Quantitative analysis of Na+ and Ca2+ current contributions on spike initiation in the newt olfactory receptor cell

Fusao Kawai, Takashi Kurahashi, Akimichi Kaneko

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9 Citations (Scopus)


The contribution of Na+ (I(Na)) and T-type Ca2+ (I(Ca,T)) currents on the action potential initiation in newt olfactory receptor cells (ORC) was investigated quantitatively. Since both the Na+ channel and T-type Ca2+ channel show rapid inactivation, it was questioned how much I(Na) and I(Ca,T) are activated during the gradually depolarizing initial phase of the receptor potential. Because the conventional voltage clamp technique does not allow direct current measurement during voltage changes, we estimated the amplitude of I(Na) and I(Ca,T) in an ionic current model. The model was constructed based on voltage clamp experiments. The estimated ratio of I(Ca,T)/I(Na) during the action potential induced by ramp current injection was 0.59±0.03 (mean±SD) under control Ringer's solution. This ratio was more than twice as large as that (0.25) obtained from the previous voltage clamp experiment using step commands. This result suggests that the T-type Ca2+ channel carries a more significant amount of current to generate the action potentials than expected previously.

Original languageEnglish
Pages (from-to)367-376
Number of pages10
JournalJapanese Journal of Physiology
Issue number4
Publication statusPublished - 08-1997
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Physiology


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