When we feel pain in response to harmful stimuli it is the result of messages sent from pain sensors in the periphery of the body to the brain. These pain sensors – or nociceptors – often lie beneath the skin and detect and signal the presence of tissue-damaging stimuli or the existence of tissue damage. One particular nociceptor, vanilloid receptor-1 (VR1), relays sensory messages to the brain in response to thermal and painful chemical stimuli and is generally regarded as the major pain sensor.
In conditions such as arthritis or infection, the tissue involved at these sites becomes acidic. While normal human tissue has a neutral pH of approximately 6.5 - 7.5 (similar to water), tissue acidosis can cause a drop in cellular pH below 6.0 closer to that of household vinegar. When the cellular environment becomes acidic, both VR1 and a second nociceptor - acid sensing ion channels (ASICs) - are activated. In previous experiments in mice, scientists have found that the activation of VR1 requires extremely severe acidification - pH less than 6.0. This suggests that another pain sensor plays a role in nociception, specifically at pH levels greater than 6.0. Despite experimental data revealing that mouse neurons lacking ASICs are severely deficient in their responses to acidic stimuli, controversy remains about the function of ASICs in mammals.
In a study reported in the October 21 issue of the Journal of Clinical Investigation (JCI) by Shinya Ugawa and colleagues from the Nagoya City University Medical School, Japan, the authors demonstrated that both VR1 and ASICs are involved in the sensing of acid-evoked pain in humans and that each type of nociceptor mediates this pain perception at very specific pH ranges. The authors infused solutions of varying pH levels under the skin of the underside of the upper forearm of healthy male volunteers who were subsequently asked to estimate the intensity of the induced pain on a 0-10 scale. To determine which particular nociceptor was activated at each pH level, the authors systematically blocked ASICs-mediated pain perception with the ASICs inhibitor amiloride or VR1-mediated pain perception with the VR1-inhibitor capsazepine and then recorded the intensity of pain indicated by the subject in response to the solutions of various pH. Ugawa and colleagues found that amiloride potently blocked pain induced by solutions with a pH greater than 6.0, while capsazepine did not. At pH levels below 5.0, amiloride was less effective in reducing pain and capsazepine had a partial blocking effect.
Brooke Grindlinger, PhD | EurekAlert!
New vaccine production could improve flu shot accuracy
25.07.2017 | Duke University
Chances to treat childhood dementia
24.07.2017 | Julius-Maximilians-Universität Würzburg
Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers
Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...
Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.
At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...
3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects
A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...
Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.
For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...
What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.
To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...
21.07.2017 | Event News
19.07.2017 | Event News
12.07.2017 | Event News
25.07.2017 | Physics and Astronomy
25.07.2017 | Earth Sciences
25.07.2017 | Life Sciences