S5 and S6 and a connecting loop, also part of the structure, make up the pore, a non-selective cation channel which consists of a highly conserved hydrophobic region.

A range of diverse components are required for the high level of specificity in response to cold and menthol stimuli which eventually lead to ion flow through the protein channel.

[5] The TRPM8 protein is expressed in sensory neurons, and it is activated by cold temperatures and cooling agents, such as menthol and icilin whereas WS-12 and CPS-369 are the most selective agonists of TRPM8.

In the peripheral nervous system, TRPs respond to stimuli from temperature, pressure, inflammatory agents, and receptor activation.

Application of menthol to skin or mucous membranes results directly in membrane depolarization, followed by calcium influx via voltage-dependent calcium channels, providing evidence for the role of TRPM8 and other TRP receptors to mediate our sensory interaction with the environment in response to cold in the same way as in response to menthol.

To investigate the mechanisms of this sensitization, Wasner et al., 2004, performed A fiber conduction blockade of the superficial radial nerve in another group of subjects.

[18] Mutagenesis of protein kinase C phosphorylation sites in TRPM8 (wild type serines and threonines replaced by alanine in mutants) reduces the desensitizing response.

These antagonists physically block the receptor for cold and menthol, by binding to the S1-S4 voltage-sensing domain, preventing response.

One research group has reported that TRPM8 is activated by chemical cooling agents (such as menthol) or when ambient temperatures drop below approximately 26 °C (79 °F), suggesting that it mediates the detection of cold thermal stimuli by primary afferent sensory neurons of afferent nerve fibers.

[30] Three independent research groups have reported that mice lacking functional TRPM8 gene expression are severely impaired in their ability to detect cold temperatures.

These animals provide a great deal of insight into the molecular signaling pathways that participate in the detection of cold and painful stimuli.

Many research groups, both in universities and pharmaceutical companies, are now actively involved in looking for selective TRPM8 ligands to be used as new generation of neuropathic analgesic drugs.

Immunofluorescence showed expression of the TRPM8 protein in the ER and plasma membrane of the androgen-responsive LNCaP cell line.