Isolation and partial purification of a clonidine-displacing endogenous brain substance

Eur J Biochem. 1984 Oct 15;144(2):287-93. doi: 10.1111/j.1432-1033.1984.tb08462.x.


A new compound, designated clonidine-displacing substance (CDS), has been isolated from calf brain by ion-exchange chromatography, zone electrophoresis and high-performance liquid chromatography. CDS binds specifically to alpha 2-adrenergic receptors in rat brain and human platelet membranes, as measured in direct binding experiments using [3H]clonidine and [3H]yohimbine respectively. Unlike clonidine or other alpha 2-agonists, CDS does not affect basal levels of adenylate cyclase in human platelets at the highest concentrations obtainable. The apparent molecular mass of the compound is estimated to be 500 +/- 50 Da, as determined by gel-filtration chromatography on Sephadex G-15. The new compound is thermostable, not affected by proteolytic enzymes, such as trypsin, chymotrypsin, pronase, papain and pyroglutamase, or by boiling in 0.2 M HCl for 5 min. It does not bind to alpha 1-receptors in rat brain or to beta-adrenergic receptors in turkey erythrocytes, since it is unable to displace [3H]prazosin and [125I]cyanopindolol from alpha 1 and beta-receptors respectively.

MeSH terms

  • Adenylyl Cyclase Inhibitors
  • Animals
  • Binding, Competitive
  • Blood Platelets / enzymology
  • Brain Chemistry*
  • Cattle
  • Chromatography / methods
  • Clonidine / metabolism*
  • Electrophoresis, Agar Gel
  • Erythrocytes / metabolism
  • Humans
  • Imidazoline Receptors
  • In Vitro Techniques
  • Iodocyanopindolol
  • Molecular Weight
  • Pindolol / analogs & derivatives
  • Pindolol / metabolism
  • Prazosin / metabolism
  • Rats
  • Receptors, Adrenergic, alpha / metabolism
  • Receptors, Adrenergic, alpha-2*
  • Turkeys
  • Yohimbine / metabolism


  • Adenylyl Cyclase Inhibitors
  • Imidazoline Receptors
  • Receptors, Adrenergic, alpha
  • Receptors, Adrenergic, alpha-2
  • Yohimbine
  • Iodocyanopindolol
  • Pindolol
  • Clonidine
  • Prazosin