Properties of voltage dependent potassium currents in acutely isolated rat oculomotor neurons.
Voltage-dependent potassium currents in oculomotor neurons (OMNs) were studied with whole-cell patch clamp recordings. Fast inactivating outward currents (I(fast)) had half activation voltage (Vh) of -37.1 mV with slope factor (Vc) of 10.9 mV. I(fast) had half inactivation voltage (Vh) of -66.5 mV and Vc of 11.4 mV. I(fast) decayed with a time constant(tau) of 5.1 ms at +10 mV. I(fast) were sensitive to 4-aminopyridine, showing 50% inhibitory concentration (IC(50)) of 0.97 mM. Slowly inactivating outward currents (I(slow)) had two components. The low-concentration-TEA-sensitive currents had Vh of -3.7 mV with Vc of 9.7 mV in activation and had Vh of -54.7 mV with Vc of 23.8 mV in inactivation. The persistent currents had Vh of 7.4 mV and Vc of 11.8 mV in activation and Vh of -54.4 mV and Vc of 21.2 mV in inactivation. Decay of I(slow) (+10 mV) followed a double exponential time course (tau 215, 1165.6 ms). Low-concentration-TEA-sensitive currents were blocked completely by tetraethylammonium (TEA) of 3 mM with an IC(50) of 1.52 mM. Higher concentrations (3-20 mM) of TEA blocked the persistent currents, with an IC(50) of 6.9 mM.
Lin
Min
M
Department of Physiology, Faculty of Medicine, Mie University, 2-174 Edobashi, Tsu City, Mie 514-8507, Japan. yamamoto@doc.medic.mie-u.ac.jp
Nishimura
Yoshihiro
Y
Asahara
Toshihiro
T
Shibuya
Hiroshi
H
Kumazawa
Yuichi
Y
Kitagawa
Hirofumi
H
Yamamoto
Tetsuro
T
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D002469:Cell Separation; D009046:Motor Neurons / Q000166:cytology / Q000502:physiology; D009802:Oculomotor Nerve / Q000166:cytology / Q000502:physiology*; D018408:Patch-Clamp Techniques / Q000379:methods; D024642:Potassium Channels, Voltage-Gated / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D024642:Potassium Channels, Voltage-Gated