| The purpose of this study was to compare the effects of invasive and toxigenic organisms on small intestinal motor activity. Six dogs were implanted with 2 two-way cannulae 25 and 105cm distal to the ligament of Treitz. An intraluminal catheter was placed 5cm distal to the proximal cannula. The 75cm between the catheter and distal cannula constituted the study segment. Contractions of the small intestine were recorded with strain gauge force transducers. Cholera toxin (CT) and Trichinella spiralis (TS) were used to study toxigenic and invasive mechanisms, respectively. In the fasted state, CT increased the fluid output of the study segment 5 fold by 120 min post injection. The migrating motor complex (MMC) cycle length was reduced and the percent of phase II was increased at the expense of phase I after CT. CT also caused inhibition of migrating clustered contractions. TS resulted in an increase in the incidence and proximal origin of giant migrating contractions (GMCs) during the period of time the dogs had diarrhea. There was also an increase in the incidence of retrograde giant contractions, with 71% being followed by vomiting. The MMC cycle length was increased as a result of intestinal fibrillation during TS infection. In the fed state, cholera toxin resulted in an increase in mean transit time (MTT) and a decrease in the frequency, duration, amplitude, area, and distance of propagation of propagating contractions. These same parameters for nonpropagating contractions were not changed. TS resulted in a decrease in both propagating and nonpropagating contraction parameters with propagating contractions being affected to a larger degree. TS also induced GMCs in the fed state, which were not seen in control recordings. In conclusion, diarrhea induced by CT and TS may be due to different mechanisms. CT results in a classic small intestinal secretory diarrhea with the motor activity acting to counter the effect of increased secretions. In contrast, the diarrhea induced by TS may be the result of altered small intestinal motor activity. |
