Characterization of muscarinic receptors on the isolated guinea pig ileum at pharmacologically low concentrations

Abstract

1. 1. Several selective and non-selective muscarinic agonists (McN-A-343, RS-86, arecoline, oxotremorine-M, pilocarpine, cis-dioxolane, and acetylcholine) were examined for relaxant activity in the isolated guinea-pig ileum at pharmacologically low concentrations. 2. 2. The concentrations studied include: 1 × 10 −12M, 3 × 10 −12M, 1 × 10 −11M, 3 × 10 −11M and 1 × 10 −10M. 3. 3. None of the compounds exhibited relaxant activity in both the field and non-field stimulated ileum. 4. 4. All of the above compounds exert muscarinic agonist activity in a concentration range of 1 × 10 −9M to 1 × 10 −6M (Williams et al., 1992). 5. 5. Thus, in the isolated guinea-pig ileum, muscarinic agonists do not exert relaxant activity of the gastrointestinal tract at low concentrations.