Entrainment of Syrian hamster circadian activity rhythms by neonatal melatonin injections

1996 ◽  
Vol 270 (3) ◽  
pp. R533-R540 ◽  
Author(s):  
J. Grosse ◽  
A. Velickovic ◽  
F. C. Davis
Keyword(s):  
Circadian Rhythms ◽  
Suprachiasmatic Nucleus ◽  
Syrian Hamster ◽  
Circadian Activity ◽  
Syrian Hamsters ◽  
Activity Rhythms ◽  
Vehicle Injection ◽  
Two Phases ◽  
Melatonin Injection

The circadian rhythms of fetal and neonatal rodents are entrained by their mother. This entrainment is dependent upon the maternal suprachiasmatic nucleus (SCN), but the mechanism of entrainment is unknown. Administration of the pineal hormone melatonin to pregnant, SCN-lesioned female Syrian hamsters entrains the activity rhythms of their hamster pups. The aim of this study was to determine whether melatonin injected directly in neonatal Syrian hamsters is able to entrain circadian rhythms and, if so, for how long this effect persists during development. Injection of melatonin in two groups of hamster pups at opposite phases on postnatal days 1-5 entrained the onset of activity rhythms on the day of weaning to two phases 10.67 h apart. Melatonin injection did not entrain activity rhythms to opposite phases on either postnatal days 6-10 or 21-25. Vehicle injection did not entrain animals to opposite phases at any of the ages studied. These results demonstrate that melatonin is able to act directly on the neonate to cause entrainment and that this effect disappears after postnatal day 6.

Photic Response Parameters of Circadian Rhythms in The Spinifex Hopping Mouse, Notomys alexis.

1996 ◽  
Vol 19 (1) ◽  
pp. 11
Author(s):  
A.J.P. Francis ◽  
G.J. Coleman
Keyword(s):  
Circadian Rhythms ◽  
Phase Relations ◽  
Constant Light ◽  
Constant Darkness ◽  
Biological Clocks ◽  
Circadian Activity ◽  
Activity Rhythms ◽  
Controlled Conditions ◽  
Australian Native Rodent ◽  
Photic Response

Circadian rhythms are generated endogenously by biological clocks or 'pacemakers', which are responsive to significant environmental stimuli termed zeitgebers. Interactions between pacemakers and zeitgebers provide the basis for synchronisation by light-dark (LD) cycles, and the characteristics of each of these elements determines the phase-relations maintained between an animal's circadian activity rhythms and the natural temporal environment. We report here the basic photic response parameters for an Australian native rodent, Notomys alexis. Under controlled conditions of constant darkness or constant light, N. alexis were found to 'free-run', and with periods different from 24 hours. Under LD cycles N. alexis were strictly nocturnal although, compared to other rodents, entrainment to LD cycles was relatively unstable. This may indicate that N. alexis are not strongly dependent on the LD cycle as a zeitgeber.

Responsiveness to melatonin and its receptor expression in the aging circadian clock of mice

1997 ◽  
Vol 273 (6) ◽  
pp. R1855-R1860 ◽  
Author(s):  
Susan Benloucif ◽  
Monica I. Masana ◽  
Margarita L. Dubocovich
Keyword(s):  
Suprachiasmatic Nucleus ◽  
Phase Shifts ◽  
Receptor Expression ◽  
Circadian Activity ◽  
Melatonin Receptor ◽  
Activity Rhythms ◽  
Age Related ◽  
Melatonin Administration ◽  
Timing System ◽  
Circadian Timing System

This study determined the effect of age on the efficacy of melatonin treatment to phase shift circadian activity rhythms and on melatonin receptor expression in the suprachiasmatic nucleus (SCN) and paraventricular nucleus of the thalamus (PVNT) of C3H/HeN mice. The circadian rhythm of 2-[125I]iodomelatonin binding, assessed at three times of the day [circadian times (CT) 2, 10, and 18], showed a modest age-related decrease in the SCN but not the PVNT of old C3H/HeN mice (24 mo). There was a tendency for age to reduce Mel1a melatonin receptor mRNA expression in the suprachiasmatic nucleus during the day, but not during the night. The magnitude of phase shifts of circadian activity rhythms (advances or delays) induced by administration of melatonin at CT 10 or CT 2 was identical in young and old C3H/HeN mice. Together, these results suggest that the decrease in melatonin receptor expression in the SCN had little effect on melatonin-induced phase shifts of circadian activity rhythms. We conclude that the responsiveness of the circadian timing system to melatonin administration does not decrease with age.

A Morning Bright Light Therapy Intervention to Improve Circadian Health in Adolescent Cancer Survivors: Methods and Preliminary Feasibility

2020 ◽  
pp. 104345422097545
Author(s):  
Valerie E. Rogers ◽  
Catriona Mowbray ◽  
Zahra Rahmaty ◽  
Pamela S. Hinds
Keyword(s):  
Circadian Rhythm ◽  
Circadian Rhythms ◽  
Adverse Events ◽  
Health Outcomes ◽  
Cancer Survivors ◽  
Light Therapy ◽  
Circadian Activity ◽  
Activity Rhythms ◽  
Adolescent Cancer ◽  
Therapy Intervention

Circadian rhythm disturbances are common among children with cancer, and are associated with poor health outcomes. Social zeitgeber theory suggests that intervening in the cascade of events that disrupt circadian rhythms may improve health outcomes. Light, most potently sunlight, is a “zeitgeber,” or environmental cue instrumental in maintaining entrainment of circadian rhythms. Bright white light (BWL) therapy, a proxy for sunlight, has been used successfully to prevent deterioration of circadian rhythms in adult cancer patients, and to reentrain these rhythms in adolescents with circadian rhythm disorders. This study aimed to develop and assess preliminary feasibility of a BWL therapy intervention for supporting circadian health of adolescent cancer survivors. We hypothesized that adolescents could independently manage BWL in their home, coordinated by nurses using a mail-, phone- and internet-based format, with minimal side effects. Adolescents were instructed to use BWL for 30 minutes daily on awakening, for 28 days. Actigraphs, measuring the circadian activity rhythms of sleep and wake, were worn for 7 days at baseline and Week 4. Adverse events were screened serially. Analyses were descriptive and nonparametric. Eight adolescents participated. On average, BWL was used on 61% of days, for 15 minutes per day. Adverse events were generally mild, although one participant discontinued BWL due to persistent BWL-related nausea. This nurse-guided remote BWL therapy intervention in adolescent cancer survivors demonstrated preliminary feasibility. Future studies with larger samples are required to verify the feasibility of this study, and to determine its safety and effectiveness in supporting circadian activity rhythms.

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