology
• Molecular Endocrinology

Background:

• Hypothalamic peptide hormones regulate anterior pituitary function, except for prolactin.
• Prolactin plays a crucial role in mammalian reproduction and lactation.
• A specific prolactin-releasing hormone has remained elusive despite its importance.

Purpose of the Study:

• To identify a novel peptide hormone that regulates prolactin secretion.
• To characterize the receptor mediating the action of this potential hormone.
• To investigate the role of novel hypothalamic factors in pituitary regulation.

Main Methods:

• Isolation of complementary DNA encoding an orphan receptor (hGR3) specifically expressed in the human pituitary.
• Screening of hypothalamic extracts for the endogenous ligand of hGR3.
• In vitro functional assays using rat anterior pituitary cells to assess prolactin-releasing activity.

Main Results:

• Identification of a novel peptide from the hypothalamus as the endogenous ligand for hGR3.
• The newly identified peptide shares no sequence similarity with known peptides or proteins.
• This peptide was confirmed as a potent prolactin-releasing factor in rat anterior pituitary cells.

Conclusions:

• The novel peptide, named prolactin-releasing peptide, is a potent stimulator of prolactin secretion.
• This discovery identifies a specific ligand for the orphan receptor hGR3, a G-protein-coupled receptor.
• The findings advance the understanding of hypothalamic-pituitary axis regulation, particularly prolactin control.