Modulation of excitability by α-dendrotoxin-sensitive potassium channels in neocortical pyramidal neurons
Date
2001
Authors
Bekkers, John
Delaney, Andrew James
Journal Title
Journal ISSN
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.
Description
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
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Source
Journal of Neuroscience
Type
Journal article