The distribution of small neurons stained for NAAG in neocortex was very similar to the distribution of GAD-positive interneurons (Figure 7). However, double labeling experiments showed that fewer than 50% of the NAAG-positive neurons in monkey
Figure 5. ASPA (A), NAA (B) and NAAG (C) in rat corpus callosum. Aspartoacylase (ASPA) is the only enzyme known in the brain that acts to deacetylate NAA. ASPA expression was predominantly observed in oligodendrocytes in white matter such as corpus callosum (A), as well as throughout the brain and spinal cord. NAA expression in oligodendrocytes was very low, possibly because it is broken down rapidly by ASPA (B). NAAG expression was relatively low in the corpus callosum of the rat, being present in a relatively small number of axons (C). In the cortical white matter from monkey, far more NAAG containing axons were observed, reflecting the greater expression of NAAG in pyramidal cells. Bar = 100^m.
neocortex were double-labeled for GAD67 (data not shown), suggesting that many small, NAAG-expressing neurons in cortex may be peptidergic rather than GABAergic.
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