The Effects of Salicylate on Auditory Evoked Potential Amplitwde from the Auditory Cortex and Auditory Brainstem

Tinnitus has often been studied using salicylate in animal models as they are capable of inducing temporary hearing loss and tinnitus. Studies have recently observed enhancement of auditory evoked responses of the auditory cortex (AC) post salicylate treatment which is also shown to be related to tinnitus like behavior in rats. The aim of this study was to observe if enhancements of the AC post salicylate treatment are also present at structures in the brainstem. Four male Sprague Dawley rats with AC implanted electrodes were tested for both AC and auditory brainstem response (ABR) recordings pre and post 250 mg/kg intraperitoneal injections of salicylate. The responses were recorded as the peak to trough amplitudes of P1-N1 (AC), ABR wave V, and ABR wave II. AC responses resulted in statistically significant enhancement of amplitude at 2 hours post salicylate with 90 dB stimuli tone bursts of 4, 8, 12, and 20 kHz. Wave V of ABR responses at 90 dB resulted in a statistically significant reduction of amplitude 2 hours post salicylate and a mean decrease of amplitude of 31% for 16 kHz. Wave II amplitudes at 2 hours post treatment were significantly reduced for 4, 12, and 20 kHz stimuli at 90 dB SPL. Our results suggest that the enhancement changes of the AC related to salicylate induced tinnitus are generated superior to the level of the inferior colliculus and may originate in the AC.