It is now widely accepted that one cause of tinnitus is the release of excessive amounts of the
neurotransmitter glutamate by hair cells in the inner ear. Normally, glutamate plays a vital role in
communication between nerve cells, making them more likely to send a signal onwards. However,
when the cells are subjected to stress - for example by exposure to loud noise or to drugs that are
toxic to hair cells - they over-produce glutamate, causing a negative effect known as excitotoxicity.
The result is that the original connections between hair cells and the nerves that carry signals from
the inner ear on to the brain are destroyed, but can later be replaced by the growth of new ones.
These new connections are of a different type to the originals and function differently, becoming
over-active when glutamate is released. The over-activity is then perceived as tinnitus