Women with irritable bowel syndrome cannot effectively turn-off a pain modulation mechanism in the brain, which causes them to be more sensitive to abdominal pain, say UCLA researchers. The findings, appearing in the Journal of Neuroscience, may lead to a greater understanding of irritable bowel syndrome and novel new treatments. Affecting 10 to 15 percent of the U.S. population, irritable bowel syndrome (IBS) causes discomfort in the abdomen, along with diarrhea and/or constipation. Currently there is no cure and treatments only lessen symptoms. "A large number of patients with irritable bowel disease suffer major decrements in their quality of life," said UCLA's Dr. Emeran Mayer. "Our research team studies the brain activity underlying the pain experience in patients with chronic pain disorders like IBS."
Previous research has shown that the brain can prepare for pain in ways that either inhibit or amplify the sensory experience. When expected pain is predictable, tolerable, inescapable and will result in a reward - like a doctor's injection to improve your health - most people tell their brain to inhibit the intensity of the pain experience. One way they do this is by turning down the gain within brain circuits that process the pain signal -- similar to turning down the volume on a stereo amplifier - in order to make the body's perception of pain less acute.
When anticipated pain is perceived as escapable and potentially dangerous - such as burning your hand on a hot stove - most people tell their brain to amplify the pain response, which is like increasing the volume on a stereo amplifier, in order to react faster and minimize possible tissue damage. The new study showed that IBS patients cannot turn down the "amplifier" of the pain response, even when expected pain is not dangerous, which makes them more sensitive to even mild discomfort.
"The abdominal hypersensitivity that is a hallmark of IBS may represent an inability to downregulate pain and emotional arousal circuits, said co-researcher Steven Berman. "IBS patients may have an inability to inhibit the competing tendency to upregulate emotional arousal in order to escape pain faster."
As expected, IBS patients reported lower pain thresholds and more anxiety than healthy women. Anxiety correlated with more brain activity during anticipation, but not receipt of pain. "Additional research may reveal that some pain patients have a primary difference in their brain's reaction to pain," said Mayer. "If we can identify receptors and genes associated with these abnormal brain responses, we should improve both identification of predisposed patients and development of effective remedies."
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Source: University of California - Los Angeles
