The excitotoxin quinolinic acid is present and unevenly distributed in the rat brain

The presence of quinolinic acid (2,3-pyridinedicarboxylic acid, QA) in the rat brain has been demonstrated using a mass-spectrometric method. Distribution studies indicate that this molecule is more concentrated in the cortex (2.1 nmol/g wet weight) than in other brain areas. Tryptophan, a possible QA precursor, administered in large doses, increases the cortical content of QA. The contrary occurs when rats are pretreated with p-chlorophenylalanine, a drug capable of decreasing brain tryptophan concentration. The neurotoxin 5,7-dihydroxytryptamine is inactive. Our findings support the idea that QA merits special attention as a potential transmitter and as an endogenous excitotoxin in brain.