Reversible developmental change in the ability of ciliary ganglion neurons to extend neurites in culture.

From stages 35 to 40 in the chicken embryo, ciliary ganglion neurons undergo a developmental change which is detected in our assay system as a marked decline in the ability to extend neurites when placed in culture. This developmental loss is observed when the neurons are placed in culture as single, dissociated cells or as undissociated ganglion explants. The loss of the ability to extend neurites in culture is not a transitory phenomenon, for no recovery of this ability is observed during the rest of embryonic development or posthatching. There is a close temporal correlation between the embryonic period during which the ability of ciliary ganglion neurons to extend neurites declines and the period (stages 35 to 40) when these neurons form functional peripheral synapses in the embryo. The ability to extend neurites rapidly is not recovered during normal development as long as the ganglion and its connections within the organism remain intact. However, if the ciliary ganglia are removed from a stage 40 embryo and cultured for 3 to 4 days before being dissociated, the neurons have largely recovered their ability to initiate neurite outgrowth rapidly. This recovery after removal from the embryo is also presumably responsible for the eventual dense outgrowth of neurites from stage 40 ganglion explants after a 3- to 4-day delay in culture. Our results, in conjunction with similar results from other systems, suggest a cause and effect relationship between the establishment or disruption of peripheral connections and the loss or recovery, respectively, of the ability to extend neurites rapidly.