Oscillations of receptor-operated cationic current and internal calcium in single guinea-pig ileal smooth muscle cells

Pflugers Arch. 1993 Sep;424(5-6):431-8. doi: 10.1007/BF00374905.


In single cells isolated from guinea-pig ileal smooth muscle, held under voltage clamp at -40 mV or -50 mV by patch pipette in the whole-cell recording mode, carbachol (CCh) evoked an oscillatory inward cationic current. The frequency of current oscillations increased with increasing CCh concentration. CCh-evoked current oscillations were followed very closely by oscillations in intracellular free Ca2+ estimated from the Indo-1 signal, and were abolished by inclusion of EGTA in the pipette solution. Ryanodine and heparin, but not nifedipine, blocked the generation of current oscillations. CCh-evoked current oscillations were abolished upon withdrawal of extracellular calcium and restored upon its reintroduction. Inclusion of GTP[gamma S] in the pipette solution caused the generation of an oscillatory inward current, which was blocked by ryanodine. The present results are consistent with the hypothesis that CCh-evoked cationic current is gated by activation of a G protein and is steeply dependent on [Ca2+]i, fluctuations in the release of Ca2+ from stores during carbachol's action produce oscillations in [Ca2+]i which cause similar oscillations in the cationic current.

MeSH terms

  • Animals
  • Calcium / metabolism*
  • Carbachol / pharmacology
  • Egtazic Acid / pharmacology
  • Guanosine 5'-O-(3-Thiotriphosphate) / pharmacology
  • Guinea Pigs
  • Heparin / pharmacology
  • Ileum / metabolism*
  • Male
  • Membrane Potentials
  • Muscle, Smooth / metabolism*
  • Nifedipine / pharmacology
  • Receptors, Cell Surface / metabolism
  • Ryanodine / pharmacology
  • Signal Transduction


  • Receptors, Cell Surface
  • Ryanodine
  • Guanosine 5'-O-(3-Thiotriphosphate)
  • Egtazic Acid
  • Carbachol
  • Heparin
  • Nifedipine
  • Calcium