[Cerebral ischemia-hypoxia and biophysical mechanisms of neurodegeneration and neuroprotection effects].

Neuronal responses to hypoxia-ischemia can be acute or chronic. In the early stages neuronal responses to ischemia-hypoxia are dependent on the modulation of ion channels. Acute responses relay mainly on O2-regulated ion channels which mediate adaptive changes in neuron excitability. Energy failure, an early consequence of hypoxia-ischemia, causes disruption of ionic homeostasis and accumulation of extracellular neurotransmitters. NMDA and AMPA/kainate receptors and Ca2+ channels contribute to excitotoxic neuronal degeneration. Excitotoxicity leads to increased Ca2+ influx, which can activate cytotoxic intracellular pathways. Reactive oxygen species (oxygen free radicals) generated during ischemia-reperfusion contribute to the injury. Oxygen free-radicals serve as important signalling molecules that trigger inflammation and apoptosis. Excitatory amino acid-receptor antagonists and Ca2+ channels blockers can provide neuroprotection in experimental models of hypoxia-ischemia but disrupt normal brain function. Because of their relative lack of behavioral side-effects, voltage-dependent Na+ channels blockers may have advantage over other neuroprotective mechanisms. The blockade of voltage-gated Na+ channels reduces the excitability of neurons, Na+ influx and the accumulation of intracellular Na+. These improve the ionic homeostasis and cellular energy levels and prevent ischemia-hypoxia induced neuronal injury and neuronal damage mediated by Ca2+ overload.