title: Differential contribution of Kv4-containing channels to A-type, voltage-gated potassium currents in somatic and visceral dorsal root ganglion neurons.
abstract: Little is known about electrophysiological differences of A-type transient K(+) (KA) currents in nociceptive afferent neurons that innervate somatic and visceral tissues. Staining with isolectin B4 (IB4)-FITC classifies L6-S1 dorsal root ganglion (DRG) neurons into three populations with distinct staining intensities: negative to weak, moderate, and intense fluorescence signals. All IB4 intensely stained cells are negative for a fluorescent dye, Fast Blue (FB), injected into the bladder wall, whereas a fraction of somatic neurons labeled by FB, injected to the external urethral dermis, is intensely stained with IB4. In whole-cell, patch-clamp recordings, phrixotoxin 2 (PaTx2), a voltage-gated K(+) (Kv)4 channel blocker, exhibits voltage-independent inhibition of the KA current in IB4 intensely stained cells but not the one in bladder-innervating cells. The toxin also shows voltage-independent inhibition of heterologously expressed Kv4.1 current, whereas its inhibition of Kv4.2 and Kv4.3 currents is voltage dependent. The swapping of four amino acids at the carboxyl portion of the S3 region between Kv4.1 and Kv4.2 transfers this characteristic. RT-PCRs detected Kv4.1 and the long isoform of Kv4.3 mRNAs without significant Kv4.2 mRNA in L6-S1 DRGs. Kv4.1 and Kv4.3 mRNA levels were higher in laser-captured, IB4-stained neurons than in bladder afferent neurons. These results indicate that PaTx2 acts differently on channels in the Kv4 family and that Kv4.1 and possibly Kv4.3 subunits functionally participate in the formation of KA channels in a subpopulation of somatic C-fiber neurons but not in visceral C-fiber neurons innervating the bladder.
authors.affiliation: Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; Department of Urology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan; and.
authors.forename: Takakazu
authors.initials: T
authors.lastname: Yunoki
authors.affiliation: Department of Environmental and Occupational Health, University of Pittsburgh Graduate School of Public Health, Pittsburgh, Pennsylvania; Department of Bioengineering, Nagaoka University of Technology, Nagaoka, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Takimoto
authors.affiliation: Department of Environmental and Occupational Health, University of Pittsburgh Graduate School of Public Health, Pittsburgh, Pennsylvania;
authors.forename: Kaori
authors.initials: K
authors.lastname: Kita
authors.affiliation: Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania;
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Funahashi
authors.affiliation: Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; Department of Urology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan; and.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Takahashi
authors.affiliation: Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania;
authors.forename: Hiroko
authors.initials: H
authors.lastname: Matsuyoshi
authors.affiliation: Department of Urology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan; and.
authors.forename: Seiji
authors.initials: S
authors.lastname: Naito
authors.affiliation: Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania; nyos@pitt.edu.
authors.forename: Naoki
authors.initials: N
authors.lastname: Yoshimura
mesh_terms: D000578:Amidines; D000818:Animals; D016466:CHO Cells; D003412:Cricetulus; D005260:Female; D005727:Ganglia, Spinal / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009619:Nociceptors / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D016133:Polymerase Chain Reaction; D026902:Potassium Channel Blockers / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D051637:Shaker Superfamily of Potassium Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012867:Skin / Q000294:innervation*; D014162:Transfection; D001743:Urinary Bladder / Q000294:innervation*
chemical_list: D000578:Amidines; D026902:Potassium Channel Blockers; D012333:RNA, Messenger; D051637:Shaker Superfamily of Potassium Channels; C031455:diamidino compound 253-50
keywords: A-type K channel; Kv4 channel; dorsal root ganglion; nociceptive C-fiber; phrixotoxin 2