Journal of Applied Physiology, Vol 39, Issue 2 215-220, Copyright © 1975 by American Physiological Society
Adaptation of brain monoamine synthesis to hypoxia in the rat
J. N. Davis
Oxygen is a substrate in the synthesis of the neurotransmitters,
norepinephrine, dopamine, and serotonin. Changes in environmental oxygen
appear to cause corresponding alterations in brain monoamine synthesis in
vivo. The effect of chronic hypoxia was studied by exposing rats to 10%
oxygen for up to 36 h. Brain monoamine synthesis, estimated in vivo,
decreased initially and then returned to control levels, despite continued
exposure to 10% oxygen. During this apparent adaptation to hypoxia, there
were no changes in the concentration of brain serotonin, norepinephrine,
dopamine, or tryptophan, while brain tryosine increased after 24 h of
exposure. Tyrosine hydroxylase activity in vitro was not altered by the
exposure to 10% oxygen. Evidence of hypoxic adaptation in these rats, a
rightward shift of their hemoglobin dissociation curves, was found after 24
h of exposure. The adaptation of brain monoamine synthesis to hypoxia
appeared to correlate with adaptive changes in brain tissue oxygen rather
than any change in the intraneuronal regulation of amine synthesis.
