Metabolism of putrescine in the central nervous system

The metabolism of putrescine in rat brain was studied systematically by the intraventricular injection of radioactive diamine. Putrescine injected into the brain was metabolized mainly to polyamines, spermidine, and spermine. A small portion of the radioactivity of putrescine was incorporated into gamma-glutamylputrescine, putreanine, gamma-aminobutyric acid, and homocarnosine. Comparison of the specific radioactivities of gamma-aminobutyric acid and homocarnosine after the injection of radioactive putrescine with those after the injection of radioactive glutamic acid indicated that there may be a metabolic pool of gamma-aminobutyric acid (putrescine-gamma-aminobutyric acid system) which is different from the glutamic acid-gamma-aminobutyric acid system and which is effectively used for synthesis of the dipeptide.