Evidence for a persistent Na-conductance in identified command neurones of the snail, Helix pomatia

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10 Citations (Scopus)

Abstract

Neurones RPa3 and LPa3 were identified as 'command' neurones in the Helix parietal ganglia. The physiological role of these cells is the integration of sensory information before triggering withdrawal behaviour. Properties of the Na-channels are poorly understood in these neurones which produce Na +-dependent action potentials in Ca2+-free solution. Our aim was to describe the kinetic properties and TTX-sensitivity of the Na-channels of these cells, and to provide evidence for the existence of a persistent inward sodium current (INaP) in them. Two-microelectrode voltage- and patch-clamp techniques were used on isolated or semi-isolated neurones. The kinetics and potential dependence of the transient inward sodium current (INaT) agreed well with those obtained on other molluscan neurones. We concluded that INaT present in these neurones is slow and TTX-resistant (kD=8 μM of TTX) and has two components with different rates of inactivation. In addition, the presence of an I NaP component was revealed. We showed that INaP is neither an artifact nor the contribution of a Ca-channel or a 'window' current. With slow voltage ramp pulses INaP could be activated and separated from INaT. Like INaT it appeared to be TTX-resistant and Na-dependent. INaP was upregulated by increased pH (8.0) and decreased by elevated extracellular Mg2+ concentration parallel with the INaT. Our results suggest that INaP originates from the same set of sodium channels that underlie INaT.

Original languageEnglish
Pages (from-to)16-25
Number of pages10
JournalBrain research
Volume989
Issue number1
DOIs
Publication statusPublished - Jan 1 2003

Keywords

  • Command neuron
  • Snail
  • Tetrodotoxin sensitivity
  • Transient and sustained Na-channel

ASJC Scopus subject areas

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

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