Department of Psychology and Behavioural Sciences

Dopaminergic tone does not influence pain levels during placebo interventions in patients with chronic neuropathic pain

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  • Ina Skyt
  • Kurosh Moslemi, Department of Neurology, Aarhus University Hospital, Denmark., Denmark
  • Cathrine Baastrup, Denmark
  • Kasper Grosen
  • ,
  • Fabrizio Benedetti, University of Turin, Italy
  • Gitte L Petersen
  • ,
  • Donald D Price, University of Florida, United States
  • Kathryn T Hall, Brigham and Women's Hospital, Boston, MA, Harvard Medical School, Boston, United States
  • Ted J Kaptchuk, Harvard Medical School, Boston, Denmark
  • Peter Svensson
  • Troels S Jensen
  • Lene Vase

Placebo effects have been reported in patients with chronic neuropathic pain. Expected pain levels and positive emotions are involved in the observed pain relief, but the underlying neurobiology is largely unknown. Patients with neuropathic pain are highly motivated for pain relief, and as motivational factors such as expectations of reward, as well as pain processing in itself, are related to the dopaminergic system, it can be speculated that dopamine release contributes to placebo effects in neuropathic pain. Nineteen patients with neuropathic pain after thoracic surgery were tested during a placebo intervention consisting of open and hidden applications of the pain-relieving agent lidocaine (2 mL) and no treatment. The dopamine antagonist haloperidol (2 mg) and the agonist levodopa/carbidopa (100/25 mg) were administered to test the involvement of dopamine. Expected pain levels, desire for pain relief, and ongoing and evoked pain were assessed on mechanical visual analog scales (0-10). Significant placebo effects on ongoing (P ≤ 0.003) and evoked (P ≤ 0.002) pain were observed. Expectancy and desire accounted for up to 41.2% and 71.5% of the variance in ongoing and evoked pain, respectively, after the open application of lidocaine. We found no evidence for an effect of haloperidol and levodopa/carbidopa on neuropathic pain levels (P = 0.071-0.963). Dopamine seemed to influence the levels of expectancy and desire, yet there was no evidence for indirect or interaction effects on the placebo effect. This is the first study to suggest that dopamine does not contribute to placebo effects in chronic neuropathic pain.

Original languageEnglish
JournalPain
Volume159
Issue2
Pages (from-to)261-272
Number of pages12
ISSN0304-3959
DOIs
Publication statusPublished - 2018

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