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

Transient appearance of immunoreactivity for Ca-binding protein (spot 35-calbindin) in small principal neurons in the superior cervical ganglion of pre-weanling rats

Immunoreactivity for rat cerebellar calbindin, termed spot 35-calbindin, is transiently expressed largely in numerous small principal neurons of the superior cervical ganglion in pre-weanling rats and disappears by the fourth postnatal week. Preganglionic denervation results in a slower rate of disappearance of the immunoreactivity in ganglion neurons. This finding suggests that small principal neurons in the superior cervical ganglion may exert some yet to be determined Ca-mediated functions that are not shared with larger neurons at the pre-weanling stage.

Tryptophan hydroxylase activity in hypothalamus and brainstem of neonatal and adult rats treated with hydrocortisone or parachlorophenylalanine

The present study has been undertaken to determine whether glucocorticoid, and parachlorophenylalanine (PCPA, a tryptophan hydroxylase inhibitor) affects tryptophan hydroxylase (TPH) levels in brainstem and hypothalamus of neonatal and adult rats. Our results show that: (1) administration of hydrocortisone causes small but significant increases in TPH activity of neonatal brainstem: (2) treatment with PCPA plus glucocorticoid results in a marked decrease of TPH activity in brainstem and hypothalamus of both neonatal and adult rats.

Division of small intensely fluorescent cells in neonatal rat superior cervical ganglion is inhibited by glucocorticoids

Postnatal genesis of small, intensely fluorescent cells was studied in the rat superior cervical ganglion by combining immunocytochemistry of tyrosine hydroxylase with tritiated thymidine autoradiography. After injection of tritiated thymidine during the first postnatal week, silver grains were observed over the nuclei of many small cells with intense staining for tyrosine hydroxylase, suggesting that SIF cells are dividing postnatally. Cell counts in ganglia of rats sacrificed 2 h after tritiated thymidine showed that the rate of SIF cell proliferation was highest during the first postnatal week with approximately 20% of SIF cells dividing and that the rate declined thereafter. Counts of labeled SIF cells at 30 days in rats injected with tritiated thymidine on days 0, 2, 4, 6, 8, 10 or 14 revealed a peak of SIF cell birthdays on day 8. In these long-survival experiments, many labeled SIF cells were present in adult superior cervical ganglions. In contrast, only one labeled principal neuron was observed in a total of 450 sections. Glucocorticoid treatment of the rats during the first postnatal week paradoxically increased the number of SIF cells, but inhibited the rate of SIF cell proliferation. Dividing SIF cells immunoreactive for both tyrosine hydroxylase and phenylethanolamine N-methyltransferase were observed in glucocorticoid-treated rats. These observations suggest that many SIF cells are dividing during the first postnatal week. After cessation of division, these cells either remain SIF cells or die, but do not differentiate into principal neurons. Since glucocorticoids do not stimulate SIF cell proliferation, they must increase the number of SIF cells by biasing the differentiation of precursor cells in the superior cervical ganglion and/or enhancing SIF cell survival.

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.

Effect of pre- and/or postganglionic nerve division on hydrocortisone-induced small intensely fluorescent cells in the rat superior cervical ganglion

Daily hydrocortisone injections into newborn rats cause in a week about a 10-fold increase in the number of small intensely fluorescent cells in the superior cervical ganglion of the rat, as compared with untreated rats of the same age. The glucocorticoid-induced increase in the number of small intensely fluorescent cells is reversible. After discontinuation of the glucocorticoid treatment there is a significant decrease in the number of these cells during the 2nd postnatal week. The purpose of the present study was to investigate the significance of the innervation of the superior cervical ganglion on the fate of newly formed, hydrocortisone-induced small intensely fluorescent cells after discontinuation of the hydrocortisone treatment. Three-day-old rats were injected daily with hydrocortisone for 7 days. At the age of 10 days the pre- and/or postganglionic trunk(s) on one side were divided and the contralateral side served as control. Seven or thirty days after discontinuation of the hydrocortisone injections and the operation (i.e. at the age of 17 or 40 days) the rats were killed and the small intensely fluorescent cells were counted. The number of small intensely fluorescent cells, as expected, was greatly increased by the hydrocortisone injections. However, discontinuation of the treatment resulted in a decrease in the number of these cells in unoperated 40-day-old rats to a level, which is significantly less than the mean cell number/ganglion in totally untreated adult rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of hydrocortisone on immunohistochemically demonstrable phenylethanolamine-N-methyltransferase in cultures of embryonic and postnatal superior cervical ganglia

Pre- and postnatal superior cervical ganglia of the rat were cultured in Rose chambers for 1-7 days with or without hydrocortisone. Phenylethanolamine-N-methyltransferase (PNMT) was demonstrated by indirect immunofluorescence technique. In cultures without added hydrocortisone, no cells or fibres showed PNMT-immunoreactivity, without regard to the time in culture or the developmental stage at the time of explantation. The first PNMT-immunoreactive cells in hydrocortisone-containing cultures appeared 3 days after the explantation of E14 ganglia, or 1 day after the explantation of E15 ganglia, i.e. at the developmental stage E16-E17. The cultures of neither E14 nor E15 ganglia showed marked fibre growth from the PNMT-immunoreactive cell bodies. On the other hand, in the hydrocortisone-containing cultures of newborn or postnatal rats, there was extensive nerve fibre formation from the PNMT-immunoreactive cells in the course of the culture. PNMT-immunoreactive cells did not appear in hydrocortisone-containing cultures of ganglia taken from rats older than 17 postnatal days.