Two distinct types of transient outward currents in area postrema neurons in rat brain slices

Makoto Funahashi, Yoshihiro Mitoh, Ryuji Matsuo

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10 Citations (Scopus)


We investigated the electrophysiological properties of the area postrema neurons in acutely prepared rat brain slices using the whole-cell patch-clamp technique. Two different types of transient outward potassium current (Ito), fast and slow, were found in the area postrema. Both the decay time constant and rise time were significantly faster in the fast Ito than in the slow Ito. Both current-clamp and voltage-clamp recordings revealed that the activation of fast and slow Ito contributes to generation of the different spiking patterns, late spiking and interrupted spiking, respectively. The activation and inactivation of both Ito were strongly voltage-dependent. Curve fitting by the Boltzmann equation revealed no significant difference in the activation and inactivation curves for each Ito except that the slope factor of inactivation was larger for fast Ito. Both Ito were suppressed dose-dependently by application of 4-aminopyridine. Each spiking pattern was enhanced when cells were held at a more hyperpolarized membrane potential, i.e. a longer latency of the first spike or longer interspike interval between the first and second spikes. The voltage-dependent modulation of the spiking pattern was consistent with the voltage-dependent activation of Ito. The present study shows significant subdivisions of the area postrema neurons distinguished by a difference in the kinetics of Ito and spiking patterns. We discuss the role of Ito as the ionic current underlying neuronal excitability.

Original languageEnglish
Pages (from-to)31-45
Number of pages15
JournalBrain Research
Issue number1-2
Publication statusPublished - Jun 28 2002


  • Area postrema
  • Rat
  • Slice
  • Transient outward potassium current
  • Whole-cell patch-clamp

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology


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