Ultrastructural and immunocytochemical characterization of the rat non-preganglionic Edinger-Westphal nucleus.

The rodent non-preganglionic Edinger-Westphal nucleus (npEW) is involved in the stress adaptation response. Here we describe the ultrastructural organization of this nucleus in the unchallenged rat, using different tissue fixation and embedding methods, and postembedding immunogold labeling. In this way we have (1) identified Ucn1-immunopositive neurons, (2) described the ultrastructure of these neurons with focus on cell organelles involved in secretion (rough endoplasmic reticulum, Golgi apparatus, secretory granules), (3) demonstrated the subcellular coexistence of Ucn1 with cocaine- and amphetamine-related transcript peptide, and (4) classified various morphological types and configurations of synaptic contact present in the npEW and, specifically, on the npEW-Ucn1 neurons. The data obtained provide the morphological basis for future studies on the plastic effects of acute and chronic stressors as well as feeding conditions specifically affecting the secretory activity of npEW-Ucn1 neurons.