Mucosal stimulation applied at the anal or oral end of the colon evokes a premature colonic migrating motor complex (CMMC) in the Tph1+/+ colon. Similarly, EFS (0.5 ms, 5 Hz for 1 s, 20 V) applied at the oral end (0) also evokes a premature propagating CMMC. Spontaneous CMMCs and the responses to mucosal stimulation are blocked by ondansetron (1 μm), which does not, however, affect the propagating CMMC evoked by EFS. The CMMC evoked by EFS is, however, blocked by hexamethonium.