Visceral hypersensitivity: facts, speculations, and challenges

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Abstract
Enteroendocrine cells in the lining of the gut serve as chemical and mechanical transducers for local reflexes (for example, peristalsis) or initiation of afferent projections to the central nervous system.1 2 As with somatic sensation, gut afferent signals reach conscious perception through a three neurone chain.2 The first order neurone, whose cell body is in the dorsal root ganglion, terminates in the dorsal column laminae of the spinal cord (fig 1). En passant fibres project to noradrenergic neurones in prevertebral ganglia, and this reflex centre results in modulation of viscus functions, including motility. Somatic and visceral afferents converge on dorsal horn neurones and result in viscerosomatic projection or referred pain. Descending modulatory fibres (serotonergic, adrenergic, and possibly others) from brain stem centres such as the periaqueductal grey alter the sensitivity of the dorsal horn neurones and thus serve to centrally control the intensity of perception during visceral stimulation (fig1).1