Fetal nigral transplants in the lateral ventricle of adult rats. A long-term morphological study

The substantia nigra from rats of 16 and 17 gestational days grafted into the lateral ventricle of adult rats grew into isolated or partially integrated transplants in 80% of the rats. The morphological details of the transplants were studied at intervals of 30-360 days. The neurons grew, differentiated and were comparable to age-matched controls until 150 days. Thereafter, the neurons showed progressive aging changes like dendritic thickening, clear spaces, membrane-bound vacuoles and increase in lysosomes in the cytoplasm. The numerical density per unit volume (Nv) of normal neurons significantly decreased with simultaneous increase in Nv of glial cells by 360 days. These changes were slower to develop in the partially integrated transplants: it is concluded that target tissue interaction is necessary for prolonged survival of the grafted tissue