It's not all in your head: Descending neural mechanisms of placebo-induced pain control

Aug 26, 2009

A new study reveals that when it comes to pain control, the "placebo effect" involves evolutionarily old pain control pathways in the human brainstem, the part of the brain that is continuous with the spinal cord. The research, published by Cell Press in the August 27th issue of the journal Neuron, provides fascinating mechanistic insight into how and why simply expecting that a treatment will reduce pain can act as an effective analgesic.

Placebo analgesia refers to an individual's relief from pain following administration of a chemically inert substance and is thought to be due to a person's belief that a potent pain medication was administered. Endogenous opioids, which are naturally produced by the brain in small amounts and play a key role in the relief of pain and anxiety, have been implicated in placebo analgesia. Brain imaging studies have shown that placebo analgesia stimulates release of endogenous opioids from higher brain regions associated with pain modulation and is associated with a decrease in signals from pain-sensitive areas.

"It has been hypothesized that placebo analgesia also recruits the opioidergic descending pain control system, which inhibits pain processing in the and, therefore, subsequently reduces pain-related responses in the brain, leading to a decreased pain experience," explains lead study author Falk Eippert from the University Medical Center Hamburg-Eppendorf in Germany. However, thus far this has not been demonstrated experimentally.

Eippert and colleagues employed sophisticated brain imaging techniques to examine both higher cortical and lower brainstem responses in two groups of subjects: one receiving a drug called naloxone, which blocks opioid signaling, and one group with a natural opioid state. Expectations of pain relief were induced in both groups using an established placebo analgesia paradigm.

The researchers found that naloxone reduced behavioral placebo effects as well as placebo-induced decreases in pain-related brain responses. Most importantly, they also observed that, under placebo, cortical areas interacted with brainstem structures implicated in pain control and that these interactions were dependent on endogenous opioids and were related to the strength of experienced placebo effects.

"Taken together, our findings show that opioid signaling in pain-modulating areas and the projections to downstream effectors of the descending pain control system are crucially important for placebo analgesia," concludes Eippert. "It will be interesting to see whether opioid-dependent activation of the descending pain control system is a common feature of different forms of modulation, such as hypnosis and attentional distraction, which share some common neuroanatomical features."

Source: Cell Press (news : web)

Explore further: Why your nose can be a pathfinder

add to favorites email to friend print save as pdf

Related Stories

Brain region central to placebo effect identified

Jul 18, 2007

Researchers have pinpointed a brain region central to the machinery of the placebo effect—the often controversial phenomenon in which a person’s belief in the efficacy of a treatment such as a painkilling drug influences ...

Pain relief effectiveness down to mind-set?

Dec 21, 2006

Research by the Human Pain Research Group at The University of Manchester suggests that people's responses to placebo or 'dummy' pain relief varies according to their way of thinking.

Medicinal marijuana effective for neuropathic pain in HIV

Aug 06, 2008

In a double-blind, placebo-controlled clinical trial to assess the impact of smoked medical cannabis, or marijuana, on the neuropathic pain associated with HIV, researchers at the University of California, San Diego School ...

Recommended for you

Researchers track down cause of eye mobility disorder

2 hours ago

Imagine you cannot move your eyes up, and you cannot lift your upper eyelid. You walk through life with your head tilted upward so that your eyes look straight when they are rolled down in the eye socket. ...

How kids' brain structures grow as memory develops

3 hours ago

Our ability to store memories improves during childhood, associated with structural changes in the hippocampus and its connections with prefrontal and parietal cortices. New research from UC Davis is exploring ...

User comments : 0

More news stories

Down's chromosome cause genome-wide disruption

The extra copy of Chromosome 21 that causes Down's syndrome throws a spanner into the workings of all the other chromosomes as well, said a study published Wednesday that surprised its authors.

Ebola virus in Africa outbreak is a new strain

The Ebola virus that has killed scores of people in Guinea this year is a new strain—evidence that the disease did not spread there from outbreaks in some other African nations, scientists report.

Freight train industry to miss safety deadline

The U.S. freight railroad industry says only one-fifth of its track will be equipped with mandatory safety technology to prevent most collisions and derailments by the deadline set by Congress.