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Abstract C. elegansneurons were thought to be non-spiking until our recent discovery of action potentials in the sensory neuron AWA; however, the extent to which theC. elegansnervous system relies on analog or digital coding is unclear. Here we show that the enteric motor neurons AVL and DVB fire synchronous all-or-none calcium-mediated action potentials following the intestinal pacemaker during the rhythmicC. elegansdefecation behavior. AVL fires unusual compound action potentials with each depolarizing calcium spike mediated by UNC-2 followed by a hyperpolarizing potassium spike mediated by a repolarization-activated potassium channel EXP-2. Simultaneous behavior tracking and imaging in free-moving animals suggest that action potentials initiated in AVL propagate along its axon to activate precisely timed DVB action potentials through the INX-1 gap junction. This work identifies a novel circuit of spiking neurons inC. elegansthat uses digital coding for long-distance communication and temporal synchronization underlying reliable behavioral rhythm.