Kv4.2 mRNA abundance and A-type K(+) current amplitude are linearly related in basal ganglia and basal forebrain neurons.
A-type K(+) currents are key determinants of repetitive activity and synaptic integration. Although several gene families have been shown to code for A-type channel subunits, recent studies have suggested that Kv4 family channels are the principal contributors to A-type channels in the somatodendritic membrane of mammalian brain neurons. If this hypothesis is correct, there should be a strong correlation between Kv4 family mRNA and A-type channel protein or aggregate channel currents. To test this hypothesis, quantitative single-cell reverse transcription-PCR analysis of Kv4 family mRNA was combined with voltage-clamp analysis of A-type K(+) currents in acutely isolated neurons. These studies revealed that Kv4.2 mRNA abundance was linearly related to A-type K(+) current amplitude in neostriatal medium spiny neurons and cholinergic interneurons, in globus pallidus neurons, and in basal forebrain cholinergic neurons. In contrast, there was not a significant correlation between estimates of Kv4.1 or Kv4.3 mRNA abundance and A-type K(+) current amplitudes. These results argue that Kv4.2 subunits are major constituents of somatodendritic A-type K(+) channels in these four types of neuron. In spite of this common structural feature, there were significant differences in the voltage dependence and kinetics of A-type currents in the cell types studied, suggesting that other determinants may create important functional differences between A-type K(+) currents.
Tkatch
T
T
Department of Physiology and Institute for Neuroscience, Northwestern University Medical School, Chicago, Illinois 60611, USA.
Baranauskas
G
G
Surmeier
D J
DJ
D000818:Animals; D001479:Basal Ganglia / Q000502:physiology*; D002462:Cell Membrane / Q000502:physiology; D002795:Choline O-Acetyltransferase / Q000032:analysis; D003342:Corpus Striatum / Q000502:physiology; D003712:Dendrites / Q000502:physiology*; D004594:Electrophysiology / Q000379:methods; D005917:Globus Pallidus / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D017072:Neostriatum / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D009928:Organ Specificity; D016133:Polymerase Chain Reaction; D015221:Potassium Channels / Q000145:classification / Q000235:genetics* / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D016548:Prosencephalon / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D051672:Shal Potassium Channels; D013779:Tetrodotoxin / Q000494:pharmacology
C497017:Kcnd1 protein, rat; C497023:Kcnd3 protein, rat; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger; D051672:Shal Potassium Channels; D013779:Tetrodotoxin; D002795:Choline O-Acetyltransferase