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Medicine Science

Neuron Path Discovery May Change Our Conception of Itching 161

Posted by timothy
from the just-please-don't-find-the-tickling-paths dept.
Hugh Pickens writes "Historically, many scientists have regarded itching as just a less intense version of pain, though decades spent searching for itch-specific nerve cells have been unfruitful. Now, Nature reports that neuroscientist Zhou-Feng Chen and his colleagues at Washington University in St. Louis, Missouri have found the first behavioral evidence that there are separate circuits of nerve cells to convey itchiness and pain, and their studies suggest that itch and pain signals are transmitted along different pathways in the spinal cord. 'Most people accept that there are specific, highly specialized neurons for sensations like taste,' says Chen. 'But for pain and itch this is much more controversial.'" (Continues below.)
"Two years ago, Chen's group discovered that a cell-surface protein called the gastrin-releasing peptide receptor (GRPR) is important for sensing itchiness but not pain in mice. When Chen and his colleagues destroyed GRPR-bearing neurons by means of a cell toxin, the mice reacted to painful stimuli just like normal mice, licking themselves and flinching or jumping in response to heat, highly irritant chemicals and mechanical pressure. But when the researchers injected the animals with chemicals that normally cause scratching, such as histamine, they barely responded, and the greater the number of GRPR-expressing neurons destroyed, the more subdued was the scratching response."
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Neuron Path Discovery May Change Our Conception of Itching

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  • by grub (11606) * <slashdot@grub.net> on Friday August 07, 2009 @01:37AM (#28982787) Homepage Journal

    [...] the first behavioral evidence that there are separate circuits of nerve cells to convey itchiness and pain, and their studies suggest that itch and pain signals are transmitted along different pathways in the spinal cord.

    This got me thinking...

    You know how it is when you're stuck in a conversation at work with Bob the Office Drone and you get a terrible itch building up in waves across your scrotum? The kind that makes you force a smile on your face while you're thinking "Man oh man, I wish Bob would fuck off so I could scratch myself!"

    Well... quadriplegics don't get that! Lucky bastards.

    Guess I'm a "the glass is 3% full" kind-of-guy.

    .
    • by DMUTPeregrine (612791) on Friday August 07, 2009 @02:27AM (#28983039) Journal
      Some do, actually. Phantom Limb syndrome does weird things. The worst bit is it's totally impossible to scratch it.
      • Phantom Scrotum Syndrome?

      • by CODiNE (27417)

        If they're only missing one limb then scratching the other side usually makes it stop. Now if you've lost BOTH limbs to that terrible accident then... errrr... well there's always transcendental meditation.

        • I saw something interesting about that. They used mirrors to make it seem to the person that the missing limb was actually there...in some cases it helped those symptoms.

          The (oversimplified) idea was that once your brain sees yourself with the missing limb apparently there and alright...it stops thinking that there is something wrong. I can't remember where I saw this.
          • by CastrTroy (595695)
            Also reminds me of this [scientificamerican.com]. They touch your hand (which is hidden) and a fake hand at the same time, and your mind begins to think the fake hand is your own.
          • by treeves (963993)
            This reminds me of something I read in a book by Richard Restak, a neurologist and author of several books on the brain. You can do an exercise with another person to fool your brain into accepting an inanimate object as being a part of your body. Sit in a chair across from the other person at a solid opaque table and have the other person tap your thigh (under the table where you can't see it) in exact synchrony with them tapping the table top. It has to be perfectly synchronized or it won't work. Do this
      • by skeffstone (1299289) on Friday August 07, 2009 @06:45AM (#28984229)
        This awesome TED talks talks about phantom limbs, and one way to truly remove them! http://www.ted.com/talks/lang/eng/vilayanur_ramachandran_on_your_mind.html [ted.com] Grab a cup of coffee, and enjoy! :)
      • by shaitand (626655)

        You know. I just realized that there is actually a condition under which I might consider castration... phantom blowjob syndrom. Where my phantom member always feels like I'm getting head.

    • Re: (Score:2, Funny)

      by dov_0 (1438253)

      you're stuck in a conversation at work with Bob the Office Drone and you get a terrible itch building up in waves across your scrotum? The kind that makes you force a smile on your face while you're thinking "Man oh man, I wish Bob would fuck off so I could scratch myself!"

      You wait til people are gone before you scratch?

    • Well... quadriplegics don't get that! Lucky bastards.

      Are you sure, quads get phantom limb pain, so I assume phantom limb itching is also likely; imagine an itch that can't be scratched. I burned my hand a few years ago, at the burn clinic they, in a teaching hospital, aways ask about pain, never about itching. Finally one Dr. from another hospital casually mentioned that benedryl would stop the itching. Imagine the gritty itch from a bad sunburn lasting for 3 months, God bless that Dr.

    • by PopeRatzo (965947) *

      As my old friend Willy the Pimp used to say, "I hate the itch, but I love that scratch."

  • Ouch. Torturous. (Score:3, Insightful)

    by BobSixtyFour (967533) on Friday August 07, 2009 @01:39AM (#28982791)

    "Mice that had lost the GRPR-producing neurons reacted to painful stimuli just like normal mice, licking themselves and flinching or jumping in response to heat, highly irritant chemicals and mechanical pressure."

    Poor mice :(

    • by DNS-and-BIND (461968) on Friday August 07, 2009 @02:02AM (#28982929) Homepage
      If hooking a car battery up to a monkey's brain will help find the cure for AIDS and save somebody's life, I have two things to say... the red is positive and the black is negative.
      --Nick Dipaolo
      • by Rakshasa Taisab (244699) on Friday August 07, 2009 @02:16AM (#28983005) Homepage
        Hey, I'd be all ok even if it was your brain being wired up for some car battery shocks.
      • by dcollins (135727) on Friday August 07, 2009 @02:44AM (#28983109) Homepage

        "If hooking a car battery up to a monkey's brain will help find the cure for AIDS and save somebody's life, I have two things to say... the red is positive and the black is negative.
        --Nick Dipaolo"

        What if it's a hundred monkeys? A million monkeys? A billion? What if there's a 5% chance it might help? What if it's a researcher who thinks it might help, but hasn't been right to date?

        • by The_mad_linguist (1019680) on Friday August 07, 2009 @02:48AM (#28983125)

          They're just monkeys.

          Lazy bastards haven't finished my copy of Hamlet.

          Work harder, you ingrates!

          • They might not have finished your copy of Hamlet, but have produced an enormous amount of Perl code.

        • by z0idberg (888892)

          What if you had AIDS and it might cure you?

        • Re: (Score:3, Funny)

          by nacturation (646836) *

          What if it's a hundred monkeys? A million monkeys? A billion? What if there's a 5% chance it might help? What if it's a researcher who thinks it might help, but hasn't been right to date?

          As long as it's not an infinite number of monkeys brains being bashed in with an infinite number of typewriters because then we'd not only destroy the complete works of Shakespeare, but also the cure for every problem there is.

        • by pipingguy (566974) *
          OK then, let's replace the monkeys with animal rights activists then. Same screeching noises and poo-flinging but less guilt.
        • What if it's a hundred monkeys? A million monkeys? A billion?

          This is a ridiculous rhetorical situation for several reasons. Mostly because frying monkey brains isn't going to cure aids, but also because you're not going to get a billion damn monkeys.

          What if there's a 5% chance it might help?

          Another ridiculous point: describe to me how a research experiment might have a "5% chance" instead of "Well, it seems like it might work, but we won't know until we test" you know, like every research project out there. You think you have a cure and it's only afterward that you find out that you do or don't, there's no

        • What if it's a hundred monkeys? A million monkeys? A billion?

          Then you'd probably have enough dead monkeys to open up your own chain restaurant. Thankfully, fried monkey brain and fried monkey toes are still a delicacy in some parts of the world.

      • by Krneki (1192201)
        I'm positive this will work, HIV positive.
      • by MobyDisk (75490)

        Dammit! I CANNOT find the red terminal on this monkey!

    • by Fluffeh (1273756)
      You should see what they do to test the products we all use everyday. Double ouchies.
      • by superwiz (655733)
        Better test them on monkey than on animal rights activists. I would actually be against any animal-rights activists that would volunteer to take a monkey's place in an experiment. Peoples' well-being comes before animals'.
        • by Golddess (1361003)

          Peoples' well-being comes before animals'.

          I take it then that you are against other people smoking, drinking, eating fatty foods, red meat, white meat, fish, or even simply living (just to name a few things), even if it does not affect you in any way?

          If someone wants to volunteer themselves to be a guinea pig, I say let them.

          • by superwiz (655733)
            That's a false analogy. I am not suggesting that animal rights activists should go to jail for volunteering to take a place of a monkey (not that this is even scientifically useful or feasible but just to humor the ethical question). What I am suggesting is that a scientist who would accept their donation of themselves while an experiment could be performed on a monkey would be acting unethically. They should chose to harm an animal if it can spare a suffering of a human being.
      • by darpo (5213)
        Speak for yourself. Some of us do our best to buy product brands -- my laundry detergent and dish soap, for example -- that aren't tested on animals.
  • by syousef (465911) on Friday August 07, 2009 @01:40AM (#28982795) Journal

    I propose the name "STD detection neuron pathway". Now hand me that cream and leave me alone.

  • Itch (Score:5, Insightful)

    by Tofof (199751) on Friday August 07, 2009 @01:42AM (#28982809)
    Great. After reading that, now I'm keenly aware of itching sensations all over my body - not unlike watching someone yawn.
  • by WindBourne (631190) on Friday August 07, 2009 @01:42AM (#28982813) Journal
    I have always thought that Evolution prefers the minimal amounts needed for life (greater complexity is difficult to maintain UNLESS for a reason). As such, it would be easier on life if the same neuron conveys pain and itch. Yet, Evolution chose to do something different.

    I wonder what was the stimuli for that?
    • by ZackSchil (560462) on Friday August 07, 2009 @01:49AM (#28982843)

      Removal of parasites, probably.

    • Re: (Score:3, Interesting)

      by wizardforce (1005805)

      the two sensations could have evolved at differing times. pain would be most useful to prevent damage and the abiltiy to sense an itch is useful for correcting problems such as dry skin, certain chemical exposure etc. pain is associated with injury perhaps cells that sense an itch don't work the same way [no one has lopped off an arm and felt an itch for it after all...]

      • by ZackSchil (560462) on Friday August 07, 2009 @01:58AM (#28982909)

        [no one has lopped off an arm and felt an itch for it after all...]

        Clearly you've never lost a limb. Phantom limb sensations cover pressure, pain, temperature, and irritation. You definitely can feel an itch on an arm or leg that has been lopped off.

        • if someone hacks off an arm they are not going to experience anything other than pain first.

          • by WindBourne (631190) on Friday August 07, 2009 @03:24AM (#28983279) Journal
            Actually, I used to be an EMT back in the 80's. I can tell you that it was easier to deal with ppl that lost fingers or limbs because they RARELY felt it. Likewise, the guy who had been in a gasoline explosion (but his pain was to come; horrible injury to have). The reason is that their body regularly shut down in terms of pain. OTH, a compound fracture of the femur was wicked painful. The gal was screaming, but did not notice the bit that we drilled into her knee. The reason is that all the various muscles around the femur had contracted and the muscles were cramping. Severe pain, but not enough for her body to shut it down. Likewise, a nail had been pulled off and in another case, a piece of wood had gone under a nail (accident), etc. In each case, the pain was enormous, but not enough to shut them down.
            • When the thought "Wow I'm not screaming like a school girl" runs through your mind, you know your really fucked up.

        • by mcgrew (92797)

          It doesn't even have to be lopped off. A friend of mine lost all use of one of his arms in a motorcycle wreck, and even though the limb is still there but the nerves were severed, he still feels pain. The doctors can't do anything about it.

        • Re: (Score:3, Funny)

          by pipingguy (566974) *
          'Tis but a scratch.
    • by Renraku (518261) on Friday August 07, 2009 @02:37AM (#28983083) Homepage

      The reason for pain is to make you escape something.

      Such as burning yourself on a stove, getting stabbed, bitten, stung, etc. You don't want these things to happen. Pain is strongly connected with negative in most minds. At least, most pain..

      The reason for itching is to call your attention to something.

      It's kind of the difference between a critical error and an error. One's a dire warning, and the other one is just an exclamation. It would be very fucking useful to distinguish between the two. One, so that you don't freak out every time you walk through some grasses that tickle your legs. Two, so you don't beat your bed-mate to death when they rub up against you. Three, so you don't let bugs chew on you or flip out every time one does.

      I'll bet the 'itching' pathways have other uses as well. Perhaps the tickling response is there?

      • by ShakaUVM (157947) on Friday August 07, 2009 @03:33AM (#28983327) Homepage Journal

        >>I'll bet the 'itching' pathways have other uses as well. Perhaps the tickling response is there?

        Tickling, I believe, is linked with touch. Your brain suppresses/mutes touches done to yourself, which is why most people can't tickle themselves. How does the brain tell? If your motion and the sensation come within a threshold of each other, it mutes the sensation. I think there's something like a 45ms threshold involved - when people moved a machine that then moved a tickling finger, if they added a delay of more than 45ms to it, suddenly people could tickle themselves.

        There's a lot of interesting hacks inside the human brain.

        • by HTH NE1 (675604)

          Tickling, I believe, is linked with touch. Your brain suppresses/mutes touches done to yourself, which is why most people can't tickle themselves.

          You can't tickle yourself with numb fingers either.

          And yet masturbation works.

    • by bronney (638318)

      You don't touch yourself much do you?? Sexual stimuli is very close to itching. Try it, you might like it.

    • Re: (Score:3, Insightful)

      Actually, this is possibly an excellent example of evolution minimizing complexity through the tactic of re-purposing the same system to be used in different ways in different parts of an organism. As the article notes, the neurons that may be specific to itchiness have a cell surface protein called gastrin-releasing peptide receptor. Gastrin, as the name might suggest, also plays a role in the gastrointestinal system, where it is involved in signaling the release of hydrochloric acid. What do your diges
    • by Dahamma (304068)

      I think you are anthropomorphizing a very broad theory/process waaay too much...

      Evolution is basically a series of random changes that results in a higher overall rate of survival. There is really nothing logical or simplifying about it - for example, the vast majority of a human brain, or even the human DNA sequence, is unused. Could be "obsolete" structures, or just random changes/development that never served a purpose but also never had any negative consequences.

      If someone were able to design a human

      • Back in 79/80, when I was in my Genetics class, I had the weird idea as applied to cells. In particular, prof said that DNA was mostly empty space and did absolutely nothing. In addition, it was well known at that time that DNA and RNA only served as mapping and they had absolutely no other function. I told the prof that that kind of logic made zero sense. My rational was that cells will go towards the minimal energy usage and maintaining millions and even billions of base pairs is VERY expensive. I suggest
      • by shiftless (410350)

        for example, the vast majority of a human brain, or even the human DNA sequence, is unused.

        [citation needed]

  • by rrohbeck (944847) on Friday August 07, 2009 @02:42AM (#28983099)

    Remember, every successful FOSS project started with a developer who had an itch to scratch. Clearly we need more itching.

    • Obviously so did porn. Not sure if "scratch" is the right word there, though ;)

    • Remember, every successful FOSS project started with a developer who had an itch to scratch.

      When I say a niche, I don't mean an itch like you have when you have an itch. I mean a niche like you have when you have a notch.

  • This is old news (Score:5, Informative)

    by The_mad_linguist (1019680) on Friday August 07, 2009 @02:51AM (#28983139)

    Saw it in Science News last year. November 22, 2008.

    http://www.sciencenews.org/view/feature/id/38338/title/Itch [sciencenews.org]

  • Torture (Score:4, Interesting)

    by mr100percent (57156) * on Friday August 07, 2009 @03:55AM (#28983447) Homepage Journal

    I hope they don't use this to build the Agony Booth found in Star Trek.

  • by mrjb (547783) on Friday August 07, 2009 @04:23AM (#28983561)
    After a dentist visit with local anesthesia, I got bitten by a mosquito which caused a terrible itch on my cheek- but I couldn't feel my scratching to relief it. NOT FUN.
  • I recall a documentary where a woman had lost her sense of touch, but she still responded to stroking. The explanation was two different systems of nerves. A particularly interesting bit was that the sense of stroking was much slower, as if the signals only travelled around one meter per second. Given the fine line between stroking and tickling, this seems like the same phenomenon as in the article.
  • by DynaSoar (714234) on Friday August 07, 2009 @05:55AM (#28983991) Journal

    A nice article and summary. Not entirely new nor inclusive of present theory unfortunately.

    Pain is handled by two channels: nocioception, the sensation itself, and the perceptual distress component. This can easily be seen in the actions of the agents affecting each. Sensation is blocked by anesthesia. Interpretation of the pain signal is altered by analgseia -- you may still feel a sensation but you don't care, or at lest you're not so bothered by it. There are different neural pathways and processes to handle these.

    It is likely that itching relates to pain in this fashion. The sensation of pressure or stretching of the skin in certain places would be common to all as their are receptors in the skin for these. A parallel pathway governing perceptual interpretation of that sensation, possibly the same one as for pain, would also exist. The resulting interpretation based on personal experience and/or genetically determined wiring would cause different interpretations of the same experience on different individuals, the same individual under different conditions, or (as is common) different locations on the same individual.

    • by Zerth (26112)

      When I got my wisdom teeth out, I was given an analgesic instead of anesthesia. I knew it hurt like a bitch, but I thought it was the coolest thing ever, since it didn't bother me in the least.

      My dentist said he kind of regretted giving me the choice, because the assistant had to keep me from poking at the sockets and getting in the way.

      Man, was I wishing for some more analgesic when I only had painkillers the next day. I'd rather be in pain and not give a shit then have the choice between kinda hurts vs

  • the phantom itch

    http://www.newyorker.com/reporting/2008/06/30/080630fa_fact_gawande?currentPage=all [newyorker.com]

    same neurological basis as a phantom limb, but far more rare (blessedly so)

    it is probably one of the greatest definitions of hell on earth. the itch that never, ever goes away:

    M. was willing to consider such possibilities. Her life had been a mess, after all. But the antidepressant medications often prescribed for O.C.D. made no difference. And she didn't actually feel a compulsion to pull out her hair. She simply felt itchy, on the area of her scalp that was left numb from the shingles. Although she could sometimes distract herself from it--by watching television or talking with a friend--the itch did not fluctuate with her mood or level of stress. The only thing that came close to offering relief was to scratch.
    "Scratching is one of the sweetest gratifications of nature, and as ready at hand as any," Montaigne wrote. "But repentance follows too annoyingly close at its heels." For M., certainly, it did: the itching was so torturous, and the area so numb, that her scratching began to go through the skin. At a later office visit, her doctor found a silver-dollar-size patch of scalp where skin had been replaced by scab. M. tried bandaging her head, wearing caps to bed. But her fingernails would always find a way to her flesh, especially while she slept.
    One morning, after she was awakened by her bedside alarm, she sat up and, she recalled, "this fluid came down my face, this greenish liquid." She pressed a square of gauze to her head and went to see her doctor again. M. showed the doctor the fluid on the dressing. The doctor looked closely at the wound. She shined a light on it and in M.'s eyes. Then she walked out of the room and called an ambulance. Only in the Emergency Department at Massachusetts General Hospital, after the doctors started swarming, and one told her she needed surgery now, did M. learn what had happened. She had scratched through her skull during the night--and all the way into her brain.

    ...

    The second theory seemed less likely. If the nerves to her scalp were dead, how would you explain the relief she got from scratching, or from the local anesthetic? Indeed, how could you explain the itch in the first place? An itch without nerve endings didn't make sense. The neurosurgeons stuck with the first theory; they offered to cut the main sensory nerve to the front of M.'s scalp and abolish the itching permanently. Oaklander, however, thought that the second theory was the right one--that this was a brain problem, not a nerve problem--and that cutting the nerve would do more harm than good. She argued with the neurosurgeons, and she advised M. not to let them do any cutting.
    "But I was desperate," M. told me. She let them operate on her, slicing the supraorbital nerve above the right eye. When she woke up, a whole section of her forehead was numb--and the itching was gone. A few weeks later, however, it came back, in an even wider expanse than before. The doctors tried pain medications, more psychiatric medications, more local anesthetic. But the only thing that kept M. from tearing her skin and skull open again, the doctors found, was to put a foam football helmet on her head and bind her wrists to the bedrails at night.
    She spent the next two years committed to a locked medical ward in a rehabilitation hospital--because, although she was not mentally ill, she was considered a danger to herself. Eventually, the staff worked out a solution that did not require binding her to the bedrails. Along with the football helmet, she had to wear white mitts that were secured around her wrists by surgical tape. "Every bedtime, it looked like they were dressing me up for Halloween--me and the guy next to me," she told me.
    "The guy next to you?" I asked. He had had shingles on his neck, she explain

    • Mod parent up. Good link to an utterly fascinating article, though, from the article, it seems to suggest not so much that itch is a function of nerves/nerve endings insofar as itch is a function of the brain. The linked article even makes car analogies. A must read. :)
      • i have tinnitus

        which, really, is "phantom hearing"

        i hear a steady tone all day, and its not in my ear, its in my brain. i've grown used to it, accepting the fact i'll have this my whole life, and so it doesn't really bother me that much anymore, i go whole weeks now barely paying it any attention, and your mind just edits it out of daily life

        but in the article they talk about the guy with the phantom limb pain... and they do a little trick with him standing perpendicular to mirror, and the brain sees two ar

        • by schweini (607711)
          I just thought of an experiment:
          Assuming your tinnitus is a near-constant frequency sine wave, what happens if you try to cancel the imaginary sound out using an external sound?
          I have no idea whether it's even possible to try to sync soundwaves that exactly by hand/mind, but maybe you can hear/perceive some interference, at least?
          I'm not saying that this could be a cure for tinnitus, but me, at least, would be fascinated if imaginary sounds can interfere and maybe even cancel out physical sounds...
          • noise cancellation by matching the frequencies and volumes is actually not that wacky, because the tone i hear is very high frequency, very low volume, perfectly constant and a perfect tone. meaning it is simple, not complex. so it wouldn't be difficult to match and cancel out

            however, the problem is, like a phantom limb, phantom hearing is deafness... its just that with tinnitus the matching circuitry in the brain is left in the on position rather than the off position

            the tiny hairs in my ear at that freque

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