The adrenergic receptors (or adrenoceptors) are a class of G protein-coupled receptors G protein-coupled receptors , also known as seven-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptor, and G protein-linked receptors (GPLR), comprise a large protein family of transmembrane receptors that sense molecules outside the cell and activate inside signal transduction pathways and, ultimately, that are targets of the catecholamines Catecholamines are sympathomimetic "fight-or-flight" hormones released by the adrenal glands in response to stress. They are part of the sympathetic nervous system, especially noradrenaline Norepinephrine (abbreviated norepi or NE) or noradrenaline (BAN) (abbreviated NA or NAd) is a catecholamine with multiple roles including as a hormone and a neurotransmitter (norepinephrine) and adrenaline Epinephrine is a hormone and neurotransmitter.. It increases heart rate, contracts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. Chemically, epinephrine is a catecholamine, a monoamine produced only by the adrenal glands from the amino acids phenylalanine and tyrosine (epinephrine). Although dopamine Dopamine is a catecholamine neurotransmitter that occurs in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this phenethylamine functions as a neurotransmitter, activating the five types of dopamine receptors—D1, D2, D3, D4, and D5—and their variants. Dopamine is produced in several areas of the brain, is a catecholamine, its receptors are in a different category.

Many cells possess these receptors, and the binding of an agonist An agonist is a chemical that binds to a receptor of a cell and triggers a response by that cell. Agonists often mimic the action of a naturally occurring substance. Whereas an agonist causes an action, an antagonist blocks the action of the agonist and an inverse agonist causes an action opposite to that of the agonist will generally cause a sympathetic response (e.g. the fight-or-flight response The "fight-or-flight response", also called the "fight-or-flight-or-freeze response", the "fright, fight or flight response", "hyperarousal" or the "acute stress response", was first described by Walter Cannon in 1929). For instance, the heart rate Heart rate is the number of heartbeats per unit of time - typically expressed as beats per minute - which can vary as the body's need for oxygen changes, such as during exercise or sleep. The measurement of heart rate is used by medical professionals to assist in the diagnosis and tracking of medical conditions. It is also used by individuals, will increase and the pupils The pupil is a hole located in the center of the iris of the eye that allows light to enter the retina. It appears black because most of the light entering the pupil is absorbed by the tissues inside the eye. In humans the pupil is round, but other species, such as some cats, have slit pupils. In optical terms, the anatomical pupil is the eye's will dilate, energy will be mobilized, and blood flow diverted from other non-essential organs to skeletal muscle Skeletal muscle is a form of striated muscle tissue existing under control of the somatic nervous system. It is one of three major muscle types, the others being cardiac and smooth muscle. As its name suggests, most skeletal muscle is attached to bones by bundles of collagen fibers known as tendons.

Contents 1 Subtypes 1.1 Roles in circulation 1.2 Comparison 1.3 α receptors 1.3.1 α1 receptor 1.3.2 α2 receptor 1.4 β receptors 1.4.1 β1 receptor 1.4.2 β2 receptor 1.4.3 β3 receptor 2 See also 3 References 4 Further reading 5 External links

Subtypes

There are two main groups of adrenergic receptors, α and β, with several subtypes.

• α receptors have the subtypes α₁ (a G_q G proteins are a family of proteins involved in transmitting chemical signals outside the cell, and causing changes inside the cell. They communicate signals from many hormones, neurotransmitters, and other signaling factors coupled receptor) and α₂ The alpha-2 adrenergic receptor is a G protein-coupled receptor (GPCR) associated with the Gi heterotrimeric G-protein. It consists of three highly homologous subtypes, including α2A-, α2B-, and α2C-adrenergic. Some species other than humans express a fourth α2D-adrenergic receptor as well. Catecholamines like norepinephrine (noradrenaline) (a G_i coupled receptor). Phenylephrine Phenylephrine or Neo-Synephrine is an α1-adrenergic receptor agonist used primarily as a decongestant, as an agent to dilate the pupil, and to increase blood pressure. Phenylephrine has recently been marketed as a substitute for pseudoephedrine (e.g.,Sudafed ), but there are recent claims that oral phenylephrine may be no more effective as a is a selective agonist of the α receptor.
• β receptors have the subtypes β₁, β₂ The beta-2 adrenergic receptor , also known as ADRB2, is a beta-adrenergic receptor, and also denotes the human gene encoding it and β₃. All three are linked to G_s proteins (although β₂ The beta-2 adrenergic receptor , also known as ADRB2, is a beta-adrenergic receptor, and also denotes the human gene encoding it also couples to Gi)^[1], which in turn are linked to adenylate cyclase Adenylate cyclase is a lyase enzyme. It is a part of the cAMP-dependent pathway. Agonist binding thus causes a rise in the intracellular concentration of the second messenger cAMP Cyclic adenosine monophosphate is a second messenger important in many biological processes. cAMP is derived from adenosine triphosphate (ATP) and used for intracellular signal transduction in many different organisms, conveying the cAMP-dependent pathway (cyclic adenosine monophosphate). Downstream effectors of cAMP include cAMP-dependent protein kinase (PKA), which mediates some of the intracellular events following hormone binding. Isoprenaline Isoprenaline or isoproterenol (USAN, trade names Medihaler-Iso and Isuprel) is a sympathomimetic beta adrenergic agonist medication is a selective agonist.

Epinephrine binds its receptor, that associates with an heterotrimeric G protein. The G protein associates with adenylate cyclase that converts ATP to cAMP, spreading the signal (more details...) The mechanism of adrenergic receptors. Adrenaline or noradrenaline are receptor ligands to either α₁, α₂ The alpha-2 adrenergic receptor is a G protein-coupled receptor (GPCR) associated with the Gi heterotrimeric G-protein. It consists of three highly homologous subtypes, including α2A-, α2B-, and α2C-adrenergic. Some species other than humans express a fourth α2D-adrenergic receptor as well. Catecholamines like norepinephrine (noradrenaline) or β-adrenergic receptors. α₁ couples to G_q Gq protein or Gq/11 is a heterotrimeric G protein subunit that activates phospholipase C . PLC in turn hydrolyzes phosphatidylinositol (PIP2) to diacyl glycerol (DAG) and inositol triphosphate (IP3) signal transduction pathway. DAG acts as a second messenger that activates Protein Kinase C (PKC) and IP3 helps in phosphorylation of some proteins, which results in increased intracellular Ca²⁺ Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth most abundant element by mass in the Earth's crust. Calcium is also the fifth most abundant dissolved ion in seawater by both molarity and mass, after sodium, chloride, which results in smooth muscle Smooth muscle is an involuntary non-striated muscle. It is divided into two sub-groups; the single-unit and multiunit smooth muscle. Within single-unit smooth muscle tissues, the autonomic nervous system innervates a single cell within a sheet or bundle and the action potential is propagated by gap junctions to neighboring cells such that the contraction. α₂ The alpha-2 adrenergic receptor is a G protein-coupled receptor (GPCR) associated with the Gi heterotrimeric G-protein. It consists of three highly homologous subtypes, including α2A-, α2B-, and α2C-adrenergic. Some species other than humans express a fourth α2D-adrenergic receptor as well. Catecholamines like norepinephrine (noradrenaline), on the other hand, couples to G_i Gi inhibits adenylate cyclase activity, decreasing the production of cAMP from ATP, which, in turn, results in decreased activity of cAMP-dependent protein kinase. Thus, the ultimate effect of Gi is thus the opposite of cAMP-dependent protein kinase, which can be found at function of cAMP-dependent protein kinase, which causes a decrease of cAMP Cyclic adenosine monophosphate is a second messenger important in many biological processes. cAMP is derived from adenosine triphosphate (ATP) and used for intracellular signal transduction in many different organisms, conveying the cAMP-dependent pathway activity, resulting in e.g. smooth muscle relaxation. β receptors couple to G_s, and increases intracellular cAMP Cyclic adenosine monophosphate is a second messenger important in many biological processes. cAMP is derived from adenosine triphosphate (ATP) and used for intracellular signal transduction in many different organisms, conveying the cAMP-dependent pathway activity, resulting in e.g. heart muscle Cardiac muscle is a type of involuntary striated muscle found in the walls of the heart, specifically the myocardium. Cardiac muscle cells are known as cardiac myocytes . Cardiac muscle is one of three major types of muscle, the others being skeletal and smooth muscle. The cells that comprise cardiac muscle are sometimes seen as intermediate contraction, smooth muscle relaxation and glycogenolysis Glycogenolysis is the conversion of glycogen polymers to glucose monomers. Glycogen is catabolized by removal of a glucose monomer through cleavage with inorganic phosphate to produce glucose-1-phosphate. This derivative of glucose is then converted to glucose-6-phosphate, an intermediate in glycolysis.

Roles in circulation

Adrenaline reacts with both α- and β-adrenoreceptors, causing vasoconstriction and vasodilation, respectively. Although α receptors are less sensitive to epinephrine, when activated, they override the vasodilation mediated by β-adrenoreceptors. The result is that high levels of circulating epinephrine cause vasoconstriction. At lower levels of circulating epinephrine, β-adrenoreceptor stimulation dominates, producing an overall vasodilation.

Comparison

Receptor	Agonist potency order	Selected action of agonist An agonist is a chemical that binds to a receptor of a cell and triggers a response by that cell. Agonists often mimic the action of a naturally occurring substance. Whereas an agonist causes an action, an antagonist blocks the action of the agonist and an inverse agonist causes an action opposite to that of the agonist	Mechanism Second messengers are molecules that relay signals from receptors on the cell surface to target molecules inside the cell, in the cytoplasm or nucleus. They relay the signals of hormones like epinephrine , growth factors, and others, and cause some kind of change in the activity of the cell. They greatly amplify the strength of the signal	Agonists An adrenergic is a drug, or other substance, which has effects similar to, or the same as, epinephrine . Thus, it is a kind of sympathomimetic agent. Alternatively, it may refer to something which is susceptible to epinephrine, or similar substances, such as a biological receptor (specifically, the adrenergic receptors)	Antagonists An Adrenergic antagonist is a pharmaceutical substance that acts to inhibit the action of the adrenergic receptors. It is thus a type of sympatholytic
α1: A The alpha-1A adrenergic receptor , also known as ADRA1A, formerly known as the alpha-1C adrenergic receptor, is an alpha-1 adrenergic receptor, and also denotes the human gene encoding it, B, D†	Norepinephrine Norepinephrine (abbreviated norepi or NE) or noradrenaline (BAN) (abbreviated NA or NAd) is a catecholamine with multiple roles including as a hormone and a neurotransmitter > epinephrine Epinephrine is a hormone and neurotransmitter.. It increases heart rate, contracts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. Chemically, epinephrine is a catecholamine, a monoamine produced only by the adrenal glands from the amino acids phenylalanine and tyrosine >> isoprenaline Isoprenaline or isoproterenol (USAN, trade names Medihaler-Iso and Isuprel) is a sympathomimetic beta adrenergic agonist medication	Smooth muscle Smooth muscle is an involuntary non-striated muscle. It is divided into two sub-groups; the single-unit and multiunit smooth muscle. Within single-unit smooth muscle tissues, the autonomic nervous system innervates a single cell within a sheet or bundle and the action potential is propagated by gap junctions to neighboring cells such that the contraction	Gq Gq protein or Gq/11 is a heterotrimeric G protein subunit that activates phospholipase C . PLC in turn hydrolyzes phosphatidylinositol (PIP2) to diacyl glycerol (DAG) and inositol triphosphate (IP3) signal transduction pathway. DAG acts as a second messenger that activates Protein Kinase C (PKC) and IP3 helps in phosphorylation of some proteins: phospholipase C Phospholipase C is a class of enzymes that cleave phospholipids just before the phosphate group . It is most commonly taken to be synonymous with the human forms of this enzyme, which plays an important role in eukaryotic cell physiology, particularly signal transduction pathways. Thirteen kinds of mammalian phospholipase C are classified into six (PLC) activated, IP3 and calcium Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth most abundant element by mass in the Earth's crust. Calcium is also the fifth most abundant dissolved ion in seawater by both molarity and mass, after sodium, chloride, up	(Alpha-1 agonists An adrenergic alpha-agonist is a drug that selectively stimulates alpha adrenergic receptors. The alpha-adrenergic receptor has two subclasses α1 and α2) Noradrenaline Norepinephrine (abbreviated norepi or NE) or noradrenaline (BAN) (abbreviated NA or NAd) is a catecholamine with multiple roles including as a hormone and a neurotransmitter Phenylephrine Phenylephrine or Neo-Synephrine is an α1-adrenergic receptor agonist used primarily as a decongestant, as an agent to dilate the pupil, and to increase blood pressure. Phenylephrine has recently been marketed as a substitute for pseudoephedrine (e.g.,Sudafed ), but there are recent claims that oral phenylephrine may be no more effective as a Methoxamine Methoxamine is an α1-adrenergic receptor agonist, similar in structure to phenylephrine and 2,5-DMA. It induces vasoconstriction of skin and splanchnic blood vessels, thereby increasing peripheral vascular resistance and raising mean arterial blood pressure. Because of its hypertensive effects, it may evoke a compensatory reflex bradycardia via Cirazoline Cirazoline is a nonselective agonist of the alpha-1 adrenergic receptor , and an antagonist to the alpha-2 adrenergic receptor. It is believed that this combination of properties could make cirazoline an effective effective vasoconstricting agent Xylometazoline Xylometazoline is a drug which is used as a nasal decongestant. It is a topical decongestant that is applied directly into the nose, either as a spray or as drops	(Alpha-1 blockers Alpha-1 blockers constitute a variety of drugs which block α1-adrenergic receptors in arteries and smooth muscles) Alfuzosin Alfuzosin is an α1 receptor antagonist used to treat benign prostatic hyperplasia (BPH). It works by relaxing the muscles in the prostate and bladder neck, making it easier to urinate Doxazosin Doxazosin mesylate, a quinazoline compound sold by Pfizer under the brand names Cardura and Carduran, is an alpha blocker used to treat high blood pressure and benign prostatic hyperplasia Phenoxybenzamine It is used in the treatment of hypertension, and specifically that caused by pheochromocytoma. It has a slower onset and a longer lasting effect compared with other alpha blockers Phentolamine Prazosin Tamsulosin Terazosin (TCA:s) Amitriptyline Clomipramine Doxepin Trimipramine
α2: A, B, C	Epinephrine ≥ norepinephrine >> isoprenaline	Smooth muscle constriction and neurotransmitter inhibition	Gi: adenylate cyclase inactivated, cAMP down	(Alpha-2 agonists) Dexmedetomidine Medetomidine Romifidine Clonidine Brimonidine Detomidine Lofexidine Xylazine Tizanidine Guanfacine Amitraz	(Alpha-2 blockers) Phentolamine Yohimbine Idazoxan Atipamezole
β1	Isoprenaline > epinephrine = norepinephrine	Heart muscle contraction	Gs: adenylate cyclase activated, cAMP up	Noradrenaline Isoprenaline Dobutamine	(Beta blockers) Metoprolol Atenolol
β2	Isoprenaline > epinephrine >> norepinephrine	Smooth muscle relaxation	Gs: adenylate cyclase activated, cAMP up (also Gi, see β2)	(Short/long) Salbutamol (Albuterol in USA) Bitolterol mesylate Formoterol Isoprenaline Levalbuterol Metaproterenol Salmeterol Terbutaline Ritodrine	(Beta blockers) Butoxamine Propranolol
β3	Isoprenaline = norepinephrine > epinephrine	Enhance lipolysis	Gs: adenylate cyclase activated, cAMP up	L-796568 [2] Amibegron Solabegron	SR 59230A

^†There is no α_1C receptor. At one time, there was a subtype known as C, but was found to be identical to one of the previously discovered subtypes. To avoid confusion, naming was continued with the letter D.

α receptors

α receptors have several functions in common, but also individual effects. Common (or still unspecified) effects include:

• Vasoconstriction of arteries to heart (coronary artery).^[3]
• Vasoconstriction of veins^[4]
• Decrease motility of smooth muscle in gastrointestinal tract^[5]

α₁ receptor

Main article: Alpha-1 adrenergic receptor

Alpha1-adrenergic receptors are members of the G protein-coupled receptor superfamily. Upon activation, a heterotrimeric G protein, Gq, activates phospholipase C (PLC). The PLC cleaves phosphatidylinositol 4,5-bisphosphate (PIP2) which in turn causes an increase in inositol triphosphate (IP3) and diacylglycerol (DAG). The former interacts with calcium channels of endoplasmic and sarcoplasmic retuculum thus changing the calcium content in a cell. This triggers all other effects.

Specific actions of the α₁ receptor mainly involves smooth muscle contraction. It causes vasoconstriction in many blood vessels including those of the skin, gastrointestinal system, kidney (renal artery)^[6] and brain^[7]. Other areas of smooth muscle contraction are:

• ureter
• vas deferens
• hair (erector pili muscles)
• uterus (when pregnant)
• urethral sphincter
• bronchioles (although minor to the relaxing effect of β₂ receptor on bronchioles)
• blood vessels of ciliary body (stimulation causes mydriasis)

Further effects include glycogenolysis and gluconeogenesis from adipose tissue^[8] and liver, as well as secretion from sweat glands^[8] and Na⁺ reabsorption from kidney.^[8]

Antagonists may be used in hypertension.

α₂ receptor

Main article: Alpha-2 adrenergic receptor

There are 3 highly homologous subtypes of α₂ receptors: α2A, α2Β, and α2C.

Specific actions of the α₂ receptor include:

• inhibition of insulin release in pancreas.^[8]
• induction of glucagon release from pancreas.
• contraction of sphincters of the gastrointestinal tract
• negative feedback in the neuronal synapses

β receptors

β₁ receptor

Main article: Beta-1 adrenergic receptor

Specific actions of the β₁ receptor include:

• Increase cardiac output, by raising heart rate (positive chronotropic effect) and increasing impulse conduction and increasing contraction thus increasing the volume expelled with each beat (increased ejection fraction).

β₂ receptor

Main article: Beta-2 adrenergic receptor

Specific actions of the β₂ receptor include the following:

• Smooth muscle relaxation, e.g. in bronchi.^[8]
• Lipolysis in adipose tissue.^[9]
• Anabolism in skeletal muscle.^[10][11]
• Relax non-pregnant uterus
• Relax detrusor urinae muscle‎ of bladder wall
• Dilate arteries to skeletal muscle
• Glycogenolysis and gluconeogenesis
• Contract sphincters of GI tract
• Thickened secretions from salivary glands.^[8]
• Inhibit histamine-release from mast cells
• Increase renin secretion from kidney

β₃ receptor

Main article: Beta-3 adrenergic receptor

Specific actions of the β₃ receptor include:

• Enhancement of lipolysis in adipose tissue. Beta-3 activating drugs could theoretically be used as weight-loss agents, but are limited by the side effect of tremors.

See also

• Beta adrenergic receptor kinase
• Beta adrenergic receptor kinase-2

References

1. ^ Chen-Izu Y, Xiao RP, Izu LT, Cheng H, Kuschel M, Spurgeon H, Lakatta EG (November 2000). "G(i)-dependent localization of beta(2)-adrenergic receptor signaling to L-type Ca(2+) channels". Biophys. J. 79 (5): 2547–56. doi:10.1016/S0006-3495(00)76495-2. PMID 11053129.
2. ^ Nisoli E, Tonello C, Landi M, Carruba MO (1996). "Functional studies of the first selective β₃-adrenergic receptor antagonist SR 59230A in rat brown adipocytes". Mol. Pharmacol. 49 (1): 7–14. PMID 8569714. http://molpharm.aspetjournals.org/cgi/content/abstract/49/1/7.
3. ^ Woodman OL, Vatner SF (1987). "Coronary vasoconstriction mediated by α₁- and α₂-adrenoceptors in conscious dogs". Am. J. Physiol. 253 (2 Pt 2): H388–93. PMID 2887122. http://ajpheart.physiology.org/cgi/content/abstract/253/2/H388.
4. ^ Elliott J (1997). "Alpha-adrenoceptors in equine digital veins: evidence for the presence of both α₁- and α₂-receptors mediating vasoconstriction". J. Vet. Pharmacol. Ther. 20 (4): 308–17. doi:10.1046/j.1365-2885.1997.00078.x. PMID 9280371.
5. ^ Sagrada A, Fargeas MJ, Bueno L (1987). "Involvement of α₁ and α₂ adrenoceptors in the postlaparotomy intestinal motor disturbances in the rat". Gut 28 (8): 955–9. doi:10.1136/gut.28.8.955. PMID 2889649.
6. ^ Schmitz JM, Graham RM, Sagalowsky A, Pettinger WA (1981). "Renal α₁ and α₂ adrenergic receptors: biochemical and pharmacological correlations". J. Pharmacol. Exp. Ther. 219 (2): 400–6. PMID 6270306. http://jpet.aspetjournals.org/cgi/content/abstract/219/2/400.
7. ^ Circulation & Lung Physiology I M.A.S.T.E.R. Learning Program, UC Davis School of Medicine
8. ^ ^{a b c d e f} Fitzpatrick, David; Purves, Dale; Augustine, George (2004). "Table 20:2". Neuroscience (Third ed.). Sunderland, Mass: Sinauer. ISBN 0-87893-725-0.
9. ^ Large V, Hellström L, Reynisdottir S, et al. (December 1997). "Human beta-2 adrenoceptor gene polymorphisms are highly frequent in obesity and associate with altered adipocyte beta-2 adrenoceptor function". J. Clin. Invest. 100 (12): 3005–13. doi:10.1172/JCI119854. PMID 9399946.
10. ^ Kline WO, Panaro FJ, Yang H, Bodine SC (February 2007). "Rapamycin inhibits the growth and muscle-sparing effects of clenbuterol". J. Appl. Physiol. 102 (2): 740–7. doi:10.1152/japplphysiol.00873.2006. PMID 17068216.
11. ^ Kamalakkannan G, Petrilli CM, George I, et al. (April 2008). "Clenbuterol increases lean muscle mass but not endurance in patients with chronic heart failure". J. Heart Lung Transplant. 27 (4): 457–61. doi:10.1016/j.healun.2008.01.013. PMID 18374884.

Further reading

• Rang HP, Dale MM, Ritter JM, Moore PK (2003). "Chapter 11: Noradrenergic transmission". Pharmacology (5^th ed.). Elsevier Churchill Livingstone. ISBN 0-443-07145-4.
• Rang HP, Dale MM, Ritter JM, Flower RJ (2007). "Chapter 11: Noradrenergic transmission". Rang and Dale's Pharmacology (6^th ed.). Elsevier Churchill Livingstone. pp. 169–170. ISBN 0-443-06911-5.

External links

• The Adrenergic Receptors
• "Adrenoceptors". IUPHAR Database of Receptors and Ion Channels. International Union of Basic and Clinical Pharmacology. http://www.iuphar-db.org/GPCR/ChapterMenuForward?chapterID=1274.
• Basic Neurochemistry: α- and β-Adrenergic Receptors
• Brief overview of functions of the beta-3 receptor
• Theory of receptor activation
• Desensitization of beta-1-receptors
• UMich Orientation of Proteins in Membranes protein/pdbid-2rh1 - 3D structure of beta-2 adrenergic receptor in membrane

Adrenergics Receptor Ligands α1 Agonists: 5-FNE • 6-FNE • Amidephrine • Anisodamine • Anisodine • Cirazoline • Dipivefrine • Dopamine • Ephedrine • Epinephrine (Adrenaline) • Etilefrine • Ethylnorepinephrine • Indanidine • Levonordefrin • Metaraminol • Methoxamine • Methyldopa • Midodrine • Naphazoline • Norepinephrine (Noradrenaline) • Octopamine • Oxymetazoline • Phenylephrine • Phenylpropanolamine • Pseudoephedrine • Synephrine • Tetrahydrozoline Antagonists: Abanoquil • Adimolol • Ajmalicine • Alfuzosin • Amosulalol • Arotinolol • Atiprosin • Benoxathian • Buflomedil • Bunazosin • Carvedilol • CI-926 • Corynanthine • Dapiprazole • DL-017 • Domesticine • Doxazosin • Eugenodilol • Fenspiride • GYKI-12,743 • GYKI-16,084 • Indoramin • Ketanserin • L-765,314 • Labetalol • Mephendioxan • Metazosin • Monatepil • Moxisylyte (Thymoxamine) • Naftopidil • Nantenine • Neldazosin • Nicergoline • Niguldipine • Pelanserin • Phendioxan • Phenoxybenzamine • Phentolamine • Piperoxan • Prazosin • Quinazosin • Ritanserin • RS-97,078 • SGB-1,534 • Silodosin • SL-89.0591 • Spiperone • Talipexole • Tamsulosin • Terazosin • Tibalosin • Tiodazosin • Tipentosin • Tolazoline • Trimazosin • Upidosin • Urapidil • Zolertine * Note that many TCAs, TeCAs, antipsychotics, ergolines, and some piperazines like buspirone, trazodone, nefazodone, etoperidone, and mepiprazole all antagonize α1-adrenergic receptors as well, which contributes to their side effects such as orthostatic hypotension. α2 Agonists: (R)-3-Nitrobiphenyline • 4-NEMD • 6-FNE • Amitraz • Apraclonidine • Brimonidine • Clonidine • Detomidine • Dexmedetomidine • Dihydroergotamine • Dipivefrine • Dopamine • Ephedrine • Ergotamine • Epinephrine (Adrenaline) • Esproquin • Etilefrine • Ethylnorepinephrine • Guanabenz • Guanfacine • Guanoxabenz • Levonordefrin • Lofexidine • Medetomidine • Methyldopa • Mivazerol • Naphazoline • Norepinephrine (Noradrenaline) • Phenylpropanolamine • Piperoxan • Pseudoephedrine • Rilmenidine • Romifidine • Talipexole • Tetrahydrozoline • Tizanidine • Tolonidine • Urapidil • Xylazine • Xylometazoline Antagonists: 1-PP • Adimolol • Atipamezole • BRL-44408 • Buflomedil • Cirazoline • Efaroxan • Esmirtazapine • Fluparoxan • GYKI-12,743 • GYKI-16,084 • Idazoxan • Mianserin • Mirtazapine • MK-912 • NAN-190 • Olanzapine • Phentolamine • Phenoxybenzamine • Piperoxan • Piribedil • Rauwolscine • Rotigotine • SB-269,970 • Setiptiline • Spiroxatrine • Sunepitron • Tolazoline • Yohimbine * Note that many atypical antipsychotics and azapirones like buspirone and gepirone (via metabolite 1-PP) antagonize α2-adrenergic receptors as well. β Agonists: 2-FNE • 5-FNE • Amibegron • Arbutamine • Arformoterol • Arotinolol • BAAM • Bambuterol • Befunolol • Bitolterol • Broxaterol • Buphenine • Carbuterol • Cimaterol • Clenbuterol • Denopamine • Deterenol • Dipivefrine • Dobutamine • Dopamine • Dopexamine • Ephedrine • Epinephrine (Adrenaline) • Etafedrine • Etilefrine • Ethylnorepinephrine • Fenoterol • Formoterol • Hexoprenaline • Higenamine • Indacaterol • Isoetarine • Isoprenaline (Isoproterenol) • Isoxsuprine • Labetalol • Levonordefrin • Levosalbutamol • Mabuterol • Methoxyphenamine • Methyldopa • N-Isopropyloctopamine • Norepinephrine (Noradrenaline) • Orciprenaline • Oxyfedrine • Phenylpropanolamine • Pirbuterol • Prenalterol • Ractopamine • Procaterol • Pseudoephedrine • Reproterol • Rimiterol • Ritodrine • Salbutamol (Albuterol) • Salmeterol • Solabegron • Terbutaline • Tretoquinol • Tulobuterol • Xamoterol • Zilpaterol • Zinterol Antagonists: Acebutolol • Adaprolol • Adimolol • Afurolol • Alprenolol • Alprenoxime • Amosulalol • Ancarolol • Arnolol • Arotinolol • Atenolol • Befunolol • Betaxolol • Bevantolol • Bisoprolol • Bopindolol • Bormetolol • Bornaprolol • Brefonalol • Bucindolol • Bucumolol • Bufetolol • Buftiralol • Bufuralol • Bunitrolol • Bunolol • Bupranolol • Burocrolol • Butaxamine • Butidrine • Butofilolol • Capsinolol • Carazolol • Carpindolol • Carteolol • Carvedilol • Celiprolol • Cetamolol • Cicloprolol • Cinamolol • Cloranolol • Cyanopindolol • Dalbraminol • Dexpropranolol • Diacetolol • Dichloroisoprenaline • Dihydroalprenolol • Dilevalol • Diprafenone • Draquinolol • Dropranolol • Ecastolol • Epanolol • Ericolol • Ersentilide • Esatenolol • Esmolol • Esprolol •Eugenodilol • Exaprolol • Falintolol • Flestolol • Flusoxolol • Hydroxycarteolol • Hydroxytertatolol • ICI-118,551 • Idropranolol • Indenolol • Indopanolol • Iodocyanopindolol • Iprocrolol • Isoxaprolol • Isamoltane • Labetalol • Landiolol • Levobetaxolol • Levobunolol • Levocicloprolol • Levomoprolol • Medroxalol • Mepindolol • Metalol • Metipranolol • Metoprolol • Moprolol • Nadolol • Nadoxolol • Nafetolol • Nebivolol • Neraminol • Nifenalol • Nipradilol • Oberadilol • Oxprenolol • Pacrinolol • Pafenolol • Pamatolol • Pargolol • Parodilol • Penbutolol • Penirolol • PhQA-33 • Pindolol • Pirepolol • Practolol • Primidolol • Procinolol • Pronethalol • Propafenone • Propranolol • Ridazolol • Ronactolol • Soquinolol • Sotalol • Spirendolol • SR 59230A • Sulfinalol • TA-2005 • Talinolol • Tazolol • Teoprolol • Tertatolol • Terthianolol • Tienoxolol • Tilisolol • Timolol • Tiprenolol • Tolamolol • Toliprolol • Tribendilol • Trigevolol • Xibenolol • Xipranolol Reuptake Inhibitors NET Selective Norepinephrine Reuptake Inhibitors: Atomoxetine (Tomoxetine) • Ciclazindol • Esreboxetine • Mazindol • Nisoxetine • Reboxetine • Talopram • Talsupram • Tandamine • Viloxazine; Norepinephrine-Dopamine Reuptake Inhibitors: Amineptine • Bupropion (Amfebutamone) • Fencamine • Fencamfamine • Lefetamine • Levophacetoperane • LR-5182 • Manifaxine • Methylphenidate • Nomifensine • O-2172 • Radafaxine; Serotonin-Norepinephrine Reuptake Inhibitors: Bicifadine • Desvenlafaxine • Duloxetine • Levomilnacipran • Milnacipran • Sibutramine • Venlafaxine; Serotonin-Norepinephrine-Dopamine Reuptake Inhibitors: Brasofensine • Diclofensine • DOV-102,677 • DOV-21,947 • DOV-216,303 • JNJ-7925476 • JZ-IV-10 • Methylnaphthidate • Naphyrone • NS-2359 • PRC200-SS • SEP-225,289 • SEP-227,162 • Tesofensine; Tricyclic Antidepressants: Amitriptyline • Butriptyline • Cianopramine • Clomipramine • Desipramine • Dosulepin • Doxepin • Imipramine • Lofepramine • Nortriptyline • Protriptyline • Trimipramine; Tetracyclic Antidepressants: Amoxapine • Maprotiline • Mianserin • Oxaprotiline • Setiptiline; Others: Cocaine • CP-39,332 • EXP-561 • Fezolamine • Nefazodone • Nefopam • Pridefrine • Tapentadol • Tramadol • Ziprasidone VMAT Ibogaine • Reserpine • Tetrabenazine Releasing Agents Morpholines: Fenbutrazate • Morazone • Phendimetrazine • Phenmetrazine; Oxazolines: 4-Methylaminorex • Aminorex • Clominorex • Cyclazodone • Fenozolone • Fluminorex • Pemoline • Thozalinone; Phenethylamines (also Amphetamines, Cathinones, Phentermines, etc): 2-OH-PEA • 4-CAB • 4-FA • 4-FMA • 4-MA • 4-MMA • Alfetamine • Amfecloral • Amfepentorex • Amfepramone • Amphetamine (Dextroamphetamine, Levoamphetamine) • Amphetaminil • β-Me-PEA • BDB • Benzphetamine • BOH • Buphedrone • Butylone • Cathine • Cathinone • Clobenzorex • Clortermine • D-Deprenyl • Dimethylamphetamine • Dimethylcathinone (Dimethylpropion, Metamfepramone) • DMA • DMMA • EBDB • Ephedrine • Ethcathinone • Ethylamphetamine • Ethylone • Fenethylline • Fenproporex • Flephedrone • Fludorex • Furfenorex • Hordenine • IAP • IMP • L-Deprenyl (Selegiline) • Lisdexamfetamine • Lophophine • MBDB • MDA (Tenamfetamine) • MDEA • MDMA • MDMPEA • MDOH • MDPEA • Mefenorex • Mephedrone • Mephentermine • Methamphetamine (Dextromethamphetamine, Levomethamphetamine) • Methcathinone • Methedrone • Methylone • NAP • Ortetamine • Paredrine • pBA • pCA • Pentorex (Phenpentermine) • Phenethylamine • Pholedrine • Phenpromethamine • Phentermine • Phenylpropanolamine • pIA • Prenylamine • Propylamphetamine • Pseudoephedrine • Tiflorex • Tyramine • Xylopropamine • Zylofuramine; Piperazines: 2C-B-BZP • BZP • MBZP • mCPP • MDBZP • MeOPP • pFPP; Others: 2-Amino-1,2-dihydronaphthalene • 2-Aminoindane • 2-Aminotetralin • 2-Benzylpiperidine • 4-Benzylpiperidine • 5-IAI • Clofenciclan • Cyclopentamine • Cypenamine • Cyprodenate • Feprosidnine • Gilutensin • Heptaminol • Hexacyclonate • Indanorex • Isometheptene • Methylhexanamine • Octodrine • Phthalimidopropiophenone • Propylhexedrine (Levopropylhexedrine) • Tuaminoheptane Enzyme Inhibitors Anabolism PAH 3,4-Dihydroxystyrene TH 3-Iodotyrosine • Aquayamycin • Bulbocapnine • Metirosine • Oudenone AAAD Benserazide • Carbidopa • Genistein • Methyldopa DBH Bupicomide • Disulfiram • Dopastin • Fusaric Acid • Nepicastat • Phenopicolinic Acid • Tropolone PNMT CGS-19281A • SKF-64139 • SKF-7698 Catabolism MAO Nonselective: Benmoxin • Caroxazone • Echinopsidine • Furazolidone • Hydralazine • Indantadol • Iproclozide • Iproniazid • Isocarboxazid • Isoniazid • Linezolid • Mebanazine • Metfendrazine • Nialamide • Octamoxin • Paraxazone • Phenelzine • Pheniprazine • Phenoxypropazine • Pivalylbenzhydrazine • Procarbazine • Safrazine • Tranylcypromine; MAO-A Selective: Amiflamine • Bazinaprine • Befloxatone • Befol • Brofaromine • Cimoxatone • Clorgiline • Esuprone • Harmala alkaloids (Harmine, Harmaline, Tetrahydroharmine, Harman, Norharman, etc) • Methylene Blue • Metralindole • Minaprine • Moclobemide • Pirlindole • Sercloremine • Tetrindole • Toloxatone • Tyrima; MAO-B Selective: D-Deprenyl • L-Deprenyl (Selegiline) • Ladostigil • Lazabemide • Milacemide • Mofegiline • Pargyline • Rasagiline * Note that MAO-B inhibitors also influence norepinephrine/epinephrine levels since they inhibit the breakdown of their precursor dopamine. COMT Entacapone • Tolcapone Others Precursors L-Phenylalanine → L-Tyrosine → L-DOPA (Levodopa) → Dopamine • L-DOPS (Droxidopa) Cofactors Ferrous Iron (Fe2+) • S-Adenosyl-L-Methionine • Vitamin B3 (Niacin, Nicotinamide → NADPH) • Vitamin B6 (Pyridoxine, Pyridoxamine, Pyridoxal → Pyridoxal Phosphate) • Vitamin B9 (Folic Acid → Tetrahydrofolic Acid) • Vitamin C (Ascorbic Acid) • Zinc (Zn2+) Others Activity Enhancers: BPAP • PPAP; Release Blockers: Bethanidine • Bretylium • Guanadrel • Guanazodine • Guanclofine • Guanethidine • Guanoxan; Toxins: Oxidopamine (6-Hydroxydopamine)

Transmembrane receptor: G protein-coupled receptors Class A: Rhodopsin like Neurotransmitter Adrenergic α1 (A, B, D) · α2 (A, B, C) · β1 · β2 · β3 Purinergic Adenosine (A1, A2A, A2B, A3) · P2Y (1, 2, 4, 5, 6, 8, 9, 10, 11, 12, 13, 14) Serotonin (all but 5-HT3) 5-HT1 (A, B, D, E, F) · 5-HT2 (A, B, C) · 5-HT (4, 5A, 6, 7) Other Acetylcholine (M1, M2, M3, M4, M5) · Dopamine (D1, D2, D3, D4, D5) · Histamine (H1, H2, H3, H4) · Melatonin (1A, 1B, 1C) · TAAR (1, 2, 3, 5, 6, 8, 9) Metabolites and signaling molecules Eicosanoid CysLT (1, 2) · LTB4 (1, 2) · FPRL1 · OXE · Prostaglandin (DP (1, 2), EP (1, 2, 3, 4), FP) · Prostacyclin · Thromboxane Other Bile acid · Cannabinoid (CB1, CB2, GPR (18, 55, 119)) · EBI2 · Estrogen · Free fatty acid (1, 2, 3, 4) · Lactate · Lysophosphatidic acid (1, 2, 3, 4, 5, 6) · Lysophospholipid (1, 2, 3, 4, 5, 6, 7, 8) · Niacin (1, 2) · Oxoglutarate · PAF · Sphingosine-1-phosphate (1, 2, 3, 4, 5) · Succinate Peptide Neuropeptide B/W (1, 2) · FF (1, 2) · S · Y (1, 2, 4, 5) · Neuromedin (B, U (1, 2)) · Neurotensin (1, 2) Other Anaphylatoxin (C3a, C5a) · Angiotensin (1, 2) · Apelin · Bombesin (BRS3, GRPR, NMBR) · Bradykinin (B1, B2) · Chemokine · Cholecystokinin (A, B) · Endothelin (A, B) · Formyl peptide (1, 2, 3) · FSH · Galanin (1, 2, 3) · GHB receptor · Gonadotropin-releasing hormone (1, 2) · Ghrelin · Kisspeptin · Luteinizing hormone/choriogonadotropin · MAS (1, 1L, D, E, F, G, X1, X2, X3, X4) · Melanocortin (1, 2, 3, 4, 5) · MCHR (1, 2) · Motilin · Opioid (Delta, Kappa, Mu, Nociceptin & Zeta, but not Sigma) · Orexin (1, 2) · Oxytocin · Prokineticin (1, 2) · Prolactin-releasing peptide · Relaxin (1, 2, 3, 4) · Somatostatin (1, 2, 3, 4, 5) · Tachykinin (1, 2, 3) · Thyrotropin · Thyrotropin-releasing hormone · Urotensin-II · Vasopressin (1A, 1B, 2) Miscellaneous Orphan GPR (1, 3, 4, 6, 12, 15, 17, 18, 19, 20, 21, 22, 23, 25, 26, 27, 31, 32, 33, 34, 35, 37, 39, 42, 44, 45, 50, 52, 55, 61, 62, 63, 65, 68, 75, 77, 78, 81, 82, 83, 84, 85, 87, 88, 92, 101, 103, 109A, 109B, 119, 120, 132, 135, 137B, 139, 141, 142, 146, 148, 149, 150, 151, 152, 153, 160, 161, 162, 171, 173, 174, 176, 177, 182, 183) Other Adrenomedullin · Olfactory · Opsin (3, 4, 5, 1LW, 1MW, 1SW, RGR, RRH) · Protease-activated (1, 2, 3, 4) · SREB Class B: Secretin like Orphan GPR (56, 64, 97, 98, 110, 111, 112, 113, 114, 115, 116, 123, 124, 125, 126, 128, 133, 143, 144, 155, 157) Other Brain-specific angiogenesis inhibitor (1, 2, 3) · Cadherin (1, 2, 3) · Calcitonin · CALCRL · CD97 · Corticotropin-releasing hormone (1, 2) · EMR (1, 2, 3) · Glucagon (GR, GIPR, GLP1R, GLP2R) · Growth hormone releasing hormone · PACAPR1 · GPR · Latrophilin (1, 2, 3, ELTD1) · Methuselah-like proteins · Parathyroid hormone (1, 2) · Secretin · Vasoactive intestinal peptide (1, 2) Class C: Metabotropic glutamate / pheromone Taste TAS1R (1, 2, 3) · TAS2R (1, 3, 4, 5, 8, 9, 10, 12, 13, 14, 16, 19, 20, 30, 31, 38, 39, 40, 41, 42, 43, 45, 46, 50) Other Calcium-sensing receptor · GABA B (1, 2) · Glutamate receptor (Metabotropic glutamate (1, 2, 3, 4, 5, 6, 7, 8)) · GPRC6A · GPR (156, 158, 179) · RAIG (1, 2, 3, 4) Class F: Frizzled / Smoothened Frizzled Frizzled (1, 2, 3, 4, 5, 6, 7, 8, 9, 10) Smoothened Smoothened

Categories: Adrenergic receptors | G protein coupled receptors

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