CONTRALATERAL PROJECTIONS BY PREGANGLIONIC NEURONS TO THE SYMPATHETICTRUNK 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 a xons) on one side of puffer fish, Takifugu niphobles, horseradish pero xidase was applied to the other side of the sympathetic trunk. Retrogr adely labeled sympathetic preganglionic neurons were found bilaterally in the central autonomic nucleus (a distinct cell column in the rostr al part of the spinal cord). The contralaterally labeled neurons were located almost exclusively in the caudal part of the nucleus. These re sults suggest that some sympathetic preganglionic neurons in teleosts, unlike those in other vertebrates, send their axons across the midlin e to the contralateral nerve roots. (C) 1997 Elsevier Science B.V.