(S)-camphor

TRPV3 cation channels are molecular sensors that play a role in nociception and thermosensation by inducing thermal sensation and heat-induced hyperalgesia. Camphor interacts with TRPV3 channels via pore-region cysteine residues, leading to channel activation and a rise in intracellular calcium levels. Camphor also activates TRPV1 and a TRPV1-like current in dorsal root ganglion (DRG) neurons but inhibits the ankyrin-repeat TRP 1 (TRPA1) channel expressed in most nociceptive DRG neurons, which is responsible for the detection of temperature. The precise role of TRPA1 current inhibition on the analgesic properties of camphor is unclear. Repeated stimulation by camphor leads to sensitization of the TRPV1 and TRPV3 channels, resulting in desensitization, or reduced channel response that likely leads to the analgesic effects of camphor. Camphor also activates cold-sensitive transient receptor potential melastatin 8 (TRPM8) and sensitizes cold-induced calcium transients, which explains the cooling effect of camphor following dermal application. Additionally, camphor was shown to inhibit the TRPM8 receptor response to menthol.