Columbia scientists have found a new use for an old hormone.
Gonadotropin, previously thought to only promote steroid secretion from
the gonads, also acts directly on the brain to promote sex behavior.
Multiple sites of action of this pituitary hormone integrate courtship
behaviors with reproduction. The findings were reported in the Feb. 7
issue of Proceedings of the National Academy of Sciences by postdoctoral
fellow Eun Jin Yang, graduate fellow Brian Nasipak, and Darcy B. Kelley,
professor of biological sciences.
The novel action of gonadotropin was discovered in the South African
clawed frog, a species whose sensitivity to the form of this hormone
made in the placenta resulted in the first human pregnancy test in the
1930s. Gonadotropin stimulates females to lay eggs, accept male
advances, and, as the Kelley laboratory previously reported, sing a
rapping song that is acoustically arousing to males. Gonadotropin also
stimulates a male song that attracts females. Some of the findings have
been captured on video.
"The male frogs are calling in a kind of vocal duel," Kelley said of one
clip. "The winner continues to sing and the loser shuts up. They ignore
the female; all that matters is their own battle." These new findings
show that effects on song in males are via brain regions implicated in
song production and perception. Mammals and birds also have these
hormone receptors, though no one knows how they function. Gonadotropin
might also act as a brain aphrodisiac in humans.