The effect of motilin on the electrical activity of rabbit circular duodenal muscle

The effect of 13-norleucine motilin on electrical activity and membrane resistance of the rabbit circular duodenal muscle was studied with intracellular recording techniques. Electrical slow waves without spikes occurred in Krebs solution made twice hypertonic by addition of sucrose. The slow waves were basic organ specific type rhythm (BOR). Their mean frequency was 18.1.min-1, the mean amplitude from trough to peak was 11.4 mV and mean membrane potential during the trough was -59.1 mV. Motilin (1.10(-7) g/ml) had the following effects: (1) The membrane depolarized by a mean of 10.9 mV. (2) Membrane resistance was reduced. (3) The BOR slow waves were either reduced or abolished. (4) Slow fluctuations of membrane potential characteristic of a minute-type rhythm (MR) appeared. (5) Trains of spikes occurred at the crests of the MR and were associated with contraction of the muscle.