Identification of inosine and hypoxanthine as endogenous inhibitors of [³H] diazepam binding in the central nervous system

Endogenous inhibitors of [³H] diazepam binding have recently been isolated from bovine brain (1). These factors which competitively inhibit [³H] diazepam binding to synaptosomal membrane preparations have been characterized as dialyzable, heat stable, and resistant to degradation by proteolytic enzymes. Further purification by gel filtration, ion-exchange chromatography, thin-layer chromatography, ultraviolet spectroscopy and high pressure liquid chromatography demonstrate that these compounds are inosine and hypoxanthine.