Transcerebral exchange kinetics of nitrite and calcitonin gene-related peptide in acute mountain sickness: evidence against trigeminovascular activation?
OBJECTIVE
High-altitude headache is the primary symptom associated with acute mountain sickness, which may be caused by nitric oxide-mediated activation of the trigeminovascular system. Therefore, the present study examined the effects of inspiratory hypoxia on the transcerebral exchange kinetics of the vasoactive molecules, nitrite (NO(2)(*)), and calcitonin gene-related peptide (CGRP).


METHODS
Ten males were examined in normoxia and after 9-hour exposure to hypoxia (12.9% O(2)). Global cerebral blood flow was measured by the Kety-Schmidt technique with paired samples obtained from the radial artery and jugular venous bulb. Plasma CGRP and NO(2)(*) were analyzed via radioimmunoassay and ozone-based chemiluminescence. Net cerebral exchange was calculated by the Fick principle and acute mountain sickness/headache scores assessed via clinically validated questionnaires.


RESULTS
Hypoxia increased cerebral blood flow with a corresponding increase in acute mountain sickness and headache scores (P<0.05 vs normoxia). Hypoxia blunted the cerebral uptake of NO(2)(*), whereas CGRP exchange remained unaltered. No relationships were observed between the change (hypoxia-normoxia) in cerebral NO(2)(*) or CGRP exchange and acute mountain sickness/headache scores (P>0.05).


CONCLUSIONS
These findings argue against sustained trigeminovascular system activation as a significant event in acute mountain sickness.
Bailey
Damian M
DM
Taudorf
Sarah
S
Berg
Ronan M G
RM
Jensen
Lars T
LT
Lundby
Carsten
C
Evans
Kevin A
KA
James
Philip E
PE
Pedersen
Bente K
BK
Moller
Kirsten
K
D000328:Adult; D000532:Altitude Sickness / Q000378:metabolism* / Q000503:physiopathology*; D001923:Brain Chemistry / Q000502:physiology*; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D006261:Headache / Q000378:metabolism; D006801:Humans; D000860:Hypoxia / Q000378:metabolism; D007700:Kinetics; D049449:Luminescence; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D011795:Surveys and Questionnaires; D014276:Trigeminal Nerve / Q000503:physiopathology*
D009569:Nitric Oxide; D015740:Calcitonin Gene-Related Peptide