Intensely fluorescent cells in embryonic and postnatal superior cervical ganglia of the rat cultured with or without hydrocortisone.

Pre- and postnatal superior cervical ganglia of the rat were cultured in Rose chambers for 1-7 days with or without hydrocortisone. Fibre growth of the principal nerve cells was observed by phase contrast microscopy, and the explants were then processed for formaldehyde-induced catecholamine fluorescence. The ganglia of 13-day-old embryos cultured for 7 days in the control medium did not show fibre growth and contained only one type of fluorescent cells, the weakly fluorescent, presumably principal nerve cell, while in the older ganglia the principal nerve cells formed a fibre network, and the ganglia also contained a few small intensely fluorescent cells some of which had short processes. The ganglia of 15-day-old embryos and newborn rats cultured for 1 day in a control medium contained cells that showed a continuous range of weak through bright fluorescence. In the course of the culture, the cells of intermediate fluorescence intensity disappeared, and the number of the intensely fluorescent cells greatly decreased, more slowly in the newborn than in the embryonic ganglia. The intensely fluorescent cells in the newborn, but not those in the embryonic ganglia transiently produced marked fibre growth within the explants. All embryonic ganglia and 6-day-old or younger postnatal ganglia cultured in hydrocortisone-containing medium for 7 days showed a much greater number of intensely fluorescent cells than the corresponding control ganglia. Examination of the cultures 1, 2, 4, or 7 days after the explantation showed that in both pre- and postnatal ganglia hydrocortisone resulted in the appearance of both neuroendocrine and fibre-growing types of intensely fluorescent cells. These observations support the idea that during a limited period of pre- and postnatal development, the sympathetic ganglia contain a population of cells which are able to change their phenotype in the presence of glucocorticoids.