Variation of capsaicin-sensitive motor activities along the rat gastrointestinal tract

Variation in motility may be a character to move gut contents. The aim of present study was to assess whether the rat upper gastrointéstinal motilities were variable according to the segments or studied periods under systemic capsaicin treatment. Sedated rats were intubated with a catheter to feed a suspension containing both charcoal and radiochromium motility markers. Capsaicin in the doses of 0.5 mg kg-1, 1 mg kg-1, 5 mg kg-1 or vehicle were simultaneously injected via intraperitoneal route. They were sacrificed at 5 min or 30 min later and the whole gut was removed. Charcoal transit in the small intestine was computed while the radioactivities of stomach and ten equally divided small intestinal segments were counted to obtain the gastric emptying and geometric center of intestinal transit, respectively. Large dose treatment inhibited early gastric emptying (p < 0.05), whereas late gastric emptying remained unchanged. Larger dose treatment inhibited charcoal represented transit in the early (p < 0.05) and late periods (p < 0.01). The intestinal transits seen with geometric center were almost similar to these of charcoal representation (p < 0.01). In conclusion, capsaicin-sensitive gastric emptying changes with studied periods while intestinal transit is always inhibited at any period. We confirm the notion of variation in capsaicin-sensitive motor responses along the rat upper digestive organ.