Transient receptor potential vanilloid type 1, or TRPV1, acts as a receptor for capsaicin, as well as a detector of rises in temperature to signal burning. Because of this, it registers capsaicin as heat, and thus is responsible for the hot taste of chili peppers that we experience. Typically located on thin, unmyelinated C fibers (thus travels somewhat slowly by neuron standards and adapts slowly, providing the second wave of pain).
- C-fibers

TRPV1

Detects higher temperatures than TRPV1, does not respond to capsaicin, and found on larger nerve fibers like A-delta fibers (meaning they convey data and adapt much faster, provide initial sharp first wave of pain). These fibers detect burning sensations that require quick action to alleviate, such as when you touch a hot stove. 
- A-delta fibers

TRPM3

Also known as the cool-menthol receptor 1, the TRPM8 receptor is a member of the TRP family but responds to cool temperatures. It is found on small C fibers, thereby transferring information relatively slowly. 

TRPM8

Two itch systems, one producing itchiness from histamines and the other not, both use TRPV1 receptors and use slowly conducting C fibers to send action potentials (as seen in heat-detecting neurons). However, TRP receptors for itching exclusively use the neurotransmitter natriuretic polypeptide B (Nppb) to stimulate neurons in the dorsal horn. Scratching the area of these receptors provides temporary relief by silencing these receptors with neuropeptide Y released from the spinal cord upon scratching. 

TRP Receptors for Itching

Messeguer, A., Planells-Cases, R., & Ferrer-Montiel, A. (2006). Physiology and pharmacology of the vanilloid receptor. Current neuropharmacology, 4(1), 1–15. https://doi.org/10.2174/157015906775202995

Physiology and Pharmacology of the Vanilloid Receptor

A family of transient receptors that detect compounds with vanilloids (compounds with a vanillyl group). The type of receptor determines the type of pain information detected. 
- TRPV1
- TRPM3
- TRPM8
- TRP receptors for itching

Johns Hopkins University

University of Rochester

Peripheral receptors and nerve fibers that respond to pain. There are 3 different kinds of painful stimuli nociceptors can be attuned to: chemical, physical, and thermal. Some nociceptors respond to itch sensations. 
- TRPV1 (temperature)
- TRMP3 (higher temperature)
- CMR1 (cold)
- Nppb (itch)
- Nav 1.7 (mechanical pain)

Nociceptors

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

Transient Receptor Potential Vanilloid Type

A voltage gated sodium channel expressed in many free nerve endings. Action potentials initiated by these channels seem to be connected with the general sensation of pain. Encoded by gene SCN9A. 

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