Analgesia pp 393-413 | Cite as

Placebo and Endogenous Mechanisms of Analgesia

Part of the Handbook of Experimental Pharmacology book series (HEP, volume 177)


The discovery of the endogenous systems of analgesia has produced a large amount of research aimed at investigating their biochemical and neurophysiological mechanisms and their neuroanatomical localization. Nevertheless, the neurobiological acquisitions on these mechanisms have not been paralleled by behavioural correlates in humans—in other words, by the understanding of when and how these endogenous mechanisms of analgesia are activated. Until recent times one of the most studied behavioural correlates of endogenous analgesia was stress-induced analgesia, in which the activation of endogenous opioid systems is known to be involved. By contrast, today the placebo analgesic effect represents one of the best-described situations in which this endogenous opioid network is naturally activated in humans. Therefore, not only is placebo research helpful towards improving clinical trial design and medical practice, but it also provides us with a better understanding of the endogenous mechanisms of analgesia.


Placebo Endogenous opioids Expectation Conditioning Clinical trials 


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© Springer-Verlag Berlin Heidelberg 2006

Authors and Affiliations

  1. 1.Department of Neuroscience, Clinical and Applied Physiology ProgrammeUniversity of Turin Medical SchoolTurinItaly

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