title: Effects of ammonia on monoamine oxidase and enzymes of GABA metabolism in mouse brain.
abstract: Acute and chronic ammonia toxicity was produced in the mice by intraperitoneal injection of ammonium chloride (200 mg/kg) and by exposure of mice to ammonia vapours (5% v/v) continuously for 2 days and 5 days respectively. The ammonia content was elevated in the cerebellum, cerebral cortex and brain stem and in liver. In acute ammonia intoxication there was a decrease in the monoamine oxidase (MAO) activity in all the three regions of brain. In chronic ammonia toxicity (2 days of exposure) a significant increase in the activity of MAO was observed in the cerebral cortex while in cerebellum and brain stem there was a significant decrease. In cerebral cortex and cerebellum there was a rise in the activity of MAO as a result of exposure to ammonia vapours for 5 days. A significant decrease was observed in the activity of glutamate decarboxylase (GAD) in all the three regions of the brain both in acute and chronic ammonia toxicity (2 days). There was a decrease in the activity of this enzyme only in the cerebral cortex in the animals exposed to ammonia for 5 days. The activity of GABA-aminotransferase (GABA-T) showed a significant rise in cerebellum and a fall in the brain stem in acute ammonia toxicity. In chronic ammonia toxicity GABA-T showed a rise in all the three regions of brain. Chronic ammonia toxicity produced a significant decrease in the content of glutamate in all the three regions without a significant change in the content of aspartate. GABA and glutamine. The content of alanine increased in all the three regions of brain under these experimental conditions. The ratio of glutamate + aspartate/GABA and glutamate/glutamine showed a decrease in all the three regions as a result of ammonia toxicity.
mesh_terms: D000612:4-Aminobutyrate Transaminase / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism; D000613:Aminobutyrates / Q000378:metabolism*; D000641:Ammonia / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000201:enzymology*; D005968:Glutamate Decarboxylase / Q000378:metabolism; D051379:Mice; D008995:Monoamine Oxidase / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D000613:Aminobutyrates; D005680:gamma-Aminobutyric Acid; D000641:Ammonia; D008995:Monoamine Oxidase; D000612:4-Aminobutyrate Transaminase; D005968:Glutamate Decarboxylase