Serotonin

5-HTserotonergic5-hydroxytryptamineserotonergic system5HTserotonergic neuronsserotonin systems5-HT (serotonin)5-HT 4 5-HT receptor
Serotonin or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter.wikipedia
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Tryptophan

L-tryptophanTrptryptophan metabolism
Biochemically, the indoleamine molecule derives from the amino acid tryptophan, via the (rate-limiting) hydroxylation of the 5 position on the ring (forming the intermediate 5-hydroxytryptophan), and then decarboxylation to produce serotonin.
Tryptophan is also a precursor to the neurotransmitter serotonin, the hormone melatonin and vitamin B3.

Tryptophan hydroxylase

hydroxylationtryptophan 5-hydroxylasetryptophan 5-monooxygenase
Biochemically, the indoleamine molecule derives from the amino acid tryptophan, via the (rate-limiting) hydroxylation of the 5 position on the ring (forming the intermediate 5-hydroxytryptophan), and then decarboxylation to produce serotonin.
Tryptophan hydroxylase (TPH) is an enzyme involved in the synthesis of the neurotransmitter serotonin.

Monoamine neurotransmitter

monoaminemonoaminesmonoamine neurotransmitters
Serotonin or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter.
Examples are dopamine, serotonin and epinephrine.

Raphe nuclei

raphe nucleusraphe raphe nuclei
However, it is also produced in the central nervous system (CNS), specifically in the Raphe nuclei located in the brainstem.
They function as autoreceptors in the brain and decrease the release of serotonin.

Serotonin–norepinephrine reuptake inhibitor

SNRIserotonin-norepinephrine reuptake inhibitorSNRIs
Several classes of antidepressants, such as the SSRIs and the SNRIs among others, interfere with the normal reabsorption of serotonin after it is done with the transmission of the signal, therefore augmenting the neurotransmitter levels in the synapses.
SNRIs are monoamine reuptake inhibitors; specifically, they inhibit the reuptake of serotonin and norepinephrine.

Serotonergic

serotoninergic5-HTserotonergic agent
The remainder is synthesized in serotonergic neurons of the CNS, where it has various functions.
Serotonergic or serotoninergic means "pertaining to or affecting serotonin".

Enteric nervous system

neurogastroenterologyentericenteric nervous plexus
Serotonin is primarily found in the enteric nervous system located in the gastrointestinal tract (GI tract).
These neurons communicate through many neurotransmitters similar to the CNS, including acetylcholine, dopamine, and serotonin.

Indolamines

indoleamineIndolamineindoleamines
Biochemically, the indoleamine molecule derives from the amino acid tryptophan, via the (rate-limiting) hydroxylation of the 5 position on the ring (forming the intermediate 5-hydroxytryptophan), and then decarboxylation to produce serotonin.
A common example of an indolamine is the tryptophan derivative serotonin, a neurotransmitter involved in mood and sleep.

Indole

indolesindolicindol
There follows oxidation by aldehyde dehydrogenase to 5-HIAA, the indole acetic-acid derivative.
The amino acid tryptophan is an indole derivative and the precursor of the neurotransmitter serotonin.

Agonist

full agonistagonistsreceptor agonist
Additionally, serotonin is stored in blood platelets and is released during agitation and vasoconstriction, where it then acts as an agonist to other platelets.

Monoamine transporter

MATmonoamine reuptake transporterreuptake transporter
This is accomplished through the specific monoamine transporter for 5-HT, SERT, on the presynaptic neuron.
Three major classes of MATs (SERT, DAT, NET) are responsible for the reuptake of their associated amine neurotransmitters (serotonin, dopamine, norepinephrine).

Serotonin transporter

SERTserotoninSLC6A4
This is accomplished through the specific monoamine transporter for 5-HT, SERT, on the presynaptic neuron.
This transport of serotonin by the SERT protein terminates the action of serotonin and recycles it in a sodium-dependent manner.

5-HT1A receptor

5-HT 1A 5-HT 1A receptor5-HT1A
The serotonin 1A receptor (or 5-HT 1A receptor) is a subtype of serotonin receptor (5-HT receptor) that binds the neurotransmitter serotonin (5-hydroxytryptamine, 5-HT).

Sertraline

ZoloftLustralSertraline Hydrochloride
However, the PMAT, despite its relatively low serotonergic affinity, has a considerably higher transport 'capacity' than SERT, "resulting in roughly comparable uptake efficiencies to SERT in heterologous expression systems.” The study also suggests some SSRIs, such as fluoxetine and sertraline anti-depressants, inhibit PMAT but at IC 50 values which surpass the therapeutic plasma concentrations by up to four orders of magnitude. Therefore, SSRI monotherapy is "ineffective" in PMAT inhibition. At present, no known pharmaceuticals are known to appreciably inhibit PMAT at normal therapeutic doses. The PMAT also suggestively transports dopamine and norepinephrine, albeit at K m values even higher than that of 5-HT (330–15,000 μmoles/L).
Sertraline is believed to work by increasing serotonin effects in the brain.

Reuptake

re-uptakereabsorptionuptake
Several classes of antidepressants, such as the SSRIs and the SNRIs among others, interfere with the normal reabsorption of serotonin after it is done with the transmission of the signal, therefore augmenting the neurotransmitter levels in the synapses.
The members of this new family include transporters for dopamine, norepinephrine, serotonin, glycine, proline and GABA.

Fluoxetine

ProzacProzakSarafem
However, the PMAT, despite its relatively low serotonergic affinity, has a considerably higher transport 'capacity' than SERT, "resulting in roughly comparable uptake efficiencies to SERT in heterologous expression systems.” The study also suggests some SSRIs, such as fluoxetine and sertraline anti-depressants, inhibit PMAT but at IC 50 values which surpass the therapeutic plasma concentrations by up to four orders of magnitude. Therefore, SSRI monotherapy is "ineffective" in PMAT inhibition. At present, no known pharmaceuticals are known to appreciably inhibit PMAT at normal therapeutic doses. The PMAT also suggestively transports dopamine and norepinephrine, albeit at K m values even higher than that of 5-HT (330–15,000 μmoles/L).
Its mechanism of action is not entirely clear but believed to be related to increasing serotonin activity in the brain.

5-HT2A receptor

5-HT 2A 5-HT 2A receptor5HT 2A
In humans, levels of 5-HT 1A receptor activation in the brain show negative correlation with aggression, and a mutation in the gene that codes for the 5-HT 2A receptor may double the risk of suicide for those with that genotype.
This is the main excitatory receptor subtype among the GPCRs for serotonin, although 5-HT 2A may also have an inhibitory effect on certain areas such as the visual cortex and the orbitofrontal cortex.

5-HT3 receptor

5-HT 3 5-HT 3 receptor5-HT3
Except for the 5-HT 3 receptor, a ligand-gated ion channel, all other 5-HT receptors are G-protein-coupled receptors (also called seven-transmembrane, or heptahelical receptors) that activate an intracellular second messenger cascade.
The 5-HT 3 receptor belongs to the Cys-loop superfamily of ligand-gated ion channels (LGICs) and therefore differs structurally and functionally from all other 5-HT receptors (5-hydroxytryptamine, or serotonin) receptors which are G protein-coupled receptors.

Aromatic L-amino acid decarboxylase

DOPA decarboxylasearomatic L -amino acid decarboxylasearomatic amino acid decarboxylase
Biochemically, the indoleamine molecule derives from the amino acid tryptophan, via the (rate-limiting) hydroxylation of the 5 position on the ring (forming the intermediate 5-hydroxytryptophan), and then decarboxylation to produce serotonin.
In normal dopamine and serotonin (5-HT) neurotransmitter synthesis, AADC is not the rate-limiting step in either reaction.

G protein-coupled receptor

G-protein coupled receptorG protein-coupled receptorsGPCR
Except for the 5-HT 3 receptor, a ligand-gated ion channel, all other 5-HT receptors are G-protein-coupled receptors (also called seven-transmembrane, or heptahelical receptors) that activate an intracellular second messenger cascade.
biogenic amines (e.g., dopamine, epinephrine, norepinephrine, histamine, serotonin, and melatonin);

5-HT2B receptor

5-HT 2B 5-HT 2B receptorHTR2B
Through 5-HT 1B receptors, it negatively regulates bone mass, while it does so positively through 5-HT 2B receptors and 5-HT 2C receptors.
5-HT 2B is a member of the 5-HT 2 receptor family that binds the neurotransmitter serotonin (5-hydroxytryptamine, 5-HT).

5-HT4 receptor

5-HT 4 5-HT 4 receptor 4
This gene is a member of the family of human serotonin receptors, which are G protein-coupled receptors that stimulate cAMP production in response to serotonin (5-hydroxytryptamine).

5-HT6 receptor

5-HT 6 5-HT 6 receptorHTR6
The 5HT 6 receptor is a subtype of 5HT receptor that binds the endogenous neurotransmitter serotonin (5-hydroxytryptamine, 5HT).

5-HT7 receptor

5-HT 7 5-HT 7 receptor5HT 7
The 5-HT 7 receptor is a member of the GPCR superfamily of cell surface receptors and is activated by the neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) The 5-HT 7 receptor is coupled to G s (stimulates the production of the intracellular signaling molecule cAMP) and is expressed in a variety of human tissues, particularly in the brain, the gastrointestinal tract, and in various blood vessels.

Reticular formation

reticular activating systemreticulospinal tractascending reticular activating system
There are nine raphe nuclei, designated B1-B9, which contain the majority of serotonin-containing neurons (some scientists chose to group the nuclei raphes lineares into one nucleus), all of which are located along the midline of the brainstem, and centered on the reticular formation.
The raphe nuclei are the place of synthesis of the neurotransmitter serotonin, which plays an important role in mood regulation.