Survival and development of ciliary ganglion neurones grown alone in cell culture

Abstract

NEURONAL cell death is a conspicuous part of development for many neuronal populations in the vertebrate nervous system^1,2. Although little is known about the mechanisms that control neurone death, it seems that interactions with the postsynaptic target tissue are important. Thus, for the chick ciliary ganglion (CG), Landmesser and Pilar showed that half of the neurones present die between days 8 and 13 in the embryo. Before cell death, all the neurones extend processes to the periphery. Ablating the periphery early in development causes more than 90% of the neurones to die at the normal time³. We have previously shown that nearly all the neurones from chick CG, including those destined to die in vivo, can survive and develop in cell culture when ganglia from 8-d-old embryos are dissociated and grown with skeletal myotubes⁴. Many of the neurones innervate myotubes in these conditions. Are neuromuscular synapses necessary to prevent the death of ciliary ganglion neurones? We report here that they are not. Culture medium conditioned by contact with heart or skeletal muscle cells permits complete long-term survival of the dissociated neurones grown in the absence of other cell types. The neurones develop levels of choline acetyltransferase (CAT) activity comparable to those obtained for neurones grown with myotubes.