Ultrastructural features and acetylcholinesterase histochemistry of the rat habenular complex

The ultrastructural features and the acetylcholinesterase (AChE) localization of the rat habenula have been studied. On the basis of different morphology and AChE content, it is suggested that at least two types of neurons are present in the medial habenula (MHb) and three types of neurons in the lateral habenula (LHb). In particular, actively AChE-synthesizing neurons have been noticed in both LHb and MHb. Some unusual ultrastructural arrangements of the endoplasmic reticulum have been described in habenular neurons. Finally, the most common types of synaptic contacts present in the habenular complex have been surveyed.