Gamma-aminobutyric acid and inhibition in the septal nuclei of the rat.

1. The electrophoretic application of gamma-aminobutyrate (GABA) and glycine to septal neurones inhibited their discharge, but the currents required to cause equivalent degrees of inhibition were always smaller for GABA than for glycine.2. The actions of GABA but not those of glycine were antagonized by bicuculline and not by strychnine and vice versa.3. The recurrent collateral inhibition of lateral septal neurones and the direct inhibition of medial cells evoked by stimulation of the fimbria were blocked by bicuculline but not by strychnine.4. The bursting patterns of discharge of laterally situated medial septal neurones was disrupted by bicuculline, but required a longer application of the drug than was needed to block the direct fimbrial inhibition. It is suggested that this disruption is due to diffusion of the drug to affect the inhibitory interneurones of the lateral septum.5. It is concluded that the inhibitory processes in the septum involve GABA as the synaptic transmitter.