Study sheds light on how the brain shifts between sleep/awake states under anesthesia

Aug 26, 2010

Despite the fact that an estimated 25 million patients per year in the U.S. undergo surgeries using general anesthesia, scientists have only been able to hypothesize exactly how anesthetics interact with the central nervous system. They previously thought that the processes of "going under" and waking up from anesthesia affected the brain in the same way.

Now, researchers at the University of Pennsylvania School of Medicine have established in animal models that the brain comes in and out of a state of induced unconsciousness through different processes. The findings, published in PLoS One, may help researchers better understand serious sleep disorders and states of impaired consciousness such as comas.

"One major unanswered question in neuroscience is how the brain transitions between conscious and unconscious states," said senior author Max B. Kelz, MD, PhD, assistant professor of Anesthesiology and Critical Care. "Our results suggest that the brain keeps track of whether it is conscious or offline in an unconscious state. We are working to understand the mechanisms through which the brain accomplishes this feat. Studying general anesthetics in animal models offers a controllable means to investigate this newly recognized behavioral barrier that separates conscious from unconscious states."

Induction of anesthesia is commonly attributed to drug-induced modifications of neuronal function, whereas emergence from anesthesia has been thought to occur passively, with the elimination of the anesthetic from sites in the (CNS). If this were true, then CNS anesthetic concentrations on induction and emergence would be indistinguishable.

However, by generating anesthetic dose response data in both and mice, the researchers demonstrated that the forward and reverse paths through which anesthetic-induced unconsciousness arises and dissipates are not identical. Instead the animal subjects exhibited a delay in return to a state of consciousness despite the reduced concentration of the anesthetic.

The researchers observed that once a group of animal subjects underwent a transition from wakefulness to anesthetic-induced unconsciousness, the subjects exhibited resistance to the return of the wakeful state. Based on their findings, the authors propose a fundamental and biologically conserved state, which they call neural inertia, a tendency of the CNS to resist transitions between consciousness and unconsciousness.

"The findings from this study may provide insights into the regulation of sleep as well as states in which return of consciousness is pathologically impaired such as some types of coma," said Kelz. "This line of research may one day help us to develop novel drugs and targeted therapies for patients who have different forms of or who have the potential to awaken from coma but remain stuck in comatose states for months or years."

Explore further: Lost memories might be able to be restored, new study indicates

add to favorites email to friend print save as pdf

Related Stories

Anesthesia and Alzheimer's

Apr 25, 2008

In studies of human brain cells, the widely-used anesthetic desflurane does not contribute to increased production of amyloid-beta protein; however, when combined with low oxygen conditions, it can produce more of this Alzheimer’s ...

Recommended for you

Researchers unlock mystery of skin's sensory abilities

17 hours ago

Humans' ability to detect the direction of movement of stimuli in their sensory world is critical to survival. Much of this stimuli detection comes from sight and sound, but little is known about how the ...

Tackling neurotransmission precision

Dec 18, 2014

Behind all motor, sensory and memory functions, calcium ions are in the brain, making those functions possible. Yet neuroscientists do not entirely understand how fast calcium ions reach their targets inside ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.