Mechanisms mediating the effects of cholecystokinin on avian small intestine longitudinal smooth muscle.
The aims of this study were (1) to define the effects of CCK-8s and related peptides on chicken ileum longitudinal smooth muscle and (2) to explore the mechanisms by which such effects occur. The effects of CCK-8s were assayed in vitro on chicken longitudinal ileal strips. CCK-8s produced contraction of ileal strips (EC50 8.8.10(-9) M). CCK-8ns and CCK-4 did not have remarkable contractile effects even when added at concentrations 200-times higher than the EC50 for CCK-8s. L365,260 slightly inhibited the effects of CCK-8s whereas L364,718 was ineffective. Tetrodotoxin (10(-6) M) markedly decreased the effects of CCK-8s. Atropine (10(-6) M) did not modify the neurally mediated effects of CCK-8s, whereas ketanserin (10(-5) M) decreased the response to CCK-8s. Substance P-desensitized preparations exhibited reduced responses to CCK-8s. Our results indicate that CCK receptors present in chicken ileum behave similarly but not identically to the CCK-A receptor described in mammals. Most of these CCK receptors are neurally located but a minor proportion is also present on smooth muscle. The neurally mediated response to CCK-8s does not involve cholinergic mechanisms, but serotonin and substance P releasing neurons.
Martín
M T
MT
Department of Physiology and Cell Biology, Universitat Autònoma de Barcelona, Bellaterra, Spain.
Fernández
E
E
Fernández
A G
AG
Goñalons
E
E
D000109:Acetylcholine / Q000494:pharmacology; D000595:Amino Acid Sequence; D000704:Analysis of Variance; D000818:Animals; D002645:Chickens; D002766:Cholecystokinin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D007082:Ileum / Q000187:drug effects / Q000294:innervation / Q000502:physiology*; D066298:In Vitro Techniques; D007650:Ketanserin / Q000494:pharmacology; D008297:Male; D008322:Mammals; D008719:Methiothepin / Q000494:pharmacology; D008969:Molecular Sequence Data; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000294:innervation / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D010446:Peptide Fragments / Q000494:pharmacology; D011949:Receptors, Cholecystokinin / Q000187:drug effects / Q000502:physiology; D018040:Receptors, Neurokinin-1 / Q000187:drug effects / Q000502:physiology; D012844:Sincalide / Q000494:pharmacology; D013329:Structure-Activity Relationship; D013373:Substance P / Q000494:pharmacology; D013758:Tetragastrin / Q000494:pharmacology
D010446:Peptide Fragments; D011949:Receptors, Cholecystokinin; D018040:Receptors, Neurokinin-1; D013758:Tetragastrin; D013373:Substance P; D008719:Methiothepin; D002766:Cholecystokinin; D007650:Ketanserin; D012844:Sincalide; D000109:Acetylcholine