Twelve-hour days in the brain and behavior of split hamsters.
Summary of "Twelve-hour days in the brain and behavior of split hamsters."
Hamsters will spontaneously 'split' and exhibit two rest-activity cycles each day when housed in constant light (LL). The suprachiasmatic nucleus (SCN) is the locus of a brain clock organizing circadian rhythmicity. In split hamsters, the right and left SCN oscillate 12 h out of phase with each other, and the twice-daily locomotor bouts alternately correspond to one or the other. This unique configuration of the circadian system is useful for investigation of SCN communication to efferent targets. To track phase and period in the SCN and its targets, we measured wheel-running and FOS expression in the brains of split and unsplit hamsters housed in LL or light-dark cycles. The amount and duration of activity before splitting were correlated with latency to split, suggesting behavioral feedback to circadian organization. LL induced a robust rhythm in the SCN core, regardless of splitting. The split hamsters' SCN exhibited 24-h rhythms of FOS that cycled in antiphase between left and right sides and between core and shell subregions. In contrast, the medial preoptic area, paraventricular nucleus of the hypothalamus, dorsomedial hypothalamus and orexin-A neurons all exhibited 12-h rhythms of FOS expression, in-phase between hemispheres, with some detectable right-left differences in amplitude. Importantly, in all conditions studied, the onset of FOS expression in targets occurred at a common phase reference point of the SCN oscillation, suggesting that each SCN may signal these targets once daily. Finally, the transduction of 24-h SCN rhythms to 12-h extra-SCN rhythms indicates that each SCN signals both ipsilateral and contralateral targets.
Affiliation
Department of Psychology, Columbia University, New York, NY, USA Department of Psychology, Barnard College, New York, NY, USA Department of Pathology and Cell Biology, Columbia University Medical Center, New York, NY, USA.
Journal Details
This article was published in the following journal.
Name: The European journal of neuroscience
ISSN: 1460-9568
Pages:
Links
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/22703520
- DOI: http://dx.doi.org/10.1111/j.1460-9568.2012.08166.x
Medical and Biotech [MESH] Definitions
Split-brain Procedure
Complete severing of the CORPUS CALLOSUM. In humans it is usually performed to treat medically intractable, multifocal EPILEPSY. EXPERIMENTAL ANIMAL MODELS of split brain preparations are used in research.
Higher Nervous Activity
A term used in Eastern European research literature on brain and behavior physiology for cortical functions. It refers to the highest level of integrative function of the brain, centered in the CEREBRAL CORTEX, regulating language, thought, and behavior via sensory, motor, and cognitive processes.
Infant Mortality
Postnatal deaths from BIRTH to 365 days after birth in a given population. Postneonatal mortality represents deaths between 28 days and 365 days after birth (as defined by National Center for Health Statistics). Neonatal mortality represents deaths from birth to 27 days after birth.
Maximum Allowable Concentration
The maximum exposure to a biologically active physical or chemical agent that is allowed during an 8-hour period (a workday) in a population of workers, or during a 24-hour period in the general population, which does not appear to cause appreciable harm, whether immediate or delayed for any period, in the target population. (From Lewis Dictionary of Toxicology, 1st ed)
Premature Birth
CHILDBIRTH before 37 weeks of PREGNANCY (259 days from the first day of the mother's last menstrual period, or 245 days after FERTILIZATION).
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