Electron microscopic investigation of a giant neuron identified in the right parietal ganglion of Lymnaea stagnalis (L).

The ultrastructure of a giant neuron (GRP1) identified in the right parietal ganglion of Lymnaea stagnalis was examined. The results suggest that GRP1 is a neurosecretory cell. The perikaryon is characterized by many neurosecretory-like granules of variable electron density. The average diameter (longer axis) of the granules was 1850 A. Furthermore highly-developed rough endoplasmic reticulum and Golgi complex were observed in the cytoplasm. Synapse-like structures were often found on the somatic membrane, but typical, true synaptic endings were not seen.