Excitotoxic swelling occurs in oxygen and glucose deprived human cortical slices

The experimental evidence linking glutamate to ischemic neuronal injury is derived from in vitro or in vivo animal stroke models. We, therefore, developed an in vitro preparation to determine whether glutamate contributes to early neuronal swelling in oxygen and glucose deprived (OGD) human neocortical slices. In order to monitor neuronal swelling, we measured extracellular tissue resistance in brain slices by passing constant current pulses through two electrodes and recording the voltage drop between them. We verified that NMDA (30 microM) or OGD induced a rise in tissue resistance in rat neocortical slices. We then examined human neocortical slices from 11 patients undergoing resections for intractable epilepsy. Both the rodent and human neocortical slices swelled within 10 min of OGD. In both, the glutamate antagonist dizocilpine (MK-801) reduced the swelling. In the rats, MK-801 (5 microM) prolonged the latency to onset of neuronal swelling following OGD from 7.6 +/- 0.6 min (mean +/- S.E.M., n = 16) to 17.4 +/- 2.6 min (n = 6; p < 0.01). Other putative neuroprotective agents were much less effective in this paradigm. In the human slices, MK-801 again prolonged the latency to resistance increase from 8.6 +/- 0.4 min (n = 8) to 17.2 +/- 1.7 min (n = 9, p < 0.01). This is the direct demonstration that glutamate receptor activation leads to neuronal swelling in substrate deficient human brain. These results, which are similar to those obtained in the rodent brain slices, help validate the animal slices as appropriate models for the study of OGD in human brain.