Dorsal raphe nucleus

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Dorsal raphe nucleus

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Outline of the nucleus raphes dorsalis:?DRifinterfascicular subnucleus,?DRv?ventral subnucleus,?DRvl?ventrolateral subnucleus,?DRd?dorsal subnucleus,?mlf?medial longitudinal fasciculus,?Aq?cerebral aqueduct,?IVn?trochlear nucleus.

Details

Identifiers

Latin

nucleus raphes posterior, nucleus raphes dorsalis

MeSH

D065847

NeuroNames

512

NeuroLex?ID

birnlex_982

TA98

A14.1.05.604

TA2

5957

FMA

68462

Anatomical terms of neuroanatomy

[edit on Wikidata]

The?dorsal raphe nucleus?is located on the midline of the?brainstem?and is one of the?raphe nuclei. It has rostral and caudal subdivisions.

·?The rostral aspect of the?dorsal?raphe is further divided into interfascicular, ventral, ventrolateral and dorsal subnuclei.

·?The projections of the?dorsal?raphe have been found to vary topographically, and thus the subnuclei differ in their projections.[1]

An increased number of cells in the lateral aspects of the dorsal raphe is characteristic of humans and other primates

(或許對應(yīng)prefrontal ?cortex).

Contents

·?1Serotonin

·?2Projections

·?3Role in naloxone-induced morphine withdrawal

·?4Role in narcolepsy

·?5Role in depression and suicide

·?6See also

·?7References

·?8External links

Serotonin[edit]

The dorsal raphe is the largest serotonergic nucleus and provides a substantial proportion of the serotonin innervation to the forebrain.

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

The dorsal raphe nucleus is rich in?pre-synaptic?serotonin?5-HT1A?autoreceptors, and it's believed that the action of the?selective serotonin reuptake inhibitors?(SSRIs) in this region is responsible for the latency of their antidepressant effect.[3]

Projections[edit]

Ten percent of the axons from the nucleus raphe dorsalis of the rat have been shown to project to the?amygdala,[4]?while only medium cells seem to project to the caudate and putamen and olfactory bulb.[5][6]

Role in naloxone-induced morphine withdrawal[edit]

The nucleus raphes dorsalis has also been implicated in naloxone-induced morphine withdrawal. It is known that endogenous?opioid receptors?exist on the nucleus raphes 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 raphes dorsalis can partially alleviate?morphine?withdrawal symptoms via electrical stimulation of the raphe nucleus in question.[7]

(用來證明我的神經(jīng)系統(tǒng)模型的一個證據(jù))

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 raphes 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 narcolepsy[edit]

Wu M.F.?et al.?studied the nucleus raphes dorsalis as it pertained to?narcolepsy. This is logical, as the raphe nuclei have been known to play a role in the sleep/wake cycle.?Cataplexy?is the symptom of narcolepsy when full awareness of the environment is maintained, but all muscle tone is lost. This has thought to be a dissociation of what normally happens during?REM?sleep, when all muscle tone is lost except for the eyes

（because the muscles controlling eyes are controlled by pontine Ach system,and eyes’weight never change during one’s whole life.）

. The nucleus raphes dorsalis have been known to project to the lateral?hypothalamus

（where the preoptic area is）

, along with the?locus coeruleus?and the?tuberomammillary nucleus. The neurotransmitters of these three aforementioned nuclei, which project to the lateral hypothalamus, are?serotonin,?norepinephrine?and?histamine?respectively. These neurotransmitters are fully active during waking hours, partially active during non-REM sleep, and have almost ceased during REM sleep. In cats with?pontine?lesions, their normal?atonia?is not present, the raphe dorsalis is fully active, as opposed to the cessation of action under normal conditions. A muscle relaxant, known as?Mephenesin, reduces activity of the dorsal nucleus, as well as microinjections of?carbachol?(which induces atonia while awake).[8]

Role in depression and suicide[edit]

The rostral raphe nuclei, both the?median raphe nucleus?and particularly the dorsal raphe nucleus have long been implicated in depression. Some studies have suggested that the dorsal raphe may be decreased in size in people with depression and, paradoxically, an increased cell density in those who die by suicide.[9][10][11]

（People with depression have?decreased dorsal raphe, so their brain's norepinephrine and acetylcholine level is relatively high, thus the thalamic reticular formation still works ,?which means they still show avoiding behavior;?People?who die by suicide have increased?dorsal raphe, so their?brain's norepinephrine?and acetylcholine?level is?relatively low,?thus the?thalamic reticular formation is "inhibited" by serotonin,?they show no fear?behavior when planning suicide, then it's possible for them to make?harmful?act without avoiding. ）