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'Grandmother' Cells in the Brain Could Help the Body Shake Off Jet Lag
Scientists may be one step to closer to a "cure" for jet lag, according to a new study done in mice.
Jet lag occurs when the "master clock" in the brain falls out of sync with the actual time. That master clock thinks it's time to go to bed, whereas your watch says it's lunch time.
The master clock is found in an area of the brain called the suprachiasmatic nucleus (SCN). Nerve cells in the SCN take cues from the sun, syncing themselves to the 24-hour rotation of the Earth. [The Science of Jet Lag: 5 Surprising Findings]
But some of the cells in the SCN have more influence than others, according to the study, published today (July 12) in the journal Neuron. That's because around 10 percent of these cells — in both mice and humans — produce a molecule called "vasoactive intestinal polypeptide," or VIP. This very important molecule plays an essential role in how nerve cells communicate and sync with one another.
"We hypothesized that VIP neurons are like the grandmothers who are in charge of telling everyone what to do," senior study Erik Herzog, a biology professor at Washington University in St. Louis, said in a statement. But it was unknown how neuron activity led to the release of VIP neurons, according to the study.
So, to tease out how the VIP neurons talked to each other, the researchers started by recording the electrical impulses that pass through neurons and send information to neighboring cells — also known as the "action potential" — in a set of VIP neurons in a lab dish for three days.
They found that VIP neurons communicated in two ways: "Tonic" VIP neurons fired quite steadily, whereas "irregular" VIP neurons fired in double or triple bursts, with equal spaces of non-activity in between, according to the study.
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Next, the researchers aimed to "hack" these neurons in mouse brains, in order to reset their master clocks. To do so, they first needed to disrupt the master clocks in the mice: they kept the animals in the dark all day and night without any clues from the environment as to the time. Then, to "hack" the VIP neurons, the researchers delivered a zap to the cells at the same time every day, which they say was akin to flying to a new time zone, according to the statement.
The mice took longer to adapt to the "new time zone" if the VIP neurons were firing steadily, the researchers found. But when the neurons fired irregularly, the mice were able to adapt more rapidly. The difference? It was the irregular firing pattern that caused the neurons to release the VIP chemicals, Herzog said.
They also found that by activating the VIP neurons, the mice changed their wheel-running behavior. When these neurons were activated, the mice exerted less activity, running less in their wheels. This "suggests a role for VIP neurons in regulating circadian behaviors including sleep timing," the researchers wrote in the study.
"VIP, we think, is the juice that is capable of shifting the clock faster," Herzog said. The findings raise the possibility of a molecule researchers could target as a treatment for jet lag; namely, VIP. If scientists could get cells to release VIP on cue, it could potentially help people get over jet lag.
Because the study was done in mice, however, more research is needed to confirm the findings in humans.
Originally published on Live Science.
Yasemin is a staff writer at Live Science, covering health, neuroscience and biology. Her work has appeared in Scientific American, Science and the San Jose Mercury News. She has a bachelor's degree in biomedical engineering from the University of Connecticut and a graduate certificate in science communication from the University of California, Santa Cruz.