Rafe Nuclei: What They Are And What Function They Have In The Brain
Serotonin is a brain neurotransmitter closely involved in emotional regulation and aggressive behavior. The Rafe nuclei located in the brain stem, is the area with the most serotonin in the brain, and where it is secreted.
In this article we will learn in detail about these nuclei at an anatomical level, their functions and how serotonin affects our behavior.
The word “Rafe” comes from Greek, and refers to a ridge that separates two symmetrical areas of an organ or tissue. The nucleus or nuclei of the Rafe is a set of groups of neurons found in the midline of the brain stem
Specifically, the Rafe nuclei are a region of the human brain where serotonin, a brain neurotransmitter with an inhibitory effect on the brain, is synthesized and flows; Serotonin acts on receptors located in the amygdala and helps to stop aggressive behavior. Its decrease implies an increase in the aggressive response in humans.
Thus, the serotonergic system originates in the Rafe nuclei; These nuclei make up a broad network organized in the brain stem.
On the other hand, the Rafe nuclei They are part of the reticular formation one of the most primitive areas of the brain, responsible for controlling sleep rhythms.
Where are they located?
Each of the serotonergic raphe nuclei is located next to the midline of the brainstem. Let’s get to know this area of the brain:
The Rafe nuclei are located in the brain stem. The brain stem is the region responsible for the “emotional reactions” of the human being, and includes other structures such as the pons, the cerebellum, the reticular formation and the locus coeruleus. In humans, these primitive structures remain active as vital alert mechanisms for survival, and also to maintain the sleep-wake cycle and breathing
The brainstem, in turn, is made up of several very important areas such as the midbrain, the pons and the medulla oblongata. In addition to the above, it is also responsible for communicating the spinal cord and peripheral nerves with the different areas of the brain.
Core functions
As we have already seen, the main function of the Rafe nuclei is the synthesis of serotonin, the main neurotransmitter for the nervous system to function correctly. Let’s see some of the most important functions of these cores:
1. Mood regulation: serotonin (SA)
Serotonin regulates mood, and it does so by controlling negative emotions such as fear, aggression or anxiety. On the other hand, its lack or reduction can trigger disorders such as depression.
Once serotonin is synthesized in the Rafe nuclei, it is sent to the rest of the nervous system, where it fulfills its functions. Serotonin maintains and regulates mood, and controls certain aggressive behaviors (also in animals). Some medications, such as SSRIs (antidepressants), inhibit the reuptake of serotonin, causing it to increase its concentration levels in the brain; All of this implies that depressive states improve (that is, mood improves). This is why they are frequently used to treat depression (along with other serotonin enhancers such as tricyclic antidepressants, MAOIs, etc.).
On the other hand, we must know that the Rafe nuclei contain other types of neurons, not just serotonergic ones.
2. Sleep-wake cycles
The Rafe nuclei are alsoThey are involved in the regulation of sleep-wake cycles working in a synchronized manner with the hypothalamus, with which they will carry out feedback on the levels of alertness and wakefulness, consequently producing more or less serotonin.
3. Pain inhibition
Furthermore, the raphe nuclei (especially the nucleus magnus and the dorsal nucleus) are involved in pain inhibition processes.
4. Aggressive behavior
As we have seen, aggressive behavior has to do with serotonin levels (the more serotonin, the less aggressive behavior). Numerous structures are involved in the deployment and control of said behavior, such as the sensory systems (initially), the thalamus (which receives the information) and the amygdala (where the information culminates).
Anatomy of the raphe nuclei
The Rafe nuclei are divided into six small nuclei. Some of them are located in the rostral area (closer to the upper area of the brain stem), while others are located in the caudal area (the lower area).
Specifically, 85% of the brain’s serotonergic neurons are found in the rostral area. This area is composed of the nucleus of the Rafe pontis and the superior central nucleus, in the pons area, and by the nucleus of the Rafe dorsalis, in the area of the midbrain.
All these cores They connect with the areas of the brain where 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 (the latter controls the functioning of the nervous system, among other functions).
