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Dorsal raphe nucleus

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Brain: Dorsal raphe nucleus
Outline of the nucleus raphe dorsalis: DRif interfascicular subnucleus, DRv ventral subnucleus, DRvl ventrolateral subnucleus, DRd dorsal subnucleus, mlf medial longitudinal fasciculus, Aq cerebral aqueduct, IVn trochlear nucleus.
Latin nucleus raphe posterior, nucleus raphe dorsalis
Gray's subject #
Part of
BrainInfo/UW hier-503
MeSH [2]

The dorsal raphe nucleus is a part of the raphe nucleus and consists of rostral and caudal subdivisions.



Serotonin Edit


Serotonergic neurons are found throughout the dorsal raphe nucleus and tend to be larger than other cells. A substantial population of cells synthesising substance P are found in the rostral aspects, many of these co-express serotonin and substance P. There is also a population of catecholamine synthesising neurons in the rostral dorsal raphe, and these cells appear to be relatively large.[2]

The nucleus raphe dorsalis is rich in serotonin 5-HT1a autoreceptors and it is believed that it is the action of serotonin-specific reuptake inhibitors (SSRIs) in this region that is responsible for the latency of SSRI antidepressant effect.[3]


Ten percent of the axons from the nucleus raphe dorsalis have been shown to project to the amygdala,[4] while only medium cells seem to project to the caudate and putamen.[5]

Role in naloxone-induced morphine withdrawalEdit

The nucleus raphe dorsalis has also been implicated in naloxone-induced morphine withdrawal. It is known that endogenous opiate receptors exist on the nucleus raphe dorsalis, and that it is a focal point as an ascending and descending regulator. Pourshanazari et al showed in their 2000 paper that electrical stimulation of the nucleus raphe dorsalis can partially alleviate morphine withdrawal symptoms via electrical stimulation of the raphe nucleus in question.[6]

These are fascinating results; however no control was provided for the spread of electrical charge to other parts of the brain stem. It is quite possible that the charge spread to the nucleus raphe magnus and induced analgesia upon the rats. Knowing that the spread of charge across such a short area is very plausible, as is an alternate connection to the raphe magnus, these results could be called into question.

Role in narcolepsyEdit


See alsoEdit

References Edit

  1. O'Hearn E, Molliver ME. Organization of raphe-cortical projections in rat: a quantitative retrograde study. Brain Res Bull. 1984 Dec;13(6):709-26.
  2. Baker KG, Halliday GM, Hornung J-P, Geffen LB, Cotton RGH, Tork I. Distribution, morphology and number of monoamine-synthesizing and substance P-containing neurons in the human dorsal raphe nucleus. Neuroscience. 1991;42(3):757-75.
  3. Briley M, Moret C. Neurobiological mechanisms involved in antidepressant therapies. Clin Neuropharmacol. 1993 Oct;16(5):387-400.
  4. Ma QP, Yin GF, Ai MK, Han JS. Serotonergic projections from the nucleus raphe dorsalis to the amygdala in the rat. Neurosci Lett. 1991 Dec 16;134(1):21-4.
  5. Steinbusch HW, Nieuwenhuys R, Verhofstad AA, Van der Kooy D. The nucleus raphe dorsalis of the rat and its projection upon the caudatoputamen. A combined cytoarchitectonic, immunohistochemical and retrograde transport study. Journal of Physiology (Paris). 1981;77(2-3):157-74.
  6. Pourshanazari, A.A. ; Alaei ; Rafati ; Effects of Electrical Stimulation of Nucleus Raphe Dorsalis on initiation of morphine self administration in rats. Medical Journal of Islamic Academy of Sciences 13:2, 63-67, 2000)
  7. Wu et al. Activity of Dorsal raphe cells across the sleep-waking cycle during cataplexy in narcoleptic dogs. Journal of Physiology. 2004 Jan 1;554 (Pt 1):202-15)[1].

Mesencephalon (midbrain)


tectum: corpora quadrigemina, inferior colliculi, superior colliculi



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