Physiological significance of the contractions of the rabbit proximal colon

In humans and in carnivores the motor activity of the colon was separated into various types based on records of the intraluminal pressure. However, little is actually known about the physiological significance of the various pressure waves. The aim of the present investigation was to clarify the basic pattern of colonic motility in a herbivorous species. Motility of the proximal colon was studied by strain gauge transducer records combined either with fluoroscopy or by direct visual observation in conscious and anaesthetized rabbits. In the proximal colon three types of contraction were found: (1) high frequency repetitive contractions, (2) low frequency rises of the base line, and (3) monophasic progressive waves. The frequency of the repetitive contractions was 13.8 contractions/min at the oral site and 16.3 contractions/min at the aboral site of the proximal colon. The mean duration of the repetitive contractions was 3.2 +/- 1 s. They coincided with orally migrating (1-2 mm/s) shallow annular constrictions which represented haustral activity. The low frequency rises of the base line (mean duration 13 +/- 47 s) were associated with aborally migrating (7 mm/min) deep annular constrictions representing segmental activity. The monophasic progressive waves represented peristaltic contractions. The mean durations of the monophasic waves 5.5 +/- 1.2 s (period of hard faeces formation), and 9.7 +/- 2.8 s (period of soft faeces formation), the average rates of progression were 3.2 +/- 1.2 cm/s (period of hard faeces production), and 1.3 +/- 0.6 cm/s (period of soft faeces production). The results proved that the colonic motility of rabbits consisted of a complex motor pattern. The present classification was similar but not identical with that described in carnivores and man. Further comparative studies on other mammals are necessary to decide whether the motor activity of the colon is comparable between various species.