A role of nitric oxide as an inhibitor of gamma-aminobutyric acid transaminase in rat brain.
The present study has been aimed to investigate the effect of nitric oxide (NO) on the concentration of gamma-aminobutyric acid (GABA) in rat brain. The concentrations of GABA and glutamate and the activities of glutamic acid decarboxylase (GAD) and gamma-aminobutyric acid transaminase (GABA-T) were determined in groups of animals 5 and 30 min after intraperitoneal injection of a NO-increasing dose (1,000 mg/kg) of its precursor, L-arginine and a dose (50 mg/kg) of N-nitro-L-arginine methyl ester (L-NAME) that inhibits NO synthesis from L-arginine. L-arginine-induced elevation of NO concentration was accompanied by an increased concentration of GABA in the brain. GABA-T activity was inhibited in these animals. NO-decreasing action of L-NAME coincided with a reduction in the concentration of GABA and an enhancement of GABA-T activity. Both L-arginine and L-NAME did not alter the activity of GAD and the concentration of glutamate. An interpretation of these data suggests that NO has a GABA-T-inhibiting role in the brain.
Paul
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Department of Pharmacology and Environmental Toxicology, Dr. ALM Postgraduate Institute of Basic Medical Sciences, University of Madras, Taramani, Chennai, India.
Jayakumar
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AR
D000612:4-Aminobutyrate Transaminase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D001120:Arginine / Q000494:pharmacology*; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D005968:Glutamate Decarboxylase / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D007700:Kinetics; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology*; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D051381:Rats; D017208:Rats, Wistar; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D009569:Nitric Oxide; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D001120:Arginine; D019001:Nitric Oxide Synthase; D000612:4-Aminobutyrate Transaminase; D005968:Glutamate Decarboxylase; D019331:NG-Nitroarginine Methyl Ester