Three types of voltage-dependent calcium current in cultured rat hippocampal neurons.
Voltage-dependent calcium (Ca2+) currents in cultured rat hippocampal neurons were studied with the whole-cell recording mode of the patch-clamp technique. On the basis of the voltage-dependence of activation, kinetics of inactivation and pharmacology, 3 types of Ca2+ currents were distinguished. The low-threshold Ca2+ current (Il) was activated at -60 mV, and completely inactivated during a 100-ms depolarization to -40 mV (time constant: tau = 16 +/- 1 ms). The high-threshold currents (Ih), which were activated at -20 mV, could be separated into two types. The high-threshold, fast inactivating current (Ih,f) decayed quickly during a maintained depolarization (tau = 33 +/- 3 ms at 0 mV), whereas the high-threshold, slowly inactivating current (Ih,s) decayed with a much slower time constant (tau = 505 +/- 42 ms at 0 mV). The inactivations of Ih,f and Ih,s exhibited different time- and voltage-dependencies. Nickel ions (Ni2+, 25 microM) markedly suppressed Il, but little affected Ih. Cadmium ions (Cd2+, 10 microM) almost completely suppressed Ih, but left a small amount of Il. Lanthanum ions (La3+, 10 microM) almost completely suppressed both Il and Ih. Ih,s was sensitive to block by the dihydropyridine antagonist nicardipine (10 microM).
Ozawa
S
S
Department of Physiology, School of Medicine, Gunma University, Japan.
Tsuzuki
K
K
Iino
M
M
Ogura
A
A
Kudo
Y
Y
D000818:Animals; D015220:Calcium Channels / Q000502:physiology*; D002478:Cells, Cultured; D004594:Electrophysiology; D005333:Fetus / Q000166:cytology*; D006624:Hippocampus / Q000166:cytology* / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D051381:Rats
D015220:Calcium Channels