Functional characterisation of tachykinin receptors in the circular muscle layer of the mouse ileum.
OBJECTIVE
Tachykinins are important mediators in neuromuscular signalling but have not been thoroughly characterised in the mouse gut. We investigated the participation of tachykinin receptors in contractility of circular muscle strips of the mouse ileum.


RESULTS
Electrical field stimulation (EFS) of excitatory nonadrenergic noncholinergic (NANC) nerves induced frequency-dependent contractions which were mimicked by substance P (SP). Desensitisation of SP and NK(1), NK(2) or NK(3) receptors significantly reduced contractions to EFS. The NK(1) receptor blocker RP67580 significantly inhibited NANC contractions to EFS. The NK(2) and NK(3) receptor blockers nepadutant and SR142801 did not affect NANC contractions per se but increased the RP67580-induced inhibition of NANC contractions to EFS. Contractions to SP were significantly reduced by RP67580 but not affected by nepadutant or SR142801. The NK(1) and NK(2) receptor agonists, septide and [beta-ala(8)]-NKA 4-10 (beta-A-NKA), respectively, but not the NK(3) receptor agonist senktide-induced dose-dependent contractions. Atropine inhibited and l-NNA augmented contractions to septide. Contractions to beta-A-NKA were insensitive to atropine but augmented by l-NNA.


CONCLUSIONS
Tachykinins mediate NANC contractions to EFS in the mouse small intestine. Endogenously released tachykinins activate mainly NK(1) receptors, located on cholinergic nerves and smooth muscle cells and, to a lesser degree, NK(2) and NK(3) receptors, most likely located presynaptically.
De Schepper
Heiko U
HU
Division of Gastroenterology, Faculty of Medicine, University of Antwerp, Universiteitsplein 1, Wilrijk B-2610, Belgium.
De Winter
Benedicte Y
BY
Seerden
Tom C
TC
Herman
Arnold G
AG
Pelckmans
Paul A
PA
De Man
Joris G
JG
D000200:Action Potentials / Q000187:drug effects; D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D014150:Antipsychotic Agents / Q000494:pharmacology; D001285:Atropine / Q000494:pharmacology; D004558:Electric Stimulation; D007082:Ileum / Q000502:physiology*; D007211:Indoles / Q000494:pharmacology; D054833:Isoindoles; D051379:Mice; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009119:Muscle Contraction / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D019335:Nitroarginine / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D018040:Receptors, Neurokinin-1 / Q000502:physiology*; D018041:Receptors, Neurokinin-2 / Q000502:physiology*; D013373:Substance P / Q000031:analogs & derivatives / Q000494:pharmacology*
D000700:Analgesics; D014150:Antipsychotic Agents; D007211:Indoles; D054833:Isoindoles; D018727:Muscarinic Antagonists; D010446:Peptide Fragments; D010880:Piperidines; D018040:Receptors, Neurokinin-1; D018041:Receptors, Neurokinin-2; C071693:7,7-diphenyl-2-(1-imino-2-(2-methoxyphenyl)ethyl)perhydroisoindol-4-one; D019335:Nitroarginine; D013373:Substance P; C054725:septide; D001285:Atropine; C091554:SR 142801; D011761:Pyrrolidonecarboxylic Acid