STIMULATION OF NEURON SURVIVAL BY BASIC FGF AND CNTF IS A DIRECT EFFECT AND NOT MEDIATED BY NONNEURONAL CELLS - EVIDENCE FROM SINGLE CELL-CULTURES

The multifunctional proteins, basic fibroblast growth factor (bFGF) and ciliary neurotrophic factor (CNTF), share a capacity to promote in vitro and in vivo survival of several, partly overlapping neuron populations. Whether they can affect neurons directly or whether their supportive effects are mediated by non-neuronal cells and their growth factor products has been addressed in this study by establishing single neuron cultures from embryonic chick ciliary ganglia. Cultures with one or two neurons and without any non-neuronal cells were obtained by limiting dilution of ganglionic cell suspensions on 96-well microtiter plates. In the presence of bFGF about 80% of the wells that contained 1 or 2 neurons at the time of seeding, had this (these) neuron(s) maintained after 1 and 5 days. Absence of bFGF resulted in the death of neurons in over 80% of the wells screened. Identical results were obtained with CNTF. These data demonstrate the effectiveness of bFGF and CNTF at the single neuron level, but do not rule out that the factors may act indirectly on neurons, particularly in complex in vitro and in vivo situations.