Spike propagation in the smooth muscle of the guinea-pig taenia coli.

1. Spike activity was produced by external field stimulation of the guinea-pig taenia coli. Spikes were evoked by depolarization of the muscle membrane. Though the activity was usually also observed during hyperpolarization, this was shown to be conducted activity from the depolarized region of the tissue. Spike conduction was blocked when hyperpolarization exceeded 10 mV.2. The shape of the conducted spike was influenced by membrane polarization. Sometimes a notch appeared on the spike and sometimes the spike was split into two by hyperpolarization. This is probably due to the fact that functional bundles form a network and that the branches between bundles are more susceptible to the membrane polarization.3. There was a critical spike amplitude for normal propagation. Therefore, different spike amplitudes were observed near the stimulating electrode, but only spikes of nearly full size amplitude were recorded far from the stimulating electrode, i.e. at a distance of more than 5 mm.4. When repetitive stimulation was applied, the spike amplitude decreased with increasing frequency of stimulation. No steady level was reached, however, but the spike amplitude fluctuated at about 0.3 c/s.