The differential expression patterns of messenger RNAs encoding Nogo-A and Nogo-receptor in the rat central nervous system.

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 neuron which lacks 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.