Light-Induced Functional Pinealectomy: Expression of MT2 Receptors in Liver Cells of C57BL/6 Mice after Melatonin Treatment.

We performed an immunohistochemical study of MT2 melatonin receptor expression in the liver of C57BL/6 mice with modeled light-induced functional pinealectomy and after melatonin administration by the indirect avidin-biotin peroxidase ABC method. The animals were kept for 14 days under constant lighting. Intragastric administration of melatonin in physiological doses (1 mg/kg body weight for 14 days) to mice with light-induced functional pinealectomy resulted in a 2-fold increase in the relative expression area of MT2 receptors in liver cells in comparison with that in animals kept under standard lighting conditions, 24-h lighting for 14 days, or 24-h lighting receiving placebo (intragastric administration of 200 ml distilled water). Melatonin treatment had practically no effect on MT2 staining intensity. Our results attest to the important role of MT2 receptors in melatonin synthesis disorders and can serve as the basis for the development of therapeutic strategies aimed at melatonin receptors.