Monoamine neurotransmitters in diffuse reversible forebrain ischemia and early recirculation: increased dopaminergic activity.

Regional levels of brain monoamines and their metabolites were examined in a rat model of reversible and diffuse forebrain ischemia with and without reperfusion. During ischemia, blood flow decreased by 87 to 95%, but recovered to control values during recirculation. Norepinephrine and serotonin decreased in the cerebral cortex and hippocampus during ischemia and diminished further during recirculation. On the other hand, dopamine and its metabolites, 3,4-dihydroxyphenylacetic acid and homovanillic acid, which were not much affected by ischemia, increased markedly in the cerebral cortex and striatum during recirculation, with a decrease in the ratio of dopamine to its metabolites. These results suggest central dopaminergic hyperactivity during recirculation, which may be related to the selective vulnerability of the striatum in similar models of reversible forebrain ischemia.