From: LARRY KLAES (ljk4_at_msn.com)
Date: Sat Jul 17 2004 - 08:09:05 PDT
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From: cunews_at_cornell.edu<mailto:cunews_at_cornell.edu>
To: CUNEWS-LIFE_SCIENCE-L_at_cornell.edu<mailto:CUNEWS-LIFE_SCIENCE-L_at_cornell.edu> ; CUNEWS-SCIENCE-L_at_cornell.edu<mailto:CUNEWS-SCIENCE-L_at_cornell.edu>
Sent: Thursday, July 15, 2004 3:53 PM
Subject: Cornell News: hormones and hearing
Hormone boost that helps female fish tune in to males' love songs
could also affect sensitivity of human hearing, Cornell biologists
report
EMBARGOED UNTIL THURSDAY, JULY 15, 2004, 2 P.M., EST
Contact: Roger Segelken
Office: 607-255-9736
E-mail: hrs2_at_cornell.edu<mailto:hrs2_at_cornell.edu>
ITHACA, N.Y. -- Without enough estrogen-like hormone in their
systems, female plainfin midshipman fish turn a deaf ear to the
alluring love songs of the males. And, according to Cornell
University biologists, a similar steroid-sensitive response could
underlie changes in the hearing sensitivity of humans. The
biologists experimentally boosted levels of the steroid hormone in
non-reproductive females of the fish species Porichthys notatus,
temporarily altering their inner-ear auditory mechanism so they could
hear the males' hum-like advertisement call that says, essentially:
"I have prepared a nest under a rock in shallow water, so deposit
your eggs for me to fertilize, and together we'll make beautiful
small fry."
Altering steroid hormone levels did not change the reproductive
status of the females; the eggs they carried were still immature and
were not ready to be deposited, even if the hearing-enhanced females
had been attracted to the males' nests. Rather, the Cornell
biologists found a hormonal trigger for a complex auditory system.
Andrew H. Bass, the Cornell professor of neurobiology and behavior
who led the research team that reported the findings in the July 16,
2004, issue of Science ("Steroid-dependent Auditory Plasticity Leads
to Adaptive Coupling of Sender and Receiver") comments: "We suspected
that enhancing the sensitivity of the females' ears to the upper
harmonics of the males' hums should improve detection of their
vocalizations. Upper harmonics propagate farther in shallow water
environments like those where midshipman males build nests and sing
their love song to attract females.
"But the females can't process this vital information and respond
appropriately if they can't hear it. Steroid hormones appear to
provide a key molecule that leads to shifts in the hearing
sensitivity of females," Bass said.
Paul M. Forlano, a graduate student in Bass's lab, and David L.
Deitcher, one of Bass's
colleagues at Cornell, also identified the estrogen receptor in the
female inner ear where the enhancement of the males' cues begins. As
Forlano notes: "This was especially important since estrogen
receptors are also present in the human inner ear but no one knows
why they might be there. Our study now suggests a possible function."
The research, he notes, is of particular relevance to women with
Turner's syndrome, a genetic aberration that results in loss of
estrogen production in the ovary, that also shows an early onset in
progressive high-frequency hearing loss.
Joseph A. Sisneros, a postdoctoral associate in Bass's lab at the
time of the study and now a faculty member at the University of
Washington, further explains: "Previous experiments in other
laboratories also suggested that steroid hormones may play a role in
causing some of the reported changes in hearing sensitivity of human
females at differing stages of the menstrual cycle. Knowing how
steroids can alter the hearing abilities of midshipman fish might
give us important clues as to how these changes in hearing occur
among humans."
Midshipman fish have long enjoyed a certain amount of local fame on
the West Coast. During their seasonal mating time, when males move
toward the shore from deep water and prepare to advertise their love
nests, the humming chorus becomes so loud and persistent that
houseboat residents often lie awake at night.
A long-time researcher on midshipman fish, Cornell's Bass notes:
"Perhaps the remarkable hum of these fish will take on new meaning
for the houseboaters when they discover that they may share some
things in common with these vocal Lotharios of the sea. And we hope
that others who study the human auditory system will be inspired by
these experiments."
The fish study, which was supported, in part, by the National
Institutes of Health, shows how steroid hormones can help shift the
sensitivity of the auditory system to pay more attention to some
social stimuli than to others, says Bass. "This system of
hormone-based prioritization helps the brain focus on the most
important stimuli, at any given time, in an ever-changing
environment. Perhaps something similar is at work in humans."
Related World Wide Web sites: The following sites provide
additional information on this news release. Some might not be part
of the Cornell University community, and Cornell has no control over
their content or availability.
oPlainfin fish facts:
oNeuroscience at Cornell:
-30-
The web version of this release may be found at
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