Modulation of excitability by α-dendrotoxin-sensitive potassium channels in neocortical pyramidal neurons

Date

2001

Authors

Bekkers, John
Delaney, Andrew James

Journal Title

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Volume Title

Publisher

Society for Neuroscience

Abstract

Many neurons transduce synaptic inputs into action potentials (APs) according to rules that reflect their intrinsic membrane properties. Voltage-gated potassium channels, being numerous and diverse constituents of neuronal membrane, are important participants in neuronal excitability and thus in synaptic integration. Here we address the role of dendrotoxin-sensitive "D-type" potassium channels in the excitability of large pyramidal neurons in layer 5 of the rat neocortex. Low concentrations of 4-aminopyridine or α-dendrotoxin (α-DTX) dramatically increased excitability: the firing threshold for action potentials was hyperpolarized by 4-8 mV, and the firing frequency during a 1-sec-long 500 pA somatic current step was doubled. In nucleated outside-out patches pulled from the soma, α-DTX reversibly blocked a slowly inactivating potassium current that comprised ∼6% of the total. This current first turned on at voltages just hyperpolarized to the threshold for spiking and activated steeply with depolarization. By assaying α-DTX-sensitive current in outside-out patches pulled from the axon and primary apical dendrite, it was found that this current was concentrated near the soma. We conclude that α-DTX-sensitive channels are present on large layer 5 pyramidal neurons at relatively low density, but their strategic location close to the site of action potential initiation in the axon may ensure that they have a disproportionate effect on neuronal excitability. Modulation of this class of channel would generate a powerful upregulation or downregulation of neuronal output after the integration of synaptic inputs.

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Keywords

Keywords: 4 aminopyridine; dendrotoxin; potassium channel; action potential; animal cell; article; cell density; controlled study; dendrite; hyperpolarization; membrane depolarization; neocortex; nerve cell excitability; nerve fiber; newborn; nonhuman; potassium cu Action potential; D-current; Dendrite; Dendrotoxin; Neocortex; Potassium channel; Pyramidal neuron

Citation

Source

Journal of Neuroscience

Type

Journal article

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