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Original Article

Pituitary Adenylate Cyclase-Activating Peptide is a Potent Modulator of Human Colonic Motility

, , , , &
Pages 625-632 | Received 14 Sep 1992, Accepted 04 Jan 1993, Published online: 08 Jul 2009
 

Abstract

Pituitary adenylate cyclase-activating peptide (PACAP) represents a novel brain-gut peptide with high sequence homology to vasoactive intestinal polypeptide (VIP). Since PACAP has been identified in the human gut, the effect of the two molecular forms PACAP-(l-38) and PACAP-(l-27), the hybrid PACAP-(l-23)VIP-(24-28), and VIP on the contractility of the longitudinal muscle of human sigmoid colon was tested in vitro. All peptides inhibited the spontaneous phasic contractions and relaxed concentration-dependently carbachol-precontracted preparations. The effects of the peptides remained unaffected by tetrodotoxin, by inhibition of phosphodiesterase activity, and by inhibition of nitric oxide synthesis. Apamin reduced only the effects of the PACAP peptides, whereas tetraethylammonium blocked only the effect of VIP. In conclusion, PACAP peptides and VIP mediate their relaxant effects via activation of specific PACAP and VIP receptors coupled to different potassium channels.

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