Local nerve blockade by tetrodotoxin induces ectopic phase 3 of the migrating myoelectric complex in dogs

The effect on the migrating myoelectric complex (MMC) of local nerve blockade in the jejunum was studied in five unanesthetized dogs. A silastic catheter was implanted in a terminal branch of a jejunal artery, perfusing a 5- to 10-cm segment, 45 cm below the ligament of Treitz. Small-bowel motor activity was studied electromyographically with implanted electrodes. Three different doses of tetrodotoxin (166, 333, 500 ng/kg/h) were administered intra-arterially for 5 h. During the 333- and 500-ng but not during the 166-ng/kg/h perfusions ectopic activity fronts started just below the perfused segment. At this time no phase-3 activity was observed in the proximal bowel. In addition to ectopic fronts normal MMCs were observed during the perfusions. These observations show that local nerve blockade induces phase-3 activity, probably by inhibiting an inhibitory nerve action.