Ever wonder why mint- flavored toothpaste creates a cooling sensation? Researchers at two institutions have determined why. They discovered nerve receptors that react to cold and menthol, a cooling agent found in mint oils.
Researchers at University of California, San Francisco reported in the Feb. 11 issue of Nature that they had identified the cold- and menthol-sensitive receptor, or CMR1. It is a type of ion channel that belongs to the transient receptor potential, or TRP, family. Environmental changes cause these channels to change the flow of ions into nerve cells and produce a nerve signal that results in a sensation. Researchers propose that CMR1 functions as a transducer of cold stimuli in the somatosensory system.
A research team from The Scripps Research Institute in La Jolla, Calif., reported in the March issue of the journal Cell that a TRP receptor called TRPM8 also reacts to cold and menthol. This ion channel becomes activated below 25 C and opens, allowing an influx of calcium ions into the axon. The axon then relays the message to the brain.
"These channels respond directly to cold temperature," said Ardem Patapoutian, Ph.D., lead author of the study. "And they offer interesting insight into the fundamental biology of cold perception."
