Slow depolarizing afterpotentials in neocortical neurons are sodium and calcium dependent

A. Friedman, J. Arens, U. Heinemann, M. J. Gutnick

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30 Scopus citations


Depolarizing afterpotentials (DAPs) were studied in intracellular recordings from neocortical slices bathed in tetrodotoxin (TTX) (1 μM) and tetraethylammonium chloride (TEA) (24 mM), to block voltage-dependent Na+ currents and most K+ currents. The DAP was Ca2+-dependent, in that its magnitude varied as a function of the duration of the preceding Ca2+ plateau. It had an apparent reversal potential of between -40 and -5 mV. The DAP was blocked when choline replaced all extracellular Na+; there was a hyperpolarizing shift in apparent reversal potential when extracellular Na+ was lowered. The DAP was blocked by amiloride (1 mM), which also decreased the preceding Ca2+ plateau. The data are consistent with the hypothesis that the DAP is due to electrogenic Na+ Ca2+ exchange.

Original languageEnglish
Pages (from-to)13-17
Number of pages5
JournalNeuroscience Letters
Issue number1
StatePublished - 20 Jan 1992


  • Brain slice
  • Calcium spike
  • Depolarizing afterpotential
  • Guinea pig
  • Intracellular recording
  • Na Ca exchanger
  • Neocortex


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