title: High extracellular potassium ion concentration attenuates the blockade action of ketanserin on Kv1.3 channels expressed in xenopus oocytes.
abstract: BACKGROUND
  Ketanserin (KT), a selective serotonin (5-HT) 2-receptor antagonist, reduces peripheral blood pressure by blocking the activation of peripheral 5-HT receptors. In this study electrophysiological method was used to investigate the effect of KT and potassium ion on Kv1.3 potassium channels and explore the role of blocker KT in the alteration of channel kinetics contributing to the potassium ion imbalances.
  
  
  METHODS
  Kv1.3 channels were expressed in xenopus oocytes, and currents were measured using the two-microelectrode voltage-clamp technique.
  
  
  RESULTS
  KCl made a left shift of activation and an inactivation curve of Kv1.3 current and accelerated the activation and inactivation time constant. High extracellular [K(+)] attenuated the blockade effect of KT on Kv1.3 channels. In the presence of KT and KCl the activation and inactivation time constants were not influenced significantly no matter what was administered first. KT did not significantly inhibit Kv1.3 current induced by tetraethylammonium (TEA).
  
  
  CONCLUSIONS
  KT is a weak blocker of Kv1.3 channels at different concentrations of extracellular potassium and binds to the intracellular side of the channel pore. The inhibitor KT of ion channels is not fully effective in clinical use because of high [K(+)](o) and other electrolyte disorders.
authors.affiliation: Department of Cardiology, Institute of Cardiovascular Diseases, Ion Channelopathy Research Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Zhen-tao
authors.initials: ZT
authors.lastname: Liang
authors.forename: Xian-pei
authors.initials: XP
authors.lastname: Wang
authors.forename: Qiu-tang
authors.initials: QT
authors.lastname: Zeng
authors.forename: Yu-hua
authors.initials: YH
authors.lastname: Liao
authors.forename: An-ruo
authors.initials: AR
authors.lastname: Zou
authors.forename: Lu
authors.initials: L
authors.lastname: Li
authors.forename: Dan-na
authors.initials: DN
authors.lastname: Tu
mesh_terms: D000818:Animals; D004594:Electrophysiology; D005260:Female; D007650:Ketanserin / Q000494:pharmacology*; D051664:Kv1.3 Potassium Channel / Q000187:drug effects* / Q000378:metabolism*; D009865:Oocytes; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D014982:Xenopus laevis
chemical_list: D051664:Kv1.3 Potassium Channel; D012702:Serotonin Antagonists; D007650:Ketanserin; D011188:Potassium