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 mi dline of the dorsal surface of the sixth abdominal (A6) ganglion of th e adult cockroach Periplaneta americana has been characterized by dire ct anterograde cobalt chloride staining. These neurons, identified as dorsal unpaired median (DUM) neurons: present a T-shaped morphology. T he soma gives rise to a single primary neurite running anteriorly in t he ganglion before dividing into two lateral neurites which run into t he left and the right side of the ganglion. A characteristic dendritic arborization arises from the lateral neurites within the ganglion. Th is major branching pattern is mainly located at the periphery of the A 6 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 experimenta l conditions, we show that cultured adult DUM neurons can survive for several weeks, and regenerate a single primary neurite dividing into t wo symmetrical lateral neurites with a number of fine processes radiat ing from the endings. This corresponds to the typical DUM neuron morph ology revealed in situ on the same preparation using the cobalt chlori de staining technique. This culture system developed for the first tim e on A6 ganglia adult DUM neurons will allow a better understanding of the physiological intracellular mechanisms involved in the neurosecre tory functions of DUM neurons, which are currently unknown.