Analysis of motor patterns in the isolated guinea-pig large intestine by spatio-temporal maps

We investigated and quantified the spontaneous patterns of motility in the isolated guinea-pig proximal and distal colon taken from adult animals. Dur ing spontaneous emptying, profiles of proximal and distal colon were record ed with a video camera, and image analysis was used to construct spatio-tem poral maps of the motions of the intestinal wall. Four patterns of motility were recorded. In the proximal colon there were neurally mediated contract ions that propagated in the aboral direction at 4.1 mm s(-1), gently pushin g the soft contents aborally; these are likely to represent spontaneous per istaltic behaviour. A second pattern, insensitive to tetrodotoxin (TTX; 0.6 muM), consisted, in both oral and aboral propagation, of shallow contracti ons of the circular muscle (ripples). These contractions propagated aborall y at 2.8 +/- 0.45 mm s(-1) and orally at 2.03 +/- 0.31 mm s(-1) (n=10). Of these TTX-resistant contractions, 22.5% propagated both orally and aborally from a common origin. The orally propagated component of these myogenic co ntractions is likely to correspond to the antiperistalsis widely described in the proximal colon. In the distal colon, two patterns of motor activity were observed. One, induced by natural or artificial pellets, consisted of peristaltic contractions that pushed the pellets aborally at 0.8 mm s(-1) a nd expelled a pellet every 108 s. In the interval between pellet propulsion and after the distal colon had emptied all of its pellets a second, nerve- mediated pattern of motor activity, consisting of clusters of annular circu lar muscle contractions separated by short dilated regions, slowly propagat ed aborally at 0.3 mm s(-1). Both of these motor patterns were abolished by TTX (0.6 muM). A latex balloon, inserted at the oral end of the empty isol ated distal colon and inflated to a size similar to faecal pellets, was pro pelled at 1.4 mm s(-1). Epoxy resin-covered natural pellets were propelled at a similar speed of 1.6 mm s(-1).Our data revealed that myogenic and neur ogenic patterns of propagated contractions in the colon occur in isolated p reparations and are involved in emptying the colon.