New insights into the brain’s innermost workings have researchers looking into ways of decreasing the body’s sensitivity to chronic pain. The latest findings provide hope that things as simple as sound or special images may one day help chronic pain patients suffer less.
Other, more profound discoveries are opening the door to intercepting pain signals as they form and using special drugs to help people feel less pain. Canadian researchers are working on that very idea, spurred along by the knowledge that memories are not as fixed as they seem.
The researchers, at Quebec City’s Laval University, have discovered ways of mitigating pain by triggering it.
The scientists were inspired by research about 15 years ago that discovered a special opportunity arising during memory recall, the process of remembering particular moments in time that have already occurred.
When a person recalls a memory, the brain’s neurochemical encoding of it activates and becomes temporarily unlocked. If a person takes a special drug during this short period of time, the memory is erased. The drug prevents the memory from forming again.
The researchers wondered if the same mechanisms were at work during the formation of memories related to pain. Their idea wasn’t to erase memories of pain, but rather interfere with it as it developed to reduce pain sensitivity.
New research uncovers the potential of reducing sensitivity to pain by triggering the sensation.
To find out if their theory was accurate, scientists injected capsaicin, the compound that makes hot peppers spicy, into the feet of mice. Capsaicin creates heat both in taste and in a physical burning sensation, but causes no lasting damage. The burning feeling also decreased pain sensitivity in the mice, allowing researchers to apply pressure and measure the point at which the mice flinched.
This initial flinching point provided researchers with a comparison point for the next part of their experiment, continued three hours later.
The second time around, researchers again gave the mice a dose of capsaicin along with a drug blocking the synthesis of proteins in the spinal cord that causes hypersensitivity to pain. The drug increased the mice’s pain tolerance, enabling them to handle about 70% of the amount of pain that they could under normal circumstances.
Researchers said the findings hold hope that one day the same process of inhibiting protein synthesis will help reduce pain sensitivity in humans. Researcher Yves De Koninck says:
“The challenge now will be to find protein synthesis inhibitors that are nontoxic and cause minimal side effects in humans.”
Meanwhile, at the University of Luxembourg, scientists are working on new methods that use the power of sound to decrease the sensation of pain. Researchers said the discovery supports the idea that it’s possible to manage pain by using mind-over-matter techniques.
The powerful mind holds the secrets for decreasing sensitivity to chronic pain, scientists say.
The idea for the study arose from the knowledge that new pain in one part of the body causes existing pain in a separate part of the body to lessen. This reaction, known as “pain inhibits pain,” is a way the nervous system allows the body to manage new, potentially more dangerous threats.
To test their ideas, scientists first inflicted pain into a subject’s foot with electrical pulses, measuring the pain caused. Then, the study subjects placed their hand in a bucket of ice water while listening to the sound of a telephone ringing through headphones.
Researchers thought that perhaps the sensation of ice water would mitigate pain from the electrical pulses. However, they soon realized that subjects experienced a drop in pain resulting from the electrical currents while simply listening to the telephone ringing; no second sensation of pain was necessary.
Scientists conditioned study subjects’ brains to blocking pain by the mere sound of a ringtone.
The sensation of pain wasn’t the only thing researchers measured. They also analyzed subjects’ facial expressions related to pain. Those listening to the ringtones also displayed less pain-related body language, such as frowning. Researcher Fernand Anton says:
“We have shown that just as the physiological reaction of saliva secretion was provoked in Pavlov’s dogs by the ringing of a bell, an analogous effect occurs regarding the ability to mask pain in humans.”
Researchers hope the finding could spell hope for people looking to manage pain by conditioning the brain with similar triggers.
Earlier research conducted by the American Pain Society explored that very topic—training the brain to react less to pain.
Scientists built off the idea that everybody has a so-called brain map that tracks, regulates, and protects different body systems. Researchers now believe that those maps aren’t fully functioning in some people with chronic pain, particularly those with phantom limb sensation and complex regional pain syndrome, but also possibly chronic back pain. When the body sustains an injury, such as a broken bone, the brain incorporates that injury into its maps, and can causes the brain to rewire itself. That rewiring, known as neuroplasticity, also provides opportunities for chronic pain patients to find relief. Scientists hypothesize that neuroplasticity can be used to correct the body maps and reduce chronic pain.
Researcher G. Lorimer Moseley says:
“The brain is the focal point of the pain experience, but the plasticity phenomena can be harnessed to help alleviate pain.”
Consider what happens in the brain when a bone breaks. First, the brain would recognize the damage and then signal pain sensations, incorporating the damage into its body maps. For chronic pain sufferers, the body maps never reflect healing even after the actual tissue has no more damage.
With damaged body maps, pain signals never go away, even after the injury heals. This leads to chronic pain.
Moseley says: “We want to gradually train the brain to stop trying to protect body tissue that doesn’t need protecting.”
Potential ways of retraining the brain include using visual images to change the brain’s perception of its body maps. Studies have shown promising results, Moseley adds.
What do you think of the potential that the brain can be retrained to feel less pain?
Image by J E Theriot via Flickr