Age-related modifications of potassium homeostasis and synaptic transmission during and after anoxia in rat hippocampal slices.

Age-related changes in the capacity of the brain to survive short anoxic episodes were studied in stratum pyramidale (region CA1) of hippocampal slices from control (6-7 months) and aged (26-27 months) rats. Our primary interest was in how aging affected the ability of slices to maintain or to recover extracellular potassium ion (K+o) homeostasis and orthodromically-stimulated field potentials during and after anoxia. During anoxia, K+o homeostasis was lost faster in slices from aged rats. Following anoxia, K+o homeostasis recovered more slowly, and synaptic transmission recovered less completely, in aged slices. These studies provide what is believed to be the first demonstration that aging diminishes the capacity of brain tissue to maintain K+o during anoxia and to recover K+o homeostasis and synaptic transmission following anoxia, and support suggestions that the aged brain is more vulnerable to anoxia.