SOME CORRELATIONS BETWEEN PICROTOXIN-INDUCED SEIZURES AND -AMINOBUTYRIC ACID IN ANIMAL BRAIN

¹ Department of Pharmacology, School of Medicine, Keio University, Tokyo, Japan

The experiments describe some interesting relationships between picrotoxin-induced seizures and -aminobutyric acid (GABA) levels in animal brain. At the preconvulsive stage, decreased GABA levels were observed in the diencephalon and mesencephalon of mouse and rabbit, whereas at the convulsive stage they returned gradually to normal. The GABA level in the cerebrum remained almost normal up to this period. At the intermediate stage between each seizure, or at the depressive stage, increased GABA levels were noted in all parts of the brain, especially in the cerebrum. In rabbits with cerebral ablations, especially with the ablation of hippocampi, GABA levels at the preconvulsive stage rose in the diencephalon and mesencephalon. The postictal electroencephalogram pattern after i.v. injection of picrotoxin is characterized by the appearance of low voltage waves restricted to the region of the hippocampi. Picrotoxin-induced seizures in mice were significantly inhibited by prior intracerebral injection of epinephrine, norepinephrine and GABA; this inhibitory effect of GABA was accelerated when epinephrine was injected previously.