Study in mice sheds light on Ambien side effects

By Julie Steenhuysen

CHICAGO (Reuters) - A new study in mice may help explain some of the rare but strange side effects in people taking the sleep drug Ambien, including sleep walking, midnight binges and even driving while not fully awake.

Ambien, made by Sanofi-Aventis, can shut down powerful brain circuits responsible for inhibiting brain activity under certain circumstances, leaving other brain circuits unchecked, researchers at Georgetown University Medical Center in Washington said.

"You are kind of releasing the brakes," said Molly Huntsman of Georgetown, who worked on the study that appears in the Proceedings of the National Academy of Sciences.

This may stimulate brain circuits that would normally be silenced. "In a way, Ambien is awakening other circuits because the brakes are not in place," Huntsman said.

To study the effects of the drug, known generically as zolpidem, Huntsman and colleagues conducted a series of experiments in mice.

The team wanted to see how mice on the drug would respond when the researchers trimmed their whiskers, which rodents use as their primary sensory system -- much like humans rely on vision to take in information about the world.

The team found that mice that were deprived of this sensory information had changes in their brain that affected the way they responded to the drug Ambien.

"It's a population of neurons that is normally in place to stop activity. We find what Ambien does is inhibit their function to inhibit," Huntsman said in a telephone interview.