By activating certain neurons only at a specific time, American biologists have succeeded in reducing the harmful effects of jet lag on mice.
This could revolutionize the daily life of frequent travelers and people working shift schedules. American biologists have succeeded in developing a tool against jet lag on mice by activating a subset of neurons involved in the establishment of daily rhythms. The results were published Thursday July 12 in the scientific journal Neuron.
“We were wondering how the body’s clock adjusts for different time zones,” says Erick Herzog, who led the study at Washington University in Saint Louis, Missouri. All of the body’s essential functions are synchronized with time by the body’s circadian clock. A small area at the bottom of the brain near the mouth reminds us to wake up and go to bed at regular times each day. This internal clock is scientifically called the suprachiasmatic nucleus or NSC. When this system is disrupted, by shifted work schedules or a trip to another continent for example, the 20,000 nerve cells in this area struggle to adjust the body to a new rhythm.
To carry out their study, Herzog and his colleagues started from “the hypothesis that the neurons of the NSC were like grandmothers responsible for telling everyone what to do” by producing VIP (vasoactive intestinal polypeptide) neurons, essential to communicate and synchronize daily rhythms.
“The code used by the VIP neurons is the key”
A student in Herzog’s laboratory named Cristina Mazuski therefore developed a system to determine the classical mechanism of VIP neurons. Thanks to this, scientists were able to identify two categories in this family: tonic VIP neurons, which act at a regular rate at spaced intervals, and irregular VIP neurons.
They then plunged mice into complete darkness for several days and nights without giving them any indication of what time it was. Thanks to the optogenetic technique (a new field of research and application, combining optics to the genetics), they activated VIP neurons only at the same time each time. “It was an important step in understanding how the suprachiasmatic nucleus keeps organisms in phase with the local light,” explains Cristina Mazuski. They and her colleagues then discovered that mice recovered from jet lag faster when VIP neurons were activated at irregular intervals.
“We are starting to understand how the time system in the brain is wired and have established that the code used by VIP neurons is really the key to setting up the body’s daily program,” says Herzog.
In October 2017, the University of Saint Louis had already published a study on the subject. The researchers found that when there was an excess of VIP, cells lost their ability to synchronize. Hopefully their work will eventually lead to a drug that can reduce the damaging effects of jet lag for people who travel a lot or work shift schedules.
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