Age-related morphometric and histochemical features of rat sympathetic neurons

The correlation between catecholamine histofluorescence, tyrosine hydroxylase (TH) immunoreactivity and accumulation of age pigment was studied in the superior cervical ganglia (SCGL) of young (3 months) and old (28 months) rats. In the young animals there was a positive correlation between TH-immunoreactivity and catecholamine stores in most of the neurons. A pigment accumulation covering the profile area was found in approximately 10 per cent of the neurons in the young rats. In these neurons strong TH-immunoreactivity was associated with weak catecholamine histofluorescence. In the ganglia of the old animals there were considerable differences between individual cells in TH-activities, catecholamine stores and amounts of age pigment. In addition, there was a marked uncoupling between TH-activity and catecholamine fluorescence in a number of neurons, i.e. there were neurons with strong TH-immunoreactivity but weak catecholamine histo- fluorescence and vice versa. The functional implications of this uncoupling are discussed in the article.