Ion distributions in brain during ischemia

The function of the central nervous system-and other organs-depends upon preservation of ionic gradients across cell membranes. In nervous tissue, the ion gradients are especially important since generation of action potentials and synaptic processes relies on transfer of ions across the plasma membrane. This report describes the fact that anoxia profoundly changes the brain interstitial ion milieu. Impaired ATP regeneration starts the chain of events that cause a breakdown of ion homeostasis. The pronounced ionic changes are not caused by impaired ion pumping but rather by opening of ion channels-probably most importantly via release of transmitter substances. Despite the severity of the ionic changes, the brain interstitial ion environment is readily normalized after the anoxic episode. The ionic disturbances are not the cause of the functional deficits encountered in anoxia but are probably of significance in the irreversible neuronal damage evolving after anoxia.