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.
Baker
M D
MD
Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520.
Ritchie
J M
JM
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