Atropine- and scopolamine-resistant subtypes of muscarinic receptors in the rabbit aorta.

S Manjeet, M K Sim

Department of Pharmacology, Faculty of Medicine, National University of Singapore.

European journal of pharmacology 1989 Dec 12

filter terms:

Tritiated acetylcholine ([3H]ACh) binds specifically to different muscarinic binding sites in the rabbit aorta. The binding of [3H]ACh to endothelial membranes was displacable by nanomolar concentrations of scopolamine but only by micromolar concentrations of atropine and homatropine. The reverse was true for smooth muscle membranes, i.e. [3H]ACh binding was displacable by nanomolar concentrations of atropine and homatropine but only by micromolar concentrations of scopolamine. Pirenzepine, AF-DX 116 and 4-diphenyl-acetoxy-N-methylpiperidine methobromide (4-DAMP) displaced the binding of [3H]ACh from both tissues in the nano- to micromolar range. Our findings indicate that endothelial receptors are characterised by a high affinity for scopolamine, which possesses a scopine base, and that muscle binding sites have a high affinity for antagonists possessing a tropine base (atropine, homatropine). Both the endothelial and smooth muscle binding sites have a low affinity for AF-DX 116, indicating that they are not of the cardiac type.

Citation

S Manjeet, M K Sim. Atropine- and scopolamine-resistant subtypes of muscarinic receptors in the rabbit aorta. European journal of pharmacology. 1989 Dec 12;174(1):99-105