Comparison of actions of ketamine and telazol on cochlear function in a rodent model of noise-induced hearing loss.

Research has shown that anesthesia used in rodent models studying trauma-related changes in the peripheral auditory system can impact the results of standard functional tests like the auditory brainstem response (ABR). The anesthetic agents may also confound the effects of potential therapeutics under evaluation in the preclinical models. Ketamine, a N-methyl-D-aspartate (NMDA) receptor antagonist, is a commonly employed anesthetic in rodent models. Studies have shown that ketamine, unlike other anesthetics, exerts minimal effects on ABR measurements. Tiletamine, a compound chemically akin to ketamine, is also an NMDA antagonist. Tiletamine combined with zolazepam (Telazol) may be a substitute for ketamine given its less severe side-effects and long-acting capacity. In this study, we serially compare cochlear function in rats exposed to hazardous noise to induce noise-induced hearing loss (NIHL) under the effects of either ketamine or telazol. Awake male Brown Norway rats were exposed to octave band noise (4-8 kHz) at 110 dB SPL for 1 h. Cochlear function was assessed over multiple time points using either intramuscular injection of ketamine (44 mg/kg) and xylazine (5 mg/kg) or intraperitoneally injected telazol (20 mg/kg) and xylazine (5 mg/kg). Changes in ABR threshold, latency, and amplitude were compared to baseline(pre-NIHL) over 28 days. Functional results demonstrated that both ketamine- and telazol-anesthetized animals experience permanent changes in thresholds following noise. While both amplitude and latency were affected by noise, there were no significant differences in the changes between ketamine and telazol groups. Our findings suggest that telazol behaves similarly to ketamine and could be an alternative in rodent model experiments for the evaluations of hearing sensitivity following noise trauma.