title: Free-running activity rhythms in the rat: entrainment by melatonin.
abstract: The pineal gland hormone melatonin may play a role in synchronization of rat circadian rhythms. Free-running activity rhythms of the rat were entrained by a daily melatonin injection, with entrainment occurring when the onset of activity coincided with the time of daily injections. When injections were stopped, activity rhythms became free-running again. Thus in pharmacological experiments, the time of day of melatonin administration is crucial.
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000187:drug effects*; D004334:Drug Administration Schedule; D008297:Male; D008550:Melatonin / Q000494:pharmacology / Q000502:physiology*; D009043:Motor Activity / Q000502:physiology*; D010870:Pineal Gland / Q000502:physiology*; D051381:Rats
chemical_list: D008550:Melatonin