A Kv3-like persistent, outwardly rectifying, Cs+-permeable, K+ current in rat subthalamic nucleus neurones.
A persistent outward K+ current (IPO), activated by depolarization from resting potential, has been identified and characterized in rat subthalamic nucleus (SThN) neurones using whole-cell voltage-clamp recording in brain slices. IPO both rapidly activated (tau = 8 ms at +5 mV) and deactivated (tau = 2 ms at -68 mV), while showing little inactivation. Tail current reversal potentials varied with extracellular K+ concentration in a Nernstian manner. Intracellular Cs+ did not alter either IPO amplitude or the voltage dependence of activation, but blocked transient (A-like) outward currents activated by depolarization. When extracellular K+ was replaced with Cs+, IPO tail current reversal potentials were dependent upon the extracellular Cs+ concentration, indicating an ability to conduct Cs+, as well as K+. IPO was blocked by Ba2+ (1 mM), 4-aminopyridine (1 mM) and tetraethylammonium (TEA; 20 mM), with an IC50 for TEA of 0.39 mM. The IPO conductance appeared maximal (38 nS) at around +27 mV, half-maximal at -13 mV, with the threshold for activation at around -38 mV. TEA (1 mM) blocked the action potential after-hyperpolarization and permitted accommodation of action potential firing at frequencies greater than around 200 Hz. We conclude that IPO, which shares many characteristics of currents attributable to Kv3.1 K+ channels, enables high-frequency spike trains in SThN neurones.
Wigmore
M A
MA
Department of Pharmacology, Division of Neuroscience, The Medical School, University of Birmingham, Vincent Drive, Edgbaston, Birmingham B15 2TT, UK.
Lacey
M G
MG
D015761:4-Aminopyridine / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000465:Algorithms; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002586:Cesium / Q000378:metabolism*; D004594:Electrophysiology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000494:pharmacology; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000819:agonists / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D051381:Rats; D017208:Rats, Wistar; D051670:Shaw Potassium Channels; D020531:Subthalamic Nucleus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D051670:Shaw Potassium Channels; D013757:Tetraethylammonium Compounds; D002586:Cesium; D001464:Barium; D015761:4-Aminopyridine; D011188:Potassium