Feeling pain in cold conditions 30/07/07. By the Wellcome Trust Researchers have identified a key component of the system that allows nerve cells to feel pain under cold conditions.

The ability to sense pain is essential for avoiding physically harmful situations. But pain that comes from the cold poses a special challenge: the low temperatures can stop nerves from functioning, as anyone who has gone numb from cold can attest. A team of scientists from Germany, Romania, Japan, Spain and University College London, UK, have now identified a protein called Nav1.8 that keeps nerves working in the cold.

Nerves transmit electrical signals by opening channels on the cell surface (like pores) that let charged molecules, such as sodium, pass into and out of the cell. Pain-sensing nerve cells use two types of sodium channel: fast and slow. The researchers found that when both are active, nerves keep functioning as the temperature drops. Using a toxin to block the fast channel had no effect on the activity in the cold, but nerves deprived of the slow channel were unable to respond as the temperatures dropped.

The researchers confirmed this finding by placing mice on a plate held at freezing temperatures. Normal mice work to keep their feet away from the cold, while mice lacking the slow channel were indifferent to the chill. So, although this protein isn't what lets nerves detect the cold, it's essential for keeping them signalling the cold to the brain as temperatures drop.

• This research was supported in part by the Wellcome Trust.

Reference

Zimmermann K et al. Sensory neuron sodium channel Nav1.8 is essential for pain at low temperatures. Nature 2007;447(7146):855-8. Abstract