are the dorsal columns. , , The dorsal column nuclei are immunoreactive for

NAAG, , as are their axons in the medial lemniscus. In thalamus, both cell bodies and neuropil of the ventral basal nucleus are labeled,23 and there is a band of neuropil labeling in layer 4 of somatosensory cortex.23

Numerous cells of origin for mossy fibers in cerebellum, including those of the spinal grey and the lateral cervical nucleus, are moderately to strongly stained for NAAG as are the fibers of the inferior and superior cerebellar peduncles, and mossy fiber endings are among the most prominent NAAG-positive elements in the cerebellar cortex.37 Up to 45% of neurons in the inferior olive are labeled, as are their axons (climbing fibers) in the cerebellum.37, 38

In somatosensory cortex, labeled neurons are mostly non-pyramidal; earlier reports of strong pyramidal cell labeling in rat somatosensory and other cortices is likely due to cross-reactivity with NAA.23, 31

3.3 Other Sensory Systems

Just as the larger neurons of the spinal ganglia contain NAAG (see above), so do most of the large cells of the vestibular ganglion,37 a few cells intercalated among the axons of the eighth nerve and some axons of the eighth nerve. In addition, all divisions of the vestibular nuclei contain NAAG-labeled cell bodies and neuropil.

It is unknown whether any of the NAAG-positive axons of the eighth nerve are auditory in origin. However, the auditory thalamic nucleus, the medial geniculate nucleus (MGN), contains both cellular and neuropil labeling28 (see also Fig. 3A of Moffett et al.26). One would expect, therefore, to find NAAG in neurons of the inferior colliculus, and, indeed, a micropunch radioimmunoassay study of rat brain found high levels of NAAG in cochlear nuclei, inferior colliculus and MGN.39

In contrast, gustatory systems may not use NAAG. The nucleus of the solitary tract, which receives taste information from the tongue, contains no NAAG-immunoreactive neurons.31

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