Inducing placebo respiratory depressant responses in humans via opioid receptors

Several lines of evidence indicate that placebos produce analgesia through the activation of endogenous opioid systems. Recently, we showed that placebos may also produce respiratory depressant responses, a typical side‐effect of narcotics, when a subject had a prior experience of respiratory depres...

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Bibliographic Details
Published in:The European journal of neuroscience 1999-02, Vol.11 (2), p.625-631
Main Authors: Benedetti, Fabrizio, Amanzio, Martina, Baldi, Sergio, Casadio, Caterina, Maggi, Giuliano
Format: Article
Language:English
Subjects:
Aged
Analgesics
Analgesics, Opioid - pharmacology
Brain Chemistry - drug effects
Brain Chemistry - physiology
Buprenorphine - pharmacology
conditioning
Conditioning (Psychology) - physiology
endogenous opioids
Ethics, Medical
Female
Hibernation
Humans
Male
Middle Aged
naloxone
Naloxone - pharmacology
Narcotic Antagonists - pharmacology
Narcotics
Opioid Peptides - metabolism
Ostomy
Pain
Patients
Physiology
Placebo effect
Placebos - pharmacology
Receptors, Opioid - metabolism
Respiration
respiratory centres
Thoracic surgery
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Summary:Several lines of evidence indicate that placebos produce analgesia through the activation of endogenous opioid systems. Recently, we showed that placebos may also produce respiratory depressant responses, a typical side‐effect of narcotics, when a subject had a prior experience of respiratory depression in the course of narcotic treatment. In the present study, we report that the placebo respiratory depression can be induced after repeated administrations of the partial opioid agonist buprenorphine. The placebo respiratory depressant effect that resulted from the buprenorphine conditioning was completely blocked by a dose of 10 mg of naloxone, indicating that it was mediated by endogenous opioids. These findings show that placebos act, via the activation of opioid receptors, not only on pain mechanisms but on the respiratory centres as well, thus mimicking a typical side‐effect of narcotics. In addition, the experimental procedure we used did not produce any expectation of respiratory depression and, similarly, the subjects did not notice any sign of respiratory discomfort. Thus, the placebo respiratory depression elicited in the present study cannot be explained on the basis of cognitive or motivational mechanisms. Rather, it appears to be a sequence effect due to learning, thus suggesting a conditioning mechanism mediated by endogenous opioids.
ISSN:0953-816X
1460-9568
DOI:10.1046/j.1460-9568.1999.00465.x