title: Effect of oxygen on neuronal excitability measured by critical flicker fusion frequency is dose dependent.
abstract: BACKGROUND
  Reactive oxygen species are involved in the functional changes necessary for synaptic plasticity, memory, and cognitive function. It is far from clear whether the increased excitability, and which forms of neuronal excitability, should be considered a part of the learning process or, rather, cellular manifestation of neuronal oxygen poisoning. It is yet to be elucidated whether oxygen (O2)-induced learning and poisoning use the same or distinct cellular pathways.
  
  
  OBJECTIVE
  We hypothesized that O2-induced neuronal excitability might use the same or an intertwined signaling cascade as the poisoning cellular pathway.
  
  
  METHODS
  Eighty-one healthy, young males, mean age 27.7 ± 4.1 (SD) years, were exposed in the hyperbaric chamber to 0.7 atmosphere absolute (ATA) O2, 1.4 ATA O2, and 2.8 ATA O2. The critical flicker fusion frequency (CFFF), oxyhemoglobin saturation (SiO2), and heart rate (HR) were measured before exposure, after 30 min of oxygen breathing while still at pressure and then after exposure.
  
  
  RESULTS
  Normobaric (0.7 ATA) O2 exposure did not affect CFFF and HR. Medium hyperbaric O2 exposure (1.4 ATA) decreased CFFF but HR remained unchanged. High hyperbaric O2 exposure (2.8 ATA) increased CFFF and diminished HR. SiO2 was similar in all investigated groups. A correlation between CFFF, HR, and SiO2 was observed only at low oxygen (0.7 ATA).
  
  
  CONCLUSIONS
  The effect of O2 on neuronal excitability measured by CFFF in young healthy men was dose dependent: 0.7 ATA O2 did not affect CFFF; CFFF were significantly jeopardized at 1.4 ATA O2, while CFFF recovered at 2.8 ATA. With 2.8 ATA O2, the CFFF and oxygen poisoning transduction pathways seemed to be intertwined.
authors.affiliation: a National Centre for Hyperbaric Medicine, Institute of Maritime and Tropical Medicine , Medical University of Gdansk , Gdynia , Poland.
authors.forename: Jacek
authors.initials: J
authors.lastname: Kot
authors.forename: Pawel J
authors.initials: PJ
authors.lastname: Winklewski
authors.forename: Zdzislaw
authors.initials: Z
authors.lastname: Sicko
authors.forename: Yurii
authors.initials: Y
authors.lastname: Tkachenko
mesh_terms: D000328:Adult; D005425:Flicker Fusion / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D008297:Male; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D009483:Neuropsychological Tests; D010100:Oxygen / Q000008:administration & dosage*; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: Critical flicker fusion frequency; Hyperbaric oxygen; Neuronal excitability; Normobaric oxygen; Oxygen poisoning