(R)-5-Oxopyrrolidine-2-carboxylic acid (D-Pyroglutamic acid) is a cyclic derivative of glutamic acid, physiologically present in mammalian tissues. It has been shown that PCA releases GABA from the cerebral cortex and displays anti-anxiety effects in a simple approach-avoidance conflict situation in the rat. In clinical pharmacology experiments, PCA significantly shortens the plasma half-life of ethanol during acute intoxication.