dorsal raphe nucleus

Extending from the anterior part of the pons through the mesencephalon, the dorsal raphe nucleus is a large raphe nucleus whose neurons are serotoninergic. It is organised into rostral and caudal subdivisions, and the rostral aspect is divided further into interfascicular, ventral, ventrolateral, and dorsal subnuclei. Those subdivisions are not merely descriptive: the projections of the dorsal raphe vary topographically, so the subnuclei differ from one another in where their fibres terminate. An increased number of cells in the lateral aspects of the nucleus is characteristic of humans and other primates. It is recorded under the designation cell group b7 and classified as a nucleus of the midbrain reticular formation.