Surely you have ever heard of serotonin, a neurotransmitter that has a lot to do with mood and whose lack is related to conditions such as depression. Serotonin is very important for our survival and well-being and today we are talking about the brain structure that makes its creation possible: the nucleus of the Rafe.
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The word "Rafe", in Greek, refers to a ridge that separates two symmetrical areas of an organ or tissue. Thus, the nucleus of the Rafe is a set of groups of neurons found in the midline of the brain stem. The brain stem, in turn, is made up of several very important areas such as the midbrain, the bridge and the medulla oblongata and is responsible for communicating the spinal cord and the nerves of the periphery with the different areas of the brain, in addition to participating in different very important functions such as breath maintenance.
In this area the nucleus of the Rafe rests together with such important structures as the bridge or the cerebellum. In addition, this nucleus is part of the reticular formation, one of the most primitive areas of the brain that is responsible for controlling sleep rhythms.
The nucleus of the Rafe is divided into six small nuclei. Some of these nuclei are located in the rostral zone, closer to the upper zone of the brainstem, while others are in the caudal group, the lower zone.
85% of brain serotonergic neurons are found in the rostral zone. This area is composed of the nucleus of the Rafe pontis and the upper central nucleus, in the area of the bridge and the Nucleus of the raphe dorsalis, in the area of the midbrain. These nuclei usually connect with the areas of the brain in which higher functions are carried out, such as the frontal areas, although the neurons of the nucleus dorsalis connect with numerous brain areas such as the orbitofrontal cortex or the hypothalamus.
In the caudal area there are fewer serotonergic neurons and there is the nucleus of the Rafe magnus, in the area of the bridge, the nucleus obscurus and the nucleus of the Rafe pallidus, of less extension, in the area of the medulla oblongata. These nuclei in the lower part of the brainstem usually project towards the spinal cord and brainstem.
The main function of these nuclei is the production of serotonin. Serotonin is a main neurotransmitter for the proper functioning of the nervous system and manages to regulate the mood by controlling negative emotions such as fear, aggressiveness or anxiety, as well as its lack can lead to disorders such as depression.
The nucleus of the Rafe synthesizes this neurotransmitter and sends it to the rest of the nervous system, making it do its job. In addition, these nuclei contain other types of neurons, not only serotonergic ones, although these are concentrated here more than in any other place in the brain.
This generation of serotonin, manages to maintain and regulate the mood and control certain aggressive behaviors. When drugs such as SSRIs are used that are able to inhibit the reuptake of serotonin by promoting its further creation, psychological states such as depression are considerably reduced, this being a widely used treatment today..
The neurons that transmit serotonin reach other points in the brain stem and appear to participate in the regulation of the circadian rhythm that this large structure manages to control. Thus, the nucleus of the Rafe is also involved in the regulation of sleep-wake cycles, working in accordance with the hypothalamus with which it will carry out feedback on alert and wakefulness levels, producing more or less serotonin..
In addition, it seems that the nuclei of the Rafe, especially the nucleus magnus and the dorsal nucleus, are involved in the processes of pain inhibition. The projections of the nuclei of the Rafe reach the spinal cord and there they inhibit the neurons of the dorsal horn that are responsible for transmitting pain information. Thus, the nervous system manages to regulate the intensity of this sensation. As we can see, there are many tasks of this interesting structure of which, however, we still do not know all its functions and secrets to discover, as well as the neurotransmitter that is most associated with it: serotonin.
https://www.sciencedirect.com/topics/neuroscience/raphe-nuclei
http://neuronbank.org/wiki/index.php/Raphe_Nuclei
https://www.frontiersin.org/articles/10.3389/fnint.2013.00060/full
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