Muscarinic M2 receptors in rat brain labeled with [3H] AF-DX 384

A. F. Castoldi, B. Fitzgerald, L. Manzo, M. Tonini, L. G. Costa

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish
Pages (from-to)371-374
Number of pages4
JournalResearch Communications in Chemical Pathology and Pharmacology
Issue number3
Publication statusPublished - 1991

ASJC Scopus subject areas

  • Pharmacology
  • Toxicology


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