The Difference between Touch and Pain no longer such a Mystery

The ability to read Braille, crack a safe, or enjoy a kiss is due to specific sensory receptors in the skin of humans. Animals also possess such sensors for touch and pain called mechanoreceptors. Both senses are of vital importance for both animals and humans. However, up until now very little was known about how these receptors function and what makes them so specific for touch or pain. Dr. Jung-Bum Shin from the research group of Dr. Gary Lewin working in the Max Delbrück Center for Molecular Medicine (MDC) Berlin-Buch, a national research laboratory in Berlin (Germany) has thrown new light onto this problem. The findings of Dr. Shin have been published online by the prestigious Journal Nature Neuroscience*. They provide the first evidence that in vertebrates (mice) certain ion channels - in this case – a calcium channel which is required specifically for the function of a touch sensing mechanoreceptor. The neuroscientist assume that similar receptors also exist in humans.

The sensory nerve cells the scientists have investigated are located next to the spinal cord and possess long arms (axons), which end in the skin. In the skin they contain sensors for touch or pain. Using microarrays the MDC scientists were able to demonstrate, that the various mechanosensors in the skin can be distinguished by the expression of single genes. “We have demonstrated for the first time that a genome-wide screen can be successfully used to identify a functionally relevant gene that is specific to one type of vertebrate mechanoreceptor”, Dr. Lewin points out. “This makes it possible to utilize gene expression as a marker for touch receptors”, he stresses.

One of the most important findings was, that one type of supersensitive mechanoreceptor possesses a special calcium channel. Calcium channels are proteins vital for the excitation of muscle and nerve cells. They are located in the membrane of a cell and act as selective pores for the exchange of calcium ions between the cell and its environment. This enables cells to communicate with each other and their surroundings.

The findings of Dr. Shin show, that the presence of this specific calcium channel greatly enhances the sensitivity of the mechanoreceptor. It is known that ion channels can be blocked by chemical substances that can be used as drugs. Calcium ion channels are physically blocked  by such drugs. One potential medical application for this new finding is to block the hypersensitivity to touch stimuli that often follows injury or inflammation of the skin. Thus drugs designed to block the calcium channel described in this study may be effective in treating some of our aches and pains

Barbara Bachtler
Press and Public Affairs
Max Delbrück Center for Molecular Medicine (MDC) Berlin-Buch
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13125 Berlin
Germany

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