Growth cones of chick sympathetic preganglionic neurons in vitro interact with other neurons in a cell-specific manner.

The ability of the growth cones of sympathetic preganglionic neurons to recognize the neurons they encounter during their outgrowth and to react to them in a cell-type-specific manner may play a role in guiding them to appropriate targets during development in vivo. In this study, we examined the in vitro growth of sympathetic preganglionic neurons as they interacted with motor neurons, dorsal root ganglion neurons, and sympathetic ganglion neurons. All of these cell types might potentially be encountered by a growing preganglionic axon. The interaction of sympathetic preganglionic growth cones with each cell type was distinct. Sympathetic preganglionic growth cones fasciculated on motor-neuron neurites, collapsed after contact with the cell bodies and neurites of dorsal root ganglion neurons, and grew across the cell bodies and neurites of sympathetic ganglion neurons. These cell-type-specific responses stand in contrast to the collapse and retraction reported to be the most common growth-cone behaviors that result from contact between central and peripheral neurons in vitro and suggest that contact-mediated recognition might be sufficient for growth to and interaction with appropriate targets.