Zsa Zsa Weerts

Chapter 4 82 Figure 4.1 Schematic depiction of nociceptive afferent innervation of the intestine. Proximal (blue) neurons travel through the vagal nerve. These neurons transduce sensory information through the nodose ganglia into the solitary tract nuclei. Distal (red) neurons travel through the splanchnic and pelvic nerves (two distinct systems). Both the splanchnic and pelvic nerves’ somata reside in the dorsal root ganglia. In addition, splanchnic nerves travel through prevertebral ganglia (not shown). The nociceptive afferents within these neurons presumably have their nerve endings (top inset) in the mucosa/submucosa and mesenteries. 12 Various stimuli (shown at the top) can activate the nociceptors, depending on the expressed TRP channels (see Table 4.2 ). Stimuli include exogenous agonists ( e.g . capsaicin or menthol), physical stimuli ( e.g . mechanical or thermal) and endogenous agonists ( e.g . prostaglandins or lipoxygenase products). Activation of nociceptors by these stimuli results in action potential generation and pain sensation. In addition, inflammatory mediators are released (neurogenic inflammation), which can result in TRP channel sensitization and local tissue inflammation. NG= nodose ganglion, STN= solitary tract nucleus, DRG= dorsal root ganglion, S= splanchnic nerves, P= pelvic nerves.