EFFECTS OF γ-AMINOBUTYRIC ACID (GABA), γ-AMINOBUTYRYL CHOLINE (GABA-CH) AND THEIR RELATED SUBSTANCES ON THE CORTICAL ACTIVITY

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Pharmacological actions of various aminoacids and choline derivatives on the cortical activity of rabbits and cats were tested electrophysiologically.
1. Among aminoacids, only ω-aminoacids have been found to have pharmacological action on the cortex. Their shorter chain series showed inhibitory action. The inhibitory action of GABA was ca. 13 times stronger as that of β-alanine. Whereas, ε-aminocaproic acid showed an excitatory action. The excitatory action of 10%ε-amino-caproic acid was completely inhibited by 1% GABA.
2. GABA-Ch, glutamyl-choline and carbamyl-choline suppressed the primary sensory evoked potential and the direct cortical response. Among them, GABA-Ch showed the most powerful inhibition.
3. In the inhibition on metrazol spike, GABA-Ch was about 1000 time as active as GABA: glutamyl or carbamyl choline was about half or one-third as active.
4. By intravenous injection, the inhibitory action of GABA on seizures induced by metrazol was compared with that of sodium phenobarbital. Its inhibitory effect was prompt and much stronger than that of phenobarbital.
5. Among isomers of GABA, only β-aminoisobutyric acid showed a slight inhibitory action.
6. GABA and β-aminoisobutyric acid could elicit surface positive potentials. The phase-inverting action of GABA on spikes induced by metrazol or β-aminocaproic acid was remarkable.
GABA-Ch or other cholines did not show such effect.
7. A characteristic action of GABA on the electrical activity of the cortex seems to be phase-inverting.