Raphespinal tract

[2][3][4] Fibers descend in the ventral portion of the lateral funiculus, mainly bilaterally to terminate in laminae I, II, and IV.[1] The tract emerges from three of the raphe nuclei, the magnus, obscurus, and pallidus.When raphe nuclei are stimulated they release serotonin which modulates the transmission of pain.[1][2] Pain pathways converging upon the raphe nuclei to modulate pain via the raphespinal tract include: Electrical stimulation of either the periaqueductal gray or (its downstream target) nucleus raphe magnus induces profund analgesia; this effect can be abolished both by transection of the raphespinal tract as well as by opioid receptor antagonists (evidencing one of the mechanisms by which opioid bring about pain relief).An electrical stimulator implant of the periaqueductal gray can be used clinically for pain management, evoking instantaneous pain relief upon activation.
Anatomical terminologyspinal cord tractmedulla oblongatalateral funiculusFiberslaminaeraphe nucleimagnusobscuruspallidusserotoninLaminae I and Vspinomesencephalic tractperiaqueductal graynucleus raphe magnusmesencephalonNociceptivegroup Cnerve fiberinterneuronslamina II (substantia gelatinosa)lamina IIIposterior grey columnlaminae V-VIIIspinoreticular tractgigantocellular raphe nucleusspinal trigeminal nucleusserotonergicenkephalinergicanalgesiaopioid receptor antagonistsopioidspasticityDorsolateral pontine reticular formation