Lack of pyloric interstitial cells of Cajal explains distinct peristaltic motor patterns in stomach and small intestine

The frequency and propagation velocity of distension-induced peristaltic contractions in the antrum and duodenum are distinctly different and depend on activation of intrinsic excitatory motoneurons as well as pacemaker cells, the interstitial cells of Cajal associated with Auerbach's plexus (ICC-AP). Because ICC are critical for coordination of motor activities along the long axis of many regions in the gut, the role of ICC in antroduodenal coordination was investigated. We used immunohistochemistry, electron microscopy, simultaneous multiple electrical recordings in vitro, and videofluoroscopy in vivo in mice and rats. A strongly reduced number of ICC-AP with loss of network characteristics was observed in a 4-mm area in the rat and a 1-mm area in the mouse pyloric region. The pyloric region showed a slow wave-free gap of 4.1 mm in rats and 1.3 mm in mice. Between antrum and duodenum, there was no interaction of electrical activities and in the absence of gastric emptying, there was no coordination of motor activities. When the pyloric sphincter opened, 2.4 s before the front of the antral wave reached the pylorus, the duodenum distended after receiving gastric content and aboral duodenal peristalsis was initiated, often disrupting other motor patterns. The absence of ICC-AP and slow wave activity in the pyloric region allows the antrum and duodenum to have distinct uncoordinated motor activities. Coordination of aborally propagating peristaltic antral and duodenal activity is initiated by opening of the pylorus, which is followed by distention-induced duodenal peristalsis. Throughout this coordinated motor activity, the pacemaker systems in antrum and duodenum remain independent.