title: Properties of Torpedo electric organ muscarinic receptors.
abstract: 1. Synaptosomes isolated from Torpedo electric organ, and incubated with [1-14C]acetate to prelabel the ACh stores, rapidly lost [14C]ACh when depolarized with high K+. The extent of this loss was typically about 10%. 2. The K+-stimulated loss (release) of [14C]ACh was inhibited by the muscarinic agonist, oxotremorine (5 microM), and effect antagonized by two muscarinic antagonists, atropine at 5 nM and pirenzepine at 2 microM. 3. Ligand-binding studies on membranes isolated from Torpedo electric organ show that the muscarinic receptors are qualitatively the same as established in other tissues. Thus antagonist binding was to a single class of sites, with nM affinity and an insensitivity to GTP. By contrast agonist binding was more complex (multi-site), with microM affinity and was sensitive to GTP (apparent lowered affinity). 4. Binding affinities of a variety of different ligands of various categories, including antidepressant drugs, were similar in Torpedo to rat brain indicating a quantitative similarity between the receptors in these diverse tissues.
mesh_terms: D000109:Acetylcholine / Q000096:biosynthesis / Q000378:metabolism*; D000818:Animals; D004557:Electric Organ / Q000378:metabolism*; D007700:Kinetics; D011813:Quinuclidinyl Benzilate / Q000378:metabolism; D011950:Receptors, Cholinergic / Q000378:metabolism*; D011976:Receptors, Muscarinic / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism; D013574:Synaptosomes / Q000378:metabolism*; D014101:Torpedo
chemical_list: D011950:Receptors, Cholinergic; D011976:Receptors, Muscarinic; D011813:Quinuclidinyl Benzilate; D000109:Acetylcholine