Nogo receptor mRNA expression in intact and regenerating CNS neurons

The expression of mRNA for Nogo-66 receptor (NgR) in unoperated adult rats and mice, and rats with nerve grafts placed in the thalamus and cerebellum to stimulate axonal regeneration, was investigated by in situ hybridization. NgR was strongly expressed in neurons of the neocortex, hippocampal formation, and amygdaloid nuclei and dorsal thalamus and moderately expressed in the red nucleus and vestibular nuclei. NgR mRNA was expressed in cerebellar deep nuclei and more strongly by granule cells than by Purkinje cells. Large regions of the forebrain, including the striatum, thalamic reticular nucleus, hypothalamus, and basal forebrain showed little or no NgR expression. NgR was weakly expressed in spinal neurons and some primary sensory neurons. Nerve implantation into the brain did not affect NgR expression. Some regeneration-competent neurons expressed NgR but others did not. Thus NgR expression was not correlated with the ability of neurons to regenerate axons into nerve grafts although Nogo-66 was strongly upregulated by some cells in the distal stumps of injured sciatic nerves. Nogo-66 transcripts were strongly expressed by many classes of CNS neurons and less strongly in white matter.