Modulation of ion gradients and glutamate release in cultured cerebellar granule cells by ouabain

J Neurochem. 1995 May;64(5):2097-104. doi: 10.1046/j.1471-4159.1995.64052097.x.


Upon addition of the cardiac glycoside ouabain to cultured cerebellar granule cells, an immediate increase in intracellular free sodium is evoked mediated by two pathways, a voltage-sensitive channel blocked by tetrodotoxin and a channel sensitive to flunarizine. Ouabain induces a steady plasma membrane depolarization in low Ca2+ medium; whereas in the presence of Ca2+, a distinct discontinuity is observed always preceded by a large increase in intracellular free Ca2+ ([Ca2+]c). The plateau component of the increase can be inhibited additively by the L-type Ca2+ channel antagonist nifedipine, the spider toxin Aga-Gl, and the NMDA receptor antagonist MK-801. Single-cell imaging reveals that the [Ca2+]c increase occurs asynchronously in the cell population and is not dependent on a critical level of extracellular glutamate or synaptic transmission between the cells. A prolonged release of glutamate is also observed that is predominantly Ca2+ dependent for the first 6-10 min after the evoked increase in [Ca2+]c. This release is four times as large as that observed with 50 mM KCl and is predominantly exocytotic because release was inhibited by tetanus toxin, the V-type ATPase inhibitor bafilomycin, and Aga-Gl. It is proposed, therefore, that ouabain induces a period of membrane excitability culminating in a sustained exocytosis above that observed upon permanent depolarization with KCl.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 6-Cyano-7-nitroquinoxaline-2,3-dione / pharmacology
  • Animals
  • Calcium / metabolism
  • Calcium / pharmacology
  • Cell Membrane / physiology
  • Cells, Cultured
  • Cerebellum / cytology
  • Cerebellum / drug effects
  • Cerebellum / metabolism*
  • Dizocilpine Maleate / pharmacology
  • Glutamic Acid / metabolism*
  • Ion Channels / metabolism*
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Nifedipine / pharmacology
  • Ouabain / pharmacology*
  • Rats
  • Rats, Wistar
  • Sodium / metabolism
  • Spider Venoms / pharmacology


  • Aga-GI toxin
  • Ion Channels
  • Spider Venoms
  • Glutamic Acid
  • Ouabain
  • Dizocilpine Maleate
  • 6-Cyano-7-nitroquinoxaline-2,3-dione
  • Sodium
  • Nifedipine
  • Calcium