Reevaluation of Ca2+ channel types and their modulation in bullfrog sympathetic neurons

Neuron. 1994 Jul;13(1):217-28. doi: 10.1016/0896-6273(94)90471-5.


With 90 mM Ba2+, the main Ca2+ current in frog sympathetic neurons peaks near +30 mV and is blocked by omega-conotoxin GVIA (omega-CgTx). It is modulated by norepinephrine (NE) in a voltage-dependent manner via a membrane-delimited mechanism. Surprisingly, a different current dominates at more negative voltages (-30 to +10 mV). That novel current is not sensitive to selective blockers of L- or N-type channels (respectively, dihydropyridines or omega-CgTx) and is inhibited weakly if at all by NE. It is selectively inactivated at -40 mV and is selectively blocked by Ni2+, whereas Cd2+ is slightly more potent against the main current. The novel current is associated with a 19 pS channel (0.6 pA at 0 mV). This channel may have been misidentified as the single-channel correlate of the whole-cell N-type Ca2+ current in some previous studies.

Publication types

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

MeSH terms

  • Animals
  • Barium / pharmacology
  • Calcium Channels / drug effects
  • Calcium Channels / physiology*
  • Dihydropyridines / pharmacology
  • Electric Conductivity
  • Ganglia, Sympathetic / drug effects
  • Ganglia, Sympathetic / physiology
  • Membrane Potentials
  • Neurons / drug effects
  • Neurons / physiology*
  • Norepinephrine / pharmacology
  • Peptides / pharmacology
  • Rana catesbeiana
  • omega-Conotoxin GVIA


  • Calcium Channels
  • Dihydropyridines
  • Peptides
  • Barium
  • 1,4-dihydropyridine
  • omega-Conotoxin GVIA
  • Norepinephrine