Prostaglandin I(2) sensory input into the enteric nervous system during distension-induced colonic chloride secretion in rat colon.
OBJECTIVE
Intestinal pressure differences or experimental distension induce ion secretion via the enteric nervous system, the sensorial origin of which is only poorly understood. This study aimed to investigate sensorial inputs and the role of afferent and interneurones in mechanically activated submucosal secretory reflex circuits.


METHODS
Distension-induced rheogenic chloride secretion was measured as increase in short-circuit current 10 min after distension (DeltaI(SC)(10); distension parameters +/- 100 microL, 2 Hz, 20 s) in partially stripped rat distal colon in the Ussing-chamber in vitro. PGE(2) and PGI(2) were measured by radioimmunoassay.


RESULTS
DeltaI(SC)(10) was 2.0 +/- 0.2 micromol h(-1) cm(-2) and could be attenuated by lobeline, mecamylamine and dimethylphenylpiperazine, indicating an influence of nicotinergic interneurones. Additionally, a contribution of afferent neurones was indicated from the short-term potentiation of DeltaI(SC)(10) by capsaicin (1 microm). As evidence for its initial event, indomethacin (1 microm) inhibited distension-induced secretion and the release of PGI(2) was directly detected after distension. Furthermore, serotoninergic mediation was confirmed by granisetron (100 microm) which was functionally localized distally to PGI(2) in this reflex circuit, as granisetron inhibited an iloprost-induced I(SC), while indomethacin did not affect serotonin-activated ion secretion.


CONCLUSIONS
Distension-induced active electrogenic chloride secretion in rat colon is mediated by a neuronal reflex circuit which includes afferent neurones and nicotinergic interneurones. It is initiated by distension-induced PGI(2) release from subepithelial cells triggering this reflex via serotoninergic 5-HT(3) receptor transmission. Functionally, this mechanism may help to protect against intestinal stasis but could also contribute to luminal fluid loss, e.g. during intestinal obstruction.
Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité, Berlin, Germany. joerg.schulzke@charite.de <joerg.schulzke@charite.de>
J D
JD
Schulzke
S
S
Pfaffenbach
A
A
Fromm
H J
HJ
Epple
H
H
Troeger
M
M
Fromm
D000818:Animals; D002211:Capsaicin / Q000494:pharmacology; D002712:Chlorides / Q000378:metabolism*; D018678:Cholinergic Agents / Q000494:pharmacology; D003106:Colon / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D015232:Dinoprostone / Q000378:metabolism / Q000494:pharmacology; D017615:Enteric Nervous System / Q000187:drug effects*; D011464:Epoprostenol / Q000378:metabolism / Q000494:pharmacology*; D007395:Interneurons / Q000187:drug effects; D007413:Intestinal Mucosa / Q000187:drug effects / Q000294:innervation; D008297:Male; D009475:Neurons, Afferent / Q000187:drug effects; D010812:Physical Stimulation; D011312:Pressure; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D011863:Radioimmunoassay; D051381:Rats; D017208:Rats, Wistar; D011978:Receptors, Nicotinic / Q000187:drug effects; D012212:Rheology; D012702:Serotonin Antagonists / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
D002712:Chlorides; D018678:Cholinergic Agents; D011978:Receptors, Nicotinic; D012702:Serotonin Antagonists; D011464:Epoprostenol; D011451:Prostaglandin-Endoperoxide Synthases; D015232:Dinoprostone; D002211:Capsaicin