Brain Tryptophan Hydroxylation: Dependence on Arterial Oxygen Tension

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Science  05 Oct 1973:
Vol. 182, Issue 4107, pp. 72-74
DOI: 10.1126/science.182.4107.72


The accumulation of cerebral 5-hydroxytryptophan after decarboxylase inhibition was decreased in rats maintained at arterial O2 tensions below 60 mm-Hg. In contrast, brain lactate was stable above 40 mm-Hg and brain adenosine triphosphate, adenosine diphosphate, and adenosine monophosphate were unchanged above 30 mm-Hg. There was a linear correlation of brain 5-hydroxytryptophan accumulation to cerebral venous O2 tension. Cerebral tryptophan hydroxylase appears to have a poor affinity for oxygen and to be affected by slight hypoxia. The resultant decreases in monoamine neurotransmitter metabolism may explain the behavioral changes of mild oxygen deprivation.