Pentylenetetrazole affects metabolism of astrocytes in culture

Cortical and cerebellar astrocytes were cultured in medium containing pentylenetetrazole (PTZ), a gamma-aminobutyric acid (GABA)(A) receptor antagonist, for 3 weeks (up to 6 mM) or 2 hr (10 mM). Cells were incubated in medium containing [U-(13)C]glutamate (0.5 mM) and unlabeled glucose (3 mM) for 2 hr and cell extracts and media were analyzed by (13)C magnetic resonance (MR) spectroscopy and high-performance liquid chromatography (HPLC). When cerebellar astrocytes were incubated with PTZ for 2 hr, the amount of glucose removed from the medium and glucose and [U-(13)C]glutamate oxidation were decreased. Metabolism in cortical astrocytes was affected only slightly; amounts of glutathione and aspartate were decreased. When cerebellar and cortical cells were cultured in the presence of PTZ for 3 weeks, the amount of glucose removed from the medium and lactate formed were increased, indicating increased glycolytic activity. Despite the increased intracellular [U-(13)C]glutamate concentration in both types of astrocytes cultured with PTZ, labeled glutamine and glutathione were unchanged, indicating intracellular compartmentation. The amount of cellular protein was decreased at 6 mM PTZ for cerebellar astrocytes and 1 mM for cortical astrocytes, indicating a differential sensitivity to the effects of PTZ. In conclusion, mitochondrial metabolism and glycolysis were decreased by short-term incubation with PTZ in cerebellar astrocytes, whereas long-term incubation affected both types of astrocytes, leading to increased glycolysis.