When male fish hum, females swim in, thanks to hormones, adaptab...( live in deep water off the Pacific Coas...)

live in deep water off the Pacific Coast of the United States three-quarters of the year. They move into shallow intertidal zones to reproduce. Males build nests under rocks and begin broadcasting their loud humming love calls to attract females. The researchers collected non-reproductive females, removed their ovaries and replaced them with implants to induce hormonal levels in the fish that mimic the natural spike in testosterone and estradiol levels in reproductive females. A month later the hormone implants caused changes in the non-reproductive females' hearing sensitivity.

"The importance of this study is that the neural plasticity we've uncovered may affect all vertebrates," said Sisneros. "This fish relies heavily on its auditory system for reproduction and our work gives us insight into how this plasticity operates. The next step is to locate where this plasticity occurs. There are four possibilities, at the sensory hair cells in the ear, in the auditory nerve, in the brain or in all three at the same time."

The jump is a big one, but Sisneros said the research eventually might have human applications. For instance, he said, "previous experiments in other laboratories suggest that steroid hormones may also play a role in causing some of the reported changes in hearing sensitivity of human females at differing stages of the menstrual cycle. Also humans have a natural loss of hearing in relationship to age. The higher frequencies tend to drop out first along with a natural drop in testosterone and estrogen. So a question arises: are natural decreases in hormone levels related to this loss of high-frequency hearing?"

Co-authors of the paper were Paul Forlano, a Cornell graduate student, and David Deitcher, a Cornell associate professor of neurobiology and behavior. They also identified the estrogen receptor in the female inner ear where the enhancement begins. "This was especially important since estrogen receptors are also pres
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Contact: Joel Schwarz
joels@u.washington.edu
206-543-2580
University of Washington
15-Jul-2004

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