Dorsal Raphe Nucleus - Serotonin

Serotonin

The dorsal raphe is the largest serotonergic nucleus and provides a substantial proportion of the serotonin innervation to the forebrain.

Serotonergic neurons are found throughout the dorsal raphe nucleus and tend to be larger than other cells. A substantial population of cells synthesizing substance P are found in the rostral aspects, many of these co-express serotonin and substance P. There is also a population of catecholamine synthesizing neurons in the rostral dorsal raphe, and these cells appear to be relatively large.

The dorsal raphe nucleus is rich in pre-synaptic serotonin 5-HT_1A autoreceptors, and it's believed that the action of the selective serotonin reuptake inhibitors (SSRIs) in this region is responsible for the latency of their antidepressant effect.