ABSTRACT
As detailed in other chapters, several syndromes may be attributed to overactivity of visceral nociceptors. Even if they have other etiologies, their symptoms may be alleviated by targeting visceral nociceptors. Irritable bowel syndrome (IBS) is a good example of a condition with unknown or multiple etiology, and is the most common disorder diagnosed by gastroenterologists (1). Many IBS symptoms originate from the colon and rectum, which must therefore be conveyed by the visceral nociceptors innervating these organs. Afferent endings innervating the colon and rectum will be the area of focus of this chapter, although much of our understanding of the colorectal sensory innervation can be applied to other viscera. This chapter deals firstly with anatomical and functional specialization of visceral afferents, with comparisons between nociceptive and non-nociceptive populations in different pathways. Second, it discusses examples of modulation of visceral afferents via specific ionotropic and metabotropic receptors, and thirdly it includes recent evidence for the identity of mechanotransduction mechanisms.
