The action of capsaicin on type I delayed rectifier K+ currents in rabbit Schwann cells.
Capsaicin, a lipophilic alkaloid, blocked type I K+ currents in rabbit cultured Schwann cells when applied by superfusion. The concentration-response relation at equilibrium was well described by a rectangular hyperbola, with a KD of 8.7 microM. The kinetics of block resembled an 'inactivation', the rate of blockade increasing with increasing concentrations of capsaicin (1-100 microM). Unlike internal tetraethylammonium (TEA) ions (5-10 mM), which preferentially reduced outward current in symmetrical high [K+], capsaicin reduced both inward and outward type I current by the same proportion. The block achieved by capsaicin during a voltage-clamp step that activated the current was relieved by subsequent hyperpolarization, and the rate of relief from block at -70 mV and -100 mV could be reasonably accounted for on the assumption that capsaicin had to unbind to allow the channels' to close.
Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520.
M D
MD
Baker
J M
JM
Ritchie
D000375:Aging; D000818:Animals; D000831:Animals, Newborn; D002211:Capsaicin / Q000494:pharmacology*; D002478:Cells, Cultured; D004594:Electrophysiology / Q000379:methods; D007700:Kinetics; D008433:Mathematics; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011817:Rabbits; D012583:Schwann Cells / Q000187:drug effects / Q000502:physiology*; D012584:Sciatic Nerve / Q000254:growth & development / Q000502:physiology*; D013126:Spinal Nerve Roots / Q000254:growth & development / Q000502:physiology*; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D019789:Tetraethylammonium; D002211:Capsaicin