The identification and characterization of a GABAergic system in the cholinergic neuroblastoma x glioma hybrid clone NG108-15

γ-Aminobutyric acid (GABA) and glutamic acid decarboxylase (GAD) activity were identified and characterized in the cholinergic neuronal cell clone NG108-15. GAD activity is similar to form A in rat brain by being temperature sensitive and independent of pyridoxal 5′-phosphate in the assay mixture. Most of the NG108-15 GAD activity is inactivated by 1 mM amino-oxyacetic acid. In contrast to NG108-15 choline acetyltransferase, GAD activity is not enhanced when cells are grown with dibutyryl cyclic AMP. The GAD activity shows a cell-density dependent increase that does not correlate with changing level of endogenous GABA. The identification of GABAergic properties in the NG108-15 clone enhances its use as a neuronal model for studies of differentiation and neurotoxicity of drugs or chemicals.