The mechanism of neuroprotection by positive modulation of Ca2+-activated K+ channels of cerebellar neurons in primary culture

Resumo

Here we show that positive modulators (CyPPA and NS309) of Ca²⁺-activated K⁺ channels of small (SK) and intermediate (IK) conductances in cerebellar neurons decrease glutamate-evoked Ca²⁺ entry into neurons independently on the presence of Mg²⁺ in extracellular media. An analysis of neuronal viability after long-term (240 min) glutamate treatments demonstrated neuroprotective action of CyPPA and NS309. Extracellular Mg²⁺ did not protect neurons from apoptosis during prolonged treatment with glutamate. Activation of SK and IK channels results in local membrane hyperpolarization, which enhances Mg²⁺ block of NMDA receptors and reduces activation of voltage-dependent Ca²⁺ channels, which can explain neuroprotection caused by CyPPA or NS309. The obtained results reveal an important role Ca²⁺-activated K⁺ channels of small and intermediate conductance in the regulation of Ca²⁺ entry into cerebellar neurons via NMDA receptors and voltage-gated Ca²⁺ channels.