JETLAG

Ask frequent flyers what they hate most about intercontinental travel and jet lag will top the list. Our biological clock can take days to reset, wreaking havoc on sleep patterns. Fortunately, a jet-lag pill may not be far away.

The clock is housed in the suprachiasmatic nucleus (SCN), a tiny cellular enclave tucked in the middle of our head. The SCN's football-shaped halves, each bread crumb-size, influence circadian variations in body temperature, memory, even the strength of our grip.

The clock requires no light to run: rats raised in lifelong darkness still show 24-hour rhythms. But without light cues, the SCN works like an imitation Rolex, slowly drifting from its proper setting.

For travelers tortured by traversing time zones, the question is how to reset the clock quickly. Researchers have identified patterns of artificial light that advance the clock, so expect "light rooms" in airports and hotels before long. But a truly convenient jet-lag cure--a pill that flight attendants could pass out with the peanuts--requires a chemical solution. Martha Gillette, Ph.D., at the University of Illinois, finds it takes a chemical cocktail to reset the clock.

When Gillette takes cells from the SCN and bathes them in cAMP (cyclic adenosine monophosphate), a ubiquitous cellular messenger, the dock moves ahead about four and a half hours--but only in the day. A related chemical, cGMP (cyclic guanosine monophosphate), advances the clock up to six hours, but only at night. Around dusk and dawn, only the hormone melatonin is effective.

Because cells all over the body use cAMP and cGMP, they aren't suitable for a jet-lag pill: they may cause too many side effects. But Gillette suspects researchers will find other neurochemicals that work largely on the SCN.

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