Serotonin neurons (5-HT) in the brain
The source nuclei for the serotonin neurons are located in the Raphe nuclei in the pons and medulla. These project throughout the brain, brain stem and spinal cord.
The serotonergic pathways spread extensively throughout the brainstem,
Outside the brain, serotonin is involved in regulation of the gastrointestinal and cardiovascular system.