Different Neural Pathways at Work Going Under, Coming Out of Anesthesia

Mouse study on brain's orexin system could lead to new drugs with fewer side effects

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MONDAY, Jan. 21, 2008 (HealthDay News) -- The neural pathway that regulates recovery of consciousness from general anesthesia is different from the one that's affected by drugs used to put patients to sleep during surgery.

That's the conclusion of a University of Pennsylvania School of Medicine study that may help in the development of improved anesthesia drugs, the researchers said.

The researchers focused on specialized neurons called orexins that regulate the body's wakeful state. They found that mice with damaged orexin systems -- similar to humans with narcolepsy -- took much longer to awake from general anesthesia than mice with normal orexin signaling systems.

However, the mice with faulty orexin systems did not fall asleep faster than normal mice when given a general anesthetic. This suggests that different processes are involved when a general anesthetic takes effect and when it wears off, the researchers said.

"The modern expectation is that anesthesiologists can simply flip a consciousness switch as easily as we might turn the room lights on or off," study author Dr. Max. B. Kelz, an assistant professor in the department of anesthesiology and critical care at the Mahoney Institute of Neurological Sciences, said in a prepared statement.

"However, what patients do not realize is that despite 160 years of widespread clinical use, the mechanisms through which the state of anesthesia arises and dissipates remain unknown," he said.

Kelz and his colleagues hope further research will lead to new ways to administer anesthesia and promote a quick, safe return to consciousness, particularly for patients who have difficulty waking up or those -- such as the elderly and people with neurodegenerative disorders -- who are more prone to anesthesia side effects.

The study findings were published this month in the journal Proceedings of the National Academy of Sciences.

More information

The American Society of Anesthesiologists has more about anesthesiology.

SOURCE: University of Pennsylvannia, news release, January 2008

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