title: Role of cholinergic neurons in the motor effects of glucagon-like peptide-2 in mouse colon.
abstract: Glucagon-like peptide-2 (GLP-2) reduces mouse gastric tone and small intestine transit, but its action on large intestine motility is still unknown. The purposes of the present study were 1) to examine the influence of GLP-2 on spontaneous mechanical activity and on neurally evoked responses, by recording intraluminal pressure from mouse isolated colonic segments; 2) to characterize GLP-2 mechanism of action; and 3) to determine the distribution of GLP-2 receptor (GLP-2R) in the mouse colonic muscle coat by immunohistochemistry. Exogenous GLP-2 (0.1-300 nM) induced a concentration-dependent reduction of the spontaneous mechanical activity, which was abolished by the desensitization of GLP-2 receptor or by tetrodotoxin, a voltage-dependent Na(+)-channel blocker. GLP-2 inhibitory effect was not affected by N(ω)-nitro-l-arginine methyl ester (a nitric oxide synthase inhibitor), apamin (a blocker of small conductance Ca(2+)-dependent K(+) channels), or [Lys1,Pro2,5,Arg3,4,Tyr6]VIP(7-28) (a VIP receptor antagonist), but it was prevented by atropine or pertussis toxin (PTX), a G(i/o) protein inhibitor. Proximal colon responses to electrical field stimulation were characterized by nitrergic relaxation, which was followed by cholinergic contraction. GLP-2 reduced only the cholinergic evoked contractions. This effect was almost abolished by GLP-2 receptor desensitization or PTX. GLP-2 failed to affect the contractile responses to exogenous carbachol. GLP-2R immunoreactivity (IR) was detected only in the neuronal cells of both plexuses of the colonic muscle coat. More than 50% of myenteric GLP-2R-IR neurons shared the choline acetyltransferase IR. In conclusion, the activation of GLP-2R located on cholinergic neurons may modulate negatively the colonic spontaneous and electrically evoked contractions through inhibition of acetylcholine release. The effect is mediated by G(i) protein.
authors: Dipartimento di Biologia cellulare e dello Sviluppo, Università di Palermo, Palermo, Italy.
authors: Antonella
authors: A
authors: Amato
authors: Alessandra
authors: A
authors: Rotondo
authors: Lorenzo
authors: L
authors: Cinci
authors: Sara
authors: S
authors: Baldassano
authors: Maria Giuliana
authors: MG
authors: Vannucchi
authors: Flavia
authors: F
authors: Mulè
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D015153:Blotting, Western; D003106:Colon / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D017615:Enteric Nervous System / Q000187:drug effects / Q000378:metabolism; D005769:Gastrointestinal Motility / Q000187:drug effects / Q000502:physiology*; D053767:Glucagon-Like Peptide 2 / Q000378:metabolism* / Q000494:pharmacology; D000067758:Glucagon-Like Peptide-2 Receptor; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D018027:Receptors, Glucagon / Q000378:metabolism
chemical_list: D053767:Glucagon-Like Peptide 2; D000067758:Glucagon-Like Peptide-2 Receptor; D018027:Receptors, Glucagon; D000109:Acetylcholine