EFFECTS OF NOISE AND SALICYLATE ON AUDITORY EVOKED-RESPONSE THRESHOLDS IN THE CHINCHILLA

The combined effects of noise and sodium salicylate on auditory sensitivity were examined in the chinchilla. Sensitivity was monitored by recording the evoked response recorded with an electrode implanted in the inferior colliculus. Sodium salicylate (300 mg/kg/day), an octave band of noise centered at 500 Hz (80 or 105 dB SPL), or both of these agents were delivered for 15 days. Threshold testing was performed at 7 frequencies before, during, and after exposure to the ototraumatic agent(s). The salicylate alone caused an average temporary threshold shift of less than 10 dB and essentially no permanent shift. Animals exposed to noise alone had temporary and permanent threshold shifts which were not significantly different from those observed in animals exposed to noise plus salicylate. The data suggest that a single daily injection of sodium salicylate, resulting in peak serum salicylate concentrations of 28 to 34 mg% 2 to 4 hours after delivery, does not exacerbate the temporary or permanent threshold shifts induced by 15-day, 24-hour-per day exposure to either a moderate- or high-level, low-frequency noise. A second series of experiments utilizing a higher dose of salicylate (450 mg/kg/day) was not completed due to a high mortality rate among subjects that received salicylate and were exposed to noise. This result was consistent with other recent examinations of the interaction of these agents.