Mechanisms mediating the effects of cholecystokinin on avian small intestine longitudinal smooth muscle
Copyright policy )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.
Male, Mammals, Neurons, Analysis of Variance, Dose-Response Relationship, Drug, Methiothepin, Molecular Sequence Data, Muscle, Smooth, In Vitro Techniques, Receptors, Neurokinin-1, Acetylcholine, Peptide Fragments, Ileum, Animals, Receptors, Cholecystokinin, Amino Acid Sequence, Ketanserin, Cholecystokinin, Chickens, Muscle Contraction
Male, Mammals, Neurons, Analysis of Variance, Dose-Response Relationship, Drug, Methiothepin, Molecular Sequence Data, Muscle, Smooth, In Vitro Techniques, Receptors, Neurokinin-1, Acetylcholine, Peptide Fragments, Ileum, Animals, Receptors, Cholecystokinin, Amino Acid Sequence, Ketanserin, Cholecystokinin, Chickens, Muscle Contraction
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