Exploring the Placebo Effect: Does Dopamine Modulation Affect Analgesia?

thank you. Listen to this article using the player above. ✖

Researchers investigated the direct causal effect of dopamine on the placebo effect in response to pain relief. This research PLoS Biologyquestioning current beliefs.

Dopamine is associated with placebo analgesia

The placebo effect is a powerful phenomenon that can influence an individual's response to physically and pharmacologically inert treatments. This effect is thought to result from a complex interaction between cognitive expectations, learning processes, and neurobiological mechanisms. In the context of analgesia, placebo analgesia refers to the perceived reduction in pain when an inactive treatment is administered to an individual.

This phenomenon is thought to activate the brain's natural pain-relieving mechanisms, which involve the release of endorphins and other neurochemicals, mimicking the effects of real painkillers. One of the neurotransmitters involved in this process is dopamine, which is involved in a variety of physiological and behavioral functions. recent research have linked dopamine-based reward mechanisms to the placebo effect, suggesting that expectations and anticipation of pain relief play an important role in shaping the brain's response to treatment.

a study A study using positron emission tomography (PET) imaging found that dopamine signaling was increased during anticipation of analgesia after administration of a placebo treatment. Although there is clear evidence that dopamine is involved in the placebo effect, its precise functional role remains poorly understood.

Dopamine modulation does not affect placebo analgesia

To investigate the role of dopamine in the placebo effect and its influence on analgesia, 168 healthy volunteers participated in a double-blind, randomized, placebo-controlled trial. Participants underwent a well-established placebo analgesic protocol and received one of three treatments during the conditioning procedure:

1. L-dopa, a precursor of dopamine that increases dopamine levels.
2. Sulpiride is a dopamine antagonist that blocks dopamine receptors and reduces dopamine activity.
3. Placebo served as a control.

On the first day, participants were introduced to two skin creams. One was a placebo cream that was incorrectly described as containing the painkiller lidocaine, and the other was a control cream that was described as being inactive. Thermal pain stimuli were applied to the participants' skin, and the temperature at the placebo site was set low to simulate an analgesic effect, while a higher temperature was used at the control site. This manipulation led participants to believe that the placebo cream was reducing their pain. This process was repeated over multiple trials, with participants rating their level of pain after each stimulus, reinforcing the placebo effect through conditioning. Testing the long-term durability of conditioned placebo analgesia.

The researchers examined participants' pain relief after conditioning on days 2 and 8 to see if changes in dopamine levels influenced the formation of positive treatment expectations and subsequent placebo analgesia. It was evaluated as follows.

Although successful in altering dopamine levels, neither L-dopa nor sulpiride affected the participants' ability to develop positive expectations for pain relief. Neither drug affected the intensity or duration of placebo analgesia compared with the control group. The initial placebo analgesia observed became undetectable by day 8 after conditioning, regardless of dopamine modulation.

Dopamine may interact with the experience of pain

This result provided evidence for the researchers' original hypothesis that dopamine plays a direct causal role in the generation or maintenance of placebo analgesia.

Although this result suggests that dopamine is not required to establish a placebo effect, the authors claim A more subtle role for neurotransmitters: “Certain dopamine-dependent aspects of reward processing, including active action and motivational aspects, may interact with the experience of pain and contribute to placebo analgesia.” be.”

Future studies aimed at understanding how dopamine-related mechanisms influence pain treatment responses will consider the complex role of dopaminergic neurotransmission in both pain perception and its modulation. There is a need.

“Our research is driven by the motivation to target the underlying mechanisms of the placebo effect to make active treatments more effective. ”, the authors said. addition.

reference: Kunkel A, Asan L, Krueger I, et al. Dopamine has no direct causal relationship to treatment expectancy formation or placebo analgesia in humans. Seymour B edition PLoS Bio. 2024;22(9):e3002772. Doi: 10.1371/journal.pbio.3002772

This article is a re-edited version of the press release below. agreement. Material has been edited for length and content.