Capsaicin and its analogues impede nocifensive response of Caenorhabditis elegans to noxious heat

Abstract Capsaicin is the most abundant pungent molecule identified in red chili peppers, and it is widely used for food flavoring, in pepper spray for self-defense devices and recently in ointments for the relief of neuropathic pain. Capsaicin and several other related vanilloid compounds are secondary plant metabolites. Capsaicin is a selective agonist of the transient receptor potential channel, vanilloid subfamily member 1 (TRPV1). After exposition to vanilloid solution, C. elegans wild type (N2) and mutants were placed on petri dishes divided in quadrants for heat stimulation. Thermal avoidance index was used to phenotype each tested C. elegans experimental groups. The data revealed for the first-time that capsaicin can impede nocifensive response of C. elegans to noxious heat (32°C – 35°C) following a sustained exposition. The effect was reversed 6h post capsaicin exposition. Additionally, we identified the capsaicin target, the C. elegans transient receptor potential channel OCR-2. Further experiments also undoubtedly revealed anti-nociceptive effect for capsaicin analogues, including ginger (Zingiber officinale) and turmeric (Curcuma longa) secondary metabolites.