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Touch Perception Altered by Chronic Pain and by Opioid Blockade
Laura K Case1, Marta Čeko1, John L Gracely1
1National Center for Complementary and Integrative Health, NIH , Bethesda, Maryland 20892.
Eneuro
|March 30, 2016
Summary
Endogenous opioids influence how we perceive touch. Opioid blockade altered touch pleasantness in healthy adults but decreased touch intensity perception in fibromyalgia patients, indicating altered opioid function in chronic pain.
Area of Science:
- Neuroscience
- Psychology
- Pain Research
Background:
- Touch is crucial for social behavior and communication, with endogenous opioids potentially mediating its rewarding aspects.
- Previous studies in monkeys suggest opioid blockade increases affiliative behaviors, hinting at enhanced touch enjoyment.
- Fibromyalgia patients exhibit reduced opioid receptor availability, suggesting altered endogenous opioid system function.
Purpose of the Study:
- To investigate the role of endogenous opioids in the perception of affective touch in healthy adults.
- To examine opioid system function in patients with fibromyalgia, a chronic pain condition.
- To assess the impact of µ-opioid blockade via naloxone on touch pleasantness and intensity perception.
Main Methods:
- Administration of naloxone (an opioid antagonist) to healthy controls and fibromyalgia patients.
- Direct observation of the effects of µ-opioid blockade on perceived pleasantness and intensity of touch.
- Assessment of C-tactile fiber function by comparing responses to slow versus fast brushing.
Main Results:
- Fibromyalgia patients at baseline showed blunted discrimination between slow and fast touch for intensity and pleasantness, indicating impaired C-tactile processing.
- Opioid blockade with naloxone tended to increase touch pleasantness in healthy individuals but significantly decreased touch intensity perception in fibromyalgia patients.
- In healthy individuals, naloxone-induced increases in pleasantness correlated with a decreased preference for slow touch, suggesting opioid influence on C-tactile input processing.
Conclusions:
- Endogenous opioids play a significant role in modulating the perception of touch.
- Altered opioid system functioning is evident in patients with chronic pain conditions like fibromyalgia.
- These findings provide further evidence for the involvement of the endogenous opioid system in affective touch processing and its dysregulation in chronic pain.
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