Objective The ultrastructure of the distal CSFcontacting neurons in the dorsal raphe and the relationships with their surrounding tissues were observed and a new morphological evidence for their functional significance was offered. Methods We combined CBHRP tracing with electron microscopic techniques and observed the ultrastructure of the distal CSFcontacting neurons in the dorsal raphe and the relationships with their surrounding tissues. Results 1.The CSFcontacting neurons have the general cytological structure of neurons; 2.CBHRP mainly is localized in the trans face of the Golgi apparatus and lysosomes; 3.There are two kinds of contrary direction synaptic relationships between the distal CSFcontacting neurons and the non CSFcontacting neurons. Conclusions 1.There are no obvious differences between the CSFcontacting neurons and other neurons in ultrastructure; 2. The Golgi apparatus and the lysosomes may exist the special function in take and transport the material from CSF; 3. The CSFcontacting neu