Striatal dopamine in acute cerebral ischemia of stroke-resistant rats

We devised the present experiments to assess the effects of ischemia on the production of dopamine in the caudate nucleus of spontaneously hypertensive stroke-resistant rats. Ringer's solution was continuously perfused at a rate of 10 microliters/min through 0.2-mm-diameter dialysis tubing implanted in the rat's caudate nucleus. After bilateral occlusion of the common carotid artery, perfusate was collected at 20-minute intervals for 120 minutes and was analyzed for monoamines and their metabolites using high-performance liquid chromatography and an electrochemical detection system. The extracellular concentration of dopamine increased abruptly approximately 3 minutes after the ischemic insult, reached a maximum at between 20 and 40 minutes after the insult, and subsequently decreased. During the 120 minutes, 3,4-dihydroxyphenylacetic acid and 5-hydroxyindole-3-acetic acid concentrations decreased significantly, whereas 5-hydroxytryptamine was not detected. Our results indicate that during cerebral ischemia a large increase in extracellular dopamine concentration in the caudate nucleus occurs, probably as a result of energy failure of the cell membranes. This leakage of dopamine may be a causal factor in the neuronal damage associated with cerebral ischemia.