FINDINGS ON PAIN, INCLUDING HOW A SPOUSE CAN SPUR THE SENSE, PROVIDE NEW INSIGHTS
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FINDINGS ON PAIN, INCLUDING HOW A SPOUSE CAN SPUR THE SENSE, PROVIDE NEW INSIGHTS.
ORLANDO, Sunday, Nov. 3 - Convinced that your wife or husband is a pain? New scientific data backs you up. Findings indicate that the mere presence of some spouses can make the brain's response to pain soar.
New research also reveals how other experiences in life, such as surgery during infancy or receiving an injury, affects the pain system. In addition, work uncovers new insights about migraine. This condition known for causing excruciating head pain, may actually result from a general sensory problem that wreaks havoc on the whole body. The new studies were reported today during the 32nd annual meeting of the Society for Neuroscience.
Together the findings could lead to the development of new ways to quell the suffering of the more than 97 million Americans who experience some type of chronic, debilitating pain each year.
In the work on spouses and pain, researchers used a technique that records brain activity, termed an electroencephalogram (EEG) to find that some husbands and wives can boost the pain response of patients with chronic back pain. "For the first time we have discovered that a social variable, namely the presence of a spouse, can influence the brain's response to pain," says the study's lead author Herta Flor, PhD, of the University of Heidelberg in Germany.
Specifically, Flor and her colleagues found that the presence of "solicitous" spouses can increase pain. These spouses had a history of dwelling on their partners' pain. "Non-solicitous spouses" caused no effect. This group did not focus on their partners' pain in the past and even tried to distract them from it.
In the study the researchers administered painful electric stimulation to 10 patients with solicitous spouses that had chronic back pain, 10 pain patients with non-solicitous spouses and 10 healthy controls. Spouses sat in the laboratory and were not allowed to interact with the patients.
"Our EEG results indicate that painful stimulation applied to the back induced brain activity in the chronic pain patients that was two and a half times higher when a solicitous spouse was in the room," says Flor. "These patients also showed more overt signs of feeling pain, such as moaning."
The anterior cingulate cortex, a brain structure that has been linked to the processing of pain, showed the most prominent increase in activity following back stimulation. "The data suggest that the painful stimulation of the back in the presence of a solicitous spouse directly activates brain regions involved in the processing of pain and leads to a more intense response," says Flor.
The presence of a solicitous spouse did not affect the brain's response to painful stimulation of the finger or non-painful stimulation.
"The findings show that the solicitous spouse has become a cue for a more intense pain experience in the back," says Flor. "Treatment of chronic pain should focus on the modification of these types of negative influences on a patient's social environment."
As a next step, the researchers plan to see if they can decrease the pain response by using biofeedback techniques to modify activity in the anterior cingulate cortex. If successful, the technique may help a large number of people with chronic pain.
In other work on animals, researchers find that untreated pain at birth leads to lowered sensitivity to pain later in life. "Our research in mice suggests that an adult's pain sensitivity may be linked to past experiences with painful or stressful experiences, including those that occur very early in life," says Wendy Sternberg, PhD, of Haverford College in Pennsylvania. "Recent medical advances allow potentially painful procedures such as surgery to be performed on infants just hours old, or in some cases, even in the womb."
In the study Sternberg and her colleagues performed abdominal surgery on 40 mice the day they were born. The researchers anesthetized the skin, cut an incision, lightly probed inside and then closed the skin with sutures. Half of the mice then received the drug morphine for pain relief and half received only a salt water solution. For a control, the researchers also treated mice that did not have surgery with either morphine or the salt water.
Once the animals reached adulthood, they were then given a series of tests that measured their pain response. "We found an overall lowering of pain sensitivity among those subjects who had surgery with no pain treatment compared to those that underwent surgery and received morphine and compared to those who did not undergo surgery," says Sternberg.
The researchers believe that the long-term effects observed in the untreated pain group are due to the pain experience associated with surgery, rather than other aspects of the surgery or the anesthesia, since no long-term effects were observed when surgery was followed by morphine treatment and therefore not painful.
"Our observation of long-term consequences of infant pain exposure in laboratory animals is an important first step in furthering our understanding of how pain-sensing pathways develop in response to early experiences," says Sternberg. "The research may eventually help us understand why individuals differ so markedly in adult pain perception, and why only some develop chronic pain conditions."
As a next step, the researchers plan to uncover the specific mechanisms that alter pain perception.
Other work reveals on a molecular level how an injury can affect the pain system. When you experience an injury, the body produces inflammatory molecules, which act on nerve endings to heighten our sense of pain. This injury response reminds us to protect the affected area from further harm and seek treatment. David Julius, PhD, of the University of California in San Francisco and his colleagues find that these molecules carry out their painful actions, in part, by targeting specific areas on a specialized sensor in nerve cells, termed the capsaicin receptor. In earlier work, Julius determined that this receptor detects hot temperatures as well as the burning pain of chili peppers.
"Our new analysis has identified a number of regions on the capsaicin receptor that also detects inflammation-related molecules and which may serve as sites for the development of new drugs that can diminish some forms of inflammation-related pain," says Julius.
In the work, the researchers studied a line of mice bred to lack the capsaicin receptor and conducted a variety of chemical studies. Results indicate that certain inflammatory-related molecules including acids, lipids, peptides and neurotrophic factors target the receptor. "We found that each of these molecules heightens our sense of pain by carrying out specific actions at the receptor that increase the responsiveness of sensory nerve fibers to a range of stimuli," says Julius. "Now that we have deciphered the specific actions that occur, we can search for ways to block them and treat the pain from tissue injury."
Other researchers examined people who suffer from migraines and found evidence that the condition is more than a bout of pain in the head. In fact, migraines may reflect an overall problem in the brain's sensory regulation system.
"Our results indicate that the skin of people with migraine headaches is less sensitive to touch, but more responsive to painful experiences," says Frances Abbott, PhD, of McGill University in Canada. "This implies that some migraine sufferers have a general problem in sensory regulation that may be related to the brain's inability to properly inhibit sensory inputs."
In the study Abbott and her colleagues administered tests of light touch and pain to 38 women who suffer from migraine headaches while they were headache-free. They also tested 14 healthy women as a control.
In the tests of touch, the women with migraines were less sensitive to light touch on their skin, not just in the head and neck region where headache is experienced, but also on their arms and legs.
"The finding implies that people with migraines have a generalized deficit in the sensitivity of the skin to non-painful stimuli," says Abbott. "Along with this deficit, several different tests also indicate that they are more sensitive to painful stimuli."
In one test of pain, the subjects had to submerge a hand in near freezing water, which produces a deep, aching pain. The subjects with migraines reported pain from the water at a much earlier time than did the healthy subjects. The researchers also administered tests that involved putting painful pressure on the subjects' arms and legs. Again, the subjects with migraines reported pain from the pressure at an earlier time.
"In general, the women with migraines also reported that they experienced more aches and pains all over their bodies, as well as cold hands and itchy skin, than did the healthy subjects," says Abbott. "Those with migraine appear to feel widespread pain and tenderness that persists in between headaches, even when they are infrequent."
The researchers believe that their findings show that the search for migraine treatments should examine the whole body and not just the head. "Headache treatments are notoriously ineffective," says Abbott. "Finding out more about how sensory deficits and widespread body pain relate to migraine may help us find better treatments."