GABA transaminase inhibitors enhance the release of endogenous GABA but decrease the release of beta-alanine evoked by electrical stimulation of slices of the rat medulla oblongata.
Slices of the rat medulla oblongata were superfused and electrically stimulated. The amount of endogenous GABA, beta-alanine and glutamate release from the slices was determined by high performance liquid chromatography with fluorometric detection. Inhibitors of GABA-transaminase (GABA-T), aminooxyacetic acid (10(-5) M), gamma-acetylenic GABA (10(-4) and 10(-3) M) and gabaculine (10(-5) M), enhanced the stimulus-evoked release of GABA and reduced that of beta-alanine, while no change was observed in the release of glutamate. These changes in amino acid release from the slices were accompanied by an increase in the content of GABA and a decrease in that of beta-alanine. The stimulus-evoked release of these amino acids was abolished by Ca2+-deprivation, in either the presence or absence of GABA-T inhibitors. These results suggest a modulatory role of GABA-T for synaptically releasable GABA and involvement of this enzyme in the synthesis of releasable beta-alanine.
D000612:4-Aminobutyrate Transaminase / Q000037:antagonists & inhibitors*; D000409:Alanine / Q000378:metabolism*; D000480:Alkynes; D000614:Aminocaproates / Q000494:pharmacology; D000625:Aminooxyacetic Acid / Q000494:pharmacology; D000818:Animals; D003509:Cyclohexanecarboxylic Acids / Q000494:pharmacology; D004558:Electric Stimulation; D005971:Glutamates / Q000378:metabolism; D018698:Glutamic Acid; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D015091:beta-Alanine / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D000480:Alkynes; D000614:Aminocaproates; D003509:Cyclohexanecarboxylic Acids; D005971:Glutamates; D015091:beta-Alanine; D000625:Aminooxyacetic Acid; C012987:gabaculine; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; C013785:4-amino-5-hexynoic acid; D000612:4-Aminobutyrate Transaminase; D000409:Alanine