Closure of potassium M-channels by muscarinic acetylcholine-receptor stimulants requires a diffusible messenger

Proc Biol Sci. 1992 Nov 23;250(1328):119-25. doi: 10.1098/rspb.1992.0139.


The M-current (IK(M)) is a slow voltage-gated K+ current which can be inhibited by muscarinic acetylcholine-receptor (mAChR) agonists. In the present experiments we have tested whether this inhibition results from a local (membrane-delimited) interaction between the receptor and adjacent channels, or whether channel closure is mediated by a diffusible messenger. To do this, single KM(+)-channel currents were recorded from membrane patches in dissociated rat superior cervical sympathetic neurons by using cell-attached patch electrodes. Channel activity was inhibited when muscarine was applied to the cell membrane outside the patch but persisted when channels were exposed to muscarine added to the pipette solution. We conclude that a diffusible molecule (or molecules) is (are) required to induce intrapatch channel closure following activation of extra-patch receptors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cells, Cultured
  • Electric Conductivity / drug effects
  • Ganglia, Sympathetic / physiology*
  • Ion Channel Gating / drug effects
  • Membrane Potentials / drug effects
  • Muscarine / pharmacology*
  • Neurons / drug effects
  • Neurons / physiology*
  • Potassium Channels / drug effects
  • Potassium Channels / physiology*
  • Rats
  • Receptors, Muscarinic / drug effects
  • Receptors, Muscarinic / physiology*
  • Tetrodotoxin / pharmacology


  • Potassium Channels
  • Receptors, Muscarinic
  • Tetrodotoxin
  • Muscarine