Heat eases pain: official

Got a painful stomach cramp? Stick a hot water bottle on it, and smile in the knowledge that science is on your side. A group of physiologists at University College, London, has proven that heat can reduce internal pain.

The research, which will be presented at the Physiological Society's annual conference, unravels the molecular processes at work, and shows that when applied to the skin, heat can actually de-activate pain sensors.

Dr Brian King, from UCL's department of Physiology, said: "The pain of colic, cystitis and period pain is caused by a temporary reduction in blood flow to or over-distension of hollow organs such as the bowel or uterus, causing local tissue damage and activating pain receptors.

"The heat doesn't just provide comfort and have a placebo effect – it actually deactivates the pain at a molecular level in much the same way as pharmaceutical painkillers work. We have discovered how this molecular process works."

A molecule called adenosine tri-phosphate, which can act as a neuro-transmitter and neuromodulator, is released by damaged (i.e. dying) and dead cells. It is used as a fuel by the body, but it also activates the P2X3 pain receptors, causing the sensation of pain.

If heat receptors, called TRPV1, in the same region are activated by the application of heat of over 40°C to the skin, they can block the signals from the P2X3 receptor, thus stopping the body from feeling any pain for up to half an hour.

Dr King says although the pain relief is only temporary, the work demonstrates that the P2X3 receptor is key to the development of new pain-killing drugs. ®