Nonadrenergic [3H]idazoxan binding sites are physically distinct from α2-adrenergic receptors

M. C. Michel, J. W. Regan, M. A. Gerhardt, R. R. Neubig, P. A. Insel, H. J. Motulsky

Research output: Contribution to journalArticlepeer-review

79 Scopus citations


We have recently demonstrated that the α2-adrenergic radioligand [3H]idazoxan also labels additional sites that do not recognize catecholamines but bind with high affinity several chemically distinct drugs previously assumed to be highly selective for α-adrenergic receptors [Mol. Pharmacol. 35:324-330 (1989)]. We now have used three approaches to distinguish the nonadrenergic [3H]idazoxan sites from α2-adrenergic receptors. (a) No nonadrenergic [3H]idazoxan binding sites were found in COS-7 cells transfected with the genes for the two known α2-adrenergic receptor subtypes. (b) The ratio of α2-adrenergic and nonadrenergic [3H]idazoxan sites in human platelet membranes varied considerably between various donors. (c) Highly purified platelet plasma membranes were enriched for α2-adrenergic receptors but did not contain any nonadrenergic [3H]idazoxan binding sites. We conclude that the nonadrenergic [3H]idazoxan binding sites are not co-expressed with α2-adrenergic receptor and at least in human platelets may be located in an intracellular compartment.

Original languageEnglish (US)
Pages (from-to)65-68
Number of pages4
JournalMolecular pharmacology
Issue number1
StatePublished - 1990

ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmacology


Dive into the research topics of 'Nonadrenergic [3H]idazoxan binding sites are physically distinct from α2-adrenergic receptors'. Together they form a unique fingerprint.

Cite this