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Relationship between intraduodenal 5-hydroxytryptamine release and interdigestive contractions in dogs
Toshiyuki Tanaka1, Akiyoshi Mizumoto, Erito Mochiki
1Second Department of Surgery, Gunma University Faculty of Medicine, 3-39-15 Shoaw-cho, Maebashi city, Gunma 371-8511, Japan.
Background:
5-hydroxytryptamine (5-HT) is released into the intestinal lumen during the fasting state. However, the relationship between the intraduodenal 5-HT and the interdigestive cyclic motor activity in conscious dogs is unclear.
Aim:
To correlate intraduodenal 5-HT concentrations with the interdigestive gastroduodenal migrating motor complex (MMC).
Methods:
6 dogs were implanted with 2 force transducers for recording gastroduodenal contractions and 2 catheters for measuring duodenal volume by a non-absorbable marker perfusion technique. Intraduodenal 5-HT concentrations were determined by high performance liquid chromatography at 5-min intervals.
Results:
During fasting, gastroduodenal motor activity cycled as the MMC; luminal 5-HT concentrations and total outputs varied cyclically in temporal association with the MMC. Mean 5-HT concentrations peaked during phase II (P<0.05 vs. phase I and III), and 5-HT outputs during phases II or III were greater than during phase I (P<0.05). Exogenous motilin (0.3 microg/kg-hr, IV) stimulated 5-HT release into the duodenal lumen with peak values (P<0.05) during motilin-induced phase II and III. Gastroduodenal motor activity was not altered, however, during exogenous intraduodenal administration of 5-HT (300 ng/mL-min).
Conclusions:
5-HT is released cyclically into the duodenal lumen in close temporal association with the MMC, but its physiologic significance in regulation of gastroduodenal motility is unknown.