ACIDIC AND BASIC FIBROBLAST GROWTH-FACTORS DELAY THE MATURATION OF NEURAL CREST-DERIVED NEURONS

Neural crest (NC) cultures were prepared from lumbosacral segments of 12 day rat embryos and maintained in a defined medium. Post-mitotic, nat, neurofilament(+) neurons with broad neuritic processes ('nascent neurons') appeared within 24 h. Timing of the next stage in neuronal differentiation, the formation of bipolar, phase-bright cells that bound tetanus toxin with long, slender neurites ('bipolar neurons'), was markedly influenced by acidic or basic fibroblast growth factor (FGF). The transition from nascent to bipolar neuron occurred several days prematurely in medium without added FGF, but took place with a time-course like that in vivo when 10 ng/ml of acidic or basic FGF was added.