Differential expression patterns of messenger RNAs encoding Nogo receptors and their ligands in the rat central nervous system.

Nogo receptors (NgR1, -2, and -3) and their ligands, i.e., myelin-derived neurite outgrowth inhibitor (Nogo)-A, myelin-associated glycoprotein (MAG), and oligodendrocyte myelin glycoprotein (OMgp), have been considered to play pivotal roles in controlling axonal regeneration and neuronal plasticity. We show here that NgR1-3 mRNAs were differentially expressed exclusively in neurons situated in the telencephalon, diencephalons, and cerebellum, whereas we could not detect any NgR1-3 mRNA expression in the mesencephalon, pons, medulla oblongata, and spinal cord. On the other hand, Nogo-A mRNA was abundantly expressed in both neurons and oligodendrocytes throughout the central nervous system (CNS). MAG and OMgp mRNAs were also abundantly expressed in oligodendrocytes throughout the CNS. Interestingly, we did not detect NgR1-3 mRNAs in monoaminergic neurons in the substantia nigra, ventral tegmental area, locus caeruleus, and raphe nuclei, which are known to have high regenerative capacity. In addition, although neurons in the reticular thalamus and cerebellar nuclei are also known to show high capacity for regeneration, NgR1-3 mRNAs were not detected there. These data indicate that NgR1-3, Nogo-A, MAG, and OMgp mRNAs are differentially expressed in the rat CNS and suggest that the level of NgR1-3 expression in a neuron might determine its regenerative capacity.