Autoreceptors can modulate 5-hydroxytryptamine release from porcine and human small intestine in vitro |
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Authors: | H Schwörer Giuliano Ramadori |
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Institution: | Zentrum Innere Medizin, Abteilung Gastroenterologie und Endokrinologie, Universit?tsklinik G?ttingen, Robert Koch Strasse 40, D-37075 G?ttingen, Germany, DE
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Abstract: | The effects of 5-hydroxytryptamine (5-HT) receptor agonists and antagonists were studied on the release of 5-HT from enterochromaffin
cells of incubated strips of porcine and human small intestine. Tetrodotoxin (1 μmol/l) was present in the incubation medium
to block neuronally mediated inputs to the enterochromaffin cells. The 5-HT1A receptor agonist (+)-8-hydroxy-dipropylaminotetralin (8-OH-DPAT, 1 μmol/l) and the 5-HT2 receptor agonist α-methyl-5-HT (1 μmol/l) increased 5-HT release by 40% in about 60% of the human preparations.These agonists
showed no effect on 5-HT release in porcine intestinal mucosa. The 5-HT3 receptor agonist 2-methyl-5-HT (3–100 μmol/l) increased 5-HT release in both species by 60% (pig) and 90% (man), respectively.
These stimulatory effects were antagonized by tropisetron (10 nmol/l). The 5-HT4 receptor agonist 5-methoxytryptamine (0.3–30 μmol/l) reduced 5-HT release by about 50% in both species. These inhibitory
effects were antagonized by tropisetron (3 μmol/l). The basal outflow of 5-HT from the intestinal mucosa was not significantly
affected by tropisetron (10 nmol/l; 3 μmol/l). The specific 5-HT4 receptor antagonist GR 113808 ((1-2-methylsulphonyl)amino]ethyl]-4-piperidinyl]methyl-1-methyl-1H-indole-3-carboxylate)
(0.1 μmol/l) which by itself did not significantly affect 5-HT release from human duodenal specimens blocked the inhibitory
effect of 5-methoxytryptamine (30 μmol/l).
These findings indicate that stimulatory 5-HT3 and inhibitory 5-HT4 receptors are present on enterochromaffin cells of the porcine and human intestinal mucosa. Under the present experimental
conditions endogenous 5-HT does not significantly activate these receptors. Stimulatory 5-HT1A and 5-HT2 receptors may additionally be present on human enterochromaffin cells.
Received: 19 September 1997/ Accepted: 29 January 1998 |
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Keywords: | Enterochromaffin cells Serotonin 5-HT receptors Mucosa |
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