GABA-modulin, a basic protein which controls GABA benzodiazepine receptor interaction, was shown to be present in high concentration in association with GABA recognition sites in rat brain synaptosomes. GM is basic in nature and it is rich in arginine and lysine residues. The above characteristics link this peptide to the general class of brain basic peptides. However physiochemical and bichemical observations indicate that GM is different from any other known basic peptide.