Finding targets for tinnitus treatment
Deafness Research UK has awarded a new grant to Dr Martine Hamann and Professor Ian Forsythe at the University of Leicester and the MRC Toxicology Unit who will investigate whether a molecule that is important for hearing is also involved in tinnitus.
[Small project grant: 2009]
Approximately five million people in the UK have tinnitus, a condition in which sounds are heard when there is no external source. These sounds can range from a temporary ‘ringing in the ears’ which may be only mildly annoying, to a more permanent and debilitating ringing, hissing or buzzing that badly affects the sufferer’s quality of life.
Previous research has shown that exposure to loud noise can lead to both tinnitus and hearing loss. Dr Hamann has found that noise exposure leading to hearing loss also leads to abnormal electrical activity in a specific part of the hearing pathway called the dorsal cochlear nucleus.
This area – located between the ear and the brain – combines information about sounds with information from other senses. So abnormal activity there could explain why some people experience phantom auditory sensations (tinnitus). Integration of auditory information with other senses in the area could also explain why the perception of tinnitus can be modulated by jaw movements or balance.
In the new study, Dr Hamann will investigate the cause of the abnormal activity observed in the dorsal cochlear nucleus. A potential candidate is a noise-induced change in behaviour of the molecules that enable nerve cells to send signals to each other. One of the key molecules is potassium which flows across the cell membrane through specific potassium ‘channels’. Dr Hamann will work with Professor Forsythe, an expert in potassium channels in the auditory system.
Recordings will be made of nerve cell activity in the dorsal cochlear nucleus of rats with noise-induced hearing loss and tinnitus. The aim is to find out whether changes to potassium signals in this region are behind the abnormal ‘over-activity’ observed.
“Potassium channels play a key role in cellular excitability within the auditory system. If abnormal potassium activity is found to be one of the causes of tinnitus then the project could lead to the manufacture of a new generation of tinnitolytic drugs that inhibit specific potassium channels. Inhibiting these channels would therefore block abnormal cellular excitability within the auditory system” says Dr Hamann. The result would be a new therapeutic treatment to prevent the tinnitus signal from occurring.
