| Abstrakt: |
The aim of this study was to determine which PGE2receptors (EP1–4receptors) influence colonic motility. Mucosa-free longitudinal smooth muscle strips of the rat middle colon spontaneously induced frequent phasic contractions (giant contractions, GCs) in vitro, and the GCs were almost completely abolished by a cyclooxygenase inhibitor, piroxicam, and by an EP3receptor antagonist, ONO-AE3-240, but enhanced by tetrodotoxin (TTX). In the presence of piroxicam, exogenous PGE2, both ONO-AE-248 (EP3agonist), and ONO-DI-004 (EP1agonist) induced GC-like contractions, and increased the frequency and amplitude. These effects of EP receptor agonists were insensitive to TTX and ω-conotoxins. In immunohistochemistry, the EP1and EP3receptors were expressed in the longitudinal smooth muscle cells. These results suggest that the endogenous PGE2spontaneously generates and enhances the frequent phasic contractions directly activating the EP1and EP3receptors expressed on longitudinal smooth muscle cells in the rat middle colon. |
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