Auditory brainstem response as a possible objective indicator for salicylate-induced tinnitus in rats.

The auditory response to an acoustic stimulus will usually be suppressed, or masked, by a preceding sound. Here, we show that forward acoustic masking at a high frequency can boost the auditory brainstem response (ABR) in rats injected with a high dose of sodium salicylate (NaSal), a tinnitus inducer. The forward narrow band noise caused a decrease in the amplitude of the ABR to a probe tone burst in normal rats, but caused an unexpected increase in the amplitude at 16 kHz in rats treated with NaSal (300 mg/kg). The observed effect could be manifested in normal rats presented with a background tone added to the masker and the probe, suggesting an underlying mechanism associated with tinnitus. We hypothesize that in NaSal-treated rats, tinnitus can "internally" mask the ABR in a similar way as an external background sound does and the "unmasking" effect of forward masking can result in a rebound of the otherwise suppressed ABR. Our study raises the possibility of using the ABR as an objective indicator for NaSal-induced tinnitus in animals. This article is part of a Special Issue entitled: Tinnitus Neuroscience.