In vivo voltammetric evidence of production of uric acid by rat caudate.

Linear sweep in vivo voltammetry with carbon paste electrodes records a prominent peak at about 340 mV in the anterior caudate of rat brain. This peak is increased by microinfusion of uric acid or xanthine oxidase (which enhances conversion of hypoxanthine and xanthine to uric acid) and is decreased or eliminated by microinfusion of uricase. Allopurinol (a specific xanthine oxidase inhibitor) also decreases this peak when given either intracranially or intraperitoneally. Co-administration of uricase and allopurinol reliably eliminate the peak in question. These data suggest that uric acid, a purine metabolite that has been thought to be absent in brain, is formed locally in rat caudate and that uric acid is the sole component of the peak at 340 mV. In vivo voltammetry may be a useful new tool for studying brain purine metabolism.