A neural "off-switch" for pain documented

In Endogenous adenosine A3 receptor activation selectively alleviates persistent pain states, a paper in Brain by researchers led from the St Louis University Medical School, scientists document their work in switching off neural pain pathways by activating an adenosine receptor.

Read the rest

Which is more painful? Childbirth vs. Getting kicked in the nuts

Science has the answers. Or, anyway, science has a fascinating look at why this particular question cannot be satisfactorily answered.

Also, being 16 weeks pregnant, this is relevant to my interests. I look forward to the subjective debate in the comments.

Obedience and fear: What makes people hurt other people?

Stanley Milgram's "Obedience to Authority" experiments are infamous classics of psychology and social behavior. Back in the 1960s, Milgram set up a series of tests that showed seemingly normal people would be totally willing to torture another human being if prodded into it by an authority figure.

The basic set-up is probably familiar to you. Milgram told his test subjects that they were part of a study on learning. They were tasked with asking questions to another person, who was rigged up to an electric shock generator. When the other person got the questions wrong, the subject was supposed to zap them and then turn up the voltage. The catch was that the person getting "zapped" was actually an actor. So was the authority figure, whose job it was to tell the test subject that they must continue the experiment, no matter how much the other person pleaded for them to stop. In Milgram's original study, 65% of the subjects continued to the end of the session, eventually "administering" 450-volt shocks.

But they weren't doing it calmly. If you read Milgram's paper, you find that these people were trembling, and digging nails into their own flesh. Some of them even had seizure-like fits. Which is interesting to know when you sit down to read about Michael Shermer's recent attempt to replicate the Milgram experiments for a Dateline segment. Told they were trying out for a new reality show, the six subjects were set up to "shock" an actor, just like in Milgram's experiments. One walked out before the test even started. The others participated, but had some interesting rationales for why they did it — and a simple ingrained sense of obedience wasn't always what was going on.

Our third subject, Lateefah, became visibly upset at 120 volts and squirmed uncomfortably to 180 volts. When Tyler screamed, “Ah! Ah! Get me out of here! I refuse to go on! Let me out!” Lateefah made this moral plea to Jeremy: “I know I'm not the one feeling the pain, but I hear him screaming and asking to get out, and it's almost like my instinct and gut is like, ‘Stop,’ because you're hurting somebody and you don't even know why you're hurting them outside of the fact that it's for a TV show.” Jeremy icily commanded her to “please continue.” As she moved into the 300-volt range, Lateefah was noticeably shaken, so Hansen stepped in to stop the experiment, asking, “What was it about Jeremy that convinced you that you should keep going here?” Lateefah gave us this glance into the psychology of obedience: “I didn't know what was going to happen to me if I stopped. He just—he had no emotion. I was afraid of him.”

Read the rest in Michael Shermer's column at Scientific American

The connections between "itch" and "ouch"

The biology of itching and the biology of pain are intertwined in interesting ways, writes graduate student and science blogger Aatish Bhatia. Understanding itching can help us better understand how to treat pain. I'd not seen Bhatia's blog before, but I'm really liking his style. He does a great job of breaking down the science in a clear way.

... In the last decade, researchers have learned about receptors in the nerves under our skin that react specifically to itchy substances. When these receptors fire, they send a signal racing up our spinal cord, headed to our brain where it creates an urge to scratch. Scientists now have a basic map of the roads that an itch takes on its way to our brain. And they have even been able to block some of these roads in mice, essentially preventing them from feeling an itch.

...The picture that is emerging is a complex one, where pain and itch signals are distinct yet subtly intertwined. Of the nerve cells under our skin, some are involved only in signalling pain, and they have pain receptors. Others are responsible for signalling different types of itches, and they have both itch and pain receptors. If the same cell has both receptors, how do we distinguish itch from ouch?

... As the biology of itching becomes better understood, the benefits are making their way from the lab to the clinic. The drug morphine is a powerful painkiller, but has a common side effect of itchiness. Women taking opiates to relieve their labour pain often experience a similar side effect. Zhou-Feng Chen and Yan-Gang Sun, authors of the GRPR receptor study, teamed up with colleagues at the newly founded Center for the Study of Itch and managed to tackle this problem. Their results, published in the current issue of the journal Cell, show that the benefits of morphine can be separated from the itch.

Via Greg Laden

Image: llama itch, a Creative Commons Attribution (2.0) image from davedehetre's photostream

Where does pain happen?

Someone stubs her toe. Where is the pain? In her mind ... or in the toe? In a recent study, laypeople indicated that they thought the pain was in the toe. (Via Scientific American Mind)

Glucosamine no better than placebo for lower back pain

A Norwegian study published in the Journal of the American Medical Association showed that glucosamine has no effect on relieving lower back pain. Six million Americans take glucosamine supplements.
For six months, he and his colleagues gave 250 adults with chronic lower back pain and degenerative osteoarthritis either 2,500 mg daily of glucosamine sulfate or a placebo. At the six-month and one-year marks, there weren't any significant differences among patients in the two groups. Both groups did seem to be helped by the placebo effect, which is common in pain patients, in which people apparently feel better simply because they are receiving treatment.
Glucosamine No Remedy for Lower Back Pain, Says Study (via Consumerist)

Hidden sensory apparatus discovered in human skin

A transatlantic team of scientists have discovered a secondary sensory system, independent of the well-understood nervous system, hidden in the skin. These may be at the root of inexplicable chronic pain syndromes like fibromyalgia.
"It's almost like hearing the subtle sound of a single instrument in the midst of a symphony," said senior author Frank Rice, PhD, a Neuroscience Professor at Albany Medical College (AMC), who is a leading authority on the nerve supply to the skin. "It is only when we shift focus away from the nerve endings associated with normal skin sensation that we can appreciate the sensation hidden in the background."

The research team discovered this hidden sensory system by studying two unique patients who were diagnosed with a previously unknown abnormality by lead author David Bowsher, M.D., Honorary Senior Research Fellow at the University of Liverpool's Pain Research Institute. These patients had an extremely rare condition called congenital insensitivity to pain, meaning that they were born with very little ability to feel pain. Other rare individuals with this condition have excessively dry skin, often mutilate themselves accidentally and usually have severe mental handicaps...

The answer appeared to be in the presence of sensory nerve endings on the small blood vessels and sweat glands embedded in the skin. "For many years, my colleagues and I have detected different types of nerve endings on tiny blood vessels and sweat glands, which we assumed were simply regulating blood flow and sweating. We didn't think they could contribute to conscious sensation. However, while all the other sensory endings were missing in this unusual skin, the blood vessels and sweat glands still had the normal types of nerve endings. Apparently, these unique individuals are able to 'feel things' through these remaining nerve endings," said Dr. Rice. "What we learned from these unusual individuals is that there's another level of sensory feedback that can give us conscious tactile information. Problems with these nerve endings may contribute to mysterious pain conditions such as migraine headaches and fibromyalgia, the sources of which are still unknown, making them very difficult to treat."

Hidden Sensory System Discovered in the Skin

(Image: Nothing But Skin, a Creative Commons Attribution photo from kevindooley's photostream)