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This Article Full Text Full Text (PDF) All Versions of this Article: 581/3/941    most recent jphysiol.2007.128454v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Guan, D. Articles by Foehring, R. C. Search for Related Content PubMed PubMed Citation Articles by Guan, D. Articles by Foehring, R. C. Related Collections Neuroscience

¹ Department of Anatomy and Neurobiology, University of Tennessee, 855 Monroe Avenue, Memphis, TN 38163, USA
² Department of Physiology, Northwestern University, 745 N. Fairbanks Court, Chicago, IL 60611, USA

We determined the expression of Kv2 channel subunits in rat somatosensory and motor cortex and tested for the contributions of Kv2 subunits to slowly inactivating K⁺ currents in supragranular pyramidal neurons. Single cell RT-PCR showed that virtually all pyramidal cells expressed Kv2.1 mRNA and 80% expressed Kv2.2 mRNA. Immunocytochemistry revealed striking differences in the distribution of Kv2.1 and Kv2.2 subunits. Kv2.1 subunits were clustered and located on somata and proximal dendrites of all pyramidal cells. Kv2.2 subunits were primarily distributed on large apical dendrites of a subset of pyramidal cells from deep layers. We used two methods for isolating currents through Kv2 channels after excluding contributions from Kv1 subunits: intracellular diffusion of Kv2.1 antibodies through the recording pipette and extracellular application of rStromatoxin-1 (ScTx). The Kv2.1 antibody specifically blocked the slowly inactivating K⁺ current by 25–50% (at 8 min), demonstrating that Kv2.1 subunits underlie much of this current in neocortical pyramidal neurons. ScTx (300 nM) also inhibited 40% of the slowly inactivating K⁺ current. We observed occlusion between the actions of Kv2.1 antibody and ScTx. In addition, Kv2.1 antibody- and ScTx-sensitive currents demonstrated similar recovery from inactivation and voltage dependence and kinetics of activation and inactivation. These data indicate that both agents targeted the same channels. Considering the localization of Kv2.1 and 2.2 subunits, currents from truncated dissociated cells are probably dominated by Kv2.1 subunits. Compared with Kv2.1 currents in expression systems, the Kv2.1 current in neocortical pyramidal cells activated and inactivated at relatively negative potentials and was very sensitive to holding potential.

(Received 17 January 2007; accepted after revision 15 March 2007; first published online 22 March 2007)
Corresponding author R. C. Foehring: Department of Anatomy and Neurobiology, University of Tennessee, 855 Monroe Avenue, Memphis, TN 38163, USA. Email: rfoehrin{at}utmem.edu

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