Cycloheximide downsynthesizes inhibitory molecules for neurite outgrowth in neural transplantation

Rat fetal substantia nigra treated with cycloheximide, a protein synthesis inhibitor, were implanted to adult rat striatum. After 4 weeks, tyrosine hydroxylase (TH)-like immunoreactive (-LI) fibers of host striatum penetrated grafts, and TH-LI neurites in the grafts elongated and mingled with the host striatal neurites. Astrocytes proliferated in the grafts without glial scar between the graft-host border. A few chondroitin sulfate- or tenascin-LI glial cells were found in the grafts, while in transplants without cycloheximide, glial scar expressed strong immunoreactivity for these molecules. Downsynthesis of these inhibitory molecules may alter the glial character and permit neurites traversing the border.