Brr! The science of feeling cold

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Brr! The science of feeling cold

Study: A single protein directs the nerves that sense chilly

sensations

http://www.msnbc.msn.com/id/22316336/

Nerves that sense the icy slap of an arctic wind or just a cool

breeze take their orders from a single protein, U.S. researchers

said on Monday, shedding new light on how we experience cold.

Prior studies have suggested cold-sensing neurons are specialized,

with some detecting painful cold sensations and others detecting

more pleasant ones.

But researchers at the University of Southern California have found

that even though most cold-sensing neurons make use of a single

protein known as TRPM8, they can detect a range of sensations.

" We all know when we stimulate our teeth with cold we get this

distinct cold sensation, " said McKemy, whose study appears in

the Journal of Neuroscience.

" You get this sharp transient shooting pain and this dulled, aching

sensation, " McKemy said in a telephone interview.

Other groups have attributed that to two different cold sensory

neurons. " There was a notion that there were neurons called cool

fibers and there were others involved in detecting cold pain, " he

said.

He said he had expected neurons that express, or produce, TRPM8 to

be of the pleasant cool variety.

To study the neurons, McKemy genetically engineered mice so that

neuron fibers that expressed this protein would be fluorescent

green. He then traced these cold-sensing fibers from sensory neurons

near the spinal cord to nerve endings in the skin.

" What our study suggests is that even though these neurons express

this single protein, it looks like they have diverse functions, " he

said.

Humans appear to share the same mechanism, he said.

McKemy said nerves that produce TRPM8 account for about 75 percent

of all cold-sensing neurons. He believes there are others that are

specific to pain, such as when the skin is burned in frostbite.

Researchers study cold-sensing neurons to grasp the molecular

mechanisms of sensation, an understanding that may lead to better

drugs for pain relief.

" If we understand the basic nuts and bolts of the molecules and

neurons and how they detect pain normally, then perhaps we can

figure out why we detect pain when we shouldn't, " McKemy said in a

statement.