BACKGROUND: As indicated by transplantation experiments in recent years, correlative neural active substances could be synthesized in the transplanted retina(TP); however, the growth and development situation of neural active substance positive neurons in TP is unclear.OBJECTIVE: To observe the differentiation and development of the neuron,and the biosynthesis of neural active substance in TP and its relationship with environment and visual center to explore the rule of development of nerve tissue and its regeneration and plasticity.DESIGN: An observatory comparative study based on animals.SETTING: Department of histology and embryology of two universities.MATERIALS: The study was conducted in the Experimental Animal Center of Guangzhou Medical College between August 2002 and March 2003. Totally 96 healthy SD rats in either gender were selected.INTERVENTIONS: Embryonal 14-day SD retina was transplantedin-between the epithalamus and hypothalamus of the midbrain in P1 rat and the right eye of the P1 rat was removed simultaneously. The development time of TP on the 9th day after operation was corresponding to the normal retina on the 1st day after born, which was then recorded as TP1, and so on. The development and differentiation was shown by histochemical method.MAIN OUTCOME MEASURES: Development and morphological observation of TP and neurons in TP.RESULTS: TP had the same structure of each layer as normal retina and its similar growth and development rule, which also could synthesize relative neural active substance. Nitricoxide synthase(NOS) -positive neuron in TP started at TP4 and reached its peak at TP12, but the number of positive neurons was kept on a relative low level after TP22.CONCLUSION: Embryonal retina could survive and remain its original growth and development rule after intracerebral transplantation, which has same structural characters as normal retina.