Korean J Physiol Pharmacol.  2016 Jan;20(1):101-109. 10.4196/kjpp.2016.20.1.101.

Brief low [Mg2+]o-induced Ca2+ spikes inhibit subsequent prolonged exposure-induced excitotoxicity in cultured rat hippocampal neurons

  • 1Department of Physiology, College of Medicine, Dankook University, Cheonan 31116, Korea.
  • 2Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea. s-hyoon@catholic.ac.kr
  • 3Catholic Neuroscience Institute, The Catholic University of Korea, Seoul 06591, Korea.


Reducing [Mg2+]o to 0.1 mM can evoke repetitive [Ca2+]i spikes and seizure activity, which induces neuronal cell death in a process called excitotoxicity. We examined the issue of whether cultured rat hippocampal neurons preconditioned by a brief exposure to 0.1 mM [Mg2+]o are rendered resistant to excitotoxicity induced by a subsequent prolonged exposure and whether Ca2+ spikes are involved in this process. Preconditioning by an exposure to 0.1 mM [Mg2+]o for 5 min inhibited significantly subsequent 24 h exposure-induced cell death 24 h later (tolerance). Such tolerance was prevented by both the NMDA receptor antagonist D-AP5 and the L-type Ca2+ channel antagonist nimodipine, which blocked 0.1 mM [Mg2+]o-induced [Ca2+]i spikes. The AMPA receptor antagonist NBQX significantly inhibited both the tolerance and the [Ca2+]i spikes. The intracellular Ca2+ chelator BAPTA-AM significantly prevented the tolerance. The nonspecific PKC inhibitor staurosporin inhibited the tolerance without affecting the [Ca2+]i spikes. While Go6976, a specific inhibitor of PKCalpha had no effect on the tolerance, both the PKCepsilon translocation inhibitor and the PKCzeta pseudosubstrate inhibitor significantly inhibited the tolerance without affecting the [Ca2+]i spikes. Furthermore, JAK-2 inhibitor AG490, MAPK kinase inhibitor PD98059, and CaMKII inhibitor KN-62 inhibited the tolerance, but PI-3 kinase inhibitor LY294,002 did not. The protein synthesis inhibitor cycloheximide significantly inhibited the tolerance. Collectively, these results suggest that low [Mg2+]o preconditioning induced excitotoxic tolerance was directly or indirectly mediated through the [Ca2+]i spike-induced activation of PKCepsilon and PKCxi, JAK-2, MAPK kinase, CaMKII and the de novo synthesis of proteins.


Ca2+ spikes; Excitotoxicity; Low [Mg2+]o preconditioning
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