Intraneuronal ion distribution during experimental oxygen/glucose deprivation. Routes of ion flux as targets of neuroprotective strategies

Ischemic neuronal injury appears to be mediated by disruption of subcellular ion distribution and, therefore, prevention of ion relocation might be neuroprotective. X-ray microanalysis was used to measure concentrations of Na, K, Ca and other elements in subcellular compartments (e.g., mitochondria) of CA1 neurons from oxygen/glucose-deprived (OGD) hippocampal slices. Results showed that OGD produced progressive loss of ion regulation in CA1 cells. Post-OGD reperfusion with normal media exacerbated the initial ion deregulation. To study neuroprotective mechanisms, we determined the ability of hypothermia (31°C) or ion channel blockade to retard intraneuronal ion disruption induced by OGD/reperfusion. Whereas Ca²⁺ channel blockade (ω-conotoxin MVIIC, 3 μM) was ineffective, hypothermia and Na⁺ channel blockers (tetrodotoxin, TTX, 1 μM; lidocaine, 200 μM) reduced ion deregulation in subneuronal compartments. Blockade of glutamate receptors (AMPA, 10 μM; the non-NMDA receptor antagonist CNQX, 10 μM/100 μM glycine; the NMDA receptor antagonist CCP, 100 μM) during OGD/reperfusion provided nearly complete protection. These findings provide a foundation for identifying potential pharmacotherapeutic approaches and for discerning corresponding mechanisms of neuroprotection.