Pharmacological properties of Ca2+-activated K+ currents of ramified murine brain macrophages

Naunyn Schmiedebergs Arch Pharmacol. 1997 Aug;356(2):233-9. doi: 10.1007/pl00005046.

Abstract

Using the whole-cell configuration of the patch clamp technique, calcium-activated potassium currents (I(K,Ca)) were investigated in ramified murine brain macrophages. In order to induce I(K,Ca) the intracellular concentration of nominal free Ca2+ was adjusted to 1 microM. The Ca2+-activated K+ current of brain macrophages did not show any voltage dependence at test potentials between -120 and +30 mV. A tenfold change in extracellular K+ concentration shifted the reversal potential of I(K,Ca) by 51 mV. The bee venom toxin apamin applied at concentrations of up to 1 microM did not affect I(K,Ca). Ca2+-activated K+ currents of ramified brain macrophages were highly sensitive to extracellularly applied charybdotoxin (CTX). The half-maximal effective concentration of CTX was calculated to be 4.3 nM. In contrast to CTX, the scorpion toxin kaliotoxin did not inhibit I(K,Ca) at concentrations between 1 and 50 nM. Tetraethylammonium (TEA) blocked 8.0% of I(K,Ca) at a concentration of 1 mM, whereas 31.4% of current was blocked by 10 mM TEA. Several inorganic polyvalent cations were tested at a concentration of 2 mM for their ability to block I(K,Ca). La3+ reduced I(K,Ca) by 72.8%, whereas Cd2+ decreased I(K,Ca) by 17.4%; in contrast, Ni2+ did not have any effect on I(K,Ca). Ba2+ applied at a concentration of 1 mM reduced I(K,Ca) voltage-dependently at hyperpolarizing potentials.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apamin / pharmacology
  • Barium / pharmacology
  • Brain / drug effects*
  • Brain / metabolism
  • Calcium / pharmacology*
  • Charybdotoxin / pharmacology
  • Macrophages / drug effects*
  • Macrophages / metabolism
  • Mice
  • Nickel / pharmacology
  • Patch-Clamp Techniques
  • Potassium Channel Blockers
  • Potassium Channels / drug effects*
  • Potassium Channels / metabolism

Substances

  • Potassium Channel Blockers
  • Potassium Channels
  • Charybdotoxin
  • Apamin
  • Barium
  • Nickel
  • Calcium