Impaired Nociception and Pain Sensation in Mice Lacking the Capsaicin Receptor

Abstract

The capsaicin (vanilloid) receptor VR1 is a cation channel expressed by primary sensory neurons of the "pain" pathway. Heterologously expressed VR1 can be activated by vanilloid compounds, protons, or heat (>43 degrees C), but whether this channel contributes to chemical or thermal sensitivity in vivo is not known. Here, we demonstrate that sensory neurons from mice lacking VR1 are severely deficient in their responses to each of these noxious stimuli. VR1-/- mice showed normal responses to noxious mechanical stimuli but exhibited no vanilloid-evoked pain behavior, were impaired in the detection of painful heat, and showed little thermal hypersensitivity in the setting of inflammation. Thus, VR1 is essential for selective modalities of pain sensation and for tissue injury-induced thermal hyperalgesia.

The suitability of chili pepper (Capsicum annuum L.) for alleviating human micronutrient dietary deficiencies: A review

“…Capsaicinoids are alkaloid compounds that give the characteristic pungency in hot chili peppers. They are bioactive molecules that are only produced in the genus Capsicum and are significant in food and medical sciences and in the defense weapon industry (Caterina et al., 2000; Chu et al., 2003). Although pepper seeds absorb capsaicin occasionally as a result of their proximity to the placenta, they are not the source of pungency Capsaicinoids are secreted only by the glands in fruit placenta.…”

“…The active principle in red peppers responsible for their medical and pharmacological use is the pungent alkaloid called capsaicin (Peña‐Alvarez, Ramírez‐Maya, & Alvarado‐Suárez, 2009). Capsaicin is the principal capsaicinoid in chili peppers that accounts for about 71% of the total capsaicinoids in majority of the pungent types, followed by dihydrocapsaicin (Caterina et al., 2000; Chu et al., 2003). According to Estrada, Bernal, Díaz, Pomar, and Merino (2002), the degree of pungency varies among different Capsicum spp.…”

“…as capsaicin and dihydrocapsaicin contents could be influenced by numerous factors like the stage of development of the fruit and the environmental growth conditions. Several research works have revealed that the higher the amount of capsaicin, the hotter the pepper, and the more the antioxidant level (Caterina et al., 2000; Chu et al., 2003). Capsaicin is most esteemed because they give relief from sore throats and fever, relief from cold symptoms, and on digestive system, they have soothing effects.…”

Molecular targets for cannabidiol and its synthetic analogues: effect on vanilloid VR1 receptors and on the cellular uptake and enzymatic hydrolysis of anandamide

“…Thus, there appears to be some overlap between the ligand recognition properties of VR1 and CB 1 receptors and, in particular, of VR1 and the AMT (De Petrocellis et al, 2000;Szallasi & Di Marzo, 2000). Although VR1, via the release of in¯ammatory and algesic peptides, is involved in in¯ammatory hyperalgesia Caterina et al, 2000), the stimulation of this receptor by capsaicin and some of its analogues leads to rapid desensitization, with subsequent paradoxical analgesic and anti-in¯ammatory e ects (Holzer, 1991;Szallasi & Blumberg, 1999). As a consequence of this tachyphylactic e ect, capsaicin, like CBD, has been used to treat arthritis (Lorton et al, 2000) and convulsions (Dib & Falchi, 1996).…”

Cannabinoids, the Heart of the Matter

“…TRPV1‐/‐ mice had no reduction in body temperature after subcutaneous injection with capsaicin, and homozygous mice show no aversion of drinking capsaicin‐supplemented drinking water 99. Furthermore, TRPV1 knockouts are hypometabolic (less oxygen consumption), hypervasoconstricted (lower‐tail skin temperature), preferred lower ambient temperature, and showed a higher locomotor activity compared with wild‐types 93.…”