The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial
Effects of oxytocin on placebo and nocebo effects in a pain conditioning paradigm: a randomized controlled trial.
Oxytocin has been shown to increase trust, decrease anxiety, and affect learning as has been observed in conditioning paradigms. Trust, anxiety, and learning are important factors that influence placebo effects. In this study, we investigated whether oxytocin can increase placebo analgesia, decrease nocebo hyperalgesia, and influence extinction processes of both. ⋯ PERSPECTIVE: The present study demonstrated that placebo analgesia and nocebo hyperalgesia can be successfully induced by conditioning and verbal suggestions. We could not confirm the hypothesis that oxytocin affects either of these phenomena. Other pharmacological agents and behavioral manipulations for increasing placebo and decreasing nocebo effects should be investigated.
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Trauma survivors may suffer from post-traumatic stress disorder (PTSD), elevated post-traumatic guilt (PG), and alterations in the pain system. However, the association between PG and alterations in pain perception and modulation among trauma survivors has not been established, nor has the possible underlying role of PG. This longitudinal study investigated: 1) the unique contribution of PG in predicting pain perception and modulation, while controlling for PTSD symptoms; and 2) the mediating role of PG in explaining pain perception and modulation among torture survivors, above and beyond PTSD symptoms. ⋯ It appears that PTSD and PG induce opposite effects on the pain modulation capacity of torture survivors, a dichotomy that may explain paradoxical pain responses among trauma survivors, as discussed. PERSPECTIVE: This longitudinal study sheds light on the possible mechanisms underlying variations in pain perception and modulation among trauma survivors. PTSD and PG each mediated opposing pain modulation profiles, suggesting that individual responses to trauma, rather than the trauma itself, influence pain responses.
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Avoidance is considered key in the development of chronic pain. However, little is known about how avoidance behavior subsequently affects pain-related fear and pain. We investigated this using a robotic arm reaching avoidance task. ⋯ PERSPECTIVE: Results indicate participants become more afraid of and sensitive to pain, when previously acquired avoidance is no longer effective. Also, participants continue to show avoidance behavior despite it being not adaptive anymore. These findings suggest that ineffective avoidance may play role in the maintenance and development of chronic pain.
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Occupational exposure to mechanical vibration can produce the hand-arm vibration syndrome (HAVS), whose most disabling symptom is persistent muscle pain. Unfortunately, the pathophysiology of HAVS pain is still poorly understood, precluding the development of mechanism-based therapies. Since interleukin 33 (IL-33) is essential for inflammation and recovery that follows skeletal muscle injury, we explored its role in muscle pain in a model of HAVS, in adult male rats. ⋯ Together these data support the suggestion that IL-33 plays a central role in vibration-induced muscle pain by action, at least in part, on skeletal muscle nociceptors. PERSPECTIVE: Our findings provide evidence of the contribution of IL-33, acting on its canonical receptor, in nociceptors, to muscle pain induced by ergonomic vibration. This suggests that targeting IL-33/ST2 signaling may be a useful strategy for the treatment of muscle pain in HAVS.
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Burn injuries are significantly painful and associated with physical and psychological impairment. However, little research to-date has examined the potential role of the subjective experience of pain in either physical or psychological impairment in this population. This may be particularly important to examine, given that the pain experience can often be a significant barrier to recovery in other pediatric populations. ⋯ Future research is needed to further examine these relationships. PERSPECTIVE: This study presents preliminary findings from a national database on pain-related outcomes both cross-sectionally and longitudinally in youth with a history of burn injury. To-date, pain-related outcomes are poorly understood in this population and the results of this study serve to inform future research and treatment-related efforts.