Effect of pre- and postganglionic nerve divisions on normal postnatal and hydrocortisone-induced development of small intensely fluorescent cells in rat superior cervical ganglion.

The left superior cervical ganglion of 3- or 23-day-old rats was subjected to pre- and/or postganglionic nerve division or sham operation, while the right ganglion was left intact. The animals were killed 20 or 60 days after the operation. Some animals were injected with 20 mg/kg hydrocortisone daily for 7 days and killed on the 8th day. Fluorescence microscopical examination revealed a normal postnatal increase in the number of small intensely fluorescent cells/ganglion after pre- or postganglionic nerve division, in spite of marked decreases in the volume of the operated ganglia. Combined pre- and postganglionic nerve division, which caused a dramatic loss of ganglion volume, entirely prevented the postnatal increase in the number of small intensely fluorescent cells. Hydrocortisone caused a large increase in the number of small intensely fluorescent cells both in intact and operated ganglia, including those in whom both pre- and postganglionic nerves had been divided. It is concluded that combined pre- and postganglionic denervation, in contrast to either operation alone, prevents the normal proliferation of the small intensely fluorescent cells possibly by causing an extensive loss of principal nerve cells which deprives the small intensely fluorescent cells of their normal contacts with the principal cells. Since the increase in the number of small intensely fluorescent cells due to hydrocortisone injections was not prevented by pre- and postganglionic denervation it must be due to a mechanism different from that responsible for the formation of small intensely fluorescent cells during normal postnatal development.