Effects of hyperglycemia on neuronal network function in an in vitro model of the ischemic penumbra

•Hyperglycemia is common in acute ischemic stroke patients, and associated with unfavorable functional outcome.•Active glucose lowering in patients with acute ischemic stroke had no effect on infarct size nor on functional outcome. A factor hampering the design and interpretation of intervention studies is that the effects of glucose concentration on the cellular level are unclear.•We observed that hyperglycemia was associated with a more rapid decline of neuronal network activity during hypoxia and more apoptosis at the cellular level.•These results provide a starting point for further studies into neurophysiological and cellular effects of hyperglycemia to mechanistically assess the role of hyperglycemia in acute ischemic stroke. Hyperglycemia is common in acute ischemic stroke, and associated with unfavorable outcome. However, the optimal glucose level is not known and cellular effects of hyperglycemia under hypoxia are largely unclear. We assessed how the extracellular glucose concentration affects cultured neuronal networks under experimental in vitro conditions, to provide a starting point for assessment of mechanisms at the neuronal network and cellular levels. We used in vitro cultured rat neuronal networks on micro-electrode arrays (MEAs) and glass coverslips. Twenty-four hours of controlled hypoxia was induced. We measured neuronal network activity during baseline (normoxia, 6 h), 24 h of hypoxia, and 6 h after reoxygenation, defined as the summed number of action potentials in 1 h bins. Apoptosis was determined intermittently with caspase 3/7 staining and microscopy. We compared groups of networks under glucose concentrations of 5.0 mmol/L, 7.0 mmol/L, 9.0 mmol/L, and 12.0 mmol/L. Overall, during hypoxia, a gradual decrease in neuronal network activity and increase in apoptosis was found. There were faster decrease in activity (p