Figure 2. The Medullary 5-HT System in the Human Brainstem.

The Medullary 5-HT System consists of 5-HT neurons (areas in red) in the midline raphé (i.e., raphé obscurus (Rob), extra-raphé (i.e., (gigantocellularis [GC], paragigantocellularis lateralis [PGCL], intermediate reticular nucleus [IRZ], and at the ventral medullary surface (arcuate nucleus [Arc]) and sites to which they project (blue areas) that do not contain 5-HT neurons but mediate homeostatic functions (e.g., hypoglossal nucleus [HG], nucleus of the solitary tract [NTS]). Figure shows coronal sections at the level of the Caudal, Mid, and Rostral medulla.