Astrocytes Found to Regulate Sleep Depth and Duration

Why do some people sleep deeply through the night and others toss and turn for hours? According to researchers at UC San Francisco, astrocytes have a role in determing how long and how deeply animals sleep.

"This is the first example where someone did an acute and fast manipulation of astrocytes and showed that it was able to actually affect sleep," said Trisha Vaidyanathan, first author of a paper published in eLife last week. "That positions astrocytes as an active player in sleep."

Comprising an estimated 25 to 30 percent of brain cells, astrocytes blanket the brain with countless bushy tendrils. This coverage allows each individual astrocyte to listen in on tens of thousands of synapses. The plentiful cells connect to each other through specialized channels, which researchers think may allow astrocytes located across the brain to function as one unified network. The hyperconnected and ubiquitous astrocytes might be able to drive synchronized signaling in neurons.

Senior author Kira Poskanzer and her team tracked changes in slow-wave activity in the brains of mice while manipulating astrocytes using a drug that can switch the cells on in genetically engineered animals. The researchers found that firing up astrocytes led to more slow-wave activity, and thus sleep, in the mice.

The team wanted to examine astrocytes' role in finer detail, asking how these cells exert their influence and what aspects of sleep they manage. In addition to the specialized junctions that join neighboring astrocytes, these cells are studded with a variety of receptor molecules that allow them to respond to signals coming from neurons and other types of cells around them. In the study the team hijacked two of these molecules, the Gi and Gq receptors, and found that they each appeared to control a distinct aspect of sleep. Activating Gq receptors made animals sleep longer, but not more deeply, according to slow-wave measurements, while engaging Gi receptors put into a much deeper slumber without affecting sleep duration.

"Depth and duration are aspects of sleep that often get glossed over and lumped together even in neuroscience," said Vaidyanathan. "But picking apart these different aspects and how they're regulated is going to be important down the line for creating more specific sleep treatments."