Scientists Discover What Makes Our Ears Ring

(Ivanhoe Newswire) -- Ever wonder what makes that sound we know as ringing in our ears?

Brain scientists at Johns Hopkins University have discovered how cells in the developing ear make their own noise, way before the ear can detect sound around the cells. This could help explain how the developing auditory system generates brain activity when there is no sound and why we hear sounds like tinnitus (ringing in the ears).

Researchers were studying non-nerve cells in the ears of young rats when they made the discovery. The so-called support cells were not thought to be involved in nerve communication. But they showed strong electrical activity similar to nerve cells. The activity occurred without sound or any external stimulus.

The scientists then found ATP (adenosine triphosphate) - a chemical mostly used as a cell’s energy currency – caused the supporting cells to change their shape. ATP then signals hair cells to release another chemical which activates the nerve cells that project into the brain.

“It is as if ATP substitutes for sound when the ear is still immature and physically incapable of detecting sound,” lead author, Dwight Bergles, Ph.D., Johns Hopkins University, was quoted as saying. “The cells we have been studying seem to be warming up the machinery that will later be used to transmit sound signals to the brain.”

The study also shows as the ear matures during the first two weeks of a rat’s life, most of the cells that release ATP disappear. By the time the rat can hear sound, all the spontaneous electrical activity in its ears has stopped.

Researchers explain while there is no longer any ATP, the hair cells continue to be able to respond to it. And exposure to loud sounds can trigger ATP release in the ear which may cause the sensation of sound when there is none, such as tinnitus.

This article was reported by Ivanhoe.com, which offers Medical Alerts by e-mail every day of the week. To subscribe, click on: http://www.ivanhoe.com/newsalert/.

SOURCE: Nature, 2007