ScienceDaily (May 13, 1998) — Hershey, Pa. --- Researchers at Penn State's College of Medicine have identified a set of neurons in the brain that may contribute to some of the undesirable side effects of pain medication.

"Opioids such as morphine and morphine-like drugs still comprise the major tool for the clinical management of pain even though the drugs can have some very serious side effects," explains Ralph Lydic, Ph.D., professor of anesthesia. "This discovery means we have specifically targeted an area in the brain and a molecule that causes side effects from pain medication. We want to try and eliminate these side effects of pain medication by building another molecule to tag onto the opioid molecule. This way the opioid could block the pain, and this new molecule could prevent the side effects."

Specifically, Lydic and his team have discovered that this set of neurons may account for morphine's ability to decrease brain production of acetylcholine, a chemical known to be essential for normal rapid eye movement (REM) sleep. Often after surgery, patients have disrupted REM sleep because of pain medication. Lydic explains that REM sleep is the dreaming phase of sleep and is essential for feeling rested. Everyone has REM sleep each night, even if we do not remember our dreams. REM sleep occurs about every 90 minutes and lasts for about 20 minutes.

"We think this is a very exciting discovery. We are trying to identify specific cells in the brain where we know brain-produced chemicals have been altered because of the pain medication administered," explains Lydic. Other common side effects from pain medications can include respiratory depression, itching, constipation, urinary retention and addiction.

The Penn State researcher says the team is trying to understand brain mechanisms that regulate consciousness as they try to improve pain control and anesthesia safety. He adds, "The discovery of anesthesia is only about 150 years old, and it is important to remember that for no anesthetic or opioid do we know exactly how these drugs work to eliminate wakefulness and block the perception of pain."

Steve Mortazavi, M.D., an anesthesia resident working with Lydic, presented the work titled "Morphine Sulfate Inhibits Acetylcholine (Ach) Release in Pontine Reticular Regions Modulating Arousal, Breathing, and Pain," this week at the annual Association of University Anesthesiologists meeting in San Francisco. Other colleagues who worked on this project include Janel Thompson, and Helen Baghdoyan, Ph.D., associate professor of anesthesia and pharmacology.

This work is funded by the National Heart, Lung and Blood Institute and by the Department of Anesthesia at Penn State's College of Medicine.

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