Small-conductance Ca2+-dependent K+ channels activated by ATP in murine colonic smooth muscle

S. D. Koh, G. M. Dick, K. M. Sanders

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32 Scopus citations


The patch-clamp technique was used to determine the ionic conductances activated by ATP in murine colonic smooth muscle cells. Extracellular ATP, UTP, and 2-methylthioadenosine 5'-triphosphate (2-MeS-ATP) increased outward currents in cells with amphotericin B-perforated patches. ATP (0.5-1 mM) did not affect whole cell currents of cells dialyzed with solutions containing ethylene glycol-bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid. Apamin (3 x 10-7 M) reduced the outward current activated by ATP by 32 ± 5%. Single channel recordings from cell-attached patches showed that ATP, UTP, and 2-MeS-ATP increased the open probability of small-conductance, Ca2+- dependent K+ channels with a slope conductance of 5.3 ± 0.02 pS. Caffeine (500 μM) enhanced the open probability of the small-conductance K+ channels, and ATP had no effect after caffeine. Pyridoxal phosphate 6- azophenyl-2',4'-disulfonic acid tetrasodium (PPADS, 10-4 M), a nonselective P2 receptor antagonist, prevented the increase in open probability caused by ATP and 2-MeS-ATP. PPADS had no effect on the response to caffeine. ATP- induced hyperpolarization in the murine colon may be mediated by P(2y)- induced release of Ca2+ from intracellular stores and activation of the 5.3-pS Ca2+-activated K+ channels.

Original languageEnglish
Pages (from-to)C2010-C2021
JournalAmerican Journal of Physiology - Cell Physiology
Issue number6 42-6
StatePublished - 1997


  • Apamin
  • Caffeine
  • Enteric inhibitory neurotransmission
  • Gastrointestinal motility
  • Ion channels
  • Purinergic receptors


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