Raphe nuclei

Infobox Brain
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Latin = nuclei raphes
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Caption = Section of the medulla oblongata at about the middle of the olive. (Raphe nuclei not labeled, but 'raphe' labeled at left.)


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MeshName = Raphe+Nuclei
MeshNumber = A08.186.211.132.659.632
DorlandsPre = n_11
DorlandsSuf = 12582773
The raphe nuclei (Latin: raphe = 'seam'; nuclei = cell 'clusters'; pronounced RAY-fee) are a moderate-size cluster of nuclei found in the brain stem. Their main function is to release serotonin to the rest of the brain. [cite book
editor = George J. Siegel
others = Bernard W. Agranoff, Stephen K. Fisher, R. Wayne Albers, Michael D. Uhler
title = Basic Neurochemistry
url = http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=bnchm
edition = Sixth
year = 1999
publisher = Lippincott Williams and Wilkins
id = ISBN 0-397-51820-X
chapter = Understanding the neuroanatomical organization of serotonergic cells in brain provides insight into the functions of this neurotransmitter
chapterurl = http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Search&db=books&doptcmdl=GenBookHL&term=raphe+AND+serotonin+release+AND+bnchm%5Bbook%5D+AND+160428%5Buid%5D&rid=bnchm.section.946#949
quote = In 1964, Dahlstrom and Fuxe (discussed in [2] ), using the Falck-Hillarp technique of histofluorescence, observed that the majority of serotonergic soma are found in cell body groups, which previously had been designated as the raphe nuclei.] Selective serotonin reuptake inhibitor (SSRI) antidepressants are believed to act in these nuclei, as well as at their targets. [cite journal | last = Briley | first=M | year=1993 |month=October |title = Neurobiological mechanisms involved in antidepressant therapies | journal = Clin Neuropharmacol | volume = 16 | issue = 5 | pages = 387–400 | url = [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=8221701&query_hl=14&itool=pubmed_docsum |doi = 10.1097/00002826-199310000-00002]

Anatomy

The raphe nuclei are traditionally considered to be the medial portion of the reticular formation, and they appear as a ridge of cells in the center and most medial portion of the brain stem.

In order from caudal to rostral, the raphe nuclei are known as the "nucleus raphe obscurus", the "raphe magnus", the "raphe pontis", the "raphe pallidus", the "nucleus centralis superior", "nucleus raphe dorsalis", "nuclei linearis intermedius" and "linearis rostralis". [cite web
year = 1998 | format = GIF
url = http://www.hallym.ac.kr/~de1610/nana/5-5.gif
title = Fig. 5. The midsagittal section of the brain stem indicating the position of the raphe nuclei
accessdaymonth = 18 April
accessyear = 2006] Some scientists chose to group the linearis nuclei into one nucleus, shrinking the number of raphe to seven, e.g.,
NeuroNames makes the following ordering: [BrainInfo|ancil|190]
* Raphe nuclei of medulla
** Nucleus raphe obscurus ("nucleus raphe obscurus")
** Nucleus raphe magnus ("raphe magnus")
** Nucleus pallidus ("raphe pallidus")

* Raphe nuclei of the pontine reticular formation
** Pontine raphe nucleus ("raphe pontis")
** Inferior central nucleus

* Raphe nuclei of the midbrain reticular formation
** Superior central nucleus ("nucleus centralis superior")
** Dorsal raphe nucleus ("nucleus raphe dorsalis")

Projections

All of these nuclei have fascinating interactions with almost every pertinent portion of the brain, but only a few of them have specifically independent interaction worth exploring in their own right. These select nuclei are discussed as follows.

Overall, the caudal raphe nuclei, including the raphe magnus, pallidus and raphe obscurus, all project towards the spinal cord and brain stem. The more-rostral nuclei, including the raphe pontis, centralis (also called median), dorsal, tend to project towards the brain areas of higher function. [cite web
author = BilZ0r | coauthors = Erowid | year = 2005
url = http://www.erowid.org/psychoactives/pharmacology/images/pharmacology_article2-4-med.png title = Figure 4. Diagram of the human brain showing the divergent serotonergic projections of the raphe nuclei to both cortical and subcortical locations throughout the brain.
format = PNG
work = The Neuropharmacology of Hallucinogens: a technical overview
publisher = Erowid Pharmacology Vaults
accessmonthday = April 18
accessyear = 2006]

The 7 raphe nuclei receive afferent connections from some of the most fascinating spots in the brain, only to project back to them and alter their processes.

Function

The raphe nuclei have a vast impact upon the central nervous system.The raphe nuclei can be of particular interest to neurologists and psychologists since many of the neurons in the nuclei (but not the majority) are serotonergic, i.e., contain serotonin - a type of monoamine neurotransmitter.Serotonin, also called 5-HT, seems to be the culprit in many of our modern psycho-pharmaceutical problems, such as anorexia, depression, and sleep disorders. It is not the sole culprit in the aforementioned disorders, but it is the area that the pharmacologists know how to affect in the best manner. It is important to note that pharmacology traditionally affects global serotonin levels, while the actions of the raphe nuclei are dependent on the complex interplay between nuclei.

Projections from the raphe nuclei also terminate in the dorsal horn of spinal gray matter where they regulate the release of enkephalins, which inhibit pain sensation.

Further reading

* cite web
last = Currie | first = David | year = 2005
url = http://faculty.etsu.edu/currie/ras.htm
title = A Lecture, Higher Brain Function: Activation of the Brain and Levels of Consciousness
publisher = East Tennessee State University
accessmonthday = April 18
accessyear = 2006
* cite journal
last = Sari | first = Youssef | year = 2004 | month = October
title = Serotonin_1B receptors: from protein to physiological function and behavior
journal = Neuroscience & Biobehavioral Reviews
volume = 28 | issue = 6 | pages = 565–582
doi = 10.1016/j.neubiorev.2004.08.008
url = http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T0J-4DPCHW4-2&_coverDate=10%2F01%2F2004&_alid=299916628&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=4864&_sort=d&view=c&_acct=C000002898&_version=1&_urlVersion=0&_userid=27541&md5=ed404d8b8b83823517993851bd03c937
accessdate = 2006-04-18

=Additional

References

See also

* Locus ceruleus
* Substantia nigra
* Pedunculopontine nucleus
* List of regions in the human brain