Neurite outgrowth from cultured CNS neurons is promoted by inhibitors of protein and RNA synthesis.

We examined the effects of changes caused by the blocking of protein and RNA synthesis on neurite outgrowth from neurons of the central nervous system (CNS) in primary culture. Exposure to cycloheximide and actinomycin-D led to dramatic increases in the length of neurites in cultures of neurons from various rat or chick CNS regions. Inhibitor-induced neurite outgrowth was observed (1) from dopaminergic neurons in mixed cultures of the rat substantia nigra or (2) in pure cultures of rat and chick neurons grown on a polyornithine/laminin substratum. These results suggest that neurite outgrowth from CNS neurons is kept restricted, at least in culture, by the continuous production of a labile neurite-inhibiting protein intrinsic to the neurons, which rapidly decays following inhibition of protein or RNA synthesis.