Neurite regeneration of long-term cultured adult insect neurosecretory cells identified as DUM neurons.

A distinctive group of neurons having cell bodies located along the midline of the dorsal surface of the sixth abdominal (A6) ganglion of the adult cockroach Periplaneta americana has been characterized by direct anterogradc cobalt chloride staining. These neurons identified as dorsal unpaired median (DUM) neurons, present a T-shaped morphology. The soma gives rise to a single primary neurite running anteriorly in the ganglion before dividing into two lateral neurites which run into the left and the right side of the ganglion. A characteristic dendritic arborization arises from the lateral neurites within the ganglion. This major branching pattern is mainly located at the periphery of the A6 ganglion and forms a symmetrical complicated network. A new culture procedure of these same adult DUM neurons has been developed from the dissociation of the median parts of the A6 ganglia. In our experimental conditions, we show that cultured adult DUM neurons can survive for several weeks, and regenerate a single primary neurite dividing into two symmetrical lateral neurites with a number of fine processes radiating from the endings. This corresponds to the typical DUM neuron morphology revealed in situ on the same preparation using the cobalt chloride staining technique. This culture system developed for the first time on A6 ganglia adult DUM neurons will allow a better understanding of the physiological intracellular mechanisms involved in the neurosecretory functions of DUM neurons, which are currently unknown.