CHANGES IN URIC-ACID DURING ACUTE INFUSION OF MPP(-OHDA, AND FECL3 - A MICRODIALYSIS STUDY IN THE SUBSTANTIA-NIGRA OF THE GUINEA-PIG(), 6)

Extracellular uric acid levels were measured in the substantia nigra o f guinea pigs via microdialysis/liquid chromatography with electrochem ical detection (LCED) during infusion (60 min) of N-methyl-4-phenylpyr idinium (MPP(+)), 6-hydroxydopamine (6-OHDA), or iron (III) chloride ( FeCl3). Striatal and substantia nigra (SN) tissues were analyzed for u ric acid (UA) and dopamine (DA) 3 h postinfusion. MPP(+) infusion resu lted in an increase in extracellular UA of 222 +/- 6%. The ipsilateral /contralateral ratio of nigral UA tissue levels was significantly incr eased over vehicle controls. Infusion of 6-OHDA produced an increase o f 362 +/- 44% in extracellular UA. No significant changes were seen in UA tissue levels in either the striatum or the SN. Infusion of FeCl3 produced a significant decrease in extracellular nigral UA levels to 2 1.5 +/- 0.7% of preinfusion levels. The ipsilateral/ contralateral rat io of nigral UA tissue levels increased by 38%, whereas the striatal r atio value decreased to 62% of the vehicle control levels. No changes in DA tissue levels were observed in any of the brain regions in the e xperimental groups. These results indicate that infusion of neurotoxin s known to affect dopaminergic cells generates an acute change in UA l evels within the nigrostriatal system of guinea pigs.