Effect of hyperoxia on neurogenic plasma protein extravasation in the rat dura mater.
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.
Schuh-Hofer
Sigrid
S
Department of Neurology, Charité Universitätsmedizin, Berlin, Germany.
Siekmann
Wiebke
W
Offenhauser
Nikolas
N
Reuter
Uwe
U
Arnold
Guy
G
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
D001798:Blood Proteins