My coworker and I recently found a preganglionic autonomic nucleus located in the dorsal gray commissure of the rat spinal cord. The cells of this nucleus, which we termed the dorsal commissural nucleus (DCN), were labeled with the retrograde transport of horseradish peroxidase (HRP). I propose to use this technique to perform a comparative study on a variety of mammals to determine if the DCN is common to this class of animals. Also, the DCN will be examined with fluorescence histochemistry for aminergic terminals which have previously been observed in abundance in the intermediolateral cell colunm. The synaptology of the pelvic ganglion of the rat will be examined with electron microscopy. The relationships of ultrastructural elements identified using anterograde and retrograde transport of HRP and degeneration will be determined.