Alpha 2-adrenoceptor subtypes in the human brain: a pharmacological delineation of [3H]RX-821002 binding to membranes and tissue sections

Eur J Pharmacol. 1996 Aug 22;310(1):83-93. doi: 10.1016/0014-2999(96)00381-0.


In order to study the characterization and localization of [3H]RX-821002 (2-methoxy-idazoxan) binding to alpha 2-adrenoceptor subtypes in several regions of the human brain, we have carried out competition studies using both autoradiography and membrane binding assays. The alpha 2A-adrenoceptor subtype was found to be predominant in the different layers of the frontal cortex, cerebellum and hippocampal formation, while in the neostriatum it was the non-alpha 2A- (alpha 2B- and alpha 2C-) adrenoceptor subtype. In the frontal cortex, in addition to binding to the alpha 2A-adrenoceptor subtype, [3H]RX-821002 bound also to a small portion of alpha 2B- and alpha 2C-adrenoceptors in layer III, and to an unidentified binding site in the external layers. In the hippocampus, both alpha 2A- and non-alpha 2A- (alpha 2B- and alpha 2C-) adrenoceptors were labelled in the dentate gyrus and the CA1 field, together with 5-HT1A receptors. 5-HT1A receptors were labelled predominantly in the stratum pyramidale layer. These results, in addition to delineate the relative presence of alpha 2-adrenoceptor subtypes, indicate that caution is needed when analyzing RX 821002 binding to human brain tissue.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenergic alpha-Antagonists / metabolism*
  • Adult
  • Autoradiography
  • Binding Sites
  • Binding, Competitive
  • Brain / metabolism*
  • Female
  • Frontal Lobe / metabolism*
  • Hippocampus / metabolism*
  • Humans
  • Idazoxan / analogs & derivatives*
  • Idazoxan / antagonists & inhibitors
  • Idazoxan / metabolism
  • Imidazoles / pharmacology
  • Indoles / pharmacology
  • Isoindoles
  • Male
  • Organ Specificity
  • Radioligand Assay


  • Adrenergic alpha-Antagonists
  • Imidazoles
  • Indoles
  • Isoindoles
  • 2-methoxyidazoxan
  • Idazoxan
  • BRL 44408