Salicylate evokes c-fos expression in the brain stem: implications for tinnitus.

Subjective tinnitus, a distracting internal noise is experienced by humans and animals. Mongolian gerbils were treated with salicylate as a tinnitus-evoking agent. After salicylate treatment, c-fos expression in auditory brain stem nuclei was as low as after saline treatment (control). Pronounced differences between groups were found, however, in areas susceptible to stress, with many immunoreactive cells in the locus coeruleus, the midbrain periaqueductal grey and the lateral parabrachial nucleus of salicylate-treated animals. These results suggest that salicylate may evoke tinnitus through a combined effect on auditory and non-auditory brain nuclei. While activity in auditory brain stem nuclei is reduced, stress-susceptible areas are activated. It seems possible that the interaction of these effects at particular locations of the brain causes tinnitus.