No abstract

No abstract

The controlled progression of contents along the gastrointestinal tract is an essential part of digestion. Different patterns of intestinal movements are involved in the physiological progression of contents along the digestive tract and are the result of the interplay between spontaneous activity of intestinal smooth muscle and enteric neural circuits (Costa & Furness, 1982;Huizinga et al. 1998). Almost one hundred years ago, Bayliss and Starling (1899) revealed the presence of polarized reflex pathways in the intestine and suggested that they were responsible for the propulsion of contents. The analysis of intestinal propulsion was significantly advanced by Trendelenburg in 1917 who showed that reproducible propulsive motor patterns could be triggered in isolated segments of guinea-pig ileum by liquid distension. This form of intestinal peristalsis elicited in vitro is dependent on the activation of enteric circuits as many investigators have demonstrated (Kosterlitz, 1968;Tonini et al. 1981;Waterman et al. 1994b).Slow distension of isolated segments of guinea-pig intestine by liquid infusion produces a neurally-mediated shortening of the longitudinal muscle (Kosterlitz & Robinson, 1959) and an increase in diameter coinciding with an inhibitory reflex mechanism involving nitric oxide (intestinal accommodation; Waterman et al. 1994a). This initial response to liquid distension has been named the 'preparatory phase' (Trendelenburg, 1917;Kosterlitz, 1968). At a threshold volume or intraluminal pressure, a contraction of the circular muscle occurs at the oral end and propagates aborally to empty the segment. This propulsive event is called the 'emptying phase' and involves the activation of different enteric neural pathways (Waterman & Costa, 1994;Waterman et al. 1994b). Despite the common description of this motor behaviour as the 'peristaltic reflex' (Kosterlitz, 1968), it has become apparent that there is a sequential activation of neural

No abstract

No abstract