Audiogenic seizure protection by elevated brain GABA concentration in mice: effects of gamma-acetylenic gaba and gamma-vinyl GABA, two irreversible GABA-T inhibitors.

gamma-Acetylenic GABA and gamma-vinyl GABA, two catalytic irreversible inhibitors of GABA-transaminase, produce marked and sustained elevations in mouse brain GABA concentrations and protect DBA/2 mice against audiogenically induced seizures in a similar dose and time-dependent manner. The acetylenic analog also inhibits GAD activity while the vinyl compound has minimal activity against this enzyme. The increase in brain GABA concentrations induced by these compounds correlates well with attenuation of audiogenic seizure intensity (r = 0.991 and 0.962 for gamma-acetylenic and gamma-vinyl GABA respectively) and with degree of seizure protection (r = 0.974 and 0.834). Seizure intensity is reduced by 50% when brain GABA is increased to 265% and 264% of control values by the two inhibitors and seizure incidence is halved at 322% and 324%. Thus, audiogenic seizure protection in genetically susceptible mice is apparently a function of whole brain GABA concentrations.