Why is mint so refreshing?
New research reveals how menthol and other chemicals that cause cold sensations act on the nervous system.
Sensory neurons in our skin detect cues from the environment — such as temperature and touch — and pass the information onto other cells in the nervous system. A protein called TRPM8 in sensory neurons is responsible for our ability to detect cool temperatures. TRPM8 sits in the membrane that surrounds the cell and forms a channel that can allow sodium and calcium ions to enter the cell. Cold temperatures activate TRPM8, which opens the channel and triggers electrical activity in the sensory neurons.
Chemicals that cause a cold sensation — such as menthol, the refreshing substance found in mint plants — can also open the TRPM8 channel. Annelies Janssens, Maarten Gees, Balazs Istvan Toth and colleagues investigated how menthol and another natural compound called mustard oil influence the opening of TRPM8. The experiments show that menthol and mustard oil both stimulate sensory neurons by opening the TRPM8 ion channel, but using different mechanisms. Mustard oil forces the channel to open faster than it normally would, whereas menthol prevents the channel from closing. Further experiments show that these mechanisms explain why some compounds stimulate sensory neurons more strongly than others.
The findings of Janssens, Gees, Toth and colleagues will help to understand how chemicals act on this class of ion channels, and how this affects the roles of the ion channels in cells. Altering the activity of TRPM8 and related ion channels may help to reduce pain in humans so a future challenge is to use these new insights to develop drugs that target these channels more efficiently.
To find out more
Read the eLife research paper on which this eLife digest is based: “Definition of two agonist types at the mammalian cold-activated channel TRPM8” (July 23, 2016).
