An HRP study on cytoarchitecture of red nucleus and origin of rubrospinal tracts in tree shrew

The cytoarchitecture of the red nucleus and the origin of the rubrospinal tracts were studied in tree shrew using HRP method. The results showed that the red nucleus in tree shrew was of shuttling form, its length was 3.7 mm and width 2 mm. At light microscopic level, large(60-100mum), medium (30-50mum) and small (10-25mum) neurons were observed in the red nucleus. The medium and small nurons scattered among the large ones. The rubrospinal tracts from different parts of the red nucleus were crossly terminated at different parts of the opposite side of the spinal cord, mainly at the cervical lumber. Those characteristics suggested that the cytoarchitecture of the red nucleus, the origin and distribution of the rubrospinal tracts in tree shrew were significantly different from those of the other mammals.