Sensory neurite growth cone guidance by substrate adsorbed nerve growth factor

The response of growth cones from embryonic chick dorsal root ganglia to a patterned substrate of adsorbed nerve growth factor (NGF) was studied. The patterned substrate presented growth cones with an adsorbed NGF pattern and NGF-free substrate. NGF-responsive growth cones from 7 and 9 day ganglia could not proceed onto NGF-free substrate, reproducing the adsorbed NGF pattern. NGF-unresponsive growth cones from 17 day ganglia did not display any preference for adsorbed NGF or NGF-free substrata, which resulted in neurites not reproducing the adsorbed NGF pattern. Neurite outgrowth from NGF responsive 7-day ganglia onto a patterned NGF substrate, in NGF-containing medium, was radially symmetrical, exhibiting no growth cone response to the patterned NGF substrate. The lack of NGF-responsive growth cone extension onto NGF-free substrate indicates that NGF is a requirement for neurite elongation. If NGF is withdrawn from growth cones by microperfusion, neurite elongation ceases. Thus, an adsorbed pattern of NGF may be duplicated because growth cones are not able to extend onto NGF-free substrate, since NGF is a requirement for neurite elongation. These results indicate that substrate adsorbed NGF can support neurite formation and elongation as well as guide the direction of neurite elongation.