Motoneuron morphology and synaptic contacts: determination by intracellular dye injection.

The structure and dendritic connections of an identified crustacean motoneuron were analyzed by intracellular injection of dye. Some processes of the neuron end in the ganglionic neuropil, but most terminate on axons which pass through the ganglion in specific, identifiable tracts. The former processes are ipsilateral to the soma, while the latter, as well as their connections, display bilateral symmetry. Structural and functional evidence suggests that the demonstrated contacts are synaptic junctions, and that the approach can therefore be used to study patterns of synaptic organization in complex neural networks.