Every night we all participate in a small biological miracle—the
transition from wakefulness to sleep. Last September researchers
at Washington State University made a notable advance in
understanding the chemical trigger that allows that shift to
happen. The key to sleep turns out to be one of the body’s most
important molecules: ATP, the compound that stores energy for
use in metabolism. Neurobiologist James Krueger and his
colleagues discovered that repeated firing of neurons in the
brain while we are awake causes them to release ATP into the
spaces between the cells. As the molecule accumulates, it bonds
to neighboring neurons and glial (support) cells; this allows
the cells to absorb other chemicals—such as tumor necrosis
factor and interleukin 1—that most likely put those cells into a
sleep state. This finding implies that sleep “is not a whole
brain phenomenon,” Krueger says. It occurs only in neural
circuits that have been most active during the day and so have
released the most ATP. Translation: Some