Navigation Links
After a time-shift, mixed signals from the circadian clock

Circadian rhythms in mammalian behavior, physiology, and biochemistry are controlled by the central clock within a brain structure known as the suprachiasmatic nucleus (SCN). The clock is synchronized to environmental cycles of light and dark. It is well known, from everyday experience, that adjusting to new light schedules takes several days, though the details of how this adaptation takes place are not well understood. Researchers now report findings that suggest this adaptation process does not necessarily involve a gradual and synchronous adaptation by the neurons that comprise the central circadian clock--rather, that different components of the clock tend to adapt to a shifted light schedule at two different speeds.

The work is reported in the May 24 issue of Current Biology by a research team led by Johanna H. Meijer of Leiden University Medical Center in The Netherlands.

The researchers studied clock-resetting behavior in rats that were exposed to a six-hour delay of the light schedule, a shift that mimics a transition from the eastern U.S. to western Europe. By performing electrophysiological analysis of cells that constitute the central circadian clock, the researchers made a surprising discovery: one part of the clock mechanism, represented by a dorsal (upper) group of cells, exhibited oscillations in activity that corresponded to slow resetting of the clock in response to the shifted light schedule, while another part of the clock, represented by a ventral (lower) group of cells, exhibited a distinct pattern of activity that corresponded to fast resetting of the clock.

Perhaps contributing to the different behavior of the two groups of clock cells are the effects on these cells of the neurotransmitter GABA, which the researchers found to excite the cells of the dorsal SCN while inhibiting neurons in the ventral SCN. Because GABA transmits information between the ventral and dorsal SCN, such differences in effect might influence, in complex ways, how the two groups of cells adapt to a shifted light schedule.

The authors conclude that the phases of activity in the ventral and dorsal clock shift with different speeds. During a schedule shift corresponding to a transition from the U.S. to western Europe, the ventral part of the clock is immediately synchronized to the new light schedule, but the dorsal part of the clock requires several days to adjust. This results temporarily in bimodal patterns of electrical activity that are generated by the clock within the SCN. Because electrical activity is the output of the circadian clock, the findings suggest that after a significant shift in light schedule, the rest of the brain is transiently--for a duration of about six days--exposed to complex signaling patterns from the circadian clock.

The researchers include Henk Albus, Mariska J. Vansteensel, Stephan Michel, and Johanna H. Meijer of Leiden University Medical Center; and Henk Albus and Gene D. Block of the University of Virginia. Research was supported by National Institutes of Health grant and by Leids Universitair Medisch Centrum Excellent Student trajectory.

Henk Albus, Mariska J. Vansteensel, Stephan Michel, Gene D. Block, and Johanna H. Meijer: "A GABAergic Mechanism Is Necessary for Coupling Dissociable Ventral and Dorsal Regional Oscillators within the Circadian Clock." Current Biology, Vol. 15, 886?93, May 24, 2005.


Source:Cell Press

Related biology news :

1. Bone Density Recovers After Teens Stop Injected Contraceptive
2. Youth With HIV Take More Risks After New Meds Introduced
3. Drug Offers Alternative to Surgical Treatment After Miscarriage
4. Menopause Symptoms May Come Back After Stopping Menopausal Hormone Therapy
5. After the yeast is gone bacteria continue to develop flavor of sparkling wine
6. Researchers Find Drug May Give Some Cardiac Protection 24 Hours After Heart Attack
7. Plants respond similarly to signals from friends, enemies
8. Edible bivalves as a source of human pathogens: signals between vibrios and the bivalve host.
9. Scientists discover that three overlapping signals in embryo help get the backbone right
10. Researchers make surprise discovery that some neurons can transmit three signals at once
11. Structure-building cell signals also may influence learning and memory
Post Your Comments:

(Date:6/9/2016)... Finland , June 9, 2016 ... National Police deploy Teleste,s video security solution to ensure the ... France during the major tournament ... data communications systems and services, announced today that its video ... Prefecture to back up public safety across the ...
(Date:6/2/2016)... 2016 The Department of Transport Management ... 44 million US Dollar project, for the , ... Personalization, Enrolment, and IT Infrastructure , to ... and implementation of Identity Management Solutions. Numerous renowned international vendors ... Decatur was selected for the most compliant and ...
(Date:6/1/2016)... , June 1, 2016 ... in Election Administration and Criminal Identification to Boost Global ... a recently released TechSci Research report, " Global Biometrics ... Region, Competition Forecast and Opportunities, 2011 - 2021", the ... billion by 2021, on account of growing security concerns ...
Breaking Biology News(10 mins):
(Date:6/27/2016)... June 27, 2016   Ginkgo Bioworks , a ... engineering, was today awarded as one of the ... the world,s most innovative companies. Ginkgo Bioworks is ... the real world in the nutrition, health and ... directly with customers including Fortune 500 companies to ...
(Date:6/24/2016)... (PRWEB) , ... June 24, 2016 , ... Researchers at ... most commonly-identified miRNAs in people with peritoneal or pleural mesothelioma. Their findings are the ... read it now. , Diagnostic biomarkers are signposts in the blood, lung fluid ...
(Date:6/23/2016)... , June 23, 2016 /PRNewswire/ - FACIT has ... Ontario biotechnology company, Propellon Therapeutics Inc. ... and commercialization of a portfolio of first-in-class WDR5 ... targets such as WDR5 represent an exciting class ... in precision medicine for cancer patients. Substantial advances ...
(Date:6/23/2016)... SANTA MONICA, Calif. , June 23, 2016  The Prostate Cancer ... to pioneer increasingly precise treatments and faster cures for prostate cancer. Members of ... 77 institutions across 15 countries. Read More About the ... ... ...
Breaking Biology Technology: