5-Hydroxytryptamine (5-HT) released from colonic mucosal enterochromaffin (EC) cells is
a major signaling molecule, which participates in the pathophysiological regulation of colonic
functions in gut disorder including irritable bowel syndrome (IBS), but the endogenous modulator
system for the 5-HT release is not yet well elucidated. Our in vitro studies in guinea-pig colon have
indicated that the cascade pathway of neuronal tachykinergic NK3 receptors and NK2 receptors on
peptide YY (PYY)-containing endocrine L cells represents an endogenous modulator system for 5-HT release from EC
cells and that melatonin, endogenous tachykinins and PYY play important roles in modulation of the release of 5-HT from
EC cells via the endogenous NK2/NK3 receptor cascade system. This review aims at examining the potential role of the
endogenous tachykinergic NK2/NK3 receptor cascade system controlling the release of 5-HT from EC cells, with special
attention being paid to the pathophysiology of gut disorders including IBS.
Keywords: Colon, enterochromaffin cells, 5-HT (5-hydroxytryptamine, serotonin) release, melatonin, peptide YY, tachykinins,
NK2 and NK3 receptors, Y1 receptors.
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