Neurotrophic factors for ciliary ganglionic(CG) neurons from chick embryo

Abstract

Development of neurons is influenced by the microenvironment where the the neurons reside. Chemical substances in the microenvironment are crucial factors to regulate the destination of neurons. We have studied some of these trophic factors which act on cultured CG neurons from 8-day embryo. 1) Neurite outgrowth factor (NOF): Chicken gizzard is rich in NOF which promotes neurite outgrowth. It is trypsin- and heat-sensitive, with a MW. of 200-300K. It facilitates neuro-muscular synaptogenesis in culture. It exerts its action through the binding to polyornithine-coated substratum(POR-well). Antibody against NOF inhibits the activity of NOF from various tissues of chick, mouse and rat, but NOF in murine tissues are 1000-3000 fold less sensitive to the antibody than that in chick. 2) Survival factor (SF): Chick embryonal eyes show high activity of SF, but gizzard also contains SF. It has a MW. about 40K and is more labile than NOF. It supports the survival of CG neurons and is crucial for the manifestation of NOF activity. 3) Neurite outgrowth inhibitory factor: It suppresses the activity of NOF when both factors co-exist. It is heat(90°C,5min)-and trypsin-resistant. It acts by competing with NOF in binding to POR-well. Although several neurotrophic factors can be discriminated in this culture system, the precise actions and structures of the trophic factors in vitro and in vivo remain to be elucidated.