New Ticks in our Biological Clock

Photo via flickr by Leo™

University of Michigan mathematicians and their British colleagues say they have identified the signal that the brain sends to the rest of the body to control biological rhythms, a finding that overturns a long-held theory about our internal clock.

The body’s main time-keeper resides in a region of the central brain called the suprachiasmatic nuclei, or SCN. For decades, researchers have believed that it is the rate at which SCN cells fire electrical pulses—fast during the day and slow at night—that controls time-keeping throughout the body.

The true signaling mechanism is very different: The timing signal sent from the SCN is encoded in a complex firing pattern that had previously been overlooked, the researchers concluded.

The SCN contains both clock cells (which express a gene call per1) and non-clock cells. For years, circadian-biology researchers have been recording electrical signals from a mix of both types of cells. That led to a misleading picture of the clock’s inner workings.

But the researchers at the University of Manchester in England were able to separate clock cells from non-clock cells by zeroing in on the ones that expressed the per1 gene. Then they recorded electrical signals produced exclusively by those clock cells. The pattern that emerged bolstered the audacious new theory.

The researchers found that during the day, SCN cells expressing per1 sustain an electrically excited state but do not fire. They fire for a brief period around dusk, then remain quiet throughout the night before releasing another burst of activity around dawn. This firing pattern is the signal, or code, the brain sends to the rest of the body so it can keep time.

Understanding how the human biological clock works is an essential step toward correcting sleep problems like insomnia and jet lag. New insights about the body’s central pacemaker might also, someday, advance efforts to treat diseases influenced by the internal clock, including cancer, Alzheimer’s disease and mood disorders.

“This work also raises important questions about whether the brain acts in an analog or a digital way,” said Dr. Mino Belle of University of Manchester.

via Science Daily

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