Nogo-A and Nogo-receptor have been considered to play pivotal roles in
controlling axonal regeneration and neuronal plasticity. We investigated the
total distribution of Nogo-A and Nogo-receptor mRNAs in the adult rat
central nervous system using in situ hybridization histochemistry. Nogo-A is
abundantly expressed in both neurons and oligodendrocytes throughout the
central nervous system. Interestingly, we could not find any neurons which
lack Nogo-A mRNA expression, indicating that Nogo-A mRNA is
universally expressed in all neurons. In contrast, Nogo-R mRNA expression
was very restricted. Nogo-R mRNA was expressed in the olfactory bulb,
hippocampus, tentia tecta, some amygdala nuclei, cerebral cortex, some
thalamic nuclei, medial habenular, whereas we could not detect it in the
other regions. Interestingly, we did not detect Nogo-R mRNA in
monoaminergic neurons, which are known to have high regenerative
capacity, in the substantia nigra, ventral tegmental area, locus caeruleus, and
raphe nuclei. In addition, although neurons in the reticular thalamus and
cerebellar nuclei are also known to show high capacity for regeneration,
Nogo-R mRNA was not detected there. These data indicate that Nogo-A and
Nogo-R mRNAs were differentially expressed in the central nervous system,
and suggest that the lack of Nogo-R expression in a given neuron might be
necessary to keep its high regenerative capacity
