Mitotic activity in adult rat brain induced by implantation of pieces of fetal rat brain and liver.

By implantation of pieces of fetal CNS into adult host brains it was found that the fetal brain tissue induced a very high mitotic activity in the adult brain at 2-4 days after implantation. The dividing cells were found within a 3-mm zone from the transplant in occipital cortex, hippocampus and brain-stem. Sham operated control animals exhibited only very few mitotic figures close to the lesion. Neither local injection of amniotic fluid nor implantation of other fetal tissues induced mitotic activity with the exception of fetal liver. Possibly, the mitogenic factor(s) released from the transplanted fetal brain is hepatic in origin.