The norepinephrine transporter (NET), also known as noradrenaline transporter (NAT), is a
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
that in humans is encoded by the solute carrier family 6 member 2 (SLC6A2)
gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
.
NET is a
monoamine transporter
Monoamine transporters (MATs) are proteins that function as integral Cell membrane, plasma-membrane Neurotransmitter transporter, transporters to regulate concentrations of extracellular monoamine neurotransmitters. The three major classes are se ...
and is responsible for the sodium-chloride (Na
+/Cl
−)-dependent
reuptake
Reuptake is the reabsorption of a neurotransmitter by a neurotransmitter transporter located along the plasma membrane of an axon terminal (i.e., the pre-synaptic neuron at a synapse) or glial cell after it has performed its function of transmi ...
of extracellular
norepinephrine
Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic compound, organic chemical in the catecholamine family that functions in the brain and human body, body as a hormone, neurotransmitter and neuromodulator. The ...
(NE), which is also known as noradrenaline. NET can also reuptake extracellular
dopamine
Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. It is an amine synthesized ...
(DA). The reuptake of these two
neurotransmitter
A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a Chemical synapse, synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell.
Neurotra ...
s is essential in regulating concentrations in the
synaptic cleft
Chemical synapses are biological junctions through which neurons' signals can be sent to each other and to non-neuronal cells such as those in neuromuscular junction, muscles or glands. Chemical synapses allow neurons to form biological neural ...
. NETs, along with the other monoamine transporters, are the targets of many antidepressants and recreational drugs. In addition, altered NET availability is associated with
ADHD
Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by symptoms of inattention, hyperactivity, impulsivity, and emotional dysregulation that are excessive and pervasive, impairing in multiple ...
.
There is evidence that
single-nucleotide polymorphisms
In genetics and bioinformatics, a single-nucleotide polymorphism (SNP ; plural SNPs ) is a germline substitution of a single nucleotide at a specific position in the genome. Although certain definitions require the substitution to be present in ...
in the NET gene (''SLC6A2'') may be an underlying factor in some of these disorders.
Gene
The norepinephrine transporter gene, SLC6A2 is located on human
chromosome 16 locus 16q12.2. This gene is encoded by 14
exon
An exon is any part of a gene that will form a part of the final mature RNA produced by that gene after introns have been removed by RNA splicing. The term ''exon'' refers to both the DNA sequence within a gene and to the corresponding sequence ...
s.
Based on the nucleotide and amino acid sequence, the NET transporter consists of 617 amino acids with 12 membrane-spanning domains. The structural organization of NET is highly homologous to other members of a sodium/chloride-dependent family of neurotransmitter transporters, including dopamine, epinephrine,
serotonin
Serotonin (), also known as 5-hydroxytryptamine (5-HT), is a monoamine neurotransmitter with a wide range of functions in both the central nervous system (CNS) and also peripheral tissues. It is involved in mood, cognition, reward, learning, ...
and
GABA transporters.
Single-nucleotide polymorphisms
A
single-nucleotide polymorphism
In genetics and bioinformatics, a single-nucleotide polymorphism (SNP ; plural SNPs ) is a germline substitution of a single nucleotide at a specific position in the genome. Although certain definitions require the substitution to be present in a ...
(SNP) is a genetic variation in which a genome sequence is altered by a single nucleotide (
A,
T,
C or
G). NET proteins with an altered amino acid sequence (more specifically, a
missense mutation
In genetics, a missense mutation is a point mutation in which a single nucleotide change results in a codon that codes for a different amino acid. It is a type of nonsynonymous substitution. Missense mutations change amino acids, which in turn alt ...
) could potentially be associated with various diseases that involve abnormally high or low plasma levels of
norepinephrine
Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic compound, organic chemical in the catecholamine family that functions in the brain and human body, body as a hormone, neurotransmitter and neuromodulator. The ...
due to altered NET function. NET SNPs and possible associations with various diseases are an area of focus for many research projects. There is evidence suggesting a relationship between NET SNPs and various disorders such as ADHD
psychiatric disorders,
postural tachycardia and
orthostatic intolerance.
The SNPs rs3785143 and rs11568324 have been related to
attention-deficit hyperactivity disorder
Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by symptoms of inattention, hyperactivity, impulsivity, and emotional dysregulation that are excessive and pervasive, impairing in multiple con ...
.
Thus far, however, the only confirmed direct association between a SNP and a clinical condition is that of the SNP, Ala457Pro, and
orthostatic intolerance.
Thirteen NET missense mutations have been discovered so far.
Abbreviations: TMD,
transmembrane domain
A transmembrane domain (TMD, TM domain) is a membrane-spanning protein domain. TMDs may consist of one or several alpha-helices or a transmembrane beta barrel. Because the interior of the lipid bilayer is hydrophobic, the amino acid residues in ...
; n/a, non-applicable.
For the table above, refer to this table of standard
amino acid abbreviations. This notation for
missense mutations, take Val69Ile for example, indicates that amino acid Val69 was changed to Ile.
Genetic variations
An
epigenetic
In biology, epigenetics is the study of changes in gene expression that happen without changes to the DNA sequence. The Greek prefix ''epi-'' (ἐπι- "over, outside of, around") in ''epigenetics'' implies features that are "on top of" or "in ...
mechanism (hypermethylation of CpG islands in the NET gene promoter region) that results in reduced expression of the noradrenaline (norepinephrine) transporter and consequently a phenotype of impaired neuronal reuptake of norepinephrine has been implicated in both
postural orthostatic tachycardia syndrome
Postural orthostatic tachycardia syndrome (POTS) is a condition characterized by an abnormally large increase in heart rate upon sitting up or standing. POTS is a disorder of the autonomic nervous system that can lead to a variety of symptoms, ...
and
panic disorder
Panic disorder is a mental disorder, specifically an anxiety disorder, characterized by reoccurring unexpected panic attacks. Panic attacks are sudden periods of intense fear that may include palpitations, sweating, shaking, shortness of breath ...
.
rs5569 is a variant of SLC6A2.
Structure

The norepinephrine transporter is composed of 12
transmembrane domain
A transmembrane domain (TMD, TM domain) is a membrane-spanning protein domain. TMDs may consist of one or several alpha-helices or a transmembrane beta barrel. Because the interior of the lipid bilayer is hydrophobic, the amino acid residues in ...
s (TMDs). The intracellular portion contains an
amino
In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...
(-) group and
carboxyl
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl group (e.g. ...
(-COOH) group. In addition, there is a large extracellular loop located between TMD 3 and 4.
The protein is composed of 617
amino acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...
s.
Function
NET functions to transport synaptically released
norepinephrine
Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic compound, organic chemical in the catecholamine family that functions in the brain and human body, body as a hormone, neurotransmitter and neuromodulator. The ...
back into the presynaptic neuron. As much as 90% of the norepinephrine released will be taken back up in the cell by NET. NET functions by coupling the influx of sodium and chloride (Na
+/Cl
−) with the transport of norepinephrine. This occurs at a fixed ratio of 1:1:1.
Both the NET and the
dopamine transporter
The dopamine transporter (DAT, also sodium-dependent dopamine transporter) is a membrane-spanning protein coded for in humans by the ''SLC6A3'' gene (also known as ''DAT1''), that pumps the neurotransmitter dopamine out of the synaptic cleft ba ...
(DAT) can transport norepinephrine and dopamine. The reuptake of norepinephrine and dopamine is essential in regulating the concentration of monoamine neurotransmitters in the synaptic cleft. The transporter also helps maintain homeostatic balances of the presynaptic neuron.

Norepinephrine (NE) is released from
noradrenergic neurons that innervate both the
CNS and
PNS. NE, also known as noradrenaline (NA), has an important role in controlling mood, arousal, memory, learning, and pain perception. NE is a part of the
sympathetic nervous system
The sympathetic nervous system (SNS or SANS, sympathetic autonomic nervous system, to differentiate it from the somatic nervous system) is one of the three divisions of the autonomic nervous system, the others being the parasympathetic nervous sy ...
.
Dysregulation of the removal of norepinephrine by NET is associated with many neuropsychiatric diseases, discussed below. In addition, many antidepressants and recreational drugs compete for the binding of NET with NE.
Transport mechanisms
The transport of norepinephrine back into presynaptic cell is made possible by the cotransport with Na
+ and Cl
−. The sequential binding of the ions results in the eventual reuptake of norepinephrine. The ion gradients of Na
+ and Cl
− make this reuptake energetically favorable. The gradient is generated by the
Na+/K+-ATPase which transports three sodium ions out and two potassium ions into the cell.
NETs have conductances similar to those of
ligand-gated ion channel
Ligand-gated ion channels (LICs, LGIC), also commonly referred to as ionotropic receptors, are a group of transmembrane ion-channel proteins which open to allow ions such as sodium, Na+, potassium, K+, calcium, Ca2+, and/or chloride, Cl− to ...
s. The expression of NET results in a leak-channel activity.
Location in the nervous system
NETs are restricted to
noradrenergic neurons and are not present on neurons that release dopamine or epinephrine.
The transporters can be found along the cell body,
axon
An axon (from Greek ἄξων ''áxōn'', axis) or nerve fiber (or nerve fibre: see American and British English spelling differences#-re, -er, spelling differences) is a long, slender cellular extensions, projection of a nerve cell, or neuron, ...
s, and
dendrite
A dendrite (from Ancient Greek language, Greek δένδρον ''déndron'', "tree") or dendron is a branched cytoplasmic process that extends from a nerve cell that propagates the neurotransmission, electrochemical stimulation received from oth ...
s of the neuron.
NETs are located away from the synapse, where norepinephrine is released. They are found closer to the plasma membrane of the cell. This requires norepinephrine to diffuse from the site it is released to the transporter for reuptake.
Norepinephrine transporters are confined to the neurons of the sympathetic system, and those innervating the adrenal medulla, lung, and placenta.
Regulation
Regulation of NET function is complex and a focus of current research. NETs are regulated at both the cellular and molecular level post-translation. The most understood mechanisms include phosphorylation by the second messenger
protein kinase C
In cell biology, protein kinase C, commonly abbreviated to PKC (EC 2.7.11.13), is a family of protein kinase enzymes that are involved in controlling the function of other proteins through the phosphorylation of hydroxyl groups of serine and t ...
(PKC).
PKC has been shown to inhibit NET function by sequestration of the transporter from the plasma membrane.
The amino acid sequence of NET has shown multiple sites related to protein kinase phosphorylation.
Post-translational modifications can have a wide range of effects on the function of the NET, including the rate of fusion of NET-containing vesicles with the plasma membrane, and transporter turnover.
Clinical significance
Orthostatic intolerance
Orthostatic intolerance (OI) is a disorder of the
autonomic nervous system
The autonomic nervous system (ANS), sometimes called the visceral nervous system and formerly the vegetative nervous system, is a division of the nervous system that operates viscera, internal organs, smooth muscle and glands. The autonomic nervo ...
(a subcategory of
dysautonomia
Dysautonomia, autonomic failure, or autonomic dysfunction is a condition in which the autonomic nervous system (ANS) does not work properly. This condition may affect the functioning of the heart, bladder, intestines, sweat glands, pupils, and ...
) characterized by the onset of symptoms upon standing. Symptoms include fatigue, lightheadedness, headache, weakness, increased heart rate/
heart palpitations, anxiety, and altered vision.
Often, patients have high plasma
norepinephrine
Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic compound, organic chemical in the catecholamine family that functions in the brain and human body, body as a hormone, neurotransmitter and neuromodulator. The ...
(NE) concentrations (at least 600 pg/ml) in relation to sympathetic outflow upon standing, suggesting OI is a hyper
adrenergic
Adrenergic means "working on adrenaline (epinephrine) or noradrenaline (norepinephrine)" (or on their receptors). When not further qualified, it is usually used in the sense of enhancing or mimicking the effects of epinephrine and norepinephrine ...
condition.
The discovery of identical twin sisters who both had OI suggested a genetic basis for the disorder.
A
missense mutation
In genetics, a missense mutation is a point mutation in which a single nucleotide change results in a codon that codes for a different amino acid. It is a type of nonsynonymous substitution. Missense mutations change amino acids, which in turn alt ...
on the NET gene (SLC6A2) was discovered in which an
alanine
Alanine (symbol Ala or A), or α-alanine, is an α-amino acid that is used in the biosynthesis of proteins. It contains an amine group and a carboxylic acid group, both attached to the central carbon atom which also carries a methyl group sid ...
residue was replaced with a
proline
Proline (symbol Pro or P) is an organic acid classed as a proteinogenic amino acid (used in the biosynthesis of proteins), although it does not contain the amino group but is rather a secondary amine. The secondary amine nitrogen is in the p ...
residue (Ala457Pro) in a highly conserved region of the transporter.
The patients’ defective NET had only 2% of the activity of the
wild-type
The wild type (WT) is the phenotype of the typical form of a species as it occurs in nature. Originally, the wild type was conceptualized as a product of the standard "normal" allele at a locus, in contrast to that produced by a non-standard, " ...
version of the gene.
The genetic defect in the NET protein results in decreased NET activity that could account for abnormally high NE plasma levels in OI. However, 40 other OI patients did not have the same missense mutation, indicating other factors contributed to the phenotype in the identical twins.
This discovery of the linkage with NET mutations that results in decreased norepinephrine
reuptake
Reuptake is the reabsorption of a neurotransmitter by a neurotransmitter transporter located along the plasma membrane of an axon terminal (i.e., the pre-synaptic neuron at a synapse) or glial cell after it has performed its function of transmi ...
activity and orthostatic intolerance suggests faulty NE uptake mechanisms can contribute to cardiovascular disease.
Therapeutic uses
Inhibition of the norepinephrine transporter (NET) has potential therapeutic applications in the treatment of
attention deficit hyperactivity disorder
Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by symptoms of inattention, hyperactivity, impulsivity, and emotional dysregulation that are excessive and pervasive, impairing in multiple con ...
(ADHD),
substance abuse
Substance misuse, also known as drug misuse or, in older vernacular, substance abuse, is the use of a drug in amounts or by methods that are harmful to the individual or others. It is a form of substance-related disorder, differing definition ...
, neurodegenerative disorders (e.g.,
Alzheimer's disease
Alzheimer's disease (AD) is a neurodegenerative disease and the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in remembering recent events. As the disease advances, symptoms can include problems wit ...
(AD) and
Parkinson's disease
Parkinson's disease (PD), or simply Parkinson's, is a neurodegenerative disease primarily of the central nervous system, affecting both motor system, motor and non-motor systems. Symptoms typically develop gradually and non-motor issues become ...
(PD)) and
clinical depression
Major depressive disorder (MDD), also known as clinical depression, is a mental disorder characterized by at least two weeks of pervasive low mood, low self-esteem, and loss of interest or pleasure in normally enjoyable activities. Intro ...
.
Major depressive disorder

Certain
antidepressant
Antidepressants are a class of medications used to treat major depressive disorder, anxiety disorders, chronic pain, and addiction.
Common side effects of antidepressants include Xerostomia, dry mouth, weight gain, dizziness, headaches, akathi ...
medications act to raise noradrenaline, such as
serotonin-norepinephrine reuptake inhibitors (SNRIs),
norepinephrine-dopamine reuptake inhibitors (NDRIs),
norepinephrine reuptake inhibitors (NRIs or NERIs) and the
tricyclic antidepressants (TCAs). The mechanism by which these medications work is that the reuptake inhibitors prevent the reuptake of serotonin and norepinephrine by the
presynaptic neuron, paralyzing the normal function of the NET. At the same time, higher levels of
5-HT are maintained in the synapse increasing the concentrations of the latter neurotransmitters. Since the noradrenaline transporter is responsible for most of the dopamine clearance in the prefrontal cortex,
SNRIs block reuptake of dopamine too, accumulating the dopamine in the synapse. However, DAT, the primary way dopamine is transported out of the cell, can work to decrease dopamine concentration in the synapse when the NET is blocked.
For many years, the number one choice in treating mood disorders like depression was through administration of TCAs, such as
desipramine (Norpramin),
nortriptyline (Arentyl, Pamelor), protriptyline (Vivactil), and
amoxapine
Amoxapine, sold under the brand name Asendin among others, is a tricyclic antidepressant (TCA). It is the N-demethylation, demethylated metabolite of loxapine. Amoxapine first received marketing approval in the United States in 1980, approximat ...
(Asendin).
SSRIs, which mainly regulate serotonin, subsequently replaced tricyclics as the primary treatment option for depression because of their better tolerability and lower incidence of adverse effects.
[Clinical Pharmacology of SSRI's: How SSRIs as a Group Differ From TCAs](_blank)
Preskorn
ADHD

Many drugs exist in the treatment of ADHD.
Dextroamphetamine
Dextroamphetamine (international nonproprietary name, INN: dexamfetamine) is a potent central nervous system (CNS) stimulant and enantiomer of amphetamine that is used in the treatment of attention deficit hyperactivity disorder (ADHD) and narc ...
(Dexedrine, Dextrostat),
Adderall
Adderall and Mydayis are trade names for a combination drug containing four salts of amphetamine. The mixture is composed of equal parts racemic amphetamine and dextroamphetamine, which produces a (3:1) ratio between dextroamphetamine and l ...
,
methylphenidate
Methylphenidate, sold under the brand names Ritalin ( ) and Concerta ( ) among others, is a central nervous system (CNS) stimulant used in the treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy. It may be taken Oral adm ...
(Ritalin, Metadate, Concerta, Daytrana), and
lisdexamfetamine
Lisdexamfetamine, sold under the brand names Vyvanse and Elvanse among others, is a stimulant medication that is used as a treatment for attention deficit hyperactivity disorder (ADHD) in children and adults and for moderate-to-severe binge ...
(Vyvanse) block reabsorption of the
catecholamines
A catecholamine (; abbreviated CA), most typically a 3,4-dihydroxyphenethylamine, is a monoamine neurotransmitter, an organic compound that has a catechol (benzene with two hydroxyl side groups next to each other) and a side-chain amine.
...
dopamine and norepinephrine through
monoamine transporter
Monoamine transporters (MATs) are proteins that function as integral Cell membrane, plasma-membrane Neurotransmitter transporter, transporters to regulate concentrations of extracellular monoamine neurotransmitters. The three major classes are se ...
s (including NET), thereby increasing levels of these
neurotransmitters
A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell.
Neurotransmitters are rele ...
in the brain. The strong
selective norepinephrine reuptake inhibitor (NRI),
atomoxetine
Atomoxetine, formerly sold under the brand name Strattera, is a selective norepinephrine reuptake inhibitor (sNRI) medication used to treat attention deficit hyperactivity disorder (ADHD) and, to a lesser extent, cognitive disengagement syndr ...
(Strattera), has been approved by the U.S.
Food and Drug Administration
The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respo ...
(FDA) to treat ADHD in adults.
The role of the NET in ADHD is similar to how it works to ease the symptoms of depression. The NET is blockaded by atomoxetine and increases NE levels in the brain. It can work to increase one's ability to focus, decrease any impulsiveness, and lessen hyperactivity in both children and adults with ADHD.
Psychostimulants
Cocaine
Cocaine
Cocaine is a tropane alkaloid and central nervous system stimulant, derived primarily from the leaves of two South American coca plants, ''Erythroxylum coca'' and ''Erythroxylum novogranatense, E. novogranatense'', which are cultivated a ...
is a powerful
psychostimulant
Stimulants (also known as central nervous system stimulants, or psychostimulants, or colloquially as uppers) are a class of drugs that increase alertness. They are used for various purposes, such as enhancing attention, motivation, cognition ...
and known to be one of the most widely used substances recreationally.
Cocaine is a nonselective,
reuptake inhibitor of the
norepinephrine
Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic compound, organic chemical in the catecholamine family that functions in the brain and human body, body as a hormone, neurotransmitter and neuromodulator. The ...
,
serotonin
Serotonin (), also known as 5-hydroxytryptamine (5-HT), is a monoamine neurotransmitter with a wide range of functions in both the central nervous system (CNS) and also peripheral tissues. It is involved in mood, cognition, reward, learning, ...
, and
dopamine
Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. It is an amine synthesized ...
transporters. This thwarts the absorption of these chemicals into the
presynaptic terminal and allows a large concentration of dopamine, serotonin and norepinephrine to build up in the synaptic cleft. The potential for cocaine addiction is thought to be a result of its effects on
dopamine transporter
The dopamine transporter (DAT, also sodium-dependent dopamine transporter) is a membrane-spanning protein coded for in humans by the ''SLC6A3'' gene (also known as ''DAT1''), that pumps the neurotransmitter dopamine out of the synaptic cleft ba ...
s in the CNS, while it has been suggested that the life-threatening cardiovascular effects of cocaine may involve the inhibition of NETs at sympathetic and CNS autonomic synapses.
Amphetamines
Amphetamines
Substituted amphetamines, or simply amphetamines, are a chemical class, class of compounds based upon the amphetamine structure; it includes all derivative (chemistry), derivative compounds which are formed by replacing, or substitution reacti ...
have an effect on
norepinephrine
Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic compound, organic chemical in the catecholamine family that functions in the brain and human body, body as a hormone, neurotransmitter and neuromodulator. The ...
levels similar to that of
cocaine
Cocaine is a tropane alkaloid and central nervous system stimulant, derived primarily from the leaves of two South American coca plants, ''Erythroxylum coca'' and ''Erythroxylum novogranatense, E. novogranatense'', which are cultivated a ...
in that they both increase NE levels in the brain.
Amphetamine-like drugs are substrates for
monoamine transporter
Monoamine transporters (MATs) are proteins that function as integral Cell membrane, plasma-membrane Neurotransmitter transporter, transporters to regulate concentrations of extracellular monoamine neurotransmitters. The three major classes are se ...
s, include NET, that cause a reversal in the direction of neurotransmitter transport.
Amphetamines cause a large accumulation of extracellular NE.
High levels of NE in the brain account for most of the profound effects of amphetamines, including alertness and anorectic, locomotor and sympathomimetic effects.
However, the effects that amphetamines have on the brain are slower but last longer than the effects cocaine has on the brain.
MDMA
3,4-Methylenedioxymethamphetamine (MDMA), commonly known as ecstasy (tablet form), and molly (crystal form), is an empathogen–entactogenic drug with stimulant and minor Psychedelic drug, psychedelic properties. In studies, it has been used ...
(3,4-Methylenedioxymethamphetamine or "ecstasy") is an amphetamine with wide recreational use. A study reported that the NET inhibitor
reboxetine reduced the stimulant effects of MDMA in humans, demonstrating the crucial role NET has in the cardiovascular and stimulant-like effects of MDMA.
Further research
The role of the NET in many brain disorders underlies the importance of understanding the (dys)regulation of the transporter. A complete model of the proteins that associate with the transporter will be useful in designing drug therapies for diseases such as
schizophrenia
Schizophrenia () is a mental disorder characterized variously by hallucinations (typically, Auditory hallucination#Schizophrenia, hearing voices), delusions, thought disorder, disorganized thinking and behavior, and Reduced affect display, f ...
,
affective disorder, and autonomic disorders. Recently discovered mechanisms of the NET, including the ability to act reversibly and as an ion channel, provide other areas of research.
Schizophrenia

The role of NE in
schizophrenia
Schizophrenia () is a mental disorder characterized variously by hallucinations (typically, Auditory hallucination#Schizophrenia, hearing voices), delusions, thought disorder, disorganized thinking and behavior, and Reduced affect display, f ...
has not been fully understood, but has stimulated research into this topic.
The only relationship that has been understood between researchers is that there is a positive correlation between increased NE levels in the brain and
spinal fluid (CSF) and activity of schizophrenia.
In one study,
clonidine
Clonidine, sold under the brand name Catapres among others, is an α2A-adrenergic receptor agonist medication used to treat high blood pressure, attention deficit hyperactivity disorder (ADHD), drug withdrawal (e.g., alcohol, opioids, or nic ...
, a drug used to treat medical conditions such as
ADHD
Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by symptoms of inattention, hyperactivity, impulsivity, and emotional dysregulation that are excessive and pervasive, impairing in multiple ...
and high blood pressure, was shown to produce a significant decrease in plasma level
MHPG (3-methoxy-4-hydroxyphenylglycol), a metabolite of NE, in the normal control group, but not in the group of schizophrenic patients.
This suggests that in schizophrenia, the
alpha-2 adrenergic receptor
The alpha-2 (α2) adrenergic receptor (or adrenoceptor) is a G protein-coupled receptor (GPCR) associated with the Gi alpha subunit, Gi heterotrimeric G-protein. It consists of three highly homologous subtypes, including α2A-adrenergic, α2A-, ...
, a presynaptic inhibitory receptor, may be less sensitive compared to normally functioning alpha-2 receptors and thus relate to elevated NE levels in the disorder.
In addition to increased NE levels in the brain and CSF, increased levels of MHPG has also been associated with a diagnosis of schizophrenia.
Impaired NE regulation in schizophrenia has been an area of interest for researchers and research on this topic is still ongoing.
Imaging
Via
positron emission tomography
Positron emission tomography (PET) is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes, and in other physiological activities including blood flow, r ...
imaging technique, NET has been selectively investigated.
11C ME@HAPTHI and
18F-MeNER are two NET selective
radio tracers for PET imaging.
Fluorescent substrates for the transporter can also be used to monitor the transporter rate in isolated organs or tissues,
although these are not suitable for clinical imaging.
Ligands and modulators
Substrates
*
Norepinephrine
Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic compound, organic chemical in the catecholamine family that functions in the brain and human body, body as a hormone, neurotransmitter and neuromodulator. The ...
* Substrate-type
norepinephrine releasing agents (e.g.,
ephedrine
Ephedrine is a central nervous system (CNS) stimulant and sympathomimetic agent that is often used to prevent hypotension, low blood pressure during anesthesia. It has also been used for asthma, narcolepsy, and obesity but is not the preferred ...
,
amphetamine
Amphetamine (contracted from Alpha and beta carbon, alpha-methylphenethylamine, methylphenethylamine) is a central nervous system (CNS) stimulant that is used in the treatment of attention deficit hyperactivity disorder (ADHD), narcolepsy, an ...
)
*
Catecholaminergic activity enhancers (e.g.,
selegiline
Selegiline, also known as L-deprenyl and sold under the brand names Eldepryl, Zelapar, and Emsam among others, is a medication which is used in the treatment of Parkinson's disease and major depressive disorder. It has also been studied and us ...
,
PPAP,
BPAP)
* Certain
noradrenergic neurotoxins (e.g.,
DSP-4,
xylamine)
Norepinephrine reuptake inhibitors (NRIs)
Selective norepinephrine reuptake inhibitors
*
Ampreloxetine
*
Atomoxetine
Atomoxetine, formerly sold under the brand name Strattera, is a selective norepinephrine reuptake inhibitor (sNRI) medication used to treat attention deficit hyperactivity disorder (ADHD) and, to a lesser extent, cognitive disengagement syndr ...
*
Nisoxetine
*
Reboxetine
*
Viloxazine
Norepinephrine–dopamine reuptake inhibitors (NDRIs)
*
Amineptine
Amineptine, formerly sold under the brand name Survector among others, is an atypical antidepressant of the tricyclic antidepressant (TCA) family. It acts as a selective and mixed dopamine reuptake inhibitor and releasing agent, and to a le ...
*
Bupropion
Bupropion, formerly called amfebutamone, and sold under the brand name Wellbutrin among others, is an atypical antidepressant that is indicated in the treatment of major depressive disorder, seasonal affective disorder, and to support smo ...
*
Desoxypipradrol
*
Levophacetoperane
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Methylenedioxypyrovalerone (MDPV)
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Methylphenidate
Methylphenidate, sold under the brand names Ritalin ( ) and Concerta ( ) among others, is a central nervous system (CNS) stimulant used in the treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy. It may be taken Oral adm ...
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Nomifensine
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Pipradrol
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Serdexmethylphenidate
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Solriamfetol
Solriamfetol, sold under the brand name Sunosi, is a wakefulness-promoting medication used in the treatment of excessive sleepiness related to narcolepsy and sleep apnea. It is taken by mouth.
Common side effects of solriamfetol include hea ...
Serotonin–norepinephrine reuptake inhibitors (SNRIs)
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Desvenlafaxine
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Duloxetine
Duloxetine, sold under the brand name Cymbalta among others, is a medication used to treat major depressive disorder, generalized anxiety disorder, obsessive–compulsive disorder, fibromyalgia, neuropathic pain, central sensitization, and ...
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Levomilnacipran
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Milnacipran
Milnacipran (trade names Ixel, Savella, Dalcipran, Toledomin) is a serotonin–norepinephrine reuptake inhibitor (SNRI) used in the clinical treatment of fibromyalgia, Major depressive disorder, and Neuropathic pain.
In the US, it is solely appr ...
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Sibutramine
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Venlafaxine
Venlafaxine, sold under the brand name Effexor among others, is an antidepressant medication of the serotonin–norepinephrine reuptake inhibitor (SNRI) class. It is used to treat major depressive disorder, generalized anxiety disorder, pani ...
Non-selective norepinephrine reuptake inhibitors
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Amitriptyline
Amitriptyline, sold under the brand name Elavil among others, is a tricyclic antidepressant primarily used to treat major depressive disorder, and a variety of pain syndromes such as neuropathic pain, fibromyalgia, migraine and tension headac ...
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Amoxapine
Amoxapine, sold under the brand name Asendin among others, is a tricyclic antidepressant (TCA). It is the N-demethylation, demethylated metabolite of loxapine. Amoxapine first received marketing approval in the United States in 1980, approximat ...
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Clomipramine
Clomipramine, sold under the brand name Anafranil among others, is a tricyclic antidepressant (TCA). It is used in the treatment of various conditions, most notably obsessive–compulsive disorder but also many other disorders, including hyper ...
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Cocaine
Cocaine is a tropane alkaloid and central nervous system stimulant, derived primarily from the leaves of two South American coca plants, ''Erythroxylum coca'' and ''Erythroxylum novogranatense, E. novogranatense'', which are cultivated a ...
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Desipramine
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Imipramine
Imipramine, sold under the brand name Tofranil, among others, is a tricyclic antidepressant (TCA) mainly used in the treatment of depression. It is also effective in treating anxiety and panic disorder. Imipramine is taken by mouth.
Common s ...
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Indeloxazine
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Maprotiline
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Mazindol
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Mianserin
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Nortriptyline
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Protriptyline
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Setiptiline
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Tapentadol
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Teniloxazine
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Tramadol
Tramadol, sold under the brand name Tramal among others, is an opioid analgesic, pain medication and a serotonin–norepinephrine reuptake inhibitor (SNRI) used to treat moderately severe pain. When taken by mouth in an immediate-release form ...
Norepinephrine releasing agents (NRAs)
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Aminorex
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Amphetamine
Amphetamine (contracted from Alpha and beta carbon, alpha-methylphenethylamine, methylphenethylamine) is a central nervous system (CNS) stimulant that is used in the treatment of attention deficit hyperactivity disorder (ADHD), narcolepsy, an ...
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Benzylpiperazine
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Cathinone
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Ephedrine
Ephedrine is a central nervous system (CNS) stimulant and sympathomimetic agent that is often used to prevent hypotension, low blood pressure during anesthesia. It has also been used for asthma, narcolepsy, and obesity but is not the preferred ...
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Lisdexamfetamine
Lisdexamfetamine, sold under the brand names Vyvanse and Elvanse among others, is a stimulant medication that is used as a treatment for attention deficit hyperactivity disorder (ADHD) in children and adults and for moderate-to-severe binge ...
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Mephedrone
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Methamphetamine
Methamphetamine (contracted from ) is a potent central nervous system (CNS) stimulant that is mainly used as a recreational drug use, recreational or Performance-enhancing substance, performance-enhancing drug and less commonly as a secon ...
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Methylenedioxymethamphetamine
3,4-Methylenedioxymethamphetamine (MDMA), commonly known as ecstasy (tablet form), and molly (crystal form), is an empathogen–entactogenic drug with stimulant and minor psychedelic properties. In studies, it has been used alongside psych ...
(MDMA)
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Methylone
Methylone, also known as 3,4-methylenedioxy-''N''-methylcathinone (MDMC), is an entactogen and stimulant drug of the amphetamine, cathinone, and benzodioxole families related to 3,4-methylenedioxymethamphetamine (MDMA; "ecstasy"). It is th ...
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Octopamine
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Phenethylamine
Phenethylamine (PEA) is an organic compound, natural monoamine alkaloid, and trace amine, which acts as a central nervous system stimulant in humans. In the brain, phenethylamine regulates monoamine neurotransmission by binding to trace ami ...
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Phenmetrazine
Phenmetrazine, sold under the brand name Preludin among others, is a stimulant drug first chemical synthesis, synthesized in 1952 and originally used as an appetite suppressant, but withdrawn drug, withdrawn from the market in the 1980s due to ...
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Phentermine
Phentermine, sold under the brand name Adipex-P among others, is a medication used together with diet and exercise to treat obesity. It is available by itself or as the combination phentermine/topiramate. Phentermine is taken by mouth.
Com ...
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Phenylpropanolamine
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Pseudoephedrine
Pseudoephedrine, sold under the brand name Sudafed among others, is a sympathomimetic medication which is used as a decongestant to treat nasal congestion. It has also been used off-label for certain other indications, like treatment of lo ...
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Tyramine
Tyramine ( ) (also spelled tyramin), also known under several other names, is a naturally occurring trace amine derived from the amino acid tyrosine. Tyramine acts as a catecholamine releasing agent. Notably, it is unable to cross the bl ...
See also
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Neurotransmitter transporter
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Sodium:neurotransmitter symporter
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Solute carrier family
The solute carrier (SLC) group of membrane transport proteins include over 400 members organized into 66 families. Most members of the SLC group are located in the cell membrane. The SLC gene nomenclature system was originally proposed by the HUGO ...
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Norepinephrine
Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic compound, organic chemical in the catecholamine family that functions in the brain and human body, body as a hormone, neurotransmitter and neuromodulator. The ...
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Monoamine transporter
Monoamine transporters (MATs) are proteins that function as integral Cell membrane, plasma-membrane Neurotransmitter transporter, transporters to regulate concentrations of extracellular monoamine neurotransmitters. The three major classes are se ...
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Orthostatic intolerance
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Single-nucleotide polymorphisms
In genetics and bioinformatics, a single-nucleotide polymorphism (SNP ; plural SNPs ) is a germline substitution of a single nucleotide at a specific position in the genome. Although certain definitions require the substitution to be present in ...
References
External links
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{{DEFAULTSORT:Norepinephrine Transporter
Amphetamine
Membrane proteins
Neurotransmitter transporters
Norepinephrine
Solute carrier family