Effect of ischemia on hydroxylase cofactor (tetrahydrobiopterin) and monoamine neurotransmitters in rat brain.

Hydroxylase cofactor, monoamine neurotransmitters and their metabolites were measured in ischemic rat brain produced by four-vessel occlusion for 30 and 60 min periods. Slight reduction of hydroxylase cofactor activity was observed in the ischemic cortex after 60 min. Dopamine increased in the brainstem, and its metabolites, 3,4-dihydroxyphenylacetic acid and homovanillic acid, increased throughout the brain. Decrease in norepinephrine was observed in the whole brain. Decrease in serotonin and increase in 5-hydroxyindoleacetic acid, a metabolite of serotonin, was observed in the ischemic cerebral cortex. The present study has revealed that there appears to be no significant relationship between hydroxylase cofactor activity and monoamine levels in the ischemic brain. Thus, the hydroxylase cofactor does not play a main role in regulating monoamine synthesis in the acute phase of brain ischemia.