Properties of voltage-gated potassium currents in nucleated patches from large layer 5 cortical pyramidal neurons of the rat
Article first published online: 13 AUG 2004
The Journal of Physiology
Volume 525, Issue 3, pages 593–609, June 2000
How to Cite
Bekkers, J. M. (2000), Properties of voltage-gated potassium currents in nucleated patches from large layer 5 cortical pyramidal neurons of the rat. The Journal of Physiology, 525: 593–609. doi: 10.1111/j.1469-7793.2000.t01-1-00593.x
- Issue published online: 13 AUG 2004
- Article first published online: 13 AUG 2004
- (Received 3 September 1999; accepted after revision 9 March 2000)
- 1Voltage-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).
- 2Two main types of current were found, an A-current (IA) and a delayed rectifier current (IK), which were blocked by 4-aminopyridine (5 mm) and tetraethylammonium (30 mm), respectively.
- 3Recovery from inactivation was mono-exponential (for IA) or bi-exponential (for IK) and strongly voltage dependent. Both IA and IK 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 (V½) and slope factor (k) values of −81.6 mV and −6.7 mV for IA, and −66.6 mV and −9.2 mV for IK. Peak activation curves were described by the Boltzmann equation with V½ and k values of −18.8 mV and 16.6 mV for IA, and −9.6 mV and 13.2 mV for IK.
- 4IA inactivated mono-exponentially during a depolarising test pulse, with a time constant (∼7 ms) that was weakly dependent on membrane potential. IK inactivated bi-exponentially with time constants (∼460 ms, ∼4.2 s) that were also weakly voltage dependent. The time to peak of both IA and IK depended strongly on membrane potential. The kinetics of IA and IK were described by a Hodgkin-Huxley-style equation of the form mNh, where N was 3 for IA and 1 for IK.
- 5These 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.