title: Suppression of sympathetic nervous system by short photoperiod and melatonin in the Syrian hamster.
abstract: Exposure to short photoperiod or melatonin treatment brings about gonadal regression in Syrian hamsters. The possible influence of these treatments on the sympathetic nervous system (SNS) in these animals was investigated. Male Syrian hamsters were exposed to either long or short photoperiod or subjected to administration of melatonin or its vehicle solution. Exposure of hamsters to 10 weeks of short photoperiod, significantly reduced the noradrenaline (NA) turnover in the heart. Daily administration of melatonin for 8 weeks also resulted in a similar suppression of NA turnover in the heart. Hamsters that were treated with melatonin maintained a lowered metabolic rate as well, at and below thermoneutral temperature. These findings suggest that in a deep hibernator, short photoperiod could suppress the peripheral sympathetic activity and that melatonin may act as the endogenous mediator.
mesh_terms: D000818:Animals; D001481:Basal Metabolism; D001831:Body Temperature; D006224:Cricetinae / Q000502:physiology*; D008027:Light; D008550:Melatonin / Q000494:pharmacology*; D008647:Mesocricetus / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism; D010101:Oxygen Consumption; D013564:Sympathetic Nervous System / Q000187:drug effects*; D013696:Temperature; D013997:Time Factors
chemical_list: D008550:Melatonin; D009638:Norepinephrine