The effect of thiopental on glutamate metabolism in mouse cerebellar astrocytes in vitro

The effect of thiopental on [U-C-13]glutamate metabolism was studied in cer ebellar astrocytes from mice using C-13 magnetic resonance spectroscopy. Th e cells were incubated with 0.5 mM [U-C-13]glutamate for 2 h in the presenc e of 1 mM thiopental and 1 mM thiopental plus 0.2 mM gamma amino butyric ac id (GABA). Labeled glutamate, glutamine, aspartate and glutathione were obs erved in cell extracts, and glutamine, aspartate and lactate in the media. Not only uniformly labeled glutamate was present in the medium, but also gl utamate derived from the tricarboxylic acid (TCA) cycle. In the presence of thiopental, the amount of unlabeled glucose and [U-C-13]glutamate removed from the medium was unchanged. This is in contrast to previous results obta ined in cortical astrocytes, showing cellular heterogeneity. The concentrat ions of [1,2,3-C-13]glutamate and [U-C-13]glutamine were increased in the c ell extracts, but unchanged in the medium, indicating an increased synthesi s and an unchanged exchange or release. It should be noted that [U-C-13]lac tate is formed from [U-C-13]glutamate via the TCA cycle and is released to the medium. In the presence of thiopental less [U-C-13] lactate was observe d in the medium. GABA had no influence on the effects of thiopental on cere bellar astrocytes. (C) 2001 Elsevier Science Ireland Ltd. All rights reserv ed.