Abstract
Survival and development of chick ciliary ganglion neurons in vivo appear to depend on information from the embryonic eye structure that contains the postsynaptic targets of the neurons. We have tested embryonic eye extracts on ciliary ganglion neurons in dissociated cell culture for stimulation of growth and development. Control conditions were chosen that permitted the long term maintenance of the neurons in the absence of tissue extracts of conditioned medium. The conditions included coating the culture substratum with fibroblast material and increasing the K+ concentration in the culture medium to 25 mM. Neurons survived for at least 3 weeks in control conditions. Two major components were resolved in eye extracts that stimulated growth and development of the neurons above the basal levels obtained with control conditions. One component, with an apparent molecular weight of about 2 X 10(4) by gel filtration analysis, stimulated neuronal growth without increasing the levels of choline acetyltransferase activity per neuron. The second component, with an apparent molecular weight of about 5 X 10(4), increased development of choline acetyltransferase levels per neuron but had no effect on neuronal growth. Both components were effective in normal K+ as well as 25 mM K+. These components may represent mechanisms by which the postsynaptic target tissue acts in vivo to direct the growth and development of ciliary ganglion neurons.