A rat model of Parkinsons disease has been established by injection of 6-hydroxydopamine (6-OHDA) solution (8 ug 6-OHDA dissolved in 4 uL physiological saline) into the left substantia nigra.Human fetal substantia nigra of the midbrain at a fetal age of 10,15,19,24,and 30 weeks was selected and prepared as a cell suspension with a live cell concentration of 10-20 ×105/ml_.This cell suspension (24 uL) was injected into rat dorsal caudate putamen on the affected side at three points.Nigral cells from donors at fetal ages 10-19 weeks were clearly able to alleviate the symptoms of Parkinsons disease.Immunohistochemistry results showed that at 2 months after transplantation of nigral cells from 10-19-week-old fetal donors,tyrosine hydroxylase (TH)-positive cells were densely dispersed throughout the transplantation site and surrounding region,displaying a round or oval appearance with small and short processes,less cytoplasm,and a large nucleus that went towards one side.There were 4.2-6.0 *103 TH-positive cells in each rat that received an effective nigral cell transplantation.With the prolongation of transplantation time,the TH-positive cells gradually grew larger,exhibiting a core-shaped,shuttle-shaped,or round appearance,with an increased number of processes,increased volume of cytoplasm,and the presence of a central nucleus.In addition,a fibrous net formed in the end region of TH-positive fibers,TH-positive cells were scattered,and there was no obvious boundary between the transplantation site and the surrounding region.At 6 months after nigral cell transplantation,there were still 4.2-6.0 ><103 TH-positive cells in each rat that received an effective nigral cell transplantation.Human fetal nigral cells at a fetal age of 10-19 weeks can be used in cell transplantation for treatment of Parkinsons disease.