Endogenous benzodiazepine receptor agonist in human and mammalian plasma

Using ultra-filtration steps and HPLC-separation, a low molecular weight ligand of the benzodiazepine receptor was isolated from plasma of various mammalian species including man. The endogenous ligand acts on benzodiazepine receptors agonistically and apparently has a receptor affinity similar to Diazepam. The ligand is not identical with Diazepam as indicated by HPLC and UV-spectroscopy.