The role of glutamate in neuronal ion homeostasis: A case study of spreading depolarization
Fig 2
Two variants of SD with intact glutamate clearance.
The left panels (a) and (c) show SD induced by perfusion with high K+, the right panels (b) and (d) are for OGD. The OGD protocol is indicated by the horizontal bar where the light sections at the beginning and the end indicate the smooth de– and reactivation of the regulatory functions. The figure shows all the familiar aspects of SD. In (a) and (b) the neuron depolarizes and the differences between Nernst potentials become very small. Depolarization is maintained for about 70 sec and ends with an abrupt repolarization drop after which the Nernst potentials slowly return to their initial values. Changes in ion concentrations in (c) and (d) correspond to the evolution of the potentials. There is, for example, a huge increase in extracellular K+ and a huge drop in extracellular Na+. The ion fluxes induce swelling of the glia cell and the neuron (see the insets), which result in shrinkage of the ECS. The time of de– and repolarization are marked by a red upward pointing and a green downward pointing triangle. These symbols will be used in the following figures to indicate these events.