Contraction of canine stomach and small bowel by intravenous administration of serotonin: a physiologic response?

Serotonin is found in large quantities in the gastrointestinal tract, where it can increase gastrointestinal motility. Whether this response represents a physiologic event has not previously been shown. In our investigation eight conscious dogs were fitted with strain gauges to monitor motility responses to serotonin. When infused intravenously, serotonin significantly increased the contraction rate and force of canine stomach, small bowel, and isolated Thiry-Vella loops. Whole blood serotonin levels monitored by radioimmunoassay showed no significant increase in levels during these infusions. Serotonin may have a physiologic function in the mediation of gastrointestinal motility.