Donald L. Martin

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gamma-Aminobutyric acid (GABA) is synthesized in brain in at least two compartments, commonly called the transmitter and metabolic compartments, and because regulatory processes must serve the physiologic function of each compartment, the regulation of GABA synthesis presents a complex problem. Brain contains at least two molecular forms of glutamate(More)
Exogenous acetate is preferentially metabolized by astrocytes in the CNS, but the biochemical basis for this selectivity is unknown. We observed that rat cortical astrocytes produce 14CO2 from 0.2 mM [14C]acetate at a rate of 0.43 nmol/min per milligram of protein, 18 times faster than cortical synaptosomes. Subsequent studies examined whether this was(More)
Rats were injected with saline or the gamma-aminobutyric acid (GABA) transaminase inhibitor gamma-vinyl-GABA for 7 days and the effects on GABA content and glutamic acid decarboxylase (GAD) activity, and the protein and mRNA levels of the two forms of GAD (GAD67 and GAD65) in the cerebral cortex were studied. gamma-Vinyl-GABA induced a 2.3-fold increase in(More)
The apoenzyme of glutamate decarboxylase [enzyme without bound cofactor, pyridoxal 5'-phosphate (pyridoxal-P)] serves as a reservoir of inactive glutamate decarboxylase (GAD) that can be activated when additional GABA synthesis is required. We have investigated which of two molecular forms of GAD is present as apoenzyme in synaptosomes and in cortex,(More)
Pig brain contains three forms of glutamate decarboxylase with pI values of 5.3, 5.5 and 5.8, referred to as the alpha-, beta- and gamma-forms respectively. These forms were purified and kinetically characterized. The major synaptic form of glutamate decarboxylase (the beta-form) migrated as a single band on electrophoresis in sodium dodecyl(More)
Increases (> 2.5-fold) in GABA levels in rat brain lead to a large decrease in the level of the 67-kDa form of glutamate decarboxylase (GAD67) through a mechanism involving either a change in GAD67 protein stability or a change in GAD67 mRNA translation. In the present study, brain levels of GABA were manipulated by treating rats with various doses of(More)