[Neuroleptics as antagonists of gamma-aminobutyric acid]

Experiments on the neurons of isolated spinal cord of rats aged 9-14 days have revealed that like picrotoxin, the neuroleptics reduce the GABA-induced depolarization of primary afferents, hyperpolarization of the motoneurons and inhibition of the function of the interneurons which exercise the inhibitory control of motoneuronal activity. The highest GABA-lytic activity was displayed by the butirophenon derivatives (droperidol and haloperidol). Triphthazin slightly yields to these drugs as regards the activity. Aminazin and levomepromazin have a moderate GABA-lytic activity, whereas thioridazin and ftorphenazin have none. A possible role of the GABA-lytic activity of the neuroleptics in their antipsychotic action is discussed.