Luminally released serotonin stimulates colonic motility and accelerates colonic transit in rats.
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.
Tsukamoto
Kiyoshi
K
Department of Surgery, Duke University Medical Center, Durham, NC 27710, USA.
Ariga
Hajime
H
Mantyh
Chris
C
Pappas
Theodore N
TN
Yanagi
Hidenori
H
Yamamura
Takehira
T
Takahashi
Toku
T
D000818:Animals; D003106:Colon / Q000187:drug effects / Q000502:physiology*; D003672:Defecation / Q000187:drug effects / Q000502:physiology; D005243:Feces / Q000737:chemistry; D005769:Gastrointestinal Motility / Q000187:drug effects / Q000502:physiology*; D005772:Gastrointestinal Transit / Q000187:drug effects / Q000502:physiology*; D008297:Male; D017294:Ondansetron / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012149:Restraint, Physical; D012701:Serotonin / Q000378:metabolism* / Q000502:physiology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013315:Stress, Psychological / Q000503:physiopathology; D013779:Tetrodotoxin / Q000494:pharmacology; D014018:Tissue Distribution
D012702:Serotonin Antagonists; D012701:Serotonin; D013779:Tetrodotoxin; D017294:Ondansetron