Tryptophan hydroxylase activity and 5-hydroxytryptamine-immunoreactive cells in the superior cervical ganglion of hydrocortisone-treated neonatal rats.

Early postnatal glucocorticoid injections led to a large increase in the number of 5-hydroxytryptamine(5-HT)-immunoreactive small cells in the rat superior cervical ganglion. Tryptophan hydroxylase (TPH) activity in ganglia from animals treated with glucocorticoids was not significantly different from saline-injected controls. Both 5-HT immunoreactivity and TPH activity were decreased in ganglia from animals treated with glucocorticoid and the TPH inhibitor parachlorophenylalanine, but not in animals treated with 5-HT uptake inhibitor fluoxetine. These results suggest that 5-HT is synthesized in the small intensely fluorescent (SIF) cells.