Dopamine (red) approaches one of the receptors (blue)
JUAN GAERTNER/SCIENCE PHOTO LIBRARY/ALAMY
Dopamine, a hormone and neurotransmitter, is generally thought to be the driving force behind pain relief due to the placebo effect, but in reality it may play little or no role in the phenomenon.
The placebo effect occurs when someone’s medical condition is relieved through the power of suggestion and expectation, such as taking a sugar pill. Dopamine, along with opioids and cannabinoids that are naturally produced in our bodies, is thought to be particularly involved in pain relief.
To get a clearer picture, Ulrike Bingel She and her colleagues at the University Hospital of Essen, Germany Treatment expectations Research Center, also in Germany. Scientists applied two creams to different parts of the arms of 168 people aged 18 to 40 with no known diseases and touched them with a heated stick. This caused mild discomfort.
The creams were identical, but participants were told that one cream contained an active pain-relieving ingredient, while the other served as a placebo.
The researchers first asked the participants to take a drug that blocks dopamine, a drug that stimulates dopamine release, or a drug that does not change dopamine levels.
The participants’ dopamine levels changed as expected, but this did not seem to affect the amount of pain they experienced or the amount of pain they expected to feel, which was rated on a scale of 0 to 10.
This suggests that dopamine is not directly involved in the placebo effect for pain relief, says Bingel. She says opioids and cannabinoids may play a more powerful role. Hormones such as oxytocin and norepinephrine may also play a role, and this could be investigated in future studies, says Bingel.
But she says it’s also possible that dopamine comes into play when people feel more motivated to relieve pain, such as when the discomfort is more severe than in this study.
Bingel says understanding the placebo effect could help us develop treatments that harness its power to better manage pain.
Lauren Atlas A study from the National Institutes of Health in Bethesda, Maryland, found that the placebo effect is probably related to “verbal instructions and social factors that vary depending on the context surrounding the treatment,” and that these factors are unlikely to be mediated by dopamine.
subject:
