[Isolation and partial purification of the endogenous inhibitor of receptor binding of 3H-L-glutamate].

The endogenous factor that inhibited 3H-L-glutamate specific binding (FIB) was isolated from the aqueous extract of the crude mitochondrial fraction of the rat cerebral cortex homogenate and partially purified. The purification procedure involved several steps of ion-exchange, gel-permeating and thin-layer chromatography. Partially purified FIB competitively inhibited 3H-L-glutamate specific binding and had the molecular weight of 450-600 Da. Glutamic acid residues were found in FIB amino acids. The functional role of the isolated factor as an endogenous modulator involved in the regulation of effective synaptic transmission of glutamatergic brain synapses is discussed.