Study identifies key cellular mechanisms behind the onset of tinnitus

Researchers in the University of Leicester's Department of Cell Physiology and Pharmacology have identified a cellular mechanism that could underlie the development of tinnitus following exposure to loud noises. The discovery could lead to novel tinnitus treatments, and investigations into potential drugs to prevent tinnitus are currently underway.

Tinnitus is a sensation of phantom sounds, usually ringing or buzzing, heard in the ears when no external noise is present. It commonly develops after exposure to loud noises (acoustic over-exposure), and scientists have speculated that it results from damage to nerve cells connected to the ears.

Although and affect around ten percent of the population, there are currently no drugs available to treat or prevent tinnitus.

University of Leicester researcher Dr Martine Hamann, who led the study published in the journal Hearing Research, said: "We need to know the implications of acoustic over exposure, not only in terms of hearing loss but also what's happening in the brain and . It's believed that tinnitus results from changes in excitability in cells in the brain - cells become more reactive, in this case more reactive to an unknown sound."

Dr Hamann and her team, including PhD student Nadia Pilati, looked at cells in an area of the brain called the dorsal cochlear nucleus - the relay carrying signals from nerve cells in the ear to the that decode and make sense of sounds. Following exposure to loud noises, some of the (neurons) in the dorsal cochlear nucleus start to fire erratically, and this uncontrolled activity eventually leads to tinnitus.

Dr Hamann said "We showed that exposure to loud sound triggers hearing loss a few days after the exposure to the sound. It also triggers this uncontrolled activity in the neurons of the dorsal cochlear nucleus. This is all happening very quickly, in a matter of days"

In a key breakthrough in collaboration with who sponsored Dr Pilati's PhD, the team also discovered the specific that leads to the neurons' over-activity. Malfunctions in specific potassium channels that help regulate the nerve cell's electrical activity mean the neurons cannot return to an equilibrium resting state.

Ordinarily, these cells only fire regularly and therefore regularly return to a rest state. However, if the potassium channels are not working properly, the cells cannot return to a rest state and instead fire continuously in random bursts, creating the of constant noise when none exists.

Dr Hamann explained: "In normal conditions the channel helps to drag down the cellular electrical activity to its resting state and this allows the cell to function with a regular pattern. After exposure to loud sound, the channel is functioning less and therefore the cell is constantly active, being unable to reach its resting state and displaying those irregular bursts."

Although many researchers have investigated the mechanisms underlying tinnitus, this is the first time that cellular bursting activity has been characterised and linked to specific potassium channels. Identifying the involved in the early stages of tinnitus opens up new possibilities for preventing tinnitus with early drug treatments.

Dr Hamann's team is currently investigating potential drugs that could regulate the damaged cells, preventing their erratic firing and returning them to a resting state. If suitable drug compounds are discovered, they could be given to patients who have been exposed to loud noises to protect them against the onset of tinnitus.

These investigations are still in the preliminary stages, and any drug treatment would still be years away.

The research was funded by a Research Councils UK fellowship to Dr Hamann, a grant from the Wellcome Trust and a PhD studentship from GlaxoSmithKline, with follow-up investigations funded by a three-month grant from Deafness Research UK. Further pharmaceutical research will be carried out by the University of Leicester in collaboration with Autifony Therapeutics Ltd via a Medical Research Council Case studentship due to start in October 2012.

Vivienne Michael, Chief Executive of Deafness Research UK, said "We're pleased to hear about this progress in such a debilitating hearing impairment. The charity continues to fund research into better treatments for tinnitus, with the ultimate aim of a cure. Our free information leaflets offer immediate help to sufferers and our national helpline provides additional support. Regularly tinnitus generates the most requests for help."

Related Stories

Study to test new tinnitus 'treatment'

Mar 20, 2012

A new clinical trial is to test whether a pocket-sized device that uses sound simulation to reboot faulty 'wiring' in the brain could cure people with the debilitating hearing disorder tinnitus.

Zebrafish may help solve ringing in vets' ears

Apr 30, 2008

Ernest Moore, an audiologist and cell biologist at Northwestern University, developed tinnitus -- a chronic ringing and whooshing sound in his ears -- twenty years ago after serving in the U.S. Army reserves medical corps. ...

Tinnitus discovery could lead to new ways to stop the ringing

Sep 12, 2011

Neuroscientists at the University of California, Berkeley, are offering hope to the 10 percent of the population who suffer from tinnitus – a constant, often high-pitched ringing or buzzing in the ears that can be annoying ...

Silence may lead to phantom noises misinterpreted as tinnitus

Jan 01, 2008

Phantom noises, that mimic ringing in the ears associated with tinnitus, can be experienced by people with normal hearing in quiet situations, according to new research published in the January 2008 edition of Otolaryngology ...

Recommended for you

Impact of whooping cough vaccination revealed

5 hours ago

The most comprehensive study to date of the family of bacteria that causes whooping cough points to more effective vaccine strategies and reveals surprising findings about the bacteria's origin and evolution. The new results ...

User comments