The excitotoxin quinolinic acid is present in the brain of several mammals and its cortical content increases during the aging process.

The distribution of the excitotoxin quinolinic acid (QUIN) has been evaluated in the brains of rabbit, guinea pig and rat, using a mass spectrometric method. Furthermore, the cortical content of this molecule has been measured during the development and the aging of the rat. The cortex contained the highest concentration of QUIN in the three species studied. During the rat development the concentration of this molecule increased and unusually high amounts of it were found in approximately 50% of 30-month-old rats.