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Pflügers Archiv

, Volume 443, Issue 1, pp 18–30 | Cite as

Identification of a novel voltage-gated Na+ channel rNav1.5a in the rat hippocampal progenitor stem cell line HiB5

  • Mads Gersdorff KorsgaardEmail author
  • Palle Christophersen
  • Philip Ahring
  • Søren-Peter Olesen
Original Article

Abstract.

A conditionally immortalised cell line, HiB5, derived from embryonic hippocampal precursor cells expressed a voltage-gated Na+ channel with electrophysiological characteristics shifted to more negative voltages and a lower sensitivity to tetrodotoxin [concentration required for half-maximal inhibition (IC50) 0.9 µM] compared with endogenous neuronal Na+ channels. The channel activation and steady-state inactivation occurred at very negative potentials with the threshold for activation at –55 mV and half-maximal inactivation at –78.7 mV. The channel was blocked by lamotrigine and sipatrigine voltage and state dependently, with potencies 5–20 times higher (IC50 12 and 1.8 µM at –80 mV respectively) than the corresponding block of endogenous Na+ channels from neurones and cloned rNav1.2a (rBIIA) α-subunits. Both compounds slowed the channel's recovery from inactivation. Whereas lamotrigine and sipatrigine had similar effects on the fast inactivated state, the effect of sipatrigine on the slow inactivation state was more pronounced, rendering this compound overall the more effective. The molecular subtype mainly expressed by HiB5 cells was identified using RT-PCR and was a novel splice variant of rNav1.5 (rNav1.5a). It differs from the known rNav1.5 version in that it lacks 53 amino acids in the intracellular loop between domains II and III. rNav1.5a was also detected in mRNA derived from rat whole brain.

Na+ channel rNav1.5a Lamotrigine Sipatrigine State-dependent HiB5 Patch-clamp Tetrodotoxin 

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Copyright information

© Springer-Verlag 2001

Authors and Affiliations

  • Mads Gersdorff Korsgaard
    • 1
    Email author
  • Palle Christophersen
    • 1
  • Philip Ahring
    • 1
  • Søren-Peter Olesen
    • 2
  1. 1.NeuroSearch A/S, Pederstrupvej 93, 2750 Ballerup, DenmarkDenmark
  2. 2.The Panum Institute, 3 Blegdamsvej, 2200 Copenhagen N, DenmarkDenmark

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