[Decrease in the activity of cerebral gamma-aminobutyric acid metabolism enzymes under the influence of kynurenines...

Content of gamma-aminobutyric acid (GABA) was unaltered in mouse brain and cerebellum after administration of D,L-kynurenine (50 mcg), quinolinic acid (5 mcg) and nicotinic acid (50 mcg) into brain ventricles. At the same time, after administration of kinurenine, quinolinic acid and nicotinic acid activity of GABA-transaminase in brain was decreased by 39%, 40% and 48, respectively; activity of glutamate decarboxylase was decreased by 27% and 36%, respectively, in this case nicotinic acid affected only slightly. Strong clonic convulsions occurred in 60% of mice after administration of kynurenine and quinolinic acid and only in 7% of mice after treatment with nicotinic acid. Deceleration in the GABA turnover and the subsequent weakening of the brain inhibitory systems were apparently essential in development of convulsions caused by the kynurenines.