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Properties of voltage‐gated potassium currents in nucleated patches from large layer 5 cortical pyramidal neurons of the rat
Author(s) -
Bekkers John M.
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.t01-1-00593.x
Subject(s) - citation , neuroscience , library science , division (mathematics) , computer science , physics , psychology , cognitive science , mathematics , arithmetic
1 Voltage‐gated potassium currents were studied in nucleated outside‐out patches obtained from large layer 5 pyramidal neurons in acute slices of sensorimotor cortex from 13‐ to 15‐day‐old Wistar rats (22–25 °C). 2 Two main types of current were found, an A‐current ( I A ) and a delayed rectifier current ( I K ), which were blocked by 4‐aminopyridine (5 m m ) and tetraethylammonium (30 m m ), respectively. 3 Recovery from inactivation was mono‐exponential (for I A ) or bi‐exponential (for I K ) and strongly voltage dependent. Both I A and I K could be almost fully inactivated by depolarising prepulses of sufficient duration. Steady‐state inactivation curves were well fitted by the Boltzmann equation with half‐maximal voltage (V ½ ) and slope factor ( k ) values of −81.6 mV and −6.7 mV for I A , and −66.6 mV and −9.2 mV for I K . Peak activation curves were described by the Boltzmann equation with V ½ and k values of −18.8 mV and 16.6 mV for I A , and −9.6 mV and 13.2 mV for I K . 4 IA inactivated mono‐exponentially during a depolarising test pulse, with a time constant (∼7 ms) that was weakly dependent on membrane potential. I K inactivated bi‐exponentially with time constants (∼460 ms, ∼4.2 s) that were also weakly voltage dependent. The time to peak of both I A and I K depended strongly on membrane potential. The kinetics of I A and I K were described by a Hodgkin‐Huxley‐style equation of the form m N h , where N was 3 for I A and 1 for I K . 5 These results provide a basis for understanding the role of voltage‐gated potassium currents in the firing properties of large layer 5 pyramidal neurons of the rat neocortex.