Persistent inward currents in cultured Retzius cells of the medicinal leech

J Comp Physiol A. 1999 Jan;184(1):49-61. doi: 10.1007/s003590050305.

Abstract

Current-clamp studies of cultured leech Retzius cells revealed inward rectification in the form of slow voltage sags in response to membrane hyperpolarization. Sag responses were eliminated in Na(+)-free saline and blocked by Cs+, but not Ba2+. Voltage clamp experiments revealed a Cs(+)-sensitive inward current activated by hyperpolarization negative to -70 mV. Cs+ decreased the frequency of spontaneous impulses in Retzius cells of intact ganglia. Plateau potentials were evoked in Retzius cells following block of Ca2+ influx with Ni2+ and suppression of K+ currents with internal tetraethylammonium. Plateau potentials continued to be expressed with Li+ as the charge carrier, but were eliminated when Na+ was replaced with N-methyl-D-glucamine. A persistent Na+ current with similar pharmacology that activated positive to -40 mV and reached its peak amplitude near -5 mV was identified in voltage-clamp experiments. Inactivation of the persistent Na+ current was slow and incomplete. The current was revealed by slow voltage ramps and persisted for the duration of 5-s voltage steps. Persistent Na+ current may underlie Na(+)-dependent bursting recorded in neurons of intact ganglia exposed to Ca2(+)-channel blockers.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Barium / pharmacology
  • Cells, Cultured
  • Cesium / pharmacology
  • Ganglia, Invertebrate / cytology
  • Ion Channel Gating / drug effects
  • Ion Channel Gating / physiology
  • Leeches
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Neurons / chemistry
  • Neurons / cytology
  • Neurons / physiology*
  • Patch-Clamp Techniques
  • Sodium / pharmacokinetics*
  • Sodium Channels / physiology*
  • Tetraethylammonium / pharmacology

Substances

  • Sodium Channels
  • Cesium
  • Barium
  • Tetraethylammonium
  • Sodium