The AudioNotch Tinnitus Treatment Blog

Interesting research offers a possible explanation as to why, even when exposed to the same external harmful noise stimulus, some individuals will develop tinnitus and other individuals will not. Extrapolating findings from research on animals may reveal why some people develop tinnitus while others do not.

Animals were exposed to a noise stimulus with the intention of destroying their hearing hair cells:

All nine noise-exposed rats showed similar patterns of severe hair cell loss at high- and mid-frequency regions in the exposed ear.

Subsequently, some of the rats expressed a protein in nervous system cells called GAP-43:

Eight of the nine showed strong up-regulation of GAP-43 in auditory nerve fibers and pronounced shrinkage of the ventral cochlear nucleus (VCN) on the noise-exposed side, and strong up-regulation of GAP-43 in the medial ventral VCN, but not in the lateral VCN or the dorsal cochlear nucleus.

The GAP-43 protein appeared to be protective in preventing tinnitus:

GAP-43 up-regulation in VCN was significantly greater in Noise-No-Tinnitus rats than in Noise-Tinnitus rats.

It appears that this protein may work in suppressing tinnitus:

GAP-43 up-regulation most likely originates from medial olivocochlear neurons. Their increased excitatory input on inhibitory neurons in VCN may possibly reduce central hyperactivity and tinnitus.

Thus take-home points are as follows:

1. Some animals did not develop tinnitus after exposure to a loud noise which caused hearing loss, likely because they produced a molecular response that appeared to suppress hyperactivity of auditory neurons that may cause tinnitus.
2. A similar mechanism may explain why some people with severe hearing loss acquire tinnitus but others do not.

Check out the paper here. 

Research that further elucidates the pathophysiology of tinnitus is exciting, as we move towards a greater and greater understanding of tinnitus.

Best,
AudioNotch