The many facets of intestinal peristalsis.

To the Editor: Seerden and co-workers (14) have produced an important study with impressive recordings that show many features of distension-induced electrical and motor activity in the mouse small intestine. Among the highlights of this paper are a clear demonstration of slow wave-driven propulsive contractions, further evidence that the longitudinal and circular muscle layers show the same slow-wave frequency but independent contraction patterns and the visualization of the burst-type appearance of action potentials, suggesting rhythmicity in the neural excitation (1, 11). However, the data are put into a context of peristalsis and segmentation that may lead to confusion. Hence, it is worthwhile to further discuss the existing motor patterns in the mouse due to the importance of the mouse as a current model in the study of gastrointestinal motility. Seerden and co-workers state, " In contrast to motility behavior in other animals, distension does not induce peristaltic contraction in the small intestine of mice. " Later it is stated that the observed motor pattern constitutes " a segmental pattern of contraction. " Seerden et al. show electrical and motor activity on distension of the small intestine and state that this is the first time that these contractions have been described in the mouse. However, the motor pattern they describe is the same as that described previously (11) and similar to the first observations of distension-induced motor activity. In 1898, Cannon studied gastric activity using X-ray imaging in response to the inges-tion of a meal and noted " that peristaltic waves are running continuously throughout the entire digestive period " (6). On the small intestine, he wrote " peristalsis is observed.. .. as a rapid movement sweeping the food without pause through several turns of the gut, " and characterized the rhythmic contractions as myogenic (5). In addition to this motor pattern, Bayliss and Starling (2) discovered that the small intestine can evoke a peristaltic reflex, orchestrated by the myenteric plexus, in response to a local distension. Hence, right from the start, it was acknowledged that several peristaltic motor patterns exist with different underlying mechanisms. We now know that Cannon described the motor patterns governed by myogenic slow-wave activity, as described by Charles Code when he wrote in 1968 (7), " If, as the PSP (pace setter potential or slow wave) passes along the small bowel, the circular muscle fibers immediately caudal to those that just contracted are excitable and contract …