Effects of combinations of sodium salicylate and noise on the auditory threshold

Thirty-nine monaural chinchillas were used to study the interaction between sodium salicylate and various TTS-producing noise paradigms. Five animals were included in each of the following three groups: 1) sodium salicylate (400 mg/kg) plus 2-4 kHz, 95 dB SPL noise band for one hour; 2) sodium salicylate (400 mg/kg) plus 4 kHz CF octave band noise at 80 dB SPL for 96 hours; and 3) sodium salicylate (400 mg/kg) plus 50 impulses having 50 musec A-duration and 158 dB peak SPL, presented at one per minute. The remaining 24 animals served as various controls in groups exposed to sodium salicylate or the noise paradigm alone. Thresholds were estimated before, during, and after exposure using the AER technique and cochleagrams were mapped for each cochlea 30 days after exposure. When sodium salicylate was combined with the various noise conditions, the maximum TTS values obtained from the combination studies were comparable to those obtained from the single agent producing the greatest TTS at a particular frequency. No consistent alteration in either magnitude or time course of posttreatment threshold shift was found following the combination treatments as compared to the individual agents alone. Hazard to the auditory system resulting from a combination of sodium salicylate and noise was concluded to be no greater than the hazard presented by either agent alone. This result is also substantiated in the histological results.