"It's been known for years that menthol and related cooling agents evoke the psychophysical sensation of cold – somehow by interacting with the aspect of the sensory nervous system that's related to cold detection," says Julius.
The current study, he says -- led by Diana M. Bautista, PhD, and Jan Siemens, PhD, of the Julius lab and Joshua M. Glazer, PhD, of the lab of co-senior author Cheryl Stucky, PhD, of the Medical College of Wisconsin – puts that question to rest.
As the mice lacking the gene were not completely insensitive to cold -- they avoided contact with surfaces below 10 degrees C, though with reduced efficiency -- the next step, says Julius, will be to illuminate this residual aspect of cold sensation.
The finding is the latest of a series of discoveries led by the Julius lab on the molecular mechanisms of temperature sensation and pain. In 1997, the lab cloned the gene for the capsaicin receptor, the main pungent ingredient in some chili peppers (Nature, Oct. 23, 1997), and in 2000 reported that, in mice, the receptor triggers the nerves to fire pain signals when they are exposed to high ambient heat or the fiery properties of peppery food. (Science, April 14, 2000). The study demonstrated that capsaicin and noxious heat elicit the sensation of burning pain through activation of the same receptor on sensory neurons.
Most recently, they identified the receptor of isothiocyanate compounds, which constitute the pungent ingredients in such plants as wasabi and yellow mustard. In response to high temperatures, the receptor produces pain and irritation.
"All of these studies use natural products to understand pain mechanisms in the periphery of the body, where they are first sensed," says Julius.
Ultimately, pain sign
Source:University of California - San Francisco