Characterization of imidazoline binding protein(s) solubilized from human brainstem: studies with [3H]idazoxan and [3H]clonidine

Neurochem Int. 1994 Aug;25(2):183-91. doi: 10.1016/0197-0186(94)90038-8.


Imidazoline binding sites from the human brainstem were solubilized with 3-[(3-cholamido-propyl)-dimethylammonio]-1-propane-sulfonate (CHAPS). [3H]idazoxan and [3H]clonidine were used as ligands to characterize the solubilized binding sites. In both the soluble and membrane fractions, [3H]idazoxan binding was saturable, stereoselective, sensitive to imidazolines and insensitive to (-)norepinephrine and to amiloride. The affinities of [3H]idazoxan for the soluble and membrane sites were similar (KD = 25 +/- 11 nM and 20 +/- 3 nM). In both soluble and membrane fractions, the alpha 2-adrenoceptor binding being masked with (-)norepinephrine, [3H]clonidine bound to a low affinity site which was insensitive to (-)norepinephrine and which exhibited the same selectivity for various drugs as the [3H]idazoxan binding site. alpha 2-adrenoceptor binding was present in the membrane and the soluble fractions although it was difficult to detect in the soluble fraction because of inhibition of [3H]rauwolscine binding by the CHAPS detergent.

MeSH terms

  • Binding Sites
  • Cell Membrane / metabolism
  • Cholic Acids
  • Chromatography, Gel
  • Clonidine / metabolism*
  • Dioxanes / metabolism*
  • Humans
  • Idazoxan
  • Imidazoles / metabolism*
  • Imidazoline Receptors
  • Norepinephrine / pharmacology
  • Receptors, Drug / isolation & purification
  • Receptors, Drug / metabolism*
  • Solubility
  • Tritium
  • Yohimbine / metabolism


  • Cholic Acids
  • Dioxanes
  • Imidazoles
  • Imidazoline Receptors
  • Receptors, Drug
  • Tritium
  • Yohimbine
  • Clonidine
  • 3-((3-cholamidopropyl)dimethylammonium)-1-propanesulfonate
  • Norepinephrine
  • Idazoxan