Halting Hormone Prevents Jet Lag: Brain Molecule Steadies the Beat of Circadian Clock in Mice

Article excerpt

A molecular timekeeper called vasopressin steadies the dally rhythms of the body and may hamper acclimatization to new time zones. Mice rapidly recover from a lab form of jet lag when researchers block the hormone in the brain.

Fluctuations in physiology and behavior move to the beat of the circadian clock. Crossing time zones or working night shifts throws the body out of sync, leading to sleep and digestive problems, says neuroscientist Hitoshi Okamura of Kyoto University in Japan, who led the study. "When we face this situation," he says, "we are forced to suffer."

The tick-tocks of the mammalian circadian clock emanate from a tiny cluster of cells called the suprachiasmatic nucleus, located deep in the brain. Neurons in the suprachiasmatic nucleus communicate those rhythms to the rest of the brain and the body by pumping out the hormone vasopressin in daily cycles. So Okamura and colleagues genetically engineered mice to lack cell-surface proteins that detect the hormone in the brain.

Then the team shifted the animals' schedule of light and darkness forward by eight hours. Normal mice took eight to 10 days to adjust to the new regimen. But the engineered mice acclimated in just two to four days, the researchers report in the Oct. …