
Logged in as a Visitor.
Properties of voltagegated potassium currents in nucleated patches from large layer 5 cortical pyramidal neurons of the rat.
J M Bekkers
J. Physiol. (Lond.),
2000
Jun
15
, 525 Pt 3, 593609
Voltagegated potassium currents were studied in nucleated outsideout patches obtained from large layer 5 pyramidal neurons in acute slices of sensorimotor cortex from 13 to 15dayold Wistar rats (2225 C). Two main types of current were found, an Acurrent (IA) and a delayed rectifier current (IK), which were blocked by 4aminopyridine (5 mM) and tetraethylammonium (30 mM), respectively. Recovery from inactivation was monoexponential (for IA) or biexponential (for IK) and strongly voltage dependent. Both IA and IK could be almost fully inactivated by depolarising prepulses of sufficient duration. Steadystate inactivation curves were well fitted by the Boltzmann equation with halfmaximal voltage (V ) 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 V and k values of 18.8 mV and 16.6 mV for IA, and 9.6 mV and 13.2 mV for IK. IA inactivated monoexponentially during a depolarising test pulse, with a time constant ( approximately 7 ms) that was weakly dependent on membrane potential. IK inactivated biexponentially with time constants ( approximately 460 ms, approximately 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 HodgkinHuxleystyle equation of the form mNh, where N was 3 for IA and 1 for IK. These results provide a basis for understanding the role of voltagegated potassium currents in the firing properties of large layer 5 pyramidal neurons of the rat neocortex.
http://www.ncbi.nlm.nih.gov/pubmed/10856115
