The first real-time imaging of intact circadian neural networks, courtesy of a fruit fly's "brain in a jar," has revealed the interior mechanisms that create jet lag, researchers say.
Scientists at the University of California, Irvine, have employed sensitive imaging techniques to record activity in fruit fly brains that were kept alive for six days in a laboratory petri dish.
By using a highly sensitive low-light camera to record neural activity of circadian clocks at the level of individual cells, they've determined the manner in which the circadian "body clock" circuit can be "reset" by light, they report in the journal Current Biology.
It's the first direct evidence of how particular neurons in circadian neural networks can react to light cues of the sort that can be affected by rapid travel from one time zone to another, such as when flying from New York to London, they said.
Daylight is one of the most powerful circadian cues that organisms use to make daily adjustments in their metabolism and daily activities, and a desynchronization of their circadian neurons as a result of changes in daylight cues is a central feature of light-induced jet lag, they explain.
"Remarkably, our work indicates that the way you feel while jet-lagged exactly reflects what your nervous system is experiencing: a profound loss of synchrony," says Todd C. Holmes, UCI professor of biophysics and physiology.
The researchers found they could shift the biological clock in the fruit fly brains two hours ahead of their original schedules with just a single light pulse cue, in a process they've dubbed "phase retuning."
After being briefly desynchronized, the entire neural circadian circuit slowly settles into a new state of synchrony, they discovered.
Normally, the researcher noted, circadian circuit light response -- which brings recovery from jet lag -- needs four days for the time shift tested in their experiment.
That suggests a temporary weakening of synchronization of those neurons governed by circadian patterns could allow a quicker adaptation, possible in just two days, by enabling a "phase retuning" to the new time zone's light cues, the researchers say.
"That two-day difference is quite a bit if it means you feel great from the beginning of your arrival, say, in Italy," Holmes said. "You're going to feel bad on the plane in any event, so it's best to get the adjustment over with so you can enjoy your destination.
"I'm certain this will lead to treatments that'll have a big impact on our travel practices."
