Development changes of growth factors for parasympathetic neurons secreted by their target cells in vitro

Trophic activities in conditioned media (CM) on target cells were quantified for their ability to maintain survival and promote neurite outgrowth of dissociated ciliary ganglia (CG) neurons from 8 day-old chick embryos in culture. CM on target cells were obtained at different stages of development. The ability of CMs to maintain neuronal survival increased almost 4-fold between 5 and 9 embryonic days, and then it was kept constant. On the other hand, neurite promoting activity was similar in all ages except in 8 days old CM that was doubled.