Ageing and Gastrointestinal Sensory Function : The Enteric Nervous System
Over the past few decades a combination of electrophysiological, morphological and molecular approaches has enabled the different populations of vagal and spinal afferents that innervate the bowel to be characterized. The sensitivity of these afferents is determined by their location in the gut wall, their relationship with other cells and structures and the receptors and ion channels that they express on their nerve terminals. An important feature of this innervation is that it is upregulated during injury, inflammation and ischaemia through changes in receptors and ion channels that determine excitability and sensitivity. In recent studies we have sought to identify how sensory mechanisms are influenced as part of the normal ageing process. Attenuated signaling was evident in different gastrointestinal afferent subpopulations conveying low and high threshold mechanosensory information and there was impairment in the ability of sensory neurons to sensitize in response to chemical mediators such as 5-HT. These sensory deficits may contribute to altered bowel habits with age and the prevalence of incontinence in the elderly.