ELECTRICAL ACTIVITY OF COCKROACH VISCERAL MUSCLE FIBERS

1. 1. Resting and synaptic potentials were recorded intracellularly from the striated visceral muscle fibers of the rectum and the passive electrical properties of the fiber membrane were estimated. 2. 2. The mean resting potential was 30·2 ± 0·8 mV (S.E.). 3. 3. Post-synaptic potentials arising from spontaneous or evoked motor nerve activity varied in shape and amplitude (up to 9 mV), had long time constants (about 70 msec) and displayed summation. Miniature post-synaptic potentials of 1 mV and less were observed. 4. 4. Neurally evoked responses appear to be pure post-synaptic potentials without superimposed depolarizing or repolarizing electrogenesis. 5. 5. Innervation appears to be multiterminal and polyneuronal with one type of axon, similar to the innervation of frog slow muscle. © 1969.