Fluorescence-histochemical and ultrastructural research on the monoaminergic neurosecretory cells of the earthworm Octolasium complanatum (Annelida: Oligochaeta).

A study of the yellow fluorescent neurons (M-NSC) of the subesophageal ganglion of the earthworm Octolasium complanatum has been made by using alternate semithin and thin sections in a correlate fluorescence and electron microscopy technique and it results that elementary neurosecretory granules are present where the yellow fluorescent substance is. These granules are similar in size and morphology to the granules of monoamine type. The intimate contact of the capillaries with the granular cytoplasmic area of the M-NSC provides evidence of a probable release of the secretion from the cell body. These results support the hypothesis of the endocrine role of the M-NSC.