This is the narrow row of more or less tightly packed neuron groups located in the middle part of the brainstem: the rif nuclei (raphe = middle seam). The raphe nuclei contain virtually all of the central nervous system's approximately 300,000 serotonin (5-HT) producing neurons , which are divided into nine groups; cell groups B1 - B9 (see refs. 11.1, 11.2; also 36 and 37/b).
The row of raphe nuclei, extending throughout the brainstem, can be divided into 8 units, here counting from the medulla oblongata upwards up to and including the mesencephalon.
1. Nucleus raphes pallidus
2. Nucleus raphes obscurus
3. Nucleus raphes magnus
4. Nucleus (raphes) centralis superior Bechterew.
5. Nucleus raphes pontis
6. Nucleus raphes medianus
7. Nucleus raphes dorsalis
8. Nucleus raphes linearis
Most talked about among these are
The nucleus raphes magnus , which gives rise to the tractus raphe-spinalis and has pain-modifying functions.
The nucleus raphes dorsalis with mood-regulating functions and located in the mesencephalon and transmits its filaments via the MFB to the cortex cerebri which in this way becomes more or less completely interwoven by extremely thin serotonin-secreting nerve fibers - the "serotonin irrigation of the cortex cerebri".
Serotoninergic neurons can be extremely richly branched. For example, a single neuron can transmit axon branches both up to areas of the cerebral cortex and down to the sacral spinal cord segments.