Regional concentrations of melatonin in the rat brain in the light and dark period

The levels of melatonin in five brain regions, whole brain, pineal and serum samples were studied in rats adapted under a photoperiod of 12 h light and 12 h dark. It was found that the melatonin levels for all the tissues obtained in the dark period were significantly higher than those obtained in the light period. Regional study of melatonin levels in the brain in the light and dark period demonstrated a high level in the hypothalamus, …