EFFECT OF N-METHYL-D-ASPARTATE AND POTASSIUM ON STRIATAL MONOAMINE METABOLISM IN IMMATURE RAT - AN IN-VIVO MICRODIALYSIS STUDY

Effects of N-methyl-D-aspartate (NMDA) and potassium on 5-day-old rat' s brain were examined. We measured extracellular striatal monoamines s uch as dopamine (DA), 3,4 dihydroxyphenylacetic acid (DOPAC), homovani llic acid (HVA), and 5-hydroxyindole-3-acetic acid (5-HIAA) using intr acerebral microdialysis. After 3 h stabilization, pups received varyin g concentrations of NMDA (1-3 mM) and potassium (200-800 mM) by intras triatal perfusion for 32 minutes. Increasing the concentration of NMDA and potassium induced a dose related DA increase (p < 0.001), whereas DOPAC, HVA, and 5-HIAA decreased significantly. Five days later the s ame animals were sacrificed and the weight reduction of their cerebral hemispheres was measured. The weight of the drug perfused side was si gnificantly reduced compared with that of the contralateral one. We ex amined next the relationship between the level of maximum DA and the r elative hemisphere weight reduction. The DA peak was highly correlated with the hemisphere weight reduction (r = 0.70, n = 52, p < 0.001 in the NMDA group, r = 0.83, n = 30, p < 0.001 in the potassium group, re spectively). These data show that each treatment alter striatal monoam ine metabolism in immature rat brain and that the extracellular DA pea k is a potential early indicator to estimate brain injury.