title: Nitric oxide influences potassium currents in inner hair cells isolated from guinea-pig cochlea.
abstract: OBJECTIVE
  Nitric oxide (NO) is a diffusible second messenger, which regulates neurotransmission, serving as the principal endothelium-derived relaxing factor. NO also acts as an ion channel modulator. Nitric oxide synthase (NOS) has been identified in the inner ear, although its physiological role remains unclear. In the present study, the effects of NO onto K currents in inner hair cells (IHCs) were investigated.
  
  
  METHODS
  IHCs were acutely isolated and K currents were recorded by conventional whole-cell voltage-clamp recordings. NO donors sodium nitroprusside (SNP) were applied directly to the cells.
  
  
  RESULTS
  In 1mM SNP solutions, the amplitude of outward K currents (IK,f and IK,s) reversely decreased; however, fast activation kinetics was preserved. In the current-voltage relationship curves, the maximal slope conductances were 53.2nS and 44.2nS in control solutions and 1mM SNP solutions, respectively. At the membrane potential of +110mV, the amplitudes of outward currents were 9.2±2.9nA in control solutions and 7.3±2.7nA in 1mM SNP solutions, showing a significant difference.
  
  
  CONCLUSIONS
  NO acts as a K channel modulator in IHCs. A fast K current suppression may account for the high-frequency hearing impairment by the prevention of fast repolarization.
authors.affiliation: Department of Otorhinolaryngology, Kyushu Central Hospital, 3-23-1 Shiobaru, Minami-ku, Fukuoka 815-8588, Japan; Department of Otorhinolaryngology, Graduate School of Medical Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan. Electronic address: kimitsuki@kyushu-ctr-hsp.com.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kimitsuki
mesh_terms: D000818:Animals; D003051:Cochlea / Q000166:cytology*; D006168:Guinea Pigs; D006199:Hair Cells, Auditory, Inner / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects*; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D009599:Nitroprusside / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000187:drug effects* / Q000378:metabolism
chemical_list: D020030:Nitric Oxide Donors; D015221:Potassium Channels; D009599:Nitroprusside; D011188:Potassium
keywords: Cochlea; Inner hair cell; Nitric oxide; Potassium current