Contralateral projections by preganglionic neurons to the sympathetic trunk of the puffer fish, Takifugu niphobles

Previous studies have shown that the sympathetic preganglionic neurons of teleosts send axons to the sympathetic trunk on the contralateral side. After severing the spinal nerve roots at a level proximal to the sympathetic ganglia (i.e., nerve roots containing the preganglionic axons) on one side of puffer fish, Takifugu niphobles, horseradish peroxidase was applied to the other side of the sympathetic trunk. Retrogradely labeled sympathetic preganglionic neurons were found bilaterally in the central autonomic nucleus (a distinct cell column in the rostral part of the spinal cord). The contralaterally labeled neurons were located almost exclusively in the caudal part of the nucleus. These results suggest that some sympathetic preganglionic neurons in teleosts, unlike those in other vertebrates, send their axons across the midline to the contralateral nerve roots. (C) 1997 Elsevier Science B.V.