SK2 channels are neuroprotective for ischemia-induced neuronal cell death

In mouse hippocampal CA1 pyramidal neurons, the activity of synaptic small-conductance Ca²⁺-activated K⁺ channels type 2 (SK2 channels) provides a negative feedback on N-methyl--aspartate receptors (NMDARs), reestablishing Mg²⁺ block that reduces Ca²⁺ influx. The well-established role of NMDARs in ischemia-induced excitotoxicity led us to test the neuroprotective effect of modulating SK2 channel activity following cerebral ischemia induced by cardiac arrest and cardiopulmonary resuscitation (CA/CPR). Administration of the SK channel positive modulator, 1-ethyl-benzimidazolinone (1-EBIO), significantly reduced CA1 neuron cell death and improved CA/CPR-induced cognitive outcome. Electrophysiological recordings showed that CA/CPR-induced ischemia caused delayed and sustained reduction of synaptic SK channel activity, and immunoelectron microscopy showed that this is associated with internalization of synaptic SK2 channels, which was prevented by 1-EBIO treatment. These results suggest that increasing SK2 channel activity, or preventing ischemia-induced loss of synaptic SK2 channels, are promising and novel approaches to neuroprotection following cerebral ischemia.