Delayed rectifier currents in rat globus pallidus neurons are attributable to Kv2.1 and Kv3.1/3.2 K(+) channels.
The symptoms of Parkinson disease are thought to result in part from increased burst activity in globus pallidus neurons. To gain a better understanding of the factors governing this activity, we studied delayed rectifier K(+) conductances in acutely isolated rat globus pallidus (GP) neurons, using whole-cell voltage-clamp and single-cell RT-PCR techniques. From a holding potential of -40 mV, depolarizing voltage steps in identified GP neurons evoked slowly inactivating K(+) currents. Analysis of the tail currents revealed rapidly and slowly deactivating currents of similar amplitude. The fast component of the current deactivated with a time constant of 11. 1 +/- 0.8 msec at -40 mV and was blocked by micromolar concentrations of 4-AP and TEA (K(D) approximately 140 microM). The slow component of the current deactivated with a time constant of 89 +/- 10 microseconds at -40 mV and was less sensitive to TEA (K(D) = 0.8 mM) and 4-AP (K(D) approximately 6 mM). Organic antagonists of Kv1 family channels had little or no effect on somatic currents. These properties are consistent with the hypothesis that the rapidly deactivating current is attributable to Kv3.1/3.2 channels and the slowly deactivating current to Kv2.1-containing channels. Semiquantitative single-cell RT-PCR analysis of Kv3 and Kv2 family mRNAs supported this conclusion. An alteration in the balance of these two channel types could underlie the emergence of burst firing after dopamine-depleting lesions.
Department of Physiology/Northwestern University Institute for Neuroscience, Northwestern University Medical School, Chicago, Illinois 60611, USA.
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Baranauskas
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Tkatch
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Surmeier
D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D051668:Delayed Rectifier Potassium Channels; D004553:Electric Conductivity; D005917:Globus Pallidus / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D009479:Neuropeptides / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000235:genetics / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051669:Shab Potassium Channels; D051670:Shaw Potassium Channels; D019789:Tetraethylammonium / Q000494:pharmacology
D051668:Delayed Rectifier Potassium Channels; C496991:Kcnb1 protein, rat; D009479:Neuropeptides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger; D051669:Shab Potassium Channels; D051670:Shaw Potassium Channels; D019789:Tetraethylammonium; D015761:4-Aminopyridine