ADRENAL-MEDULLARY GANGLION NEURONS PROJECT INTO THE SPLANCHNIC NERVE

Retrograde tract-tracing was used to study the projections of adrenal medullary ganglion neurons. The splanchnic nerve was cut close to the suprarenal ganglia and the retrograde tracer FluoroGold was applied at the site of nerve transection. Groups of adrenal medullary ganglion n eurons exhibited FlurorGold- or Fast Blue-induced fluorescence restric ted to the perikarya. Using immunohistochemistry most retrogradely lab elled ganglion neurons showed immunoreactivity for neuropeptide Y. In addition, after splanchnicotomy most ganglion neurons expressed galani n and galanin message-associated peptide immunoreactivities which coul d not be observed in control adrenals. Taken together, the present res ults strongly indicate that adrenal medullary ganglion neurons project back into the splanchnic nerve perhaps representing feedback system m odulating the preganglionic innervation of the adrenal gland.