Ontogenesis of N-acetyl-aspartate and N-acetyl-aspartyl-glutamate in rat brain.

The levels of N-acetyl-aspartate (NAA) and N-acetyl-aspartyl-glutamate (NAAG) were measured in several regions and in whole brain of rats from 15 days of gestation (DG) to adulthood by means of an isocratic HPLC method. The levels of NAAG in whole brain increased 3-fold between 15 DG and birth, which was 90% of the adult level. Whereas the levels of NAAG in spinal cord increased from 2 days to 4 weeks after birth, in forebrain regions the levels increased 2-3-fold between 2 and 8 days after birth and then declined substantially to adult levels. In contrast, in whole brain and in the several regions examined after birth, the levels of NAA rose steadily from 15 DG to adulthood with a 30-fold increase in whole brain concentration. The results of this study demonstrate the lack of correlation in the development of NAA and NAAG levels and suggest that NAAG is localized in a cell system that matures early.