An electron microscopic study of neurosecretion in the cerebral ganglion of the earthworm.

Non-synaptic, exocytotic release of neurosecretory granules in cerebral ganglion neurons was observed electron microscopically in 3 species of the oligochaete annelids Aporrectodea caliginosa, Octolasion cyaneum and Lumbricus terrestris. In addition to the features indicating exocytotic release of neurosecretory granules into perineuronal space, possible features of neurosecretion into blood vessels were seen within the cerebral ganglion. Axon terminals in synaptic contact with perikaryal profiles of cerebral ganglion neurons were also found.