In vitro electrical activity in canine colon.

In vitro slow wave activity was studied in strips of right and left canine colon with silver/silver chloride electrodes. Using visual and computer analysis, slow wave frequency and coupling was assessed between different recording sites and the effect of a cholinergic agonist on coupling and frequency was determined. A regular slow wave was always found to be present. Frequency in the left colon was slightly higher than in the right with a slight decline noted with time. Spike activity was rarely seen in unstimulated specimens. Administration of a cholinergic agonist produced a decrease in frequency with no improvement in coupling. Coupling was usually better in a circular than in a longitudinal direction. It was concluded that if electrical activity is important in the control of colon contractions, it is more likely to be involved in the control of segmentation than in propagated contractions.