Re: [silk] Now we know - How scratching can stop an itch
On Tuesday 07 Apr 2009 12:25:19 pm Kiran K Karthikeyan wrote: http://news.bbc.co.uk/2/hi/health/7976606.stm *Scientists have shown scratching helps relieve an itch as it blocks activity in some spinal cord nerve cells that transmit the sensation to the brain.* However, the effect only seems to occur during itchiness itself - scratching at other times makes no difference. While it is widely-known scratching relieves an itch, the physiological mechanisms for how this works are little understood. I am no neuroendocrine expert on itching but over the years I have developed theories which have no proof and I read idly when something related appears. One of the first things I was taught in physiology as a medical student was the ppearance of a red line on the skin called a weal when said skin is scratched with a blunt object. The weal appears because chemicals are released under the skin that cause blood vessels to dilate up and leak fluid in response to injury. Scratching achieves exactly this efect and I am surprised if there is no link between the release of local chemicals in respnse to a sctratch that help mask the itch. Shyam - are you reading? You might know. The other thing is the psychological appearance of an itch. If you are walking along a road and you stare at a good looking woman long enogh she will eventually develop a itch on her forehead that will cause her to raise her hand and scratch that itch. Funnily enough the raising of the hand also shields her face and possibly her upper chest as well from your stare. But if she is asked, she will admit only to an itch. Maybe science will either corroborate or rubbish my observations one day But I must point out that even my dog has a psychologically provoked itch. She scratches when she is upset at not being allowed to do something. shiv
[silk] Now we know - How scratching can stop an itch
Thought this was interesting :) http://news.bbc.co.uk/2/hi/health/7976606.stm *Scientists have shown scratching helps relieve an itch as it blocks activity in some spinal cord nerve cells that transmit the sensation to the brain.* However, the effect only seems to occur during itchiness itself - scratching at other times makes no difference. While it is widely-known scratching relieves an itch, the physiological mechanisms for how this works are little understood. The University of Minnesota study appears in Nature Neuroscience. Previous research has suggested that a specific part of the spinal cord - the spinothalamic tract - plays a key role. Nerve cells in this area have been shown to be more active when itchy substances are applied to the skin. Blocks activity The latest work, in primates, found that scratching the skin blocks activity of nerve cells in the spinothalamic tract during itchiness - preventing the spinal cord from transmitting signals from the scratched area of skin to the brain. Researcher Dr Glenn Giesler hopes the work could lead to ways to relieve chronic itch effectively for the first time. However, he said more information was still needed about the chemistry underpinning the effect. Professor Gil Yosipovitch, an expert on itching from Wake Forest University in North Carolina, said the finding was potentially significant. He said: Although there is a long way to go, methods that can induce a pleasurable scratch sensation without damaging the skin, via mechanical stimuli or drugs that can inhibit these neurons, could be developed to treat chronic itch. However, Professor Yosipovitch stressed that scratching and itching were complex phenomena involving factors such as emotions as well as physiology. The main open question is what happens in patients who suffer from chronic itch where scratching may actually aggravate itch perception. Professor Patrick Haggard, of University College London, said: We all know that scratching helps alleviate itch, but this elegant study helps to show how this mechanism works. It's an interesting illustration of a very general principle of the brain controlling its own inputs, in this case by making movements that triggers an interaction between scratchy touch and itch. Dr Paul Bays, based at UCL's Institute of Cognitive Neuroscience, agreed that the study provided an important part of a physiological explanation for how the sensation of itch is reduced. However, it is still unclear why scratching should have this effect, or why it is only effective for itches and not for painful sensations - which are transmitted to the brain through the same pathway. Kiran
Re: [silk] Now we know - How scratching can stop an itch
--- On Tue, 7/4/09, Kiran K Karthikeyan kiran.karthike...@gmail.com wrote: From: Kiran K Karthikeyan kiran.karthike...@gmail.com Subject: [silk] Now we know - How scratching can stop an itch To: silklist@lists.hserus.net Date: Tuesday, 7 April, 2009, 12:25 PM Thought this was interesting :) Talk of a straight line: There was a young lady of Natchez Whose clothes were always in patchez When asked why She said in reply When Ah itchez, Ah scratchez. http://news.bbc.co.uk/2/hi/health/7976606.stm *Scientists have shown scratching helps relieve an itch as it blocks activity in some spinal cord nerve cells that transmit the sensation to the brain.* However, the effect only seems to occur during itchiness itself - scratching at other times makes no difference. While it is widely-known scratching relieves an itch, the physiological mechanisms for how this works are little understood. The University of Minnesota study appears in Nature Neuroscience. Previous research has suggested that a specific part of the spinal cord - the spinothalamic tract - plays a key role. Nerve cells in this area have been shown to be more active when itchy substances are applied to the skin. Blocks activity The latest work, in primates, found that scratching the skin blocks activity of nerve cells in the spinothalamic tract during itchiness - preventing the spinal cord from transmitting signals from the scratched area of skin to the brain. Researcher Dr Glenn Giesler hopes the work could lead to ways to relieve chronic itch effectively for the first time. However, he said more information was still needed about the chemistry underpinning the effect. Professor Gil Yosipovitch, an expert on itching from Wake Forest University in North Carolina, said the finding was potentially significant. He said: Although there is a long way to go, methods that can induce a pleasurable scratch sensation without damaging the skin, via mechanical stimuli or drugs that can inhibit these neurons, could be developed to treat chronic itch. However, Professor Yosipovitch stressed that scratching and itching were complex phenomena involving factors such as emotions as well as physiology. The main open question is what happens in patients who suffer from chronic itch where scratching may actually aggravate itch perception. Professor Patrick Haggard, of University College London, said: We all know that scratching helps alleviate itch, but this elegant study helps to show how this mechanism works. It's an interesting illustration of a very general principle of the brain controlling its own inputs, in this case by making movements that triggers an interaction between scratchy touch and itch. Dr Paul Bays, based at UCL's Institute of Cognitive Neuroscience, agreed that the study provided an important part of a physiological explanation for how the sensation of itch is reduced. However, it is still unclear why scratching should have this effect, or why it is only effective for itches and not for painful sensations - which are transmitted to the brain through the same pathway. Kiran Add more friends to your messenger and enjoy! Go to http://messenger.yahoo.com/invite/
