Identification of inosine and hypoxanthine as endogenous ligands for the brain benzodiazepine-binding sites

Proc Natl Acad Sci U S A. 1979 Feb;76(2):977-81. doi: 10.1073/pnas.76.2.977.


Two endogenous ligands for the brain benzodiazepine-binding sites were isolated from bovine brain through gel filtration, paper electrophoresis, and paper chromatography. These ligands were identified as inosine and hypoxanthine, and both had a higher affinity for the brain benzodiazepine-binding sites than for benzodiazepine sites in some peripheral tissues. They did not bind to any other receptors tested, such as the opiate, muscarinic cholinergic, gamma-aminobutyric acid, and beta-adrenergic receptors. Both inosine and hypoxanthine competitively inhibited the binding of [3H]diazepam to the brain binding site.

MeSH terms

  • Animals
  • Benzodiazepines / immunology
  • Benzodiazepines / metabolism*
  • Binding Sites, Antibody
  • Binding, Competitive
  • Brain / metabolism*
  • Cattle
  • Diazepam / metabolism
  • Hypoxanthines / metabolism*
  • Inosine / metabolism*
  • Ligands
  • Receptors, Drug / metabolism*


  • Hypoxanthines
  • Ligands
  • Receptors, Drug
  • Benzodiazepines
  • Inosine
  • Diazepam