ORNITHINE AND GLUTAMIC ACID DECARBOXYLASE ACTIVITIES IN THE DEVELOPING CHICK RETINA

Abstract— γ‐Aminobutyric acid was found in 6‐day‐old chick embryo retina; approx 20% was formed from putrescine and the remainder from glutamic acid. However, at the 18th embryonic day only 1% of the γ‐aminobutyric acid synthesized in retina was derived from putrescine. These results show that γ‐aminobutyric acid is synthesized in chick embryo retina prior to synaptogenesis, and that γ‐aminobutyric acid is synthesized via two pathways. The first pathway involves the conversion of putrescine to γ‐aminobutyric acid; the second path is dependent upon the conversion of glutamic acid to γ‐aminobutyric acid, catalyzed by glutamic acid decarboxylase.