"This is a way in which puberty could be regulated, for example," Bentley said. "It adds a whole new dimension to reproductive biology, because there are a lot of clinical issues with reproduction and puberty. One side of the picture was missing (until) this new hormone came into play."
"Reproduction is something that has been studied very rigorously, and to identify a new peptide in that arena that seems to be playing such an important role is pretty phenomenal at this time," added Lance Kriegsfeld, an assistant professor of psychology at UC Berkeley who is collaborating with Tsutsui and Bentley on similar research.
In an effort to find out what regulates GnIH, Bentley again teamed up with Tsutsui and his laboratory colleagues to look at the effects of melatonin. Though birds make melatonin in the same way humans do, and the melatonin cycles through the day and through the year with changes in the length of the day, it's unclear the role it plays in the brain.
Ubuka in Japan removed all the organs in the Japanese quail, Coturnix japonica, that are known to produce melatonin and found that GnIH levels dropped significantly. When melatonin levels were increased with injections, however, GnIH levels more than tripled. Afterward, the bird brains were sent to Bentley to test for the presence and location of melatonin binding sites.
"We found that melatonin actually increases production of the messenger RNA and the mature peptide, GnIH, and it appeared to be a direct effect. The melatonin is binding to the GnIH neurons in the hypothalamus of quail," he said.
To look more closely at the role melatonin plays in the reproductive cycle of quail, the researchers also raised male birds under different lighting conditions. Quail raised in simulated short days, which
Contact: Robert Sanders
University of California - Berkeley