Light Pulses Do Not Induce C-Fos or Per1 in the SCN of Hamsters That Fail to Reentrain to the Photocycle
- 1 August 2004
- journal article
- research article
- Published by SAGE Publications in Journal of Biological Rhythms
- Vol. 19 (4), 287-296
- https://doi.org/10.1177/0748730404266771
Abstract
Circadian activity rhythms of most Siberian hamsters ( Phodopus sungorus sungorus) fail to reentrain to a 5-h phase shift of the light-dark (LD) cycle. Instead, their rhythms free-run at periods close to 25 h despite the continued presence of the LD cycle. This lack of behavioral reentrainment necessarily means that molecular oscillators in the master circadian pacemaker, the SCN, were unable to reentrain as well. The authors tested the hypothesis that a phase shift of the LD cycle rendered the SCN incapable of responding to photic input. Animals were exposed to a 5-h phase delay of the photocycle, and activity rhythms were monitored until a lack of reentrainment was confirmed. Hamsters were then housed in constant darkness for 24 h and administered a 30-min light pulse 2 circadian hours after activity onset. Brains were then removed, and tissue sections containing the SCN were processed for in situ hybridization. Sections were probed with Siberian hamster c-fosand per1mRNA probes because light rapidly induces these 2 genes in the SCN during subjective night but not at other circadian phases. Light pulses induced robust expression of both genes in all animals that reentrained to theLDcycle, but no expression was observed in any animal that failed to reentrain. None of the animals exhibited an intermediate response. This finding is the first report of acute shift in a photocycle eliminating photosensitivity in the SCN and suggests that a specific pattern of light exposure may desensitize the SCN to subsequent photic input.Keywords
This publication has 34 references indexed in Scilit:
- Coordination of circadian timing in mammalsNature, 2002
- Neurotransmitters of the retino-hypothalamic tractCell and tissue research, 2002
- GENETICS OF THE MAMMALIAN CIRCADIAN SYSTEM: Photic Entrainment, Circadian Pacemaker Mechanisms, and Posttranslational RegulationAnnual Review of Genetics, 2000
- Clock genes outside the suprachiasmatic nucleus involved in manifestation of locomotor activity rhythm in ratsEuropean Journal of Neuroscience, 2000
- Phase Shift Magnitude and Direction Determine Whether Siberian Hamsters Reentrain to the PhotocycleJournal of Biological Rhythms, 1998
- Ontogeny of a Photic Response in the Suprachiasmatic Nucleus in the Siberian Hamster (Phodopus sungorus)European Journal of Neuroscience, 1995
- Photic and circadian regulation of c-fos gene expression in the hamster suprachiasmatic nucleusNeuron, 1990
- Circadian and Photoperiodic Effects of Brief Light Pulses in Male Djungarian Hamsters1Biology of Reproduction, 1986
- Biological Rhythms and Animal BehaviorAnnual Review of Psychology, 1975