Evidence for an endogenous factor interfering with 3H-diazepam binding to rat brain membranes

An in vitro "receptor" binding assay has been used to search for an endogenous compound which possibly interacts with benzodiazepine receptors in brain. Such an endogenous 3H-diazepam binding inhibitory factor (DIF) has been found. This compound is unevenly distributed in brain and in various peripheral organs. The partially purified compound appears to have a low molecular weight (below 500) and is not inactivated by proteolytic enzymes.