Number of neurons and dexamethasone-induced SIF cells in developing sympathetic ganglia and in intraocular ganglion transplants.

Daily dexamethasone (DM) injections to newborn rats caused in a week an increase in the number of small intensely fluorescent (SIF) cells in the superior cervical ganglion to a value 9 times that in the ganglia of saline-treated controls. The number of SIF cells (per ganglion) decreased in another week both in ganglia transplanted into the anterior chamber of the eye of an adult rat and in intact ganglia of rats allowed to live for another week after discontinuation of the DM treatment. However, in both cases the number of SIF cells was significantly higher than that in the newborn rat ganglia. The number of SIF cells also decreased in transplanted ganglia from saline-treated controls, the number of SIF cells in transplants from DM-treated rats being 10 times as high as that in the transplants from saline-treated rats. The SIF cells formed large clusters in transplants from DM-treated rats and their density (cells/mm3) was significantly higher than that in the ganglia left in situ for one week after discontinuation of the DM treatment. Therefore, visual examination suggested that there is little or no loss of SIF cells due to transplantation. The transplantation caused an over 90% loss of neurons and a marked decrease in ganglion volume.