[Propulsive activity of the isolated segmental colon of the guinea pig]

Propulsive activity in segments of isolated distal colon of guinea-pig was investigated. Propulsive activity, as indicated by movements of the bolus (5 x 10 mm diameter) made of plastic with a steel wire, was recorded isometrically using a force-displacement transducer. Muscle tension of longitudinal axis was also recorded isometrically in the same preparation. In all preparations, spontaneous propulsive activity, which was due to combination of ascending excitation and descending inhibition, occurred periodically. The frequency of propulsive activity was 4.0 +/- 0.9/10 min (M +/- SE, n = 8) and the duration was 64.0 +/- 9.0 sec (M +/- SE, n = 9). The propulsive force was 16.4 +/- 3.4 g (M +/- SE, n = 10) at peak. The spontaneous propulsive activities were blocked by atropine (10(-5) g/ml). These activities were gradually decreased in frequency and in propulsive force within 2-3 hours. When spontaneous propulsive activities were negligible, carbachol (10(-9)-10(-7) g/ml) added to the bathing medium stimulated propulsive activity in a dose dependent manner.