Jet Lag Upsets Brain's Internal Clocks

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FRIDAY, April 17 (HealthDay News) -- Jet lag-related sleep problems are caused by disruption of internal clocks in two neural centers, a finding that could lead to more effective treatments, say U.S. researchers.

The University of Washington research team found that jet lag upsets two separate, but linked, groups of neurons in a brain structure called the suprachiasmatic nucleus, below the hypothalamus at the base of the brain.

One group of neurons (ventral) is synchronized with deep sleep that results from physical fatigue, and the other group of neurons (dorsal) controls the dream state of rapid eye movement (REM) sleep, the researchers explained. Normally, these two groups of neurons are synchronized with each other, but they can be thrown out of synch by jet lag or shift work.

"When we impose a 22-hour light-dark cycle on animals, the ventral center can catch up, but the dorsal doesn't adapt and defaults to its own inner cycle," Horacio de la Iglesia, an associate professor of biology, said in a University of Washington news release.

When laboratory rats used to a 25-hour light-dark cycle were exposed to a 22-hour cycle, their deep sleep quickly adapted to the 22-hour cycle, but their REM sleep continued to follow a 25-hour cycle. This meant that REM sleep didn't occur in normal progression following deep sleep, the researchers noted.

"We found that after exposing rats to a shift of the light-dark timing that simulates a trip from Paris to New York, REM sleep needed six to eight days to catch up with non-REM, or deep, sleep, the sleep you usually experience in the first part of the night," de la Iglesia said.

The findings, published online April 16 in the journal Current Biology, may help fine-tune current jet lag treatments.

"We can go back to the treatments that are believed to be effective and see where they might be acting in the circuitry of these neuron centers, then refine them to be more effective," de la Iglesia said.

-- Robert Preidt

SOURCE: University of Washington, news release, April 16, 2009

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