The alpha-2 (α
2) adrenergic receptor (or adrenoceptor) is a
G protein-coupled receptor
G protein-coupled receptors (GPCRs), also known as seven-(pass)-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptors, and G protein-linked receptors (GPLR), form a large group of evolutionarily-related p ...
(GPCR) associated with the
Gi heterotrimeric G-protein
Heterotrimeric G protein, also sometimes referred to as the ''"large" G proteins'' (as opposed to the subclass of smaller, monomeric small GTPases) are membrane-associated G proteins that form a heterotrimeric complex. The biggest non-struct ...
. It consists of three highly homologous subtypes, including
α2A-,
α2B-, and
α2C-adrenergic. Some species other than humans express a fourth α
2D-adrenergic receptor as well.
Catecholamine
A catecholamine (; abbreviated CA) 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.
Catechol can be either a free molecule or a su ...
s like
norepinephrine
Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic chemical in the catecholamine family that functions in the brain and body as both a hormone and neurotransmitter. The name "noradrenaline" (from Latin '' ad ...
(noradrenaline) 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 and ...
(adrenaline) signal through the α
2-adrenergic receptor in the
central
Central is an adjective usually referring to being in the center of some place or (mathematical) object.
Central may also refer to:
Directions and generalised locations
* Central Africa, a region in the centre of Africa continent, also known a ...
and
peripheral nervous system
The peripheral nervous system (PNS) is one of two components that make up the nervous system of bilateral animals, with the other part being the central nervous system (CNS). The PNS consists of nerves and ganglia, which lie outside the brai ...
s.
Cellular localization
The
α2A adrenergic receptor is localised in the following
central nervous system
The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...
(CNS) structures:
*
Brainstem
The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is ...
(especially the
locus coeruleus
The locus coeruleus () (LC), also spelled locus caeruleus or locus ceruleus, is a nucleus in the pons of the brainstem involved with physiological responses to stress and panic. It is a part of the reticular activating system.
The locus coer ...
)
*
Midbrain
The midbrain or mesencephalon is the forward-most portion of the brainstem and is associated with vision, hearing, motor control, sleep and wakefulness, arousal ( alertness), and temperature regulation. The name comes from the Greek ''mesos'', ...
*
Hypothalamus
The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamus ...
*
Hippocampus
The hippocampus (via Latin from Greek , 'seahorse') is a major component of the brain of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus is part of the limbic syste ...
*
Spinal cord
The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the sp ...
*
Cerebral cortex
The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex mostly consists of the six-layered neocortex, with just 10% consisting o ...
*
Cerebellum
The cerebellum (Latin for "little brain") is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as or even larger. In humans, the cerebe ...
*
Septum
In biology, a septum (Latin for ''something that encloses''; plural septa) is a wall, dividing a cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate.
Examples
Human anatomy
* Interat ...
Whereas the
α2B adrenergic receptor is localised in the following CNS structures:
[
* Olfactory system
* Thalamus
* Pyramidal layer of the hippocampus
* Cerebellar Purkinje layer
and the α2C adrenergic receptor is localised in the CNS structures:][
* Midbrain
* Thalamus
* Amygdala
* Dorsal root ganglia
* Olfactory system
* Hippocampus
* Cerebral cortex
* Basal ganglia
* Substantia nigra
* Ventral tegmentum
]
Effects
The α2-adrenergic receptor is classically located on vascular prejunctional terminals where it inhibits the release of norepinephrine (noradrenaline) in a form of negative feedback.[Cardiovascular Physiology, 3rd Edition, Arnold Publishers, Levick, J.R., Chapter 14.1, Sympathetic vasoconstrictor nerves] It is also located on the vascular smooth muscle cells of certain blood vessels, such as those found in skin arterioles or on veins, where it sits alongside the more plentiful α1-adrenergic receptor. The α2-adrenergic receptor binds both norepinephrine released by sympathetic postganglionic fibers and epinephrine (adrenaline) released by the adrenal medulla
The adrenal medulla ( la, medulla glandulae suprarenalis) is part of the adrenal gland. It is located at the center of the gland, being surrounded by the adrenal cortex. It is the innermost part of the adrenal gland, consisting of chromaffin cell ...
, binding norepinephrine with slightly higher affinity. It has several general functions in common with the α1-adrenergic receptor, but also has specific effects of its own. Agonists (activators) of the α2-adrenergic receptor are frequently used in anaesthesia where they affect sedation
Sedation is the reduction of irritability or agitation by administration of sedative drugs, generally to facilitate a medical procedure or diagnostic procedure. Examples of drugs which can be used for sedation include isoflurane, diethyl ether, ...
, muscle relaxation and analgesia through effects on the central nervous system
The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...
(CNS).
General
Common effects include:
* Suppression of release of norepinephrine
Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic chemical in the catecholamine family that functions in the brain and body as both a hormone and neurotransmitter. The name "noradrenaline" (from Latin '' ad ...
( noradrenaline) by negative feedback.
*Transient hypertension
Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high b ...
(increase in blood pressure), followed by a sustained hypotension
Hypotension is low blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood. Blood pressure is indicated by two numbers, the systolic blood pressure (the top number) and the di ...
(decrease in blood pressure).
*Vasoconstriction
Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vess ...
of certain arteries
* Vasoconstriction of arteries to heart
The heart is a muscular Organ (biology), organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as ca ...
(coronary artery
The coronary arteries are the arterial blood vessels of coronary circulation, which transport oxygenated blood to the heart muscle. The heart requires a continuous supply of oxygen to function and survive, much like any other tissue or organ o ...
); however, the extent of this effect may be limited and may be negated by the vasodilatory effect from β2 receptors
* Constriction of some vascular smooth muscle[Basic & Clinical Pharmacology, 11th Edition, McGrawHill LANGE, Katzung Betram G.; Chapter 9. Adrenoceptor Agonists & Sympathomimetic Drugs]
* Venoconstriction of veins
Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated ...
* Decrease motility of smooth muscle
Smooth muscle is an involuntary non- striated muscle, so-called because it has no sarcomeres and therefore no striations (''bands'' or ''stripes''). It is divided into two subgroups, single-unit and multiunit smooth muscle. Within single-unit ...
in gastrointestinal tract
The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and ...
* Inhibition of lipolysis
* Facilitation of the cognitive functions associated with the prefrontal cortex
In mammalian brain anatomy, the prefrontal cortex (PFC) covers the front part of the frontal lobe of the cerebral cortex. The PFC contains the Brodmann areas BA8, BA9, BA10, BA11, BA12, BA13, BA14, BA24, BA25, BA32, BA44, BA45, BA ...
(PFC; working memory, attention, executive functioning, etc.)
* Sedation[
* Analgesia
]
Individual
Individual actions of the α2 receptor include:
* Mediates synaptic transmission
Neurotransmission (Latin: ''transmissio'' "passage, crossing" from ''transmittere'' "send, let through") is the process by which signaling molecules called neurotransmitters are released by the axon terminal of a neuron (the presynaptic neuron ...
in pre- and postsynaptic nerve terminals
** Decrease release of acetylcholine
Acetylcholine (ACh) is an organic chemical that functions in the brain and body of many types of animals (including humans) as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Par ...
[
** Decrease release of ]norepinephrine
Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic chemical in the catecholamine family that functions in the brain and body as both a hormone and neurotransmitter. The name "noradrenaline" (from Latin '' ad ...
[
*** Inhibit norepinephrine system in brain
* Inhibition] of lipolysis in adipose tissue
Adipose tissue, body fat, or simply fat is a loose connective tissue composed mostly of adipocytes. In addition to adipocytes, adipose tissue contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, vascular ...
[
* Inhibition of ]insulin
Insulin (, from Latin ''insula'', 'island') is a peptide hormone produced by beta cells of the pancreatic islets encoded in humans by the ''INS'' gene. It is considered to be the main anabolic hormone of the body. It regulates the metabolism ...
release in pancreas
The pancreas is an organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdomen behind the stomach and functions as a gland. The pancreas is a mixed or heterocrine gland, i.e. it has both an ...
* Induction of glucagon
Glucagon is a peptide hormone, produced by alpha cells of the pancreas. It raises concentration of glucose and fatty acids in the bloodstream, and is considered to be the main catabolic hormone of the body. It is also used as a medication to tre ...
release from pancreas
* platelet aggregation
* Contraction of sphincters of the gastrointestinal tract
The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and ...
* Decreased secretion from salivary gland
The salivary glands in 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 minor salivary glands. Salivary ...
* Relax gastrointestinal tract
The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and ...
(presynaptic effect)
* Decreased aqueous humor fluid production from the ciliary body
Signaling cascade
The α subunit of an inhibitory G protein
G proteins, also known as guanine nucleotide-binding proteins, are a family of proteins that act as molecular switches inside cells, and are involved in transmitting signals from a variety of stimuli outside a cell to its interior. Their a ...
- Gi dissociates from the G protein, and associates with adenylyl cyclase
Adenylate cyclase (EC 4.6.1.1, also commonly known as adenyl cyclase and adenylyl cyclase, abbreviated AC) is an enzyme with systematic name ATP diphosphate-lyase (cyclizing; 3′,5′-cyclic-AMP-forming). It catalyzes the following reaction:
:A ...
. This causes the inactivation of adenylyl cyclase, resulting in a decrease of cAMP
Camp may refer to:
Outdoor accommodation and recreation
* Campsite or campground, a recreational outdoor sleeping and eating site
* a temporary settlement for nomads
* Camp, a term used in New England, Northern Ontario and New Brunswick to descri ...
produced from ATP, which leads to a decrease of intracellular cAMP. PKA
PKA may refer to:
* Professionally known as:
** Pen name
** Stage persona
* p''K''a, the symbol for the acid dissociation constant at logarithmic scale
* Protein kinase A, a class of cAMP-dependent enzymes
* Pi Kappa Alpha, the North-American so ...
is not able to be activated by cAMP, so proteins such as phosphorylase kinase
Phosphorylase kinase (PhK) is a serine/threonine-specific protein kinase which activates glycogen phosphorylase to release glucose-1-phosphate from glycogen. PhK phosphorylates glycogen phosphorylase at two serine residues, triggering a conformatio ...
cannot be phosphorylated by PKA. In particular, phosphorylase kinase is responsible for the phosphorylation and activation of glycogen phosphorylase, an enzyme necessary for glycogen breakdown. Thus in this pathway, the downstream effect of adenylyl cyclase inactivation is decreased breakdown of glycogen.
The relaxation of gastrointestinal tract motility is by presynaptic inhibition,[ Page 163] where transmitters inhibit further release by homotropic effects.
Agonists
* 4-NEMD
* 7-Me-marsanidine (also I1 agonist
An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the ag ...
)
* Agmatine (also I agonist
An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the ag ...
, NMDA, 5-HT3
The 5-HT3 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-coup ...
, nicotinic antagonist
An antagonist is a character in a story who is presented as the chief foe of the protagonist.
Etymology
The English word antagonist comes from the Greek ἀνταγωνιστής – ''antagonistēs'', "opponent, competitor, villain, enemy, ri ...
and NOS inhibitor)
* Apraclonidine
* Brimonidine
Brimonidine is a medication used to treat open-angle glaucoma, ocular hypertension, and rosacea. In rosacea it improves the redness. It is used as eye drops or applied to the skin.
Common side effects when used in the eyes include itchiness, ...
* Cannabigerol (also acts as a moderate affinity 5-HT1A receptor antagonist, and low affinity CB1 receptor antagonist).
* Clonidine
Clonidine, sold under the brand name Catapres among others, is an α2-adrenergic agonist medication used to treat high blood pressure, ADHD, drug withdrawal ( alcohol, opioids, or nicotine), menopausal flushing, diarrhea, spasticity, and c ...
(also I1 agonist
An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the ag ...
)
* Detomidine
* Dexmedetomidine
* Fadolmidine
* Guanabenz
* Guanfacine
* Lofexidine
* Marsanidine
* Medetomidine
* Methamphetamine
Methamphetamine (contracted from ) is a potent central nervous system (CNS) stimulant that is mainly used as a recreational drug and less commonly as a second-line treatment for attention deficit hyperactivity disorder and obesity. Methamp ...
* Methylphenidate
Methylphenidate, sold under the brand names Ritalin and Concerta among others, is the most widely prescribed central nervous system (CNS) stimulant medication used to treat attention deficit hyperactivity disorder (ADHD) and, to a lesser extent ...
;
* Mivazerol
* Rilmenidine
Rilmenidine is a prescription medication for the treatment of hypertension. It is marketed under the brand names Albarel, Hyperium, Iterium and Tenaxum.
Form and composition
Each tablet contains 1.544 mg rilmenidine dihydrogen phosphate, an a ...
(also I agonist
An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the ag ...
)
* Romifidine
Romifidine is a drug that is used in veterinary medicine as a sedative mainly in large animals such as horses, although it may be used in a wide variety of species. It is not used in humans, but is closely related in structure to the commonly use ...
* Talipexole (also dopamine agonist)
* Tiamenidine
* Tizanidine
* Tolonidine
* Xylazine
Xylazine is a pharmaceutical drug used for sedation, anesthesia, muscle relaxation, and analgesia in animals such as horses, cattle, and other non-human mammals. Veterinarians also use xylazine as an emetic, especially in cats. It is an anal ...
* Xylometazoline
Xylometazoline, also spelled xylomethazoline, is a medication used to reduce symptoms of nasal congestion, allergic rhinitis, and sinusitis. Use is not recommended for more than seven days. Use is also not recommended in those less than three m ...
;Partial agonists
* Oxymetazoline (also α1 agonist
An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the ag ...
)
* TDIQ
;Antagonists
* 1-PP (active metabolite of buspirone and gepirone)
* Aripiprazole
* Asenapine
* Atipamezole
* Cirazoline
* Clozapine
* Efaroxan
* Idazoxan
* Lurasidone
* Melperone
* Mianserin
Mianserin, sold under the brand name Tolvon among others, is an atypical antidepressant that is used primarily in the treatment of depression in Europe and elsewhere in the world. It is a tetracyclic antidepressant (TeCA). Mianserin is closel ...
* Mirtazapine
Mirtazapine, sold under the brand name Remeron amongst others, is an atypical antidepressant, and as such is used primarily to treat depression. Its effects may take up to four weeks, but can also manifest as early as one to two weeks. It is o ...
* Napitane
* Olanzapine
* Paliperidone
Paliperidone, sold under the trade name Invega among others, is an atypical antipsychotic. It is mainly used to treat schizophrenia and schizoaffective disorder.
It is marketed by Janssen Pharmaceuticals. An extended release formulation is a ...
(also primary active metabolite of Risperidone)
* Phenoxybenzamine
* Phentolamine
* Piribedil
* Rauwolscine
* Risperidone
* Rotigotine ( α2B antagonist, non-selective)
* Quetiapine
* Norquetiapine (primary active metabolite of Quetiapine)
* Setiptiline
* Tolazoline
Tolazoline is a non-selective competitive α-adrenergic receptor antagonist. It is a vasodilator that is used to treat spasms of peripheral blood vessels (as in acrocyanosis). It has also been used (in conjunction with sodium nitroprusside) ...
* Yohimbine
Yohimbine (), also known as quebrachine, is an indole alkaloid derived from the bark of the African tree '' Pausinystalia johimbe''; also from the bark of the unrelated South American tree ''Aspidosperma quebracho-blanco''. Yohimbine is an α2 ...
* Ziprasidone
Ziprasidone, sold under the brand name Geodon among others, is an atypical antipsychotic used to treat schizophrenia and bipolar disorder. It may be used by mouth and by injection into a muscle (IM). The IM form may be used for acute agitati ...
* Zotepine (discontinued)
Agonists
Norepinephrine
Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic chemical in the catecholamine family that functions in the brain and body as both a hormone and neurotransmitter. The name "noradrenaline" (from Latin '' ad ...
has higher affinity for the α2 receptor than has 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 and ...
, and therefore relates less to the latter's functions.[ Nonselective α2 agonists include the ]antihypertensive
Antihypertensives are a class of drugs that are used to treat hypertension (high blood pressure). Antihypertensive therapy seeks to prevent the complications of high blood pressure, such as stroke and myocardial infarction. Evidence suggests th ...
drug clonidine
Clonidine, sold under the brand name Catapres among others, is an α2-adrenergic agonist medication used to treat high blood pressure, ADHD, drug withdrawal ( alcohol, opioids, or nicotine), menopausal flushing, diarrhea, spasticity, and c ...
,[ which can be used to lower blood pressure and to reduce hot flashes associated with menopause. Clonidine has also been successfully used in indications that exceed what would be expected from a simple blood-pressure lowering drug: it has recently shown positive results in children with ]ADHD
Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by excessive amounts of inattention, hyperactivity, and impulsivity that are pervasive, impairing in multiple contexts, and otherwise age-inap ...
who have tics resulting from the treatment with a CNS stimulant
Stimulants (also often referred to as psychostimulants or colloquially as uppers) is an overarching term that covers many drugs including those that increase activity of the central nervous system and the body, drugs that are pleasurable and inv ...
drug, such as Adderall XR or methylphenidate
Methylphenidate, sold under the brand names Ritalin and Concerta among others, is the most widely prescribed central nervous system (CNS) stimulant medication used to treat attention deficit hyperactivity disorder (ADHD) and, to a lesser extent ...
; clonidine also helps alleviate symptoms of opioid withdrawal. The hypotensive effect of clonidine was initially attributed through its agonist action on presynaptic α2 receptors, which act as a down-regulator on the amount of norepinephrine released in the synaptic cleft, an example of autoreceptor
An autoreceptor is a type of receptor located in the membranes of nerve cells. It serves as part of a negative feedback loop in signal transduction. It is only sensitive to the neurotransmitters or hormones released by the neuron on which the au ...
. However, it is now known that clonidine binds to imidazoline receptors with a much greater affinity than α2 receptors, which would account for its applications outside the field of hypertension alone. Imidazoline receptors occur in the nucleus tractus solitarii and also the centrolateral medulla. Clonidine is now thought to decrease blood pressure via this central mechanism. Other nonselective agonists include dexmedetomidine, lofexidine (another antihypertensive), TDIQ (partial agonist), tizanidine (in spasms, cramping) and xylazine
Xylazine is a pharmaceutical drug used for sedation, anesthesia, muscle relaxation, and analgesia in animals such as horses, cattle, and other non-human mammals. Veterinarians also use xylazine as an emetic, especially in cats. It is an anal ...
. Xylazine has veterinary use.
In the European Union, dexmedetomidine received a marketing authorization from the European Medicines Agency
The European Medicines Agency (EMA) is an agency of the European Union (EU) in charge of the evaluation and supervision of medicinal products. Prior to 2004, it was known as the European Agency for the Evaluation of Medicinal Products or Eur ...
(EMA) on August 10, 2012, under the brand name of Dexdor. It is indicated for sedation in the ICU for patients needing mechanical ventilation.
In non-human species this is an immobilizing and anesthetic drug, presumptively also mediated by α2 adrenergic receptors because it is reversed by yohimbine, an α2 antagonist.
α2A selective agonists include guanfacine (an antihypertensive) and Brimonidine (UK 14,304).
(''R'')-3-nitrobiphenyline is an α2C selective agonist as well as being a weak antagonist
An antagonist is a character in a story who is presented as the chief foe of the protagonist.
Etymology
The English word antagonist comes from the Greek ἀνταγωνιστής – ''antagonistēs'', "opponent, competitor, villain, enemy, ri ...
at the α and α subtypes.
Antagonists
Nonselective α blockers include, A-80426, atipamezole, phenoxybenzamine, efaroxan, idazoxan*[(experimental),] and SB-269,970.
Yohimbine
Yohimbine (), also known as quebrachine, is an indole alkaloid derived from the bark of the African tree '' Pausinystalia johimbe''; also from the bark of the unrelated South American tree ''Aspidosperma quebracho-blanco''. Yohimbine is an α2 ...
*[ is a relatively selective alpha-2 blocker that has been investigated as a treatment for erectile dysfunction.
Tetracyclic antidepressants ]mirtazapine
Mirtazapine, sold under the brand name Remeron amongst others, is an atypical antidepressant, and as such is used primarily to treat depression. Its effects may take up to four weeks, but can also manifest as early as one to two weeks. It is o ...
and mianserin
Mianserin, sold under the brand name Tolvon among others, is an atypical antidepressant that is used primarily in the treatment of depression in Europe and elsewhere in the world. It is a tetracyclic antidepressant (TeCA). Mianserin is closel ...
are also potent α antagonists with mirtazapine being more selective for α2 subtype (~30-fold selective over α1) than mianserin (~17-fold).
α2A selective blockers include BRL-44408 and RX-821,002.
α2B selective blockers include ARC-239 and imiloxan.
α2C selective blockers include JP-1302 and spiroxatrine
Spiroxatrine is a drug which acts as a selective antagonist at both the 5-HT1A receptor and the α2C adrenergic receptor. It is an analog of spiperone and also has some dopamine antagonist
A dopamine antagonist, also known as an anti-dopam ...
, the latter also being a serotonin
Serotonin () or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter. Its biological function is complex and multifaceted, modulating mood, cognition, reward, learning, memory, and numerous physiological processes such as vomiting and va ...
5-HT1A antagonist.
See also
* Adrenergic receptor
The adrenergic receptors or adrenoceptors are a class of G protein-coupled receptors that are targets of many catecholamines like norepinephrine (noradrenaline) and epinephrine (adrenaline) produced by the body, but also many medications like bet ...
References
External links
*
{{DEFAULTSORT:Alpha-2 Adrenergic Receptor
Adrenergic receptors
Human proteins