Ageing and Gastrointestinal Sensory Function

Abstract

Myogenic control mechanisms play a role in all motor activities of the gut. Myogenic control systems are defi ned here as control systems that are intrinsic to the smooth muscle cells and/or interstitial cells of Cajal (ICC) and that can operate without an essential contribution of the intrinsic (ENS) and extrinsic nervous systems . In vivo however, the ENS and the myogenic control systems always work in cooperation. Although myogenic control plays a role in every gut organ, this review focuses on the peristaltic and segmentation activity of the small intestine. It provides some historical perspectives and some discussion on the development of our understanding of the cooperative nature of the myogenic and neurogenic control mechanisms . It highlights how some infl uential papers inadvertently provided hindrance to full understanding, it discusses how the guinea pig model has hampered acceptance of myogenic control systems and it provides some background into the genesis of our understanding of control mechanisms involving ICC. The Dominance of the "Law of the Intestine"Nothing has hampered the acceptance of myogenic control mechanisms more than the formulation of the " law of the intestine " by Bayliss and Starling. The likely reason is the elegant descriptions of the evidence for it and the attractive nature of such a simple and effective, easily understood mechanism. This despite the fact that Bayliss and Starling prominently described myogenic control systems as well. In Bayliss and Starling's seminal paper from 1889 where the "law of the intestine"

Ex vivo study of human visceral nociceptors

“… 45 However, we applied specific stimuli that preferentially targeted spinal nociceptors consistent with a lack of regional differences in responses. In addition, the recent demonstration of reduced visceral afferent sensitivity to noxious stimuli in aged mice, 46 and reduced afferent activity with age in human tissue, 47 48 highlights the need for further studies on visceral nociception in human tissue.…”