It's a long-held tenet of avian biology that songbirds have just two types of a key reproduction hormone, gonadotropin-releasing hormone (GnRH), and only one actually triggers a seasonal "puberty" each spring in preparation for reproduction. But the new research shows a third form of the hormone, called lamprey GnRH-III-like hormone because it was first identified in lampreys, is also present in songbird brains.
The work by scientists from the University of Washington and the University of New Hampshire shows GnRH-III can trigger the release of luteinizing hormone from the pituitary gland and influence gonad growth, something only one of the other forms of GnRH does under normal conditions.
"This is interesting because many birds breed seasonally, and they time their breeding for favorable conditions in the spring," said George Bentley, a UW post-doctoral researcher in biology.
Bentley is lead author on a paper detailing the work that will be published in the December-January edition of the journal Brain, Behavior and Evolution. Co-authors are John Wingfield, a UW biology professor; Ignacio Moore, a UW post-doctoral researcher in biology; and Stacia Sower, a professor of biochemistry and molecular biology at the University of New Hampshire. The research also was presented earlier this month at the Society for Neuroscience annual meeting in New Orleans.
Like one other form of the hormone, GnRH-III is found in the hypothalamus, where it is released to the pituitary gland, which then triggers changes in the re
Contact: Vince Stricherz
University of Washington