Luminally released serotonin stimulates colonic motility and accelerates colonic transit in rats

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology integrative and comparative physiology, 2007-07, Vol.293 (1), p.R64-R69
• Main Authors: Tsukamoto, Kiyoshi, Ariga, Hajime, Mantyh, Chris, Pappas, Theodore N, Yanagi, Hidenori, Yamamura, Takehira, Takahashi, Toku
• Format: Article
• Language: English
• Subjects: Animals; Cells; Colon; Colon - drug effects; Colon - physiology; Defecation - drug effects; Defecation - physiology; Feces - chemistry; Gastrointestinal Motility - drug effects; Gastrointestinal Motility - physiology; Gastrointestinal Transit - drug effects; Gastrointestinal Transit - physiology; Hormones; Male; Neurotransmitters; Ondansetron - pharmacology; Rats; Rats, Sprague-Dawley; Restraint, Physical; Rodents; Serotonin - metabolism; Serotonin - physiology; Serotonin Antagonists - pharmacology; Stress, Psychological - physiopathology; Tetrodotoxin - pharmacology; Tissue Distribution
• ISSN: 0363-6119; 1522-1490
• DOI: 10.1152/ajpregu.00856.2006

1 Department of Surgery, Duke University Medical Center, Durham, North Carolina; and 2 Second Department of Surgery, Hyogo College of Medicine, Nishinomiya, Japan Submitted 8 December 2006 ; accepted in final form 31 March 2007 Enterochromaffin (EC) cells of the epithelial cells release 5-HT into the lumen, as well as basolateral border. However, the physiological role of released 5-HT into the lumen is poorly understood. Concentrations of 5-HT in the colonic mucosa, colonic lumen, and feces were measured by HPLC in rats. To investigate whether intraluminal 5-HT accelerates colonic transit, 5-HT and 51 Cr were administered into the lumen of the proximal colon, and colonic transit was measured. To investigate whether 5-HT is released into the lumen, we used an ex vivo model of isolated vascularly and luminally perfused rat proximal colon. To investigate whether luminal 5-HT is involved in regulating stress-induced colonic motility, the distal colonic motility was recorded under the stress loading, and a 5-HT 3 receptor antagonist (ondansetron, 10 –6 M, 0.5 ml) was administered intraluminally of the distal colon. Tissue content of 5-HT in the proximal colon (15.2 ± 4.3 ng/mg wet tissue) was significantly higher than that in the distal colon (3.3 ± 0.7 ng/mg wet tissue), while fecal content and luminal concentration of 5-HT was almost the same between the proximal and distal colon. Luminal administration of 5-HT (10 –6 –10 –5 M) significantly accelerated colonic transit. Elevation of intraluminal pressure by 10 cmH 2 O significantly increased the luminal concentration of 5-HT but not the vascular concentration of 5-HT. Stress-induced stimulation of the distal colonic motility was significantly attenuated by the luminal administration of ondansetron. These results suggest that luminally released 5-HT from EC cells plays an important role in regulating colonic motility in rats. enterochromaffin cells; distal colon; luminal pressure; restraint stress Address for reprint requests and other correspondence: T. Takahashi, Box 3479, Duke University Medical Center, Durham, NC 27710 (e-mail: ttakahas{at}duke.edu )