Migrating action-potential complexes in vitro in cholera-exposed rabbit ileum.

The objective of this study was to determine whether cholera-exposed rabbit ileum exhibits altered myoelectric activity in vitro, without central nervous system connections. Whole-cell lysate of Vibrio cholerae, 100 mg in 1 ml saline, was injected into the jejunum of New Zealand White rabbits. Segments of ileum were removed at 12 and 24 h after inoculation and studied in vitro using myoelectric recording techniques. Propagating ring contractions were visualized and corresponded to intense action-potential activity that propagated over consecutive electrode sites. This altered myoelectric activity was similar to the previously described migrating action-potential complex (MAPC) in vivo after infection of rabbit ileum with live V. cholerae, its wholecell lysate, or the purified enterotoxin choleragen, with one exception. All MAPC activity propagated aborally in the in vivo-infected loops; in contrast 26% of the MAPCs propagated retrograde in the in vitro loops. Control segments were injected with saline, and no in vitro MAPCs were observed. Thus, the MAPC stimulated by cholera toxin may be maintained by the enteric nervous system of the gut wall. Although a role for extrinsic nerves is not excluded, our observations suggest that the small intestine may work autonomously, independent of the central nervous system.