title: Muscarinic pharmacology of the inhibition of adenylate cyclase in N18TG2 neuroblastoma cells.
abstract: This study characterizes the muscarinic cholinergic receptors associated with the inhibition of adenylate cyclase on N18TG2 neuroblastoma cell membranes. Agonists could be divided into two classes: oxotremorine, acetylcholine, carbachol and arecoline exerted the most efficacious and potent inhibition, while McN-A343, bethanechol and AHR-602 were partial agonists. Both quinuclidinyl benzilate and atropine maximally antagonized the inhibitory effect of McN-A343, carbachol and oxotremorine. Pirenzepine was almost as potent as atropine in reversing the inhibitory effect of McN-A343, but was 300 times less potent than atropine or quinuclidinyl benzilate in antagonizing the effects of either carbachol or oxotremorine. Gallamine was ineffective as an antagonist at concentrations up to 1 mM. These results suggest that the receptors that modulate this inhibition are of the M(2) type, since they were activated by carbachol, acetylcholine and oxotremorine, but much less by McN-A343 and AHR-602 (both M(1) selective agonists). The full agonists were blocked by atropine and quinuclidinyl benzilate but not by low concentrations of pirenzepine (M(1) selective antagonist).
authors.affiliation: Department of Pharmacology, St. Louis University School of Medicine, 1402 South Grand Boulevard, St. Louis, MO 63104, U.S.A.
authors.forename: M
authors.initials: M
authors.lastname: Bidaut-Russell
authors.forename: A C
authors.initials: AC
authors.lastname: Howlett