Catecholamines in paraganglionic cells of the rat superior cervical ganglion: functional aspects

In the rat SCG two types of paraganglionic cells have been identified immunohistochemically in a ratio of about 5% DBH-positive to 95% DBH-negative cells. Measurements of CAs in SIF cell clusters separated from principal neurons with the microlaser and using the technique of quantitative mass fragmentography disclosed the presence of E within paraganglionic cells, thus confirming the proposal that, besides DA, E also is stored in most cells. Following immobilization of adult rats, the majority of SIF cells revealed a time-dependent loss of formaldehyde-induced fluorescence intensity that could be ultrastructurally correlated with an increasing degranulation of small granule-containing perikarya, presumed to store DA and E. Similar results were obtained in type I cells of the rat carotid body and adrenal medullary cells, thus suggesting a mutual endocrine function. An additional interneuronal mode of modulation is assumed, since degranulated cells are capable of displaying efferent synaptic contact with postganglionic neurons. A minor cell population, storing granular vesicles similar to those in the NE-containing cells of the adrenal medulla, did not respond with degranulation to functional strain of the vegetative nervous system. Our results strongly corroborate the hypothesis that a functional dualism exists: Most paraganglionic cells can act as an interneuron and as an endocrine cell.