2024-08-19 11:00:05
Researchers have identified a new brain circuit involved in the placebo effect, particularly in pain relief.
This phenomenon, where simply expecting relief can alleviate pain without therapeutic intervention, has long been recognized. However, the underlying biological mechanisms have remained poorly understood. The study by Greg Scherrer and Chong Chen at the University of North Carolina Nord (UNC), published in Naturereveals a neural circuit connecting the cortex anterior cingulate, the trunk cerebral and the cerebellumplaying a central role in this effect.
The placebo effect often occurs in clinical trials where some participants, receiving an inactive treatment, experience an improvement in their symptoms. This complicates clinical research because it becomes difficult to distinguish the effects of the real treatment from those of the placebo. The work of Greg Scherrer’s team sheds light by showing precisely what happens in the brain in this experiment. To understand these mechanisms, the researchers first developed a mouse model to generate the expectation of pain relief. They then used several experimental methods to study in detail theactivity neuronal activity in the anterior cingulate cortex (ACC), a region already associated with the placebo effect. Using techniques such asimaging calcium, the sequencing Using single-cell RNAi and optogenetics, they observed that ACC neurons sent signals to the pontine nucleus, a brainstem region not previously associated with pain modulation.
The study found that the expectation of relief strongly activated this neural pathway, which is characterized by an abundance of opioid receptors, suggesting a key role in pain modulation. By inhibiting this pathway, the researchers disrupted placebo analgesia and lowered pain thresholds. Conversely, activating this pathway in the absence of placebo conditioning resulted in pain relief.
The scientists also observed that Purkinje cells in the cerebellum, a type of nerve cell, showed activity similar to that of ACC neurons during the expectation of relief. This finding is cellular-level evidence of the cerebellum’s involvement in the cognitive modulation of pain.
These findings open the way to new approaches to treating chronic pain, an area where current treatment options are often limited by unwanted side effects or risks of addiction. According to Greg Scherrer, these findings could make it possible to target this new neural circuit for more effective treatments.
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