title: Effect of hyperoxia on neurogenic plasma protein extravasation in the rat dura mater.
abstract: OBJECTIVE
  We aimed to study the effect of normobaric hyperoxia on neurogenic inflammation of the rat dura mater.
  
  
  BACKGROUND
  Inhalation of 100% oxygen is a first-line therapy for the treatment of acute cluster headache (CH). However, the mechanisms underlying the antinociceptive effect of oxygen are poorly understood. Sumatriptan, which is also effective in aborting CH attacks, is known to inhibit neurogenic inflammation of the dura mater. We hypothesized that hyperoxia reduces dural plasma protein extravasation in the model of electrically stimulating the rat trigeminal ganglion.
  
  
  METHODS
  Unilateral stimulation of the trigeminal ganglion was performed in anesthetized male Sprague-Dawley rats. We assessed plasma protein extravasation (PPE) in the ipsilateral dura mater under normoxic (group 1) and hyperoxic conditions (group 2: pO(2) 200 mmHg; group 3: pO(2) 300 mmHg; group 4: pO(2) 400 mmHg). The study results were compared to the effect of sumatriptan (300 microg/kg) on dural PPE.
  
  
  RESULTS
  Under normoxic conditions, the calculated extravasation ratio was 1.72 +/- 0.2. Hyperoxic treatment (groups 2, 3, 4) significantly attenuated dural PPE. At oxygen levels of 400 mmHg, the PPE ratio was 1.14 +/- 0.2 (P < .01). After IV application of sumatriptan (300 microg/kg), PPE was nearly abolished (PPE ratio: 1.06 +/-0.17).
  
  
  CONCLUSIONS
  Our findings demonstrate that hyperoxia is able to inhibit dural PPE. Hyperoxia may play an anti-inflammatory role in neurogenic inflammation, but further studies are needed to clarify whether this effect is either caused by prejunctional mechanisms or by modulation of the vascular permeability at postcapillary venules.
authors.affiliation: Department of Neurology, Charité Universitätsmedizin, Berlin, Germany.
authors.forename: Sigrid
authors.initials: S
authors.lastname: Schuh-Hofer
authors.forename: Wiebke
authors.initials: W
authors.lastname: Siekmann
authors.forename: Nikolas
authors.initials: N
authors.lastname: Offenhauser
authors.forename: Uwe
authors.initials: U
authors.lastname: Reuter
authors.forename: Guy
authors.initials: G
authors.lastname: Arnold
mesh_terms: D000818:Animals; D001798:Blood Proteins / Q000378:metabolism*; D001831:Body Temperature / Q000502:physiology; D004388:Dura Mater / Q000378:metabolism*; D018496:Hyperoxia / Q000378:metabolism*; D007249:Inflammation / Q000378:metabolism; D008297:Male; D018613:Microscopy, Confocal; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D001798:Blood Proteins