Sources of Ca2+ for different Ca(2+)-activated K+ conductances in neurones of the rat superior cervical ganglion

J Physiol. 1996 Sep 1;495 ( Pt 2)(Pt 2):353-66. doi: 10.1113/jphysiol.1996.sp021599.


1. The role of various Ca(2+)-activated K+ conductances were investigated using intracellular recording and single-electrode voltage clamp in neurones of superior cervical ganglia isolated in vitro from young adult rats. 2. Following replacement of Ca2+ with Co2+ (2 mM) or the addition of Cd2+ (100 microM), action potential amplitude and half-width either increased or decreased (in different cells), but both the after-hyperpolarization (AHP) and the outward tail current following a suprathreshold voltage step were markedly attenuated (by about 75%). 3. Addition of charybdotoxin (60 nM) or nifedipine (10 microM) increased action potential half-width (by about 25%) but had no significant effect on the AHP or tail current. 4. Addition of apamin (100 nM) or omega-conotoxin GVIA (100 nM) reduced the AHP and tail current (by about 60%) but did not significantly affect the action potential. A prolonged apamin-resistant component of the AHP present in 50% of neurones was blocked by ryanodine (20 microM). 5. Omega-Conotoxin MVIIC (150 nM) and omega agatoxin IVA (200 nM) had no significant effects on the action potential half-width or the AHP. 6. None of the Ca2+ channel blockers affected the prolonged ryanodine-sensitive component of the AHP and tail current. 7. We conclude that, in rat sympathetic neurones, Ca2+ entry via L-type channels selectively activates large conductance Ca(2+)-activated K+ channels (BK type) contributing to action potential repolarization, whereas Ca2+ entry via N-type channels selectively activates small conductance Ca(2+)-activated K+ channels (SK type) contributing to the AHP. Ca2+ entry via R-type Ca2+ channels prolongs the AHP by activating Ca2+ release from intracellular stores.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / physiology
  • Animals
  • Bradykinin Receptor Antagonists
  • Calcium / metabolism*
  • Calcium / physiology*
  • Calcium Channel Blockers / pharmacology
  • Dendrites / drug effects
  • Dendrites / physiology
  • Electrophysiology
  • Female
  • In Vitro Techniques
  • Membrane Potentials / physiology
  • Microelectrodes
  • Neurons / metabolism*
  • Patch-Clamp Techniques
  • Potassium Channels / metabolism*
  • Rats
  • Rats, Wistar
  • Receptors, Bradykinin / metabolism
  • Superior Cervical Ganglion / cytology
  • Superior Cervical Ganglion / metabolism*


  • Bradykinin Receptor Antagonists
  • Calcium Channel Blockers
  • Potassium Channels
  • Receptors, Bradykinin
  • Calcium