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Octopamine (OA), also known as ''para''-octopamine and norsynephrine among synonyms, is an
organic chemical Some chemical authorities define an organic compound as a chemical compound that contains a Carbon–hydrogen bond, carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. F ...
closely related to
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 ...
, and synthesized biologically by a homologous pathway. Octopamine is often considered the major "fight-or-flight"
neurohormone A neurohormone is any hormone produced and released by neuroendocrine cells (also called neurosecretory cells) into the blood. By definition of being hormones, they are secreted into the circulation for systemic effect, but they can also have a ro ...
of
invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...
s. Its name is derived from the fact that it was first identified in the
salivary gland The salivary glands in many vertebrates including mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands ( parotid, submandibular, and sublingual), as well as hundreds of min ...
s of the
octopus An octopus (: octopuses or octopodes) is a soft-bodied, eight-limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids. Like oth ...
. In many types of invertebrates, octopamine is an important
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 ...
and
hormone A hormone (from the Ancient Greek, Greek participle , "setting in motion") is a class of cell signaling, signaling molecules in multicellular organisms that are sent to distant organs or tissues by complex biological processes to regulate physio ...
. In
protostome Protostomia () is the clade of animals once thought to be characterized by the formation of the organism's mouth before its anus during embryonic development. This nature has since been discovered to be extremely variable among Protostomia's memb ...
s—
arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...
s,
mollusc Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...
s, and several types of
worm Worms are many different distantly related bilateria, bilateral animals that typically have a long cylindrical tube-like body, no limb (anatomy), limbs, and usually no eyes. Worms vary in size from microscopic to over in length for marine ...
s—it substitutes for norepinephrine and performs functions apparently similar to those of norepinephrine in mammals, functions that have been described as mobilizing the body and nervous system for action. In mammals, octopamine is found only in trace amounts (i.e., it is a
trace amine Trace amines are an endogenous group of trace amine-associated receptor 1 (TAAR1) agonists – and hence, monoaminergic neuromodulators – that are structurally and metabolically related to classical monoamine neurotransmitters. Compared to ...
), and no biological function has been solidly established for it. It is also found naturally in numerous plants, including
bitter orange The bitter orange, sour orange, Seville orange, bigarade orange, or marmalade orange is the hybrid citrus tree species ''Citrus'' × ''aurantium'', and its fruit. It is native to Southeast Asia and has been spread by humans to many parts of th ...
. Octopamine has been sold under trade names such as Epirenor, Norden, and Norfen for use as a sympathomimetic drug, available by prescription.


Functions


Cellular effects

Octopamine exerts its effects by binding to and activating receptors located on the surface of cells. These receptors have mainly been studied in insects, where they can be divided into distinct types: # OctαR ( alpha-adrenergic-like), are structurally and functionally similar to noradrenergic alpha-1 receptors in mammals. There are multiple subtypes of the OctαR receptor. For example, the kissing bug ('' Rhodnius prolixus'') has Octα1-R, Octα2R. # OctβR ( beta-adrenergic-like), are structurally and functionally similar to noradrenergic beta receptors in mammals. There are multiple subtypes of the OctβR receptor. For example, the fruit fly (''
Drosophila melanogaster ''Drosophila melanogaster'' is a species of fly (an insect of the Order (biology), order Diptera) in the family Drosophilidae. The species is often referred to as the fruit fly or lesser fruit fly, or less commonly the "vinegar fly", "pomace fly" ...
'') has DmOctβ1R, DmOctβ2R, and DmOctβ3R. # OAMB. The diversity of this receptor is relatively unknown. The fruit fly (Drosophila melanogaster) has two distinct isoforms which are functionally distinct: OambK3 and OambAS. # TyrR (mixed octopamine/tyramine receptors), which are structurally and functionally similar to noradrenergic alpha-2 receptors in mammals. Receptors in the TyrR class, however, are generally more strongly activated by
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 ...
than by octopamine. Phylogenetic studies claim that in ancient
bilaterians Bilateria () is a large clade of animals characterised by bilateral symmetry during embryonic development. This means their body plans are laid around a longitudinal axis with a front (or "head") and a rear (or "tail") end, as well as a left–r ...
such as '' Platynereis dumerilii'' there is a co-existence 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 ...
,
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 ...
and octopamine receptor signaling. However, due to partial overlapping in their signalling functionality tyramine and octopamine receptors have been lost in vertebrates. In vertebrates no octopamine-specific receptors have been identified. Octopamine binds weakly to receptors for
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 ...
and
epinephrine Adrenaline, also known as epinephrine, is a hormone and medication which is involved in regulating visceral functions (e.g., respiration). It appears as a white microcrystalline granule. Adrenaline is normally produced by the adrenal glands a ...
, but it is not clear whether this has any functional significance. It binds more strongly to
trace amine-associated receptor Trace amine-associated receptors (TAARs), sometimes referred to as trace amine receptors (TAs or TARs), are a class of G protein-coupled receptors that were discovered in 2001. TAAR1, the first of six functional human TAARs, has gained considerab ...
s (TAARs), especially
TAAR1 Trace amine-associated receptor 1 (TAAR1) is a trace amine-associated receptor (TAAR) protein that in humans is encoded by the ''TAAR1'' gene. TAAR1 is a primarily intracellular amine-activated and G protein-coupled receptor (GPCR) that is p ...
.


Invertebrates

Octopamine was first discovered by Italian scientist Vittorio Erspamer in 1948 in the salivary glands of the
octopus An octopus (: octopuses or octopodes) is a soft-bodied, eight-limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids. Like oth ...
and has since been found to act as a
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 ...
,
neurohormone A neurohormone is any hormone produced and released by neuroendocrine cells (also called neurosecretory cells) into the blood. By definition of being hormones, they are secreted into the circulation for systemic effect, but they can also have a ro ...
and
neuromodulator Neuromodulation is the physiological process by which a given neuron uses one or more chemicals to regulate diverse populations of neurons. Neuromodulators typically bind to metabotropic, G-protein coupled receptors (GPCRs) to initiate a secon ...
in
invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...
s. Although Erspamer discovered its natural occurrence and named it, octopamine had actually existed for many years as a pharmaceutical product. It is widely used in energy-demanding behaviors by all insects, crustaceans (crabs, lobsters, crayfish), and spiders. Such behaviors include modulating muscle tension, flying, ovulation and egg-laying, and jumping.


In non-insect invertebrates

In lobsters, octopamine seems to direct and coordinate
neurohormone A neurohormone is any hormone produced and released by neuroendocrine cells (also called neurosecretory cells) into the blood. By definition of being hormones, they are secreted into the circulation for systemic effect, but they can also have a ro ...
s to some extent in the central nervous system, and it was observed that injecting octopamine into a lobster and crayfish resulted in limb and abdomen extension. In the
nematode The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (h ...
, octopamine is found in high concentrations in adults, decreasing egg-laying and pharyngeal pumping behaviors with an antagonistic effect to
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, ...
. Octopaminergic nerves in the
mollusc Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...
may be present in the heart, with high concentrations in the nervous system.


In non-''Drosophila'' insects

In insects, octopamine is released by a select number of neurons, but acts broadly throughout the central brain, on all sense organs, and on several non-neuronal tissues. In the thoracic ganglia, octopamine is primarily released by DUM (dorsal unpaired median) and VUM (ventral unpaired median) neurons, which release octopamine onto neural, muscular, and peripheral targets. These neurons are important for mediating energy-demanding motor behaviors, such as escape-induced jumping and flight. For example, the locust DUMeti neuron releases octopamine onto the extensor tibia muscle to increase muscle tension and increase relaxation rate. These actions promote efficient leg muscle contraction for jumping. During flight, DUM neurons are also active and release octopamine throughout the body to synchronize energy metabolism, respiration, muscle activity and flight interneuron activity. Octopamine in
locusts Locusts (derived from the Latin ''locusta'', locust or lobster) are various species of short-horned grasshoppers in the family Acrididae that have a Swarm behaviour, swarming phase. These insects are usually solitary, but under certain circu ...
is four times more concentrated in the axon than in the soma, and decreases the locust's myogenic rhythm. In the
honey bee A honey bee (also spelled honeybee) is a eusocial flying insect within the genus ''Apis'' of the bee clade, all native to mainland Afro-Eurasia. After bees spread naturally throughout Africa and Eurasia, humans became responsible for the ...
, octopamine has a major role in learning and memory. In the
firefly The Lampyridae are a family of elateroid beetles with more than 2,000 described species, many of which are light-emitting. They are soft-bodied beetles commonly called fireflies, lightning bugs, or glowworms for their conspicuous production ...
, octopamine release leads to light production in the lantern. In larvae of the oriental armyworm, octopamine is immunologically beneficial, increasing survival rates in high-density populations. The emerald cockroach wasp stings the host for its larvae (a cockroach) in the head ganglion (brain). The venom blocks octopamine receptors and the cockroach fails to show normal escape responses, grooming itself excessively. It becomes docile and the wasp leads it to the wasp's den by pulling its antenna like a leash.


In ''Drosophila''

Octopamine affects almost every process of the fruit fly and is widely present in both the adult and larval fly. A non-exhaustive list of some of the areas in which Octopamine modulates: * Learning and memory * Ovulation and Egg-Laying * Locomotion * Muscle Physiology * Aggression * Alcohol and drug tolerance * Feeding * Microbiome and gut physiology * Sleep * Modulating effects of exercise * Metabolism


Vertebrates

In
vertebrate Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...
s, octopamine replaces
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 ...
in sympathetic
neuron A neuron (American English), neurone (British English), or nerve cell, is an membrane potential#Cell excitability, excitable cell (biology), cell that fires electric signals called action potentials across a neural network (biology), neural net ...
s with chronic use of
monoamine oxidase inhibitor Monoamine oxidase inhibitors (MAOIs) are a drug class, class of drugs that inhibit the activity of one or both monoamine oxidase enzymes: monoamine oxidase A (MAO-A) and monoamine oxidase B (MAO-B). They are best known as effective antidepressa ...
s. It may be responsible for the common
side effect In medicine, a side effect is an effect of the use of a medicinal drug or other treatment, usually adverse but sometimes beneficial, that is unintended. Herbal and traditional medicines also have side effects. A drug or procedure usually use ...
of
orthostatic hypotension Orthostatic hypotension, also known as postural hypotension, is a medical condition wherein a person's blood pressure drops when they are standing up ( orthostasis) or sitting down. Primary orthostatic hypotension is also often referred to as ne ...
with these agents, though there is also evidence that it is actually mediated by increased levels of ''N''-acetylserotonin. One study noted that octopamine might be an important amine that influences the therapeutic effects of inhibitors such as
monoamine oxidase inhibitor Monoamine oxidase inhibitors (MAOIs) are a drug class, class of drugs that inhibit the activity of one or both monoamine oxidase enzymes: monoamine oxidase A (MAO-A) and monoamine oxidase B (MAO-B). They are best known as effective antidepressa ...
s, especially because a large increase in octopamine levels was observed when animals were treated with this inhibitor. Octopamine was positively identified in the urine samples of mammals such as humans, rats, and rabbits treated with
monoamine oxidase inhibitor Monoamine oxidase inhibitors (MAOIs) are a drug class, class of drugs that inhibit the activity of one or both monoamine oxidase enzymes: monoamine oxidase A (MAO-A) and monoamine oxidase B (MAO-B). They are best known as effective antidepressa ...
s. Very small amounts of octopamine were also found in certain animal tissues. It was observed that within a rabbit's body, the heart and kidney held the highest concentrations of octopamine. Octopamine was found to be 93% eluted by urine within 24 hours of being produced in the body as a byproduct of Iproniazid in rabbits.


Pharmacology

Octopamine has been sold under trade names such as Epirenor, Norden, and Norfen for use in medicine as a sympathomimetic drug, available by prescription. However, very little information exists concerning its clinical usefulness or safety. It has been studied as an
antihypotensive agent An antihypotensive, also known as a vasopressor, is an agent that raises blood pressure by constricting blood vessels, thereby increasing systemic vascular resistance. This is different from inotropes which increase the force of cardiac contra ...
and has been shown to increase
blood pressure Blood pressure (BP) is the pressure of Circulatory system, circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term ...
when administered
intravenously Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutr ...
, intramuscularly, and buccally at sufficiently high doses, whereas
oral administration Oral administration is a route of administration whereby a substance is taken through the Human mouth, mouth, swallowed, and then processed via the digestive system. This is a common route of administration for many medications. Oral administ ...
was ineffective. Octopamine is an analogue of sympathomimetic
catecholamine 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. Cate ...
s like
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 ...
and
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 ...
s like
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 ...
. However, octopamine has 400- to 2,000-fold lower
affinity Affinity may refer to: Commerce, finance and law * Affinity (law), kinship by marriage * Affinity analysis, a market research and business management technique * Affinity Credit Union, a Saskatchewan-based credit union * Affinity Equity Pa ...
for the mammalian α- and β-adrenergic receptors than norepinephrine. In any case, it can produce significant sympathomimetic effects, like pressor responses, at sufficiently high doses. In
mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
s, octopamine may mobilize the release of
fat In nutrition science, nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such chemical compound, compounds, most commonly those that occur in living beings or in food. The term often refers specif ...
from
adipocytes Adipocytes, also known as lipocytes and fat cells, are the cells that primarily compose adipose tissue, specialized in storing energy as fat. Adipocytes are derived from mesenchymal stem cells which give rise to adipocytes through adipogenesis. ...
(fat cells), which has led to its promotion on the
internet The Internet (or internet) is the Global network, global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a internetworking, network of networks ...
as a slimming aid. However, the released fat is likely to be promptly taken up into other cells, and there is no evidence that octopamine facilitates weight loss. Octopamine may also increase
blood pressure Blood pressure (BP) is the pressure of Circulatory system, circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term ...
significantly when combined with other
stimulant 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, ...
s, as in some weight loss supplements. The
World Anti-Doping Agency The World Anti-Doping Agency (WADA; , AMA) is an international organization co-founded by the governments of over 140 nations along with the International Olympic Committee based in Canada to promote, coordinate, and monitor the fight against d ...
lists octopamine as a banned substance for in competition use, as a "specified stimulant" on the 2019 Prohibited List. In contrast to various other phenethylamines, octopamine is a poor or negligible
substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached ** Substrate (aquatic environment), the earthy material that exi ...
of 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).


Insecticides

The octopamine receptor is a target of insecticides, as its blockage leads to decreased
cyclic adenosine monophosphate Cyclic adenosine monophosphate (cAMP, cyclic AMP, or 3',5'-cyclic adenosine monophosphate) is a second messenger, or cellular signal occurring within cells, that is important in many biological processes. cAMP is a derivative of adenosine tri ...
(cAMP) levels. Essential oils can have such a neuro-insecticidal effect, and this octopamine-receptor mechanism is naturally utilized by plants with active insecticidal phytochemicals.


Biochemical mechanisms


Mammals

Octopamine is one of four primary
endogenous agonist In pharmacology, an endogenous agonist for a particular receptor is a compound naturally produced by the body which binds to and activates that receptor. For example, the primary endogenous agonist for serotonin receptors is serotonin, and the p ...
s of human
trace amine-associated receptor 1 Trace amine-associated receptor 1 (TAAR1) is a trace amine-associated receptor (TAAR) protein that in humans is encoded by the ''TAAR1'' gene. TAAR1 is a primarily intracellular amine-activated and G protein-coupled receptor (GPCR) that is p ...
(TAAR1) together with 3-iodothyronamine,
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 ...
and
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 ...
.


Invertebrates

Octopamine binds to its respective G-protein coupled receptors (GPCRs) to initiate a cell signal transduction pathway. At least three groups of octopamine GPCR have been defined. OctαR (OCTOPAMINE1 receptors) are more closely related to α-adrenergic receptors, while OctβR (OCTOPAMINE2 receptors) are more closely related to β-adrenergic receptors. The Octopamine/Tyramine receptors (including Oct-TyrR) can bind both ligands, and display agonist-specific coupling. Oct-TyrR is listed in both OCTOPAMINE and TYRAMINE RECEPTORS gene groups.


Biosynthesis


In insects

Octopamine acts as the
insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...
equivalent 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 ...
and has been implicated in regulating
aggression Aggression is behavior aimed at opposing or attacking something or someone. Though often done with the intent to cause harm, some might channel it into creative and practical outlets. It may occur either reactively or without provocation. In h ...
in
invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...
s, with different effects on different species. Studies have shown that reducing the neurotransmitter octopamine and preventing coding of tyramine β-hydroxylase (an
enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...
that converts
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 ...
to octopamine) decreases aggression in ''
Drosophila ''Drosophila'' (), from Ancient Greek δρόσος (''drósos''), meaning "dew", and φίλος (''phílos''), meaning "loving", is a genus of fly, belonging to the family Drosophilidae, whose members are often called "small fruit flies" or p ...
'' without influencing other behaviors.


Chemistry

Octopamine, or ''para''-octopamine, also known as 4,β-dihydroxyphenethylamine, is a
substituted phenethylamine Substituted phenethylamines (or simply phenethylamines) are a chemical class of organic compounds that are based upon the phenethylamine structure; the class is composed of all the derivative (chemistry), derivative compounds of phenethylamine ...
derivative In mathematics, the derivative is a fundamental tool that quantifies the sensitivity to change of a function's output with respect to its input. The derivative of a function of a single variable at a chosen input value, when it exists, is t ...
. It is related to analogues including phenylethanolamine (β-hydroxyphenethylamine),
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 ...
(''para''-tyramine; 4-hydroxyphenethylamine), and norfenefrine (''meta''-octopamine; 3,β-dihydroxyphenethylamine), among others.


References

{{Phenethylamines Alpha-1 adrenergic receptor agonists Antihypotensive agents Neurotransmitters Norepinephrine-dopamine releasing agents Peripherally selective drugs 4-Hydroxyphenyl compounds Phenylethanolamines Sympathomimetics TAAR1 agonists Trace amines