The release of [3H]acetylcholine ([3H]ACh) from Auerbach's plexus and the contraction of longitudinal muscle strips in response to the administration of cholecystokinin (CCK) were measured and recorded simultaneously. The peripheral CCK receptor antagonist, 3S(-)-N-(2,3-dihydro-1-methyl-2-oxo-5-phenyl-1H-1,4-benzodiazepine-3-yl)-1Hindole-2-carboxamide (L-364,718), antagonized the ACh releasing effect of CCK in a dose-dependent manner. The IC50 value and the dissociation constant (KD) were 41.0 ± 2.0 pM and 0.06 ± 0.01 nM, respectively. These results suggest that L-364,718 is a very potent antagonist of the neuronal CCK receptors.
- Acetylcholine release
- Myenteric plexus
- Neuronal cholecystokinin receptors
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