Scientists at the University of Southern California have found a way to turn off the neuron responsible for sensing cold in mice, and it could help humans who have extreme sensitivities to cold temperatures.
The neuron channel, called TRPM8, is responsible for sensing "normal cold responses in mammals," according to David McKenny, the neurobiologist responsible for the study, which was published in the Journal of Neuroscience Tuesday. By turning it off in mice, the animals turned "insensitive to cool and painfully cold temperatures" and "did not distinguish between cold and a preferred warm temperature." The mice were still able to feel warm temperatures and pain.
Though the process is currently irreversible, McKenny says if pharmaceutical companies can develop a drug that will make the effect temporary, it could be useful for patients with certain conditions that make them hypersensitive to cold temperatures.
"Some side effects of certain chemotherapy drugs cause sensitivity to the cold—so much that a cool glass of water is excruciatingly cold," he says. "Some diabetics and people who have bone injuries also show these sorts of things."
McKenny was able to eliminate the neurons by injecting mice with a form of the bacteria that causes diphtheria, which causes upper respiratory problems in humans. His team coded the bacteria to specifically kill cells containing TRPM8.
"Behaviorally, mice lacking TRPM8 channels fail to distinguish warm from cool and poorly avoid noxious cold," according to the report. Mice that were given treatment showed "no defects in heat sensing," suggesting that TRPM8 is responsible only for cold sensations.
While inhibiting TRPM8 in humans could have some therapeutic uses, McKenny says his process is unlikely to have much everyday value—don't expect to be able to take pills someday that will let you go outside in winter without a coat.
"You probably wouldn't want to do that," he says. "When we feel pain from the cold, there's a reason for that—it's your body telling you to get out of the cold. If you don't know it's cold, then that's a bad thing."