84017. Anatomical terms of neuroanatomy. The raphe nuclei ( Greek: ῥαφή, "seam") are a moderate-size cluster of nuclei found in the brain stem. They have 5-HT1 receptors which are coupled with Gi/Go-protein -inhibiting adenyl cyclase. They function as autoreceptors in the brain and decrease the release of serotonin.
The raphe nucleus is a moderate-size cluster of nuclei found in the brain stem that releases serotonin to the rest of the brain. Selective serotonin reuptake inhibitor (SSRI) antidepressants are believed to act at these nuclei. The buccal raphe, which is on the cheek and evidence of the fusion of the maxillary and mandibular processes.
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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. Some scientists chose to group the linearis nuclei into one nucleus, shrinking the number of raphe to seven, e.g., NeuroNamesmakes the following ordering: 1. Raphe nuclei of medulla 1.1. Nucleus raphe obscurus (nucleus raphe obscurus) 1.2. Nucleus raphe magnus (raphe magnus) 1.3. Nucleus pallidus (raphe pallidus) 1. Raphe nuclei of the pontine reticular formation 1.1. Pontine raphe nucleus (raphe pontis) 1.2. Inferior central nucleus 1. Raphe nuclei of the midbrain reticular formation 1.1. Superior central nucleus (nucleus centralis superior) 1...
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. 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.
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.Currie, David (2005). A Lecture, Higher Brain Function: Activation of the Brain and Levels of Consciousness. East Tennessee State University.Sari, Youssef (October 2004). Serotonin1B receptors: from protein to physiological function and behavior. Neuroscience & Biobehavioral Reviews 28(6): 565–582.
- Basic Information
- Specification of The Neurons
- Molecular Profile
During the mid-nineteen century it was observed that the serum that was left after the clotting of the blood could constrict vascular smooth muscle so as to increase the vascular tone. It was later discovered that blood platelets were a source of this substance. Rapport and his collaborators later isolated this compound and named it serotonin(5-hydrocytryptamine). Since the structure of 5-HT is hydrophilic and this would imply that I would not be able to pass through the blood-brain barrier and thus the presence of 5-HT in the blood suggested that it was produced in the brain. In 1964, Dahlstrom and Fuxe using the method of histoflurescence found that the majority of serotonergic soma was found in the midline of the brainstem. This locus had been designated as the raphe nuclei. One fact that must be kept in mind is that not all the neurons in the raphe nuclei are serotonergic.
Dahlstrom and Fuxe described nine groups of serotonin-containing cell bodies, designated B1 to B9. Fig 1 shows the nine nuclei and the regions of the brain that they innervate. The B1 to B4 are located in the midpons to caudal medulla. The largest group of serotonergic cells is B7 . It is continuous with the B6 group of cells and they together form the dorsal raphe nucleus. B8 is termed as median raphe nucleus(the nucleus central superior). Group B9 is located in the ventrolateral tegmentum of the pons of the midbrain. The dorsal and the median raphe nuclei give rise to distinct projections in the forebrain region. Within the raphe, neurons are organized into groups that send axons to specific areas of the brain. The organized innervations of fore brain structures by raphe neurons implies that the function of the neurons are dependent on their origin and terminal projections. Some researchers use a different method of nomenclature for the Raphe nuclei. NeuroNames (provide link--Pkat...
As mentioned earlier the total number of the serotonergic neurons is really small. In Rats the number of neurons is around 20,000. The neurons are generated in the early stages of embryonic development. It has been commonly observed that a day after the generation of the neurons they can start the production of 5-HT. The raphe neurons also start profuse axon tracts and project into many parts of the brain and the spinal cord. Based on the labeled 5-HT uptake experiments and immunohistochemical techniques difference in the raphe nuclei neurons have been observed. The axons of the neurons from the median raphe nucleus, type M, have coarse large spherical varicosities, while the ones from the dorsal raphe, type D, have very fine and small pleomorphic varicosities. The serotonergic neurons of the raphe nuclei exhibit spontaneous discharge activity of 1-5 spikes per second. The activity of this neurons is controlled by three different events that take place in the nuclei. The events init...
Neurotransmitter:Serotonin is a combination of the hydroxyl group in the 5 position of the indole nucleus and a primary amine nitrogen. 5-HT is released from the serotonergic varicosities into the...
Serotonin plays an important role in the modulation of mood swings, anger, anxiety, aggression, body temperature, sleep, appetite, metabolism and sexuality. Serotonin is one of the major players in stimulating vomiting. Researcher have found that mutation in the 5-HT2A receptor was common in patients with major depression and suicidal tendencies. Studies on human patients groups have also shown that lower levels of serotonin leads to the shift of the behavior pattern to aggressiveness.Gross and et al, have found that Serotonin 1A receptor acts during the development of a mice and leads to normal anxiety like behavior in adult mice. The knock – out of this receptor in these mice have shown higher levels of anxiety in the mice. Groups of Researchers have also found that mice with defective serotonin receptors or 5-HT levels show deviations from the normal pattern of behavior in case of a maze experiment. Serotonin has also been linked with SIDS ( sudden infant death syndrome). Lesurte...Basic neurochemistry 3rd edition,edited by George J. Siegel ... [et al.] (need complete reference --Pkatz21:10, 1 September 2008 (EDT)en.wikipedia.org (need more specific reference --Pkatz21:10, 1 September 2008 (EDT))Dos Santos L, et al. Serotonergic neurons in the median raphe nucleus regulate inhibitory avoidance but not escape behavior in the rat elevated T-maze test of anxiety.Psychopharmacology (Berl). 200...Gaspar P, et al. The developmental role of serotonin: news from mouse molecular genetics. Nature Reviews Neuroscience 4, 1002-1012 (December 2003) | doi:10.1038/nrn1256
Connections of the raphe nuclei with the forebrain develop at 7–8 weeks (stages 21–23), probably via the central tegmental tract, and the nuclei come to be situated within the septum medullae (stage 23). Two distinct raphe nuclei at 8 weeks (stage 23) have been reconstructed (O'Rahilly and Müller, 1999a, figures 23-27).
Serotonergic mechanisms hosted by raphe nuclei have important roles in affiliative and agonistic behaviors but the separate roles of the two nuclei are poorly understood. Here we studied the roles of the dorsal (DR) and median raphe region (MRR) in aggression by optogenetically stimulating the two nuclei. Mice received three 3 min-long stimulations, which were separated by non-stimulation ...