Accession Number : ADA259877
Title : Melatonin Action on the Circadian Pacemaker in Siberian Hamsters.
Descriptive Note : Final rept. 1 Sep 91-31 Aug 92,
Corporate Author : NORTHEASTERN UNIV BOSTON MA OFFICE OF SPONSORED PROJECTS
Personal Author(s) : Darrow, Janet M
Report Date : 31 Oct 1992
Pagination or Media Count : 20
Abstract : This research investigates the effect of the hormone melatonin on the circadian clock of mammals, by examining daily locomotor activity rhythms in melatonin-infused Siberian hamsters, under a variety of environmental lighting conditions. Under conditions of constant darkness, daily melatonin infusions synchronized the hamster activity/rest rhythm. In constant light, melatonin also acted as a weak entraining agent and prevented the internal desynchronization which occurs in Siberian hamsters and in many mammals exposed to constant light. In a series of experiments simulating jet-lag conditions, melatonin infusions were found to alter the rate of re-entrainment of the circadian system after phase-shifting of the light cycle. These melatonin effects were influenced by light intensity and by phase of the hormone infusion. Measurements of melatonin receptor levels in the suprachiasmatic nuclei of Siberian hamsters has provided preliminary evidence for a daily rhythm of receptivity to melatonin in the circadian pacemaker of the mammalian hypothalamus, which may help explain the phase-dependency of melatonin effects on phase-shifting. Results of this study are relevant to the expanding clinical use of melatonin for treatment of a variety of temporal disorders, including jet-lag.... Jet-lag, Melatonin, Circadian, Clock, Sleep/wake cycles.
Descriptors : *CIRCADIAN RHYTHMS , *HAMSTERS , *MELATONIN , *PACEMAKERS , MEASUREMENT , CLOCKS , CYCLES , INTERNAL , WAKE , DATA RATE , SLEEP , HYPOTHALAMUS , MENTAL DISORDERS , INFUSIONS , JET LAG , REPRODUCTION(PHYSIOLOGY) , ENTRAINMENT , MEDICAL RESEARCH , SYNCHRONIZATION(ELECTRONICS) , SHIFTING , PHASE , LIGHT , HORMONES
Subject Categories : Anatomy and Physiology
Medicine and Medical Research
Medical Facilities, Equipment and Supplies
Distribution Statement : APPROVED FOR PUBLIC RELEASE