The Inactivation of γ‐Aminobutyric Acid Transaminase in Dissociated Neuronal Cultures from Spinal Cord

Abstract

Dissociated cell cultures from chick embryo spinal cord have a high affinity uptake system for the neurotransmitter GABA and make functional inhibitory synaptic contacts as determined by electrophysiology (Farb, et al.). These cultures can synthesize GABA from added glutamate in a glutamate decarboxylase-dependent reaction. The cultures have a functional GABA transaminase that degrades the neurotransmitter. This enzyme can be specifically and irreversibly blocked with gabaculine. A 15 min incubation with 10-6 M-gabaculine completely inactivates the enzyme. The inactivation of the enzyme leads to an increase in GABA levels. Long-term incubation (16 days) of gabaculine in the medium does not appear to alter high affinity GABA transport, suggesting that the drug is not toxic to cells capable of accumulating GABA.