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Placebo analgesia can be blocked by opioid antagonists such as naloxone but not by hypnosis, mindfulness, and related techniques, which suggests that pain perception, but not appraisal and emotional response to pain, is dependent on opioid signaling. To test this hypothesis, investigators examined whether naloxone infusion (versus saline) altered the effectiveness of two mental techniques (mental imagery and relative relief) to alleviate heat-related pain in 20 healthy, drug-free participants.
Participants received heat that they previously rated as moderately painful. Mental imagery involved imagining a scene in which heat is pleasant rather than painful (e.g., warming one's hands at a fireplace on a cold night). Relative relief involved vi…