Scientists have succeeded in pinpointing how the sugar in food turns off the brain cells that keep us awake and makes us crave a siesta after a big meal. Although it has been known for a while that people and animals become less active and sleepy after a meal, the brain signals that are responsible for this were not understood.
Dennis Burdakov, a researcher at the University of Manchester in England who led the study, and his team, worked with specially engineered mice to demonstrate exactly how glucose blocks or “inhibits” the brain cells that make orexins. Orexins are tiny proteins that regulate our state of consciousness and respond to the ever-changing body energy state with changes in arousal, food seeking, hormone release and metabolic rate to ensure that the brain always has adequate glucose.
By genetically manipulating the mice to produce a florescent protein that lights up only in the orexin cells, the researchers could study how glucose reacts in those neurons.
Specifically, they “identified the pore in the membrane of orexin-producing cells that is responsible for the inhibiting effect of glucose,” Burdakov said.
“This previously unknown mechanism is so sensitive, it can detect minute changes in glucose levels, the type that occurs between meals, for example. This may well provide an explanation for after-meal tiredness and why it is difficult to sleep when hungry.”
Malfunction of the orexin brain cells can cause narcolepsy, when a person can’t stay awake, and is tied to obesity. A knowledge of how glucose stops orexin neurons' 'firing' can help to understand what happens in people with sleep disorders or obesity.
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