It's all in the brain
2008-03-20 13:54
London - Birds start singing in the
spring because of a biological response to longer days,
researchers said on Wednesday.
When birds are exposed to light for longer periods, certain
brain cells trigger a series of hormonal reactions telling them
to find a mating partner, which they do by singing, a team of
Japanese and British researchers reported in the journal Nature.
"While we knew what area of the brain was affected by
seasonal change, until now we did not know the exact mechanism
involved," said Peter Sharp, a researcher at the Roslin
Institute near Edinburgh, who worked on the study.
The researchers, led by Takashi Yoshimura of the Nagoya
University in Japan, scanned 38 000 genes present in brain
samples taken from Japanese quails to see which of the birds'
genes were affected by varying degrees of light.
Genes in cells on the surface of the brain switched on when
the birds received more light and began releasing a
thyroid-stimulating hormone.
The genes activated 14 hours after dawn on the first day of
sufficient length, the researchers said.
"Such knowledge would have been impossible in the past, but
advances in technology enabled us to scan thousands of genes so
that we could work out which ones are affected by seasonal
change," Sharp said.
This hormone, previously associated with growth and
metabolism, helped to stimulate the pituitary gland to secrete
other hormones. In turn this caused the birds' testes to grow,
which eventually resulted in crowing to attract a mate.
The findings could also one day lead to better treatments
for infertility because humans have the same cells in the same
part of the brain, Sharp added.
"It is sitting there and standing there with the same
characteristics as in birds," he said. "The big question is
whether these cells are involved in the reproductive system."