Chapter 4 TRPV1: A Polymodal Sensor in the Nociceptor Terminal

Publisher Summary This chapter discusses the presence of a polymodal sensor—transient receptor potential vanilloid 1 (TRPV1)—in the nociceptor terminal. TRPV1 can be viewed as a proteinaceous microcosm of the nociceptor terminal. It responds in a graded manner to diverse physical and chemical stimuli, distinguishes painful from nonpainful inputs, and changes its responsiveness as a function of its history and chemical milieu. This channel is one component of a much larger repertoire of transduction mechanisms available to nociceptors. The prominent expression of TRPV1 in unmyelinated small‐diameter neurons and its activation by noxious chemical and physical stimuli make this channel a compelling candidate transducer of painful stimuli in vivo . Among the array of stimuli that can excite nociceptors, capsaicin, protons, and noxious heat have attracted considerable attention because of their robust actions on these cells. TRPV1 is essential for nociceptive responses to capsaicin; there is evidence for a substantial contribution from TRPV1‐independent processes to acute heat nociception. TRPV1 gene disruption leads to the disappearance of nocifensive behaviors in mice injected with intraplantar capsaicin or resiniferatoxin (RTX)—a virtual elimination of capsaicin‐evoked neurogenic inflammation and a lack of avoidance of capsaicin‐containing drinking water.