[Levels of the pineal hormone melatonin and its circadian variations in the cochlea of Wistar rats].

The normal inner ear contains different elements belonging to the immune system. Some pathology of the inner ear has been attributed to autoimmune mechanisms, both humoral and cellular. Melatonin, the principal hormone of the pineal gland, modulates the immune system, is involved in autoimmune processes, and mediates free-radical and interleukine production. In a study of the presence of melatonin in rat cochlea, a day-night rhythm of melatonin in cochlea was observed. Melatonin levels are high during dark periods and low during light periods. This rhythm is synchronic with peripheral melatonin circulation. More work, both experimental and clinical, is needed to determine the role of melatonin in the inner ear and its therapeutic usefulness.