[Cytoarchitecture of the nucleus raphe dorsalis of the rat]

The nucleus raphe dorsalis of the rat was investigated by means of the Golgi rapid impregnation technique: a) Type 1 neurons: polygonal neurons with somatic spines. The axons which course towards the ventral tegmental area, there by giving off a few collaterals. b( Type 2 neurons: fusiform neurons the axons of which course in a latero-dorsal direction, emitting a few collaterals, too. c) Type 3 neurons: small pyriform neurons. The axons of these cells do not show any favoured route within the nucleus. The type 1 and type 2 neurons are considered to be efferent neurons having different modes of projection and termination. The type 1 neurons are supposed to represent the 5-HT ergic raphe dorsalis neurons. The type 3 neurons, are in probability, raphe interneurons. The findings presented here are indicative of the nucleus raphe dorsalis of the rat to have a more intricate cytoarchitecture as has been thought previously.