Effect of gamma-aminobutyric acid (GABA) on strychninization of the mammalian cerebral cortex.

Abstract

The authors observed the action of GABA on the cerebral cortex of rabbits and cats. Our interest was focused especially on the relation between the action of GABA and strychnine.1. GABA induced sometimes spontaneous surface positive waves in the cerebral cortex and its action was facilitated by strychnine.2. Among the isomers of GABA, β-aminoisobutyric acid had a similar action, but α-amino-n-butyric acid and α-aminoisobutyric acid had not such effect.3. GABA enhanced the amplitude of the initial positive component of strychnine spike at a low concentration and inhibited the second negative component at a higher concentration. As a result, phase reversal was observed in the polarity of strychnine spike.4. Phase reversal in strychnine spike was limited to the neighborhood of the spot where GABA was applied and GABA could not inhibit spreading of strychnine spike from strychninized site to other spots.5. Unrelatedness of phase reversal itself to the inhibition on corticifugal impulses was demonstrated.6. Phase reversal in the polarity of strychnine spike was likewise induced by systemic or intraventricular GABA. The differences of the action of GABA between topical and these administrations were investigated.7. GABA inhibited a facilitatory effect of strychnine on the secondary negative wave of the direct cortical response and augmented the amplitude of its positive component.8. GABA counteracted the specific facilitatory effect of strychnine on the negative component of the transcallosal response. On the contrary, GABA facilitated its positive component and generated a late negativity. The discharges of the neuronal elements which were facilitated by GABA were synchronized by strychnine.9. The effects of various corticipetal impulses on strychnine negative spike and strychnine-GABA positive spike were investigated.10. The mechanism of the action of GABA was discussed in some details.Anyhow, some antagonistic action between GABA and strychnine on the superficial cortical elements and some synergetic action between them on the deep elements were demonstrated.