AN ATTEMPT TO CORRELATE BRAIN-AREAS CONTAINING MELATONIN-BINDING SITES WITH RHYTHMIC FUNCTIONS - A STUDY IN 5 HIBERNATOR SPECIES

High affinity melatonin-binding sites have been described, by means of autoradiography with 2-I-125- melatonin as the ligand, in more than 6 0 brain areas of about 20 mammalian species, with dramatic variations in the nature and number of labelled structures among the different sp ecies studied. As melatonin is involved in the synchronization of biol ogical rhythms, we have tried to correlate the brain areas containing melatonin-binding sites with some rhythmic functions typical of given species. Therefore, we have studied the location of melatonin-binding sites in the complete brain of five long-day breeders with hibernation cycles, viz. one insectivore and four rodents. With the exception of the suprachiasmatic nuclei and the pars tuberalis of the pituitary, bo th of which contain binding sites in all five species, few reactive st ructures are common, even among species from the same family, e.g. the edible dormouse and the garden dormouse.