Out from the cold -- the gene that tells you when it's chilly

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PARIS (AFP) - Pioneering lab mice have shed light on a key gene that

detects the cold, researchers report in Thursday's issue of Nature,

the British science journal.

The rodents were engineered to lack a gene that governs a molecular

switch called transient receptor potential melastatin 8, or TRPM8.

TRPM8 is a so-called ion channel on sensory nerve fibres in the skin.

When the ambient temperature drops below 26 degrees Celsius (79

Fahrenheit), the channel opens up, admitting an influx of calcium ions

into the nerve fibre, which sends an electrical signal to the brain.

But mice without TRPM8 behaved quite normally, unable to discriminate

between hot and cold surfaces until the temperature fell below 15

degrees Celsius (59 degrees Fahrenheit), according to investigators

led by Julius at the University of California in San Francisco.

At colder temperatures, the mice avoided contact with surfaces below

10 C (50 F) but their behaviour was clumsy.

TRPM8 has been previously dubbed " the minty-cool ion channel " because

it is sensitive to menthol, a natural flavouring that also induces the

sensation of cold.

Insight into TRPM8 and other suspected thermosensitive channels could

have a medical spinoff, as they also appear to be used as a pathway

for sensing pain.

Understanding more about how they work could lead one day to smarter

pain relief with fewer side effects, it is hoped.