AMPA/kainate receptor activation mediates hypoxic oligodendrocyte death and axonal injury in cerebral white matter

We developed an in situ model to investigate the hypothesis that AMPA/kainate (AMPA/KA) receptor activation contributes to hypoxic-ischemic white matter injury in the adult brain. Acute coronal brain slices, including corpus callosum, were prepared from adult mice. After exposure to transient oxygen and glucose deprivation (OGD), white matter injury was assessed by electrophysiology and immunofluorescence for oligodendrocytes and axonal neurofilaments. White matter cellular components and the stimulus-evoked compound action potential (CAP) remained stable for 12 hr after preparation. OGD for 30 man resulted in an irreversible loss of the CAP as well as structural disruption of axons and subsequent loss of neurofilament immunofluorescence. OGD also caused wide-spread oligodendrocyte death, demonstrated by the loss of APC labeling and the gain of pyknotic nuclear morphology and propidium iodide labeling. Blockade of AMPA/KA receptors with 30 μM NBQX or the AMPA-selective antagonist 30 μM GYKI 52466 prevented OGD-induced oligodendrocyte death. Oligodendrocytes also were preserved by the removal of Ca²⁺, but not by a blockade of voltage-gated Na⁺ channels. The protective action of NBQX was still present in isolated corpus callosum slices. CAP areas and axonal structure were preserved by Ca²⁺ removal and partially protected by a blockade of voltage-gated Na⁺ channels. NBQX prevented OGD-induced CAP loss and preserved axonal structure. These observations highlight convergent pathways leading to hypoxic-ischemic damage of cerebral white matter. In accordance with previous suggestions, the activation of voltage-gated Na⁺ channels contributes to axonal damage. Overactivation of glial AMPA/KA receptors leads to oligodendrocyte death and also plays an important role in structural and functional disruption of axons.