title: Muscarinic M2 receptors in rat brain labeled with [3H] AF-DX 384.
abstract: The muscarinic antagonist AF-DX 384 (5,11-dihydro-11-(((2-(2-((dipropylamino)methyl)-1- piperidinyl)ethyl)amino)carbonyl)-6H-pyrido(2,3b)(1,4)-benzodiazepin+ ++-6-one methansulfonate) was used to label cholinergic muscarinic receptors of the M2 subtype in rat brain. In the brainstem [3H] AF-DX 384 labeled a single population of binding sites with Kd = 3-4 nM and Bmax = 430-610 fmol/mg of protein. The pharmacological profile of these sites was similar to that observed with the muscarinic M2 agonist [3H] AF-DX 116. Muscarinic M2 receptors were unequally distributed in rat brain regions: in brainstem, about 80% of total muscarinic receptors (measured with [3H] quinuclidinyl benzilate) were labeled by [3H] AF-DX 384, while in other brain areas they represented only a fraction of total binding. Because of its high specific binding, high affinity and specificity, [3H] AF-DX 384 represents a useful novel ligand to study M2 receptors in brain tissue.
authors.affiliation: Department of Environmental Health, University of Washington, Seattle 98195.
authors.forename: A F
authors.initials: AF
authors.lastname: Castoldi
authors.forename: B
authors.initials: B
authors.lastname: Fitzgerald
authors.forename: L
authors.initials: L
authors.lastname: Manzo
authors.forename: M
authors.initials: M
authors.lastname: Tonini
authors.forename: L G
authors.initials: LG
authors.lastname: Costa
mesh_terms: D000818:Animals; D001923:Brain Chemistry; D066298:In Vitro Techniques; D008297:Male; D010276:Parasympatholytics / Q000378:metabolism*; D010890:Pirenzepine / Q000031:analogs & derivatives* / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011976:Receptors, Muscarinic / Q000032:analysis*
chemical_list: D010276:Parasympatholytics; D011976:Receptors, Muscarinic; C065959:AFDX 384; D010890:Pirenzepine