Allosterically linked noncompetitive antagonist binding sites in the resting nicotinic acetylcholine receptor ion channel

Hugo R. Arias, Elizabeth A. McCardy, Erin Z. Bayer, Martin J. Gallagher, Michael P. Blanton

Research output: Contribution to journalArticle

23 Scopus citations


Previous studies have established the presence of overlapping binding sites for the noncompetitive antagonists (NCAs) amobarbital, tetracaine, and 3-trifluoromethyl-3-(m-[125I]iodophenyl) diazirine ([125I]TID) within the ion channel of the Torpedo nicotinic acetylcholine receptor (AChR) in the resting state. These well-characterized NCAs and competitive radioligand binding and photolabeling experiments were employed to better characterize the interaction of the dissociative anesthetics ketamine and thienylcycloexylpiperidine (TCP) with the resting AChR. Our experiments yielded what appear to be conflicting results: (i) both ketamine and TCP potentiated [125I]TID photoincorporation into AChR subunits; and (ii) ketamine and TCP had very little effect on [14C]amobarbital binding. Nevertheless, (iii) both ketamine and TCP completely displaced [3H]tetracaine binding (Kis ∼ 20.9 and 2.0 μM, respectively) by a mutually exclusive mechanism. To reconcile these results we propose that, in the resting ion channel, TCP and ketamine bind to a site that is spatially distinct from the TID and barbiturate locus, while tetracaine bridges both binding sites.

Original languageEnglish
Pages (from-to)121-131
Number of pages11
JournalArchives of Biochemistry and Biophysics
Issue number1
Publication statusPublished - 1 Jul 2002
Externally publishedYes



  • Conformational states
  • Equilibrium binding
  • Ketamine and phencyclidine binding sites
  • Photoaffinity labeling
  • Torpedo nicotinic acetylcholine receptor

Cite this