Monoamine-containing paraneurons in the sympathetic ganglia of mammals.

1. A combined method for glyoxylic acid induced catecholamine fluorescence and electron microscopy was introduced in this study of the small intensely fluorescent (SIF) or granule-containing (GC) cells of the sympathetic ganglia. 2. Adrenergic interneurons were demonstrated in the sympathetic ganglia of the rat and the rhesus monkey. 3. Existence of adrenergic paraneurons (neuro-endocrine cells) in the sympathetic ganglia of several mammalian species was suggesed by the following observations: a) catecholamines are contained in the granular vesicles of SIF cells; b) SIF cells are innervated by preganglionic cholinergic nerves and are often in close relation with fenestrated capillaries; c) SIF cells develop from the neuroblast which originated from the neural crest, and ; d) substantial surface areas of GC cells are covered by basal lamina alone. Figures indicating exocytosis of granular vesicles were often seen here. 4. There are remarkable species differences in quantity and quality of SIF cells and great discrepancies among the physiological, biochemical and the morphological observations on SIF cells.