THE SPINAL SYMPATHETIC PREGANGLIONIC CELL COLUMN IN THE PUFFER FISH, TAKIFUGU NIPHOBLES

Little is known about the spinal sympathetic organization in teleosts. We examined the location of the sympathetic preganglionic neurons wit h horseradish peroxidase (HRP) labeling. After HRP application to the sympathetic trunk or celiac ganglion, labeled neurons were found just dorsal - dorsolateral to the central canal. They form a cell column (c entral autonomic nucleus) at the level of the posterior rootlet of the first spinal nerve to the third spinal nerve. HRP application to the sympathetic trunk produced labeling in almost the entire central auton omic nucleus, but HRP application to the celiac ganglion produced labe ling in only the rostral half of the central autonomic nucleus. These results suggest that there is some topographical arrangement in the ro strocaudal part of the central autonomic nucleus. On the other hand, t he fact that the sympathetic preganglionic neurons are within a single cell column and have no mediolateral segregation means that the targe t-related or function-associated mediolateral arrangement found in tet rapods is lacking in this species. We also found some labeling in the central autonomic nucleus after HRP application to the cranial nerves. This may indicate that the preganglionic neurons project to the crani al nerves.