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Douleur et Analgésie

, Volume 17, Issue 1, pp 9–12 | Cite as

Mécanismes de l’effet placebo

  • F. Benedetti
Article

Résumé

De nombreuses données indiquent que l’analgésie placebo est sous-tendue par la mise en jeu des systèmes opioïdes endogènes. Premièrement, la naloxone, un antagoniste des récepteurs des opioïdes, est capable de bloquer la réponse analgésique placebo, qu’il s’agisse d’une douleur surenant dans un contexte clinique ou d’une douleur expérimentale. Deuxièmement le proglumide, un antagoniste des récepteurs de la cholécystokinine (CCK), dont les propriétés anti-opioïdes sont bien établies, potentialise l’analgésie placebo vis-à-vis des douleurs postopératoires, et des douleurs expérimentales induites par une ischémie du bras. Troisièmement, une étude en imagerie cérébrale a montré que l’analgésie provoquée par les opioïdes et l’analgésie placebo activent exactement les mêmes régions du cerveau. Les opioïdes endogènes sollicités par un placebo agissent non seulement sur les mécanismes de la douleur mais aussi sur les centres respiratoires. En outre, nous avons établi récement que l’analgésie placebo vis-à-vis de stimulations nociceptive tant phasiques que toniques s’accompagnait d’une réduction de la fréquence cardiaque. La naloxone bloque complètement et l’analgésie placebo et la réduction concomitante de la fréquence cardiaque. L’ensemble de ces données suggèrent que les systèmes opioïdes endogènes activés par un placebo sont capables d’affectur, directement ou non, diverses fonctions, comme les processus douloureux, la respiration et le système cardiovasculaire. La mise en jeu de substances endogènes par les placebos survient également dans d’autres situations pathologiques, comme les troubles moteurs.

Mots-clés

Placebo systèmes opioïdergiques cholécystokinine centres respiratoires cœur système sympathique 

Summary

Several lines of evidence indicate that placebo analgesia is mediated by the endogenous opioid systems. First, the opiate antagonist, naloxone, is capable-of blocking the placebo analgesic response, both in clinical and experimental pain. Second, on the basis of the anti-opioid action of cholecystokinin (CCK), the CCK-antagonist, proglumide, has been shown to potentiate placebo analgesia in both postoperative and experimentally-induced ischemic arm pain: Third, a brain imaging study has shown that opioid analgesia and placebo analgesia activate the very same regions of the brain. The placebo-activated endogenous opioids have been shown to act not only on pain mechanisms, but also on the respiratory centers. In addition, in a recent work we found that the placebo analgesic response to both phasic and tonic noxious stimuli was accompanied by reduced heart rate responses. Naloxone completely antagonizes both placebo analgesia and the concomitant reduced heart rate responses. All these findings suggest that placebo-activated endogenous opioid systems are capable of affecting, either directly or indirectly, different body functions, such as pain processing, the pattern of respiration, and the cardiovascular system. The activation of endogenous substances by placebos also occurs in other pathological conditions, like motor disorders.

Key-words

Placebo opioid systems cholecystokinin respiratory centers heart sympathetic system 

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Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  1. 1.Dipartimento di NeuroscienzeUniversità di TorinoTorinoItaly

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