Details

Autor(en) / Beteiligte

• Fricker, Desdemona
• Dinocourt, Céline
• Eugène, Emmanuel
• Wood, John
• Miles, Richard

Titel

Pyramidal cells of rodent presubiculum express a tetrodotoxin-insensitive Na+ current

Ist Teil von

• The Journal of physiology, 2009-09, Vol.587 (17), p.4249-4264

Ort / Verlag

Oxford, UK: The Physiological Society

Erscheinungsjahr

2009

Link zum Volltext

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• Presubicular neurons are activated physiologically by a specific preferred head direction. Here we show that firing in these neurones is characterized by action potentials with a large overshoot and a reduced firing frequency adaptation during repetitive firing. We found that a component of the sodium current of presubicular cells was not abolished by tetrodotoxin (TTX, 10 μ m ) and was activated at more depolarized voltages than TTX-sensitive currents. This inward current was completely abolished by the removal of external sodium, suggesting that sodium is the charge carrier of this TTX-insensitive (TTX-I) current. The channels responsible for the TTX-I sodium current seemed to be expressed at sites distant from the soma, giving rise to a voltage-dependent delay in current activation. The voltage required for half-maximal activation was −21 mV, and −36 mV for inactivation, which is similar to that reported for Na V 1.8 sodium channels. However, the kinetics were considerably slower, with a time constant of current decay of 1.4 s. The current was not abolished in pyramidal cells from animals lacking either the Na V 1.8 or the Na V 1.9 subunit. This, possibly novel, TTX-I sodium current could contribute to the coding functions of presubicular neurons, specifically the maintained firing associated with signalling of a stable head position.