Objective: The present study aimed to perform a morphological and morphometric analysis of the cochlear structures of C57BL/6J mice receiving oral melatonin for a period of 12 months.

Methods: 32 C57BL/6J males were divided into control and melatonin groups. The control received saline and ethanol solution and the melatonin group, 50μl of 10mg of melatonin/kg/day orally for a period of 12 months. After the experiment, the animals were sacrificed in a concentration chamber of 40% CO2, and the slides were analyzed morphologically and morphologically.

Results: The melatonin group revealed higher median density of viable cells (45±10.28cells/100μm2, 31–73, versus 32±7.47cells/100μm2, 25–48). The median area of the vascular stria was 55.0±12.27cells/100μm2 (38–80) in the control group and 59.0±16.13cells/100μm2 (40–134) in the melatonin group. Morphometric analysis of the spiral ligament reveals a higher median of total viable neurons in melatonin (41±7.47cells/100μm2, 27–60) than in the control group (31±5.68cells/100μm2, 21–44).

Conclusion: Although melatonin is a potent antioxidant, it does not completely neutralize the occurrence of presbyacusis; however, it may delay the appearance of this condition.

Keywords: Hearing loss; Cochlear; Inner ear; Melatonin; Presbyacusis.