Ischemia increases tissue and decreases extracellular levels of acid dopamine metabolites in the rat striatum: further evidence for active transport of metabolites.

During 30 minutes of global forebrain ischemia in rats, striatal intracellular levels of dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) increase at the same time extracellular levels, measured by microdialysis, decrease. If DOPAC and HVA were free to diffuse out of cells, these changes in opposite directions should not occur. These data support the theory that a membrane potential-dependent active transport system is required for DOPAC and HVA to leave striatal cells. During ischemia and subsequent to ATP depletion, neurons and glia depolarize and active transport systems fail. DOPAC and HVA, which are still being produced inside neurons and possibly glia, can not be transported out of these cells and accumulate intracellularly.