Electrical and mechanical activity in the ex vivo perfused total canine colon

Electrical and mechanical activity were studied in the ex vivo total canine colon, supported in a perfusion chamber by a supporting dog. Regular electrical activity could be recognized visually in 50--70% of the records. The frequency of this activity was in the range of 7--10/min. Fourier analysis also revealed dominant frequencies in this range. Two types of mechanical activity were observed. The first consisted of small amplitude repetitive contractions, which appeared both during quiescent periods and during vigorous contractions. The frequency of this rippling, when periodic, usually approximated that of the electrical activity. The second type consisted of large amplitude prolonged (30--135 sec) contractions. Without stimulation, the large amplitude contractions were asynchronous and not propagated. Following neostigmine, however, the large amplitude contractions were always propagated aborally and were usually associated with evacuation of the colon. The rippling contractions had a frequency similar to the regular electrical activity and are probably under their control. The large amplitude, prolonged duration contractions are unlikely, however, to be solely under myogenic control.