Changes in γ-aminobutyric acid during different stages of picrotoxininduced seizure, and the effect of pretreatment with γ-acetylenic GABA and phenobarbital.

ABSTRACT

Changes in GABA content of various brain areas during different stages of picrotoxin-induced seizures and following pretreatment with the anti-convulsants phenobarbital and γ-acetylenic GABA were studied. Picrotoxin (6mg/kg) produced clonic/tonic convulsions associated with a 34% reduction in GABA content of the sensory motor cortex. A reduction of 24% was observed 1 min before the onset of seizure and the reduction in GABA content was reversible 20 min after the convulsion. No significant changes were observed in the cerebellum or spinal cord/medulla oblongata. Pretreatment with phenobarbital (100mg/kg) delayed the onset of convulsion and decreased the mortality rate without causing any change in GABA content at the preconvulsive, convulsive or post-convulsive stages. γ-Acetylenic GABA (100mg/kg) has elevated GABA levels in different areas of the brain by 2-3-fold after 60 min treatment. This increase was reduced by 44% during the onset of picrotoxin-induced seizures. Picrotoxin convulsion can occur in the presence of normal, reduced or even elevated brain GABA content. The only consistent factor is a one-third reduction in GABA content before the onset of seizure.