MelatoninReceptors, MelatoninReceptor, Melatonin, MT1Receptor, Melatonin, MT2Pineal GlandCircadian RhythmArylalkylamine N-AcetyltransferaseAcetylserotonin O-MethyltransferaseTryptaminesPhotoperiodLightKynuramineAntioxidantsSleep Disorders, Circadian RhythmSleepRats, WistarTime FactorsRadiation DosageDrug Implants5-MethoxytryptamineLethal Dose 50SeasonsAdministration, OralDrug Administration ScheduleChronobiology DisordersProlactinDouble-Blind MethodRats, Sprague-DawleyDarkness