Survival of embryonic rat mesencephalic tissue transplanted into cerebral cortex in the presence of co-grafted embryonic striatum.

The transplantation of embryonic dopaminergic tissue is an approach to the therapy of parkinsonism. In this study we compared the development of the rat embryonic ventral mesencephalon transplanted together or without striatal tissue into the cerebral cortex of adult rats. After one month, the survival ratio was 17 of 44 when striatal tissue was co-grafted, while only 4 of 45 transplants survived when the co-graft was omitted. In the mesencephalic graft, the appearance of tyrosine hydroxylase-contaning cells was investigated by immunohistochemical method. Applying a fluorescent tracer dye, we demonstrated the growth of neural fibers from the mesencephalic tissue to the striatal co-graft. In situ, the embryonic striatal tissue is the natural target area for the developing nigrostriatal pathway. The possible role of trophic factors and postsynaptic target surfaces provided by the co-graft is discussed as basis of the adjuvant effect.