Objective Evaluation of Auditory Function of Axolotls Pre- and Post-metamorphosis and its Comparison with Rats

Objective: Axolotls possess remarkable regenerative capabilities, including the ability to regenerate the brain, spinal cord, internal organs, lateral line system cells, and inner ear hair cells.However, following metamorphosis, their regenerative capacity diminishes, accompanied by changes in auditory function.This study aimed to objectively assess these changes to enhance understanding of the relationship between metamorphosis, regeneration, and auditory function, with potential implications for regenerative biology and auditory research.Additionally, 3-month-old rats were included as a comparative model for evaluating auditory function.Methods: Auditory function in axolotls (maximum length: 20 cm) and 3-month-old rats was evaluated using auditory brainstem response (ABR) testing.ABR measurements were conducted on axolotls both pre-and post-metamorphosis using tone burst stimuli at 250 Hz, 500 Hz, 600 Hz, and 800 Hz.In rats, measurements were taken at 8, 12, 16, and 20 kHz frequencies.Results: ABR recordings in axolotls pre-and post-metamorphosis revealed that 600 Hz produced the most consistent wave morphology.Wave II latencies were significantly longer before metamorphosis compared to after metamorphosis, indicating alterations in auditory processing.In contrast, 3-month-old rats exhibited stable auditory thresholds across all tested frequencies, demonstrating consistent auditory function. Conclusion:This study presents the first successful application of ABR methodology for evaluating auditory function in axolotls, providing a comparative analysis with auditory function in 3-month-old rats.Significant changes in auditory function were observed in axolotls following metamorphosis, indicating a decline in auditory capabilities concurrent with the reduction in regenerative capacity.These findings underscore the feasibility of using ABR testing in axolotls and highlight important implications for auditory function research across different species.