A thermoreceptor is a non-specialised sense receptor, or more accurately the receptive portion of a sensory neuron, that codes absolute and relative changes in temperature, primarily within the innocuous range. In the mammalian peripheral nervous system, warmth receptors are thought to be unmyelinated C-fibres, while those responding to cold have both C-fibers and thinly myelinated A delta fibers. The adequate stimulus for a warm receptor is warming, which results in an increase in their action potential discharge rate. Cooling results in a decrease in warm receptor discharge rate. For cold receptors their firing rate increases during cooling and decreases during warming. Some cold receptors also respond with a brief action potential discharge to high temperatures, i.e. typically above 45 °C, and this is known as a paradoxical response to heat. The mechanism responsible for this behavior has not been determined.
Transient receptor potential channels are a group of ion channels located mostly on the plasma membrane of numerous animal cell types. Most of these are grouped into two broad groups: Group 1 includes TRPC, TRPV, TRPVL, TRPM, TRPS, TRPN, and TRPA. Group 2 consists of TRPP and TRPML. Other less-well categorized TRP channels exist, including yeast channels and a number of Group 1 and Group 2 channels present in non-animals. Many of these channels mediate a variety of sensations such as pain, temperature, different kinds of tastes, pressure, and vision. In the body, some TRP channels are thought to behave like microscopic thermometers and used in animals to sense hot or cold. Some TRP channels are activated by molecules found in spices like garlic (allicin), chili pepper (capsaicin), wasabi ; others are activated by menthol, camphor, peppermint, and cooling agents; yet others are activated by molecules found in cannabis or stevia. Some act as sensors of osmotic pressure, volume, stretch, and vibration. Most of the channels are activated or inhibited by signaling lipids and contribute to a family of lipid-gated ion channels.
Nav1.7 is a sodium ion channel that in humans is encoded by the SCN9A gene. It is usually expressed at high levels in two types of neurons: the nociceptive (pain) neurons at dorsal root ganglion (DRG) and trigeminal ganglion and sympathetic ganglion neurons, which are part of the autonomic (involuntary) nervous system.
The transient receptor potential cation channel subfamily V member 1 (TRPV1), also known as the capsaicin receptor and the vanilloid receptor 1, is a protein that, in humans, is encoded by the TRPV1 gene. It was the first isolated member of the transient receptor potential vanilloid receptor proteins that in turn are a sub-family of the transient receptor potential protein group. This protein is a member of the TRPV group of transient receptor potential family of ion channels. And a receptor being clearly present in bacteria, the oldest organisms on Earth known to express phosphatidylethanolamine, the precursor to endocannabinoids, in their cytoplasmic membranes, and fatty acid metabolites with affinity for this CB receptor are produced by cyanobacteria, which diverged from eukaryotes at least 2000 million years ago (MYA).
TRPV is a family of transient receptor potential cation channels in animals. All TRPVs are highly calcium selective.
TRPM is a family of transient receptor potential ion channels (M standing for wikt:melastatin). Functional TRPM channels are believed to form tetramers. The TRPM family consists of eight different channels, TRPM1–TRPM8.
Capsazepine is a synthetic antagonist of capsaicin. It is used as a biochemical tool in the study of TRPV ion channels.
Transient receptor potential cation channel, subfamily M, member 2, also known as TRPM2, is a protein that in humans is encoded by the TRPM2 gene.
Transient receptor potential cation channel, subfamily A, member 1, also known as transient receptor potential ankyrin 1, TRPA1, or The Wasabi Receptor, is a protein that in humans is encoded by the TRPA1 gene.
Transient receptor potential cation channel subfamily M member 5 (TRPM5), also known as long transient receptor potential channel 5 is a protein that in humans is encoded by the TRPM5 gene.
Transient receptor potential cation channel subfamily M (melastatin) member 8 (TRPM8), also known as the cold and menthol receptor 1 (CMR1), is a protein that in humans is encoded by the TRPM8 gene. The TRPM8 channel is the primary molecular transducer of cold somatosensation in humans. In addition, mints can desensitize a region through the activation of TRPM8 receptors.
Transient receptor potential cation channel subfamily M member 3 is a protein that in humans is encoded by the TRPM3 gene.
Transient receptor potential cation channel, subfamily V, member 3, also known as TRPV3, is a human gene encoding the protein of the same name.
Icilin (AG-3-5) is a synthetic super-agonist of the transient receptor potential M8 (TRPM8) ion channel. Although structurally not related to menthol, it produces an extreme sensation of cold, both in humans and animals. It is almost 200 times more potent than menthol, and 2.5 times more efficacious. Despite their similar effects, icilin activates the TRPM8 receptor in a different way than menthol does. Icilin has been shown to be effective in the treatment of pruritus in an experimental model of itch. It is now used as a research tool for the study of TRP channels, although despite its high potency it is less selective for TRPM8 over other related ion channels than are other compounds such as WS-12.
A-967079 is a drug which acts as a potent and selective antagonist for the TRPA1 receptor. It has analgesic and antiinflammatory effects and is used in scientific research, but has not been developed for medical use.
ASP-7663 is a chemical compound which acts as a potent, selective activator of the TRPA1 channel. It has protective effects on cardiac tissue, and is used for research into the function of the TRPA1 receptor.
Ononetin is a natural product from the deoxybenzoin group, which is found in the Russian traditional medicine plant Ononis spinosa. It acts as an inhibitor of the transient receptor potential ion channel TRPM3 and has analgesic effects in animal studies, as well as being used for research into the role of TRPM3 in the immune system dysfunction associated with chronic fatigue syndrome.
WS-12 is a chemical compound that acts as a potent and selective activator of the TRPM8 calcium channel, which is responsible for the sensation of coldness produced by menthol. It is slightly less potent as a TRPM8 activator compared to icilin, but is much more selective for TRPM8 over related calcium channels. It produces analgesic and antiinflammatory effects in animal models with similar efficacy to menthol and a reduced side effect profile.
RQ-00203078 is a drug which acts as a potent and selective blocker of the TRPM8 ion channel, which is the main receptor responsible for the sensation of cold. It was developed as a potential analgesic, and blocks the development of hyperalgesia following exposure to cold temperatures or chronic morphine administration.
AMG-333 is a drug which acts as a potent and selective blocker of the TRPM8 ion channel, which is the main receptor responsible for the sensation of cold. It was developed as a potential treatment for migraine.
