Pain
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Randomized Controlled Trial
Efficacy of melatonin in the treatment of endometriosis: a phase II, randomized, double-blind, placebo-controlled trial.
Endometriosis-associated chronic pelvic pain (EACPP) presents with an intense inflammatory reaction. Melatonin has emerged as an important analgesic, antioxidant, and antiinflammatory agent. This trial investigates the effects of melatonin compared with a placebo on EACPP, brain-derived neurotrophic factor (BDNF) level, and sleep quality. ⋯ Melatonin improved sleep quality, reduced the risk of using an analgesic by 80%, and reduced BNDF levels independently of its effect on pain. This study provides additional evidence regarding the analgesic effects of melatonin on EACPP and melatonin's ability to improve sleep quality. Additionally, the study revealed that melatonin modulates the secretion of BDNF and pain through distinct mechanisms.
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Despite similar behavioral hypersensitivity, acute and chronic pain have distinct neural bases. We used intraplantar injection of complete Freund's adjuvant to directly compare activity of pain-modulating neurons in the rostral ventromedial medulla (RVM) in acute vs chronic inflammation. Heat-evoked and von Frey-evoked withdrawal reflexes and corresponding RVM neuronal activity were recorded in lightly anesthetized animals either during the first hour after complete Freund's adjuvant injection (acute) or 3 to 10 days later (chronic). ⋯ During early immune-mediated inflammation, ON-cell spontaneous activity promotes hyperalgesia. After inflammation is established, the antinociceptive influence of OFF-cells is dominant, yet the lowered threshold for the OFF-cell pause allows behavioral responses to stimuli that would normally be considered innocuous. The efficacy of OFF-cells in counteracting sensitization of ascending transmission pathways could therefore be an important determining factor in development of chronic inflammatory pain.
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Perception of emotional stimuli alters the perception of pain. Although facial expressions are powerful emotional cues - the expression of pain especially plays a crucial role for the experience and communication of pain - research on their influence on pain perception is scarce. In addition, the opposite effect of pain on the processing of emotion has been elucidated even less. ⋯ Most important, painful thermal stimuli increased the arousal of simultaneously presented pain expressions, and in turn, pain expressions resulted in higher pain ratings compared to all other facial expressions. These findings demonstrate that the modulation of pain and emotion is bidirectional with pain faces being mostly prone to having mutual influences, and support the view of interconnections between pain and emotion. Furthermore, the special relevance of pain faces for the processing of pain was demonstrated.