Comparative Study on Modulation of Synchronized Neuronal Activity by SK Channels and Na/K-ATPase

Drug-resistant epilepsy remains a therapeutic challenge, requiring new molecular targets beyond conventional antiepileptic drugs. Small-conductance calcium-activated potassium (SK) channels and Na/K-ATPase (NKA) contribute to afterhyperpolarization via distinct mechanisms, offering complementary ways to suppress hyperexcitability. We examined SK activation and NKA modulation in synchronized epileptiform activity in a primary culture of cortical neurons obtained from rat embryos. Epileptiform discharges were induced by magnesium-free solution and assessed by patch-clamp and calcium imaging. The SK2/3 activator CyPPA (10 µM) reduced epileptiform current (EC) amplitude and integral and decreased synchronized calcium transient (CT) frequency but gradually elevated basal calcium. In contrast, ouabain (1 nM), a selective modulator of high-affinity NKA isoforms, attenuated EC amplitude, strongly suppressed CTs, and showed persistent effects after washout, accompanied by asynchronous glial calcium activity. Co-application of CyPPA with ouabain abolished CyPPA-induced calcium elevation while maintaining suppression of neuronal synchrony. The broader SK/IK activator NS309 (10 µM) reduced CT frequency and basal calcium without affecting glia. Thus, SK activation and NKA signaling suppress epileptiform synchronization through distinct yet convergent pathways: SK channels via afterhyperpolarization and NKA via afterhyperpolarization and calcium-dependent signaling. Their combination enhances efficacy and prevents adverse calcium buildup, supporting SK-NKA co-targeting as a strategy against drug-resistant epilepsy.