Behavioral model of chronic tinnitus in rats.

An animal model of tinnitus was developed to study chronic salicylate-induced tinnitus in rats. Novel features of the model included oral dosing of salicylate, test stimuli that included a range of pure tones and silence, and assessment of tinnitus for several months. Experimental subjects were given sodium salicylate in their drinking water while control subjects received normal tap water. Subjects were conditioned to press a lever for food in the presence of continuous white noise. At random intervals, offset of the noise was paired with a noxious stimulus, resulting in cessation of lever pressing during the silent test periods. At other randomly scheduled intervals, a test tone was substituted for the white noise, unpaired with noxious stimuli. When the test stimuli were pure tones, the salicylate-treated subjects suppressed less than the control subjects. One explanation for this result is that the experimental subjects' sensations of tones were noisier than those of the controls because experimental subjects were experiencing tinnitus.