CELL-SURFACE MOLECULES (NCAM AND L1) IN INTRASTRIATAL TRANSPLANTS OF EMBRYONIC MESENCEPHALON IN RATS

Cell surface molecules, NCAM and L1, reported to have a role in synapt ogenesis, growth and fasciculation of the neurites in the brain, were traced in the embryonic nigral transplants in the host striatum of adu lt rats. Substantia nigra of five, 15 and 25 postnatal days were also examined for the same molecules. Tyrosine hydroxylase label was used a s a marker to localize the nigral neurons and glial fibrillary acidic protein to detect if glial scar present. In the control as well as tra nsplants large neurons had expressed tyrosine hydroxylase. By 15th pos tnatal day tyrosine hydroxylase neurons appeared mature and were scatt ered, suggesting a well-formed neuropil. NCAM and L1 reaction was seen as a peripheral rim in most of the cells on the fifth postnatal day. The reaction was mainly in relation to the large cells and more extens ive on the 15th day. Thereafter on the 25th day, activity was negligib le. Large neurons demonstrated strong reactivity for NCAM and L1 durin g early post-transplantation days. After 30 days only smaller cells we re reactive, many of which could be identified as neurons. Strong reac tion for these molecules was present only until 60 days, though faint reaction could be detected even on the 90th day. These observations in dicate that the growth promoting molecules, the type seen in the neona tal period, can be detected normally only until the neurons mature. Pr olonged expression of these molecules by the grafted neurons indicate delay in the maturation of these cells due to absence of adequate targ et sites for synaptic connections. Some of the smaller cells expressin g these molecules after 30 days of transplantation could be astroglia, either proliferating or reactive. (C) 1996 IBRO. Published by Elsevie r Science Ltd.