Links for Keyword: Pain & Touch

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Seeing, feeling have something in common

By Rachel Ehrenberg When it comes to feeling good vibrations, the eyes have it. Experiments in mice and humans show that a protein important for eye development also plays a role in sensing vibrations. An international team has found that mice lacking a protein called c-Maf have deformed Pacinian corpuscles (shown here in a mouse’s leg), the vibration-detectors that surround mouse bones. People have Pacinian corpuscles in their palms and fingertips. When the researchers tested four people with eye cataracts due to malfunctioning c-Maf, those individuals had a hard time detecting high-frequency vibrations, the scientists report online February 16 in Science. © Society for Science & the Public 2000 - 2012

Related chapters from BP6e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain; Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 5: The Sensorimotor System; Chapter 7: Vision: From Eye to Brain
Link ID: 16394 - Posted: 02.18.2012

Robotic Rat to the Rescue

by Sarah C. P. Williams What do you get when you combine a monkey's brain with the whiskers of a rat? A robotic rodent that can sense its environment almost as well as the real thing. The new rat-bot could lead to the development of robots that can feel their way through earthquake rubble and could provide clues to how live rats analyze sensory information from their whiskers. Although recent research has helped scientists understand what information whiskers send to the brains of rodents, deciphering how rats and mice interpret that sensory information has been trickier. Previous models assumed that rodents looked at whisker movement patterns and vibrations over a set duration of time and that their brain made a decision, based on the whole of the data, about the most likely surface the whiskers were touching. If the overall data best matched the known patterns for a hard vinyl floor, for example, the rats would conclude that's the surface that they're on. But different robots created using this model of reasoning were only 50% to 80% accurate at guessing the floor underneath them after 0.4 seconds of exposure, multiple studies have found. Computational neuroscientist Nathan Lepora of the University of Sheffield in the United Kingdom and his team thought that a model of information processing recently discovered in monkeys might help the robots make better judgments on floor type. The primates don't use a single piece of evidence to make a decision about what they're seeing. Rather, their brains rely on an accumulation of data. When the monkeys watch screens of randomly moving dots, for example, different neurons sense each direction of movement: up, down, left, and right. As dots on the screen flit about, more neurons of each type begin to fire, accumulating a total activity level for the group of neurons. Once, say, the "up" neurons reach a specific threshold, they pass on the message that the dots are moving in that direction. © 2010 American Association for the Advancement of Science.

Related chapters from BP6e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain
Related chapters from MM:Chapter 5: The Sensorimotor System
Link ID: 16302 - Posted: 01.26.2012

Women found to report much more pain than men

Erin Allday, Chronicle Staff Writer A Stanford study sheds new light on the old cliche about women having a higher tolerance for pain than men - according to tens of thousands of electronic patient records, women tend to report much more severe pain than men, no matter the source of the pain. The study being released today found that when asked to rate their pain on a scale of 0 to 10 - with 0 being no pain at all, and 10 being the worst pain imaginable - women on average scored their pain 20 percent more intense than men. The results held up across a wide variety of diseases and injuries, including back and neck pain, digestive disorders, sinus infections, and even ankle strains and sprains. In almost every category researchers looked at, women reported more pain than men. "We may have to adjust our thinking about how men and women report their pain. The killer question is: Do women actually feel more pain than men?" said Dr. Atul Butte, lead author of the study, which was published in the Journal of Pain. "That may be more philosophy than anything - how can we tell that for sure?" Of course, the fact that women report more pain overall doesn't necessarily mean they have more or less tolerance to pain than men, Butte said, adding that his results have been the source of some lighthearted debate with his wife. The study doesn't explain the reason for the difference, and researchers say it could include social, psychological or biological factors. Men may be more reluctant to confess intense pain to a female nurse, for example. Women are more likely than men to suffer from depression and anxiety, two psychological conditions that can increase susceptibility to pain. © 2012 Hearst Communications Inc.

Related chapters from BP6e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 5: The Sensorimotor System; Chapter 8: Hormones and Sex
Link ID: 16290 - Posted: 01.24.2012

Rat helps pinpoint pain molecule

Katharine Sanderson An uncharted trawl through thousands of small molecules involved in the body's metabolism may have uncovered a potential route to treating pain caused by nerve damage. Neuropathic pain is a widespread and distressing condition, and is notoriously difficult to treat. So Gary Siuzdak, a chemist and molecular biologist at the Scripps Research Institute in La Jolla, California, and his team decided to take an unusual route to finding a therapy. Their results are published today in Nature Chemical Biology1. They took rats with surgically damaged paws, who were consequently suffering from neuropathic pain, and instead of analysing changes in gene expression and proteins in the animals, focused on metabolites – the biochemical intermediates and end-products of bodily processes such as respiration and the synthesis and breakdown of molecules. The science that looks at the body's metabolite composition is known as metabolomics. Using mass spectrometry, which can detect many different chemicals simultaneously, the researchers were able to identify the metabolites present in these animals 21 days after surgery. The team analysed samples of the injured rats’ blood plasma, of tissue near the injured paw, and of tissue from different areas of the spinal column, and compared the metabolites present with that of the same site in healthy rats. One particular area differed markedly between the two cases: the dorsal horn in the spinal column. © 2012 Nature Publishing Group,

What is spinal stenosis, and how serious is it? What are the treatment options?

By Chelsea Conaboy A. Spinal stenosis is a narrowing of the spinal canal that can - but does not always - cause pain in the legs and other problems. It is typically the result of degenerative effects of aging. Disks or joints in the back may bulge or vertebral bones grow spurs that push into the space where the spinal cord and nerves sit, compressing them. The condition is not uncommon, said Dr. Carol Hartigan, a physiatrist in the Spine Center at New England Baptist Hospital. Researchers using imaging tests have found that as many as 30 percent of people over age 60 may have a narrowed canal, but not all experience symptoms, she said. Especially when the narrowing happens slowly over time, the spinal cord and the nerves can adjust to the change, “like a tree that grows around a fence,’’ she said. But some people will experience pain or weakness in the front or back of their legs, often more severe when they are standing or walking. Some, depending on the location of the stenosis, can have bowel and bladder problems. Hartigan said people should see a doctor if the symptoms persist or if they are interfering with daily activities. Staying physically fit is important to controlling symptoms of stenosis, Hartigan said. Often changing the position of the spine slightly can relieve pain enough to keep moving. Some who have trouble walking, might have an easier time riding a bike or even using a treadmill. Steroid injections can provide temporary relief for some, Hartigan said. © 2012 NY Times Co.

Head Agony: Jumpy cells may underlie migraine’s sensory storm

By Laura Beil When Lewis Carroll sent Alice down the rabbit hole, she encountered a strange and twisted land with distortions of size and time. Some headache experts see something else — the possible ghosts of the author’s migraines, which can leave victims temporarily blinded, nauseated, hallucinatory, numb, unable to concentrate or seeking shelter from painful stings of light and sound. People with migraines travel between two worlds: one in which they are having a migraine and one in which they are not. “I’m very brave generally,” Tweedledum tells Alice, “only today I happen to have a headache.” But even after the headache is gone, migraine sufferers live with the dread of its return. For more than a century, researchers have been trying to step through the looking glass to find clues to the mystery of migraines, with little success. Treatments that can prevent or end migraine attacks exist only because drugs for something else were found, often by accident, to quiet the migraine’s neurological storm. “All of the major things we use were not designed for migraine at all,” says Peter Goadsby, a neurologist at the University of California, San Francisco. “It’s not good enough that one of the commonest of medical problems has treatment developed by serendipity.” A major barrier to relief, it turns out, has been that migraines, which affect 36 million people in the United States, have no known cause. But researchers now think that they are, at least, looking for the culprits in the right places. © Society for Science & the Public 2000 - 2012

High-dose opiates could crack chronic pain

Arran Frood Has a cheap and effective treatment for chronic pain been lying under clinicians' noses for decades? Researchers have found that a very high dose of an opiate drug that uses the same painkilling pathways as morphine can reset the nerve signals associated with continuous pain — at least in rats. If confirmed in humans, the procedure could reduce or eliminate the months or years that millions of patients spend on pain-managing prescription drugs. The results of the study are described today in Science1. “We have discovered a new effect of opiates when they are given, not constantly at a low dose, but at a very high dose,” says Jürgen Sandkühler, a neurophysiologist at the Center for Brain Research of the Medical University of Vienna, and a co-author of the paper. Chronic pain is a nerve condition that lingers long after the immediate, or acute, pain-causing stimulus has receded. It can follow surgery or injury, and is also associated with conditions such as rheumatoid arthritis and cancer. Sandkühler says that the original stimulus changes how the central nervous system deals with pain over time. In a model known as long-term potentiation, nerves carrying pain signals fire repeatedly, turning on a cellular pain amplifier that causes anything from exaggerated pain to outright agony on a long-term basis. © 2012 Nature Publishing Group

Think Like a Doctor: Ice Pick Pain Solved!

By LISA SANDERS, M.D. On Wednesday, we challenged Well readers to figure out the diagnosis for a middle-aged woman with a pulsating whooshing sound in her head and a sharp stabbing pain on the left side of her neck and head. Nearly 400 readers wrote in with some very thoughtful assessments of this patient’s problem. The correct diagnosis is… Hemicrania continua The only right answer we got came in around 11:15 a.m. from Sashank Prasad, a neuro-ophthalmologist from Brigham and Women’s Hospital in Boston. He says he sees a lot of headache patients because eye involvement is a common feature in many chronic headaches. It was a comment I had made to another reader, noting that the patient didn’t require surgery to get better, that helped him focus on hemicrania continua as the cause of this patient’s pain. One of the characteristics of this syndrome is that it is usually very sensitive to indomethacin, a type of medicine in the same family as ibuprofen and naproxen. The Diagnosis: Hemicrania continua is a type of daily headache first described in the early 1980s. It is characterized by the symptoms noted by this patient: persistent pain on one side of the head interspersed with episodes of much more severe pain that is often described as sharp or stabbing. The episodes are usually accompanied by other facial symptoms, including watery eyes, runny nose, eyelid swelling or constriction of the pupil. © 2012 The New York Times Company

Really? The Claim: Listening to Music Can Relieve Pain

By ANAHAD O'CONNOR Can the right sonata soothe the pain of a medical operation? A growing number of doctors have been using music in clinical settings, believing that it might have analgesic effects on patients — or at least take their minds off an otherwise painful procedure. Scientists only now are seeking to determine whether the notion is more romance than reality. In the most recent study, published in December in The Journal of Pain, 153 people were subjected to increasingly painful shocks on their hands as they listened to music. All the while, they were encouraged to engage in the songs and to identify certain notes and tones. By measuring pupil dilation and brain activity, scientists at the University of Utah found that as the subjects became focused on the melodies, they experienced more and more relief from the pain. The biggest effect was seen on the participants who were initially most anxious. A Swedish study published in 2009 reported similarly encouraging findings: Children who were given “music therapy” after minor surgery required smaller amounts of morphine than those who were not. But a meta-analysis of data on more than 3,600 patients in 51 studies, published in the Cochrane Database, found that the magnitude of the effect was not very large, so the potential usefulness in clinical practice — for now, at least — was “unclear.” THE BOTTOM LINE Listening to music during or after a medical procedure may relieve pain, but more research is needed to determine whether the effect is significant. © 2012 The New York Times Company

More powerful painkiller coming

Drug companies are working to develop a pure, more powerful version of a highly abused medicine, which has addiction experts worried that it could spur a new wave of abuse. The new pills contain the highly addictive painkiller hydrocodone, packing up to 10 times the amount of the drug as existing medications such as Vicodin. Four companies have begun patient testing, and one of them — Zogenix of San Diego — plans to apply early next year to begin marketing its product, Zohydro. If approved, it would mark the first time patients could legally buy pure hydrocodone. Existing products combine the drug with nonaddictive painkillers such as acetaminophen. Critics say they are especially worried about Zohydro, a timed-release drug meant for managing moderate to severe pain, because abusers could crush it to release an intense, immediate high. 'The next Oxycontin' "I have a big concern that this could be the next OxyContin," said April Rovero, president of the National Coalition Against Prescription Drug Abuse. "We just don't need this on the market." OxyContin, introduced in 1995 by Purdue Pharma of Stamford, Conn., was designed to manage pain with a formula that dribbled one dose of oxycodone over many hours. Abusers quickly discovered they could defeat the timed-release feature by crushing the pills. © CBC 2011

The electric mole rat acid test

By Tina Hesman Saey When life gives naked mole rats lemons, the wrinkled, buck-toothed rodents probably don’t care. They are impervious to the sting of acid. But scientists in Berlin are onto the secret of the social rodents’ acid insensitivity. Naked mole rats’ acid sensors work just fine, but a protein responsible for relaying messages about acid’s presence to the nervous system is easily blocked by the same positively charged hydrogen ions that lend substances acidity, researchers report in the Dec. 16 Science. The discovery may give researchers clues about where to target drugs that could relieve pain associated with inflammation. “I’ve been trying to figure out this question in mole rats for a number of years, and the answer has been elusive,” says Thomas Park, a neuroscientist at the University of Illinois at Chicago who was not involved in the study. It was Park who first got Gary Lewin of the Max Delbrück Center for Molecular Medicine in Berlin interested in studying naked mole rats. Lewin and Ewan St. John Smith, a postdoctoral researcher in Lewin’s lab, led the new research. Mole rats live in large social groups in burrows underground. The crowded, confined conditions cause carbon dioxide levels to rise to as high as 8 to 10 percent of the air — a concentration that would cause a person to pass out within five to 10 minutes. High carbon dioxide and low oxygen levels make body tissues acidic, something that is very painful for nearly all mammals. (Inflammation also raises acidity in tissues, producing pain.) If mole rats had not evolved a way to ignore acid the little rodents would be in constant agony, Lewin says. © Society for Science & the Public 2000 - 2011

Related chapters from BP6e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 5: The Sensorimotor System
Link ID: 16158 - Posted: 12.17.2011

Out-of-Body: A Visit to the Lab of a Master Illusionist

By Ed Yong of Nature magazine It is not every day that you are separated from your body and then stabbed in the chest with a kitchen knife. But such experiences are routine in the lab of Henrik Ehrsson, a neuroscientist at the Karolinska Institute in Stockholm, who uses illusions to probe, stretch and displace people's sense of self. Today, using little more than a video camera, goggles and two sticks, he has convinced me that I am floating a few meters behind my own body. As I see a knife plunging towards my virtual chest, I flinch. Two electrodes on my fingers record the sweat that automatically erupts on my skin, and a nearby laptop plots my spiking fear on a graph. Out-of-body experiences are just part of Ehrsson's repertoire. He has convinced people that they have swapped bodies with another person1, gained a third arm2, shrunk to the size of a doll or grown to giant proportions3. The storeroom in his lab is stuffed with mannequins of various sizes, disembodied dolls' heads, fake hands, cameras, knives and hammers. It looks like a serial killer's basement. "The other neuroscientists think we're a little crazy," Ehrsson admits. But Ehrsson's unorthodox apparatus amount to more than cheap trickery. They are part of his quest to understand how people come to experience a sense of self, located within their own bodies. The feeling of body ownership is so ingrained that few people ever think about it -- and those scientists and philosophers who do have assumed that it was unassailable. © 2011 Scientific American,

Stanford, UCSF to test ultrasound for cancer pain

Erin Allday, Chronicle Staff Writer Scientists at Stanford and UCSF are recruiting patients for two clinical trials to test the use of ultrasound waves, as an alternative to traditional radiation therapy, to ease pain in people whose cancer has spread to their bones. Earlier studies of the ultrasound treatment have been promising, and a study recently completed at Stanford and 16 other U.S. research sites found that most patients saw substantial improvement in pain control after radiation therapy had failed to work. The treatment is still considered experimental and is not available outside of clinical trials. It is being studied only as a treatment for the pain associated with metastatic bone cancer, and not for treating the cancer itself. "Radiation is very effective for most patients. But there is still a significant percentage that it doesn't work for," said Dr. Pejman Ghanouni, a Stanford radiologist who is leading ultrasound clinical trials there. "I don't view ultrasound as something that would replace radiation. It's another tool in the toolbox." Doctors have had such success in treating cancer that people are now living years longer after a diagnosis than they did decades ago, Ghanouni said. But as survival rates have increased, so have rates of metastatic disease, which occurs when the cancer has spread beyond the initial site, commonly into the bones. © 2011 Hearst Communications Inc.

Why redheads and dentists don't get along

By Emily Main Redheads may be stereotyped as having fiery tempers, but those tempers may turn to fear and loathing when they walk through the door of a dentist’s office, according to research published in the Journal of the American Dental Association. The study shows that people with a specific gene that often occurs in redheads tend to experience heightened anxiety when they pop in for a regular teeth cleaning. The details: The study’s authors recruited 144 people for the study, 67 of whom were natural redheads, and 77 who were dark-haired. The participants answered survey questions about any fears or anxieties related to dental visits, and the researchers took blood samples that they later tested for specific gene variants common in people with red hair. People with one specific gene, MC1R, were more than twice as likely to report that they avoided dental appointments because of fear and anxiety than people without that gene. Of the 85 people in the study with MC1R, 65 were redheads. What it means: It’s possible, say the researchers, that redheads with the gene in question tend to be resistant to certain pain medications. This could mean redheads are more prone than most to experience a difficult dental visit, affecting their expectations about future appointments. Redheaded or not, most of us have probably had reservations about going to the dentist at some point in our lives. But don’t let fear prevent you from getting your twice-yearly checkups. Recent studies have linked periodontal disease to a wide variety of chronic diseases, including heart disease, strokes, and type 2 diabetes. If it’s been a while since you’ve visited the dentist, you might be pleasantly surprised at the experience. “Things don’t hurt anymore,” says Kimberly A. Harms, DDS, consumer advisor for the American Dental Association. Anesthesia has become much more effective, she says, and patients don’t have to experience the pain that used to be common in dental procedures. © 2011 msnbc.com

What Is Pepper Spray?

By Eric Niiler Pepper spray, also known as oleoresin capsicum or OC, is made from the same naturally-occurring chemical that makes chili peppers hot, but at concentrations much higher. Its effects include temporary blindness, coughing and skin irritation. To make the spray used by law enforcement officers and police to control crowds, manufacturers take a concentrated oil made from chili peppers and combine it with water, glycol (a chemical used in shaving creams and liquid soaps) and a propellent such as nitrogen, according to Bob Nance, vice president of operations at Security Equipment Corp.,which makes pepper spray and other irritants at its Fenton, Mo., headquarters under the Sabre brand name. "We get it in a red, oily viscous syrup,” Nance said. “It’s the same thing you will find in hot sauce, but in higher concentrations." Interest in pepper spray was piqued after a video of campus police spraying peaceful protesters at the University of California, Davis, made the rounds on the internet this weekend, the university suspended its police chief and two officers. The video shows an officer spraying protesters in the face as they are sitting on the ground. "It causes your eyes to shut and makes breathing difficult," Nance said. "It can cause coughing and choking, and a severe burning sensation on your face. But it’s temporary, usually it lasts from 30 to 45 minutes." © 2011 Discovery Communications, LLC.

Disparities: In the E.R., the Elderly Get Less Pain Relief

By NICHOLAS BAKALAR Older people who go to an emergency room in pain are less likely to get medication for it than younger people with similar levels of distress, a new analysis has found. A seven-year nationwide study of emergency room patient data has found that 49 percent of patients over age 75 were given pain medication, compared with slightly more than 65 percent of those under age 75. The study, which included data on more than 88,000 emergency room visits, appeared online last month in Annals of Emergency Medicine. Elderly people who were cognitively impaired or otherwise unable to report pain were not included in the analysis, so that does not explain the finding. Although the reasons for the difference are unclear, the authors suggest that emergency room personnel may be concerned about adverse effects of pain medications on the elderly, or they may pay more attention to diagnosis in older patients and less to pain relief. “There are side effects of pain medications,” said Dr. Timothy Platts-Mills, the lead author of the study and an assistant professor of medicine at the University of North Carolina, Chapel Hill. “But in almost all cases, you can provide some pain relief for older adults by selecting appropriate medications or reducing doses.” © 2011 The New York Times Company

Mirrors can alleviate arthritis

By Laura Sanders WASHINGTON — Tricking people with severe arthritis into thinking their sore hand is healthy dampens their pain, a new study suggests. If confirmed, the preliminary results may offer a powerful and inexpensive way to fight persistent arthritis pain. “The results are really exciting,” said pain expert Candy McCabe of the University of Bath in England, who wasn’t involved in the study. “The whole thing is visual trickery, but the science behind it is strong.” The new technique, described November 12 at the annual meeting of the Society for Neuroscience, is a type of mirror therapy, in which the illusion of a pain-free hand makes people feel better. So far, visual feedback from mirrors has been shown to reduce some kinds of chronic pain, notably the pain felt in “phantom limbs” of amputees. But it was unclear whether mirror therapy could reduce pain produced by arthritic, inflamed joints. In the new work, Laura Case, V.S. Ramachandran and colleagues at the University of California, San Diego recruited eight volunteers who had osteo- or rheumatoid arthritis. The volunteers saw a reflection of Case’s healthy hand in the same place where their sore hand should have been. To strengthen the sensation of the hand-swap, the researchers simultaneously touched Case’s hand and the volunteer's hand, creating a unified sensation of seeing and feeling the touch. The volunteer then mimicked a series of slow hand movements made by the researcher. © Society for Science & the Public 2000 - 2011

Migraine and headaches prompt new research focused on military personnel

By Christian Torres, Army Spec. David Hunt made it through a year of deployment in central Iraq largely unscathed. But two years after returning to the United States, he faces medical retirement from the military. As Hunt, 37, describes it, there’s “really not any place” for him in the Army because of chronic migraine, the condition that has plagued him ever since an off-duty auto accident in 2006. He has fought the symptoms — nausea, vomiting and sensitivity to light — through deployments to the Arizona-Mexico border as well as Iraq. He recalls one particularly bad migraine hitting while he was alone and on guard in Arizona, and he vomited while seeking shelter from the harsh sun. “I did everything I could to just sit up and keep watch,” he said. Hunt isn’t alone in his struggle. Over the past decade, migraine and headache have become a significant problem for U.S. armed forces. A 2008 Defense Department report said diagnoses of migraine increased across all branches of the military between 2001 and 2007. Another, more recent study found that, among nearly 1,000 soldiers evacuated from Iraq and Afghanistan because of some form of headache between 2004 and 2009, two-thirds did not return to duty. “Headaches represent a significant cause of unit attrition in personnel deployed in military operations,” the study concluded. © 1996-2011 The Washington Post

Related chapters from BP6e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 5: The Sensorimotor System; Chapter 11: Emotions, Aggression, and Stress
Link ID: 15999 - Posted: 11.08.2011

Headache tree is a pain in the brain

By Rachel Ehrenberg One whiff of a plant known as the headache tree can spur intense, excruciating pain — and now scientists know why. An ingredient in the tree sets off a chain of events that eventually amps up blood flow to the brain’s outer membrane. Other headache triggers, such as chlorine, cigarette smoke and formaldehyde, interact with some of the same cellular machinery, suggesting they all work via the same pain-inducing mechanism. In the new study, an international group of researchers extracted the plant compound umbellulone from dried bay laurel leaves and then exposed various mouse and rat cells to the compound. Umbellulone tickles the same cellular detector that responds to painfully cold stimuli and the sinus-clearing scent of wasabi and mustard oil, the researchers report online October 27 in Brain. Stimulating this chemical detector ultimately triggers the release of a particular protein implicated in migraine headaches, the researchers found. This protein prompts blood vessels to swell, and scientists think this swelling puts pressure on the skull and nerves, causing pain. The new research is solid, says neuroscientist Peter Goadsby, director of the headache center at the University of California, San Francisco. Other irritants linked to headaches interact with the same chemical detector, and it may be a good target for therapy, Goadsby says. © Society for Science & the Public 2000 - 2011

Unbearable itch may no longer be a pain in anaesthesia

by Catherine de Lange THE intimate link between itch and pain has been teased apart for the first time - a development that could lead to powerful anaesthetics without any of that intolerable itching. Itch is one of the most common side effects of the anaesthetics used in procedures such as epidurals. One explanation is that itch and pain receptors are intrinsically connected. "Itch and pain are two sensations that antagonise each other," says Zhou-Feng Chen from Washington University in St Louis, Missouri. "By scratching you create a kind of mechanical pain and suppress the itch. Conversely, if you suppress pain you see more itching." To understand this mechanism better, Chen used mice to study the action of morphine, a painkiller that can cause itching. Morphine works through a receptor called MOR, and Chen suspected that different variants of the receptor might be responsible for the itch and pain responses. His team bred mice lacking one form of this receptor, called MOR1D. These mice did not scratch themselves when given morphine, though they still felt its painkilling effect (Cell, DOI: 10.1016/j.cell.2011.08.043). "It's quite exciting that we are able to segregate the two," says Cheng, who believes that separate pathways for pain and itch exist in humans too. "Our study suggests there are different ways that you can inhibit itch without interfering with analgesia." © Copyright Reed Business Information Ltd.

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