|, 5-HT2A, HTR2, 5-hydroxytryptamine receptor 2A|
|RNA expression pattern|
The mammalian 5-HT2A receptor is a subtype of the 5-HT2 receptor that belongs to the serotonin receptor family and is a G protein-coupled receptor (GPCR). This is the main excitatory receptor subtype among the GPCRs for serotonin (5-HT), although 5-HT2A may also have an inhibitory effect on certain areas such as the visual cortex and the orbitofrontal cortex. This receptor was first noted for its importance as a target of serotonergic psychedelic drugs such as LSD. Later it came back to prominence because it was also found to be mediating, at least partly, the action of many antipsychotic drugs, especially the atypical ones.
Downregulation of post-synaptic 5-HT2A receptor is an adaptive process provoked by chronic administration of selective serotonin reuptake inhibitors (SSRIs) and classical antipsychotics. Suicidal and otherwise depressed patients have had more 5-HT2A receptors than normal patients. These findings suggest that post-synaptic 5-HT2A overdensity is involved in the pathogenesis of depression.
- 1 History
- 2 Distribution
- 3 Signaling cascade
- 4 Effects
- 5 Ligands
- 6 Genetics
- 7 Neuroimaging
- 8 Role in virus endocytosis
- 9 References
- 10 Further reading
- 11 External links
Serotonin receptors were split into two classes by Gaddum and Picarelli when it was discovered that some of the serotonin-induced changes in the gut could be blocked by morphine, whilst the remainder of the response was inhibited by dibenzyline leading to the naming of M and D receptors respectively. 5-HT2A is thought to correspond to what was originally described as D subtype of 5-HT receptors by Gaddum and Picarelli. In the pre-molecular-cloning era when radioligand binding and displacement was the only major tool, spiperone and LSD were shown to label two different serotonin receptors, and neither of them displaced morphine, leading to naming of the 5-HT1, 5-HT2 and 5-HT3 receptors, corresponding to high affinity sites from LSD, spiperone and morphine respectively. Later it was shown that the 5-HT2 was very close to 5-HT1C and thus were clubbed together, renaming the 5-HT2 into 5-HT2A. Thus the 5-HT2 receptor family is composed of three separate molecular entities: the 5-HT2A (formerly known as 5-HT2 or D), the 5-HT2B (formerly known as 5-HT2F) and the 5-HT2C (formerly known as 5-HT1C) receptors.
5-HT2A is expressed widely throughout the central nervous system (CNS). It is expressed near most of the serotoninergic terminal rich areas, including neocortex (mainly prefrontal, parietal, and somatosensory cortex) and the olfactory tubercle. Especially high concentrations of this receptor on the apical dendrites of pyramidal cells in layer V of the cortex may modulate cognitive processes, working memory, and attention by enhancing glutamate release followed by a complex range of interactions with the 5-HT1A, GABAA, adenosine A1, AMPA, mGluR2/3, mGlu5, and OX2 receptors. In the rat cerebellum, the protein has also been found in the Golgi cells of the granular layer, and in the Purkinje cells.
In the periphery, it is highly expressed in platelets and many cell types of the cardiovascular system, in fibroblasts, and in neurons of the peripheral nervous system. Additionally, 5-HT2A mRNA expression has been observed in human monocytes.
The 5-HT2A receptor is known primarily to couple to the Gαq signal transduction pathway. Upon receptor stimulation with agonist, Gαq and β-γ subunits dissociate to initiate downstream effector pathways. Gαq stimulates phospholipase C (PLC) activity, which subsequently promotes the release of diacylglycerol (DAG) and inositol triphosphate (IP3), which in turn stimulate protein kinase C (PKC) activity and Ca2+ release.
There are many additional signal cascade components that include the formation of arachidonic acid through PLA2 activity, activation of phospholipase D, Rho/Rho kinase, and ERK pathway activation initiated by agonist stimulation of the receptor.
Physiological processes mediated by the receptor include:
- CNS: neuronal excitation, behavioural effects, learning, anxiety
- smooth muscle: contraction (in gastrointestinal tract & bronchi)
- vasoconstriction / vasodilation
- platelets: aggregation
- Activation of the 5-HT2A receptor with 2,5-Dimethoxy-4-iodoamphetamine (DOI) produces potent anti-inflammatory effects in several tissues including cardiovascular and gut. Other 5-HT2A agonists like LSD also have potent anti-inflammatory effects against TNF-alpha-induced inflammation.
- Activation of the 5-HT2A receptor in hypothalamus causes increases in hormonal levels of oxytocin, prolactin, ACTH, corticosterone, and renin.
- Role in memory
Activation of the 5-HT2A receptor is necessary for the effects of the "classic" psychedelics like LSD, psilocin and mescaline, which act as full or partial agonists at this receptor, and represent the three main classes of 5-HT2A agonists, the ergolines, tryptamines and phenethylamines, respectively. A very large family of derivatives from these three classes has been developed, and their structure-activity relationships have been extensively researched. Agonists acting at 5-HT2A receptors located on the apical dendrites of pyramidal cells within regions of the prefrontal cortex are believed to mediate hallucinogenic activity. Newer findings reveal that psychoactive effects of classic psychedelics are mediated by the receptor heterodimer 5-HT2A–mGlu2 and not by monomeric 5-HT2A receptors. Agonists enhance dopamine in PFC, enhances memory and plays an active role in attention and learning.
- 25I-NBOH and its 2-methoxy-analog 25I-NBOMe
- 18F FECIMBI-36, radiolabelled agonist ligand for mapping 5-HT2A / 5-HT2C receptor distribution 
- (R)-DOI, traditionally the most common 5-HT2A reference agonist used in research 
- Mexamine is a full agonist to several serotonin receptors.
- O-4310, 5-HT2A selective, claimed to have 100x selectivity over 5-HT2C and be inactive at 5-HT2B
- PHA-57378, dual 5-HT2A / 5-HT2C agonist, anxiolytic effects in animal studies.
- Methysergide, a congener of methylergonovine, used in treatment of migraine blocks 5-HT2A and 5-HT2C receptors, but sometimes acts as partial agonist, in some preparations.
- OSU-6162 acts as a partial agonist at both 5-HT2A and dopamine D2 receptors
- 25CN-NBOH, 100x selectivity for 5-HT2A over 5-HT2C, 46x selectivity over 5-HT2B.
- Juncosamine, is a structurally constrained derivative of 25B-NBOMe, which acts as a potent partial agonist with 124x selectivity for 5-HT2A over 5-HT2C, making it the most selective agonist ligand identified to date.
- Efavirenz, an antiretroviral drug, produces psychiatric side effects thought to be mediated by 5-HT2A.
- Mefloquine, an antimalarial drug, also produces psychiatric side effects which may be mediated through 5-HT2A and/or 5-HT2C receptors.
- Lisuride, an antiparkinson dopamine agonist of the ergoline class, that is also a dual 5-HT2A / 5-HT2C agonist and 5-HT2B antagonist.
Peripherally selective agonists
One effect of 5-HT2A receptor activation is a reduction in intraocular pressure, and so 5-HT2A agonists can be useful for the treatment of glaucoma. This has led to the development of compounds such as AL-34662 that are hoped to reduce pressure inside the eyes but without crossing the blood–brain barrier and producing hallucinogenic side effects. Animal studies with this compound showed it to be free of hallucinogenic effects at doses up to 30 mg/kg, although several of its more lipophilic analogues did produce the head-twitch response known to be characteristic of hallucinogenic effects in rodents.
- Trazodone is a potent 5-HT2A antagonist, as well as an antagonist on other serotonin receptors.
- Mirtazapine is a 5-HT2A, 5-HT2C, and 5-HT3 antagonist. Mirtazapine also has an antagonistic effect on H1 histamine receptors. Because of its wide spectrum of serotonergic receptor inhibition, Mirtazapine exhibits an agonistic effect on 5-HT1A receptors by funneling more serotonin to them. Mirtazapine is used as an antidepressant in patients dealing with insomnia and weight loss.
- Although ergot alkaloids are mostly nonspecific 5-HT receptor antagonists, a few ergot derivatives such as metergoline bind preferentially to members of the 5-HT2 receptor family.
- The discovery of Ketanserin was a landmark in the pharmacology of 5-HT2 receptors. Ketanserin, though capable of blocking 5-HT induced platelet adhesion, however does not mediate its well-known antihypertensive action through 5-HT2 receptor family, but through its high affinity for alpha1 adrenergic receptors. It also has high affinity for H1 histaminergic receptors equal to that at 5-HT2A receptors. Compounds chemically related to ketanserin such as ritanserin are more selective 5-HT2A receptor antagonists with low affinity for alpha-adrenergic receptors. However, ritanserin, like most other 5-HT2A receptor antagonists, also potently inhibits 5-HT2C receptors.
- Nefazodone operates by blocking post-synaptic serotonin type-2A receptors and to a lesser extent by inhibiting pre-synaptic serotonin and norepinephrine (noradrenaline) reuptake.
- Atypical antipsychotic drugs like clozapine, olanzapine, quetiapine, risperidone and asenapine are relatively potent antagonists of 5-HT2A as are some of the lower potency old generation/typical antipsychotics. Other antagonists are MDL-100,907 (prototype of another new series of 5-HT2A antagonists) and cyproheptadine.
- Pizotifen is a non-selective antagonist.
- LY-367,265 - dual 5-HT2A antagonist / SSRI with antidepressant effects
- 2-alkyl-4-aryl-tetrahydro-pyrimido-azepines are subtype selective antagonists (35g: 60-fold).
- AMDA and related derivatives are another family of selective 5-HT2A antagonists.
- Hydroxyzine (Atarax)
- AC-90179 - potent and selective inverse agonist at 5-HT2A, also 5-HT2C antagonist.
- Nelotanserin (APD-125) - selective 5-HT2A inverse agonist developed by Arena Pharmaceuticals for the treatment of insomnia. APD-125 was shown to be effective and well tolerated in clinical trials.
- Eplivanserin (Sanofi Aventis), a sleeping pill that reached phase II trials (but for which the application for approval was withdrawn), acts as a selective 5-HT2A inverse agonist.
- Pimavanserin (ACP-103) - more selective than AC-90179, orally active, antipsychotic in vivo, now FDA approved for the treatment of treat hallucinations and delusions associated with Parkinson’s disease.
5-HT2A-receptor ligands may differentially activate the transductional pathways (see above). Studies evaluated the activation of two effectors, PLC and PLA2, by means of their second messengers. Compounds displaying more pronounced functional selectivity are 2,5-DMA and 2C-N. The former induces IP accumulation without activating the PLA2 mediated response, while the latter elicits AA release without activating the PLC mediated response.
Recent research has suggested potential signaling differences within the somatosensory cortex between 5-HT2A agonists that produce headshakes in the mouse and those that do not, such as lisuride, as these agents are also non-hallucinogenic in humans despite being active 5-HT2A agonists. One known example of differences in signal transduction is between the two 5-HT2A agonists serotonin and DOI that involves differential recruitment of intracellular proteins called β-arrestins, more specifically arrestin beta 2.
Role of lipophilicity
A set of ligands were evaluated. For agonists, a highly significant linear correlation was observed between binding affinity and lipophilicity. For ligands exhibiting partial agonist or antagonist properties, the lipophilicity was consistently higher than would be expected for an agonist of comparable affinity.
The 5-HT2A receptors is coded by the HTR2A gene. In humans the gene is located on chromosome 13. The gene has previously been called just HTR2 until the description of two related genes HTR2B and HTR2C. Several interesting polymorphisms have been identified for HTR2A: A-1438G (rs6311), C102T (rs6313) and His452Tyr (rs6314). Many more polymorphisms exist for the gene. A 2006 paper listed 255.
Associations with psychiatric disorders
Several studies have seen links between the -1438G/A polymorphism and mood disorders, such as bipolar disorder and major depressive disorder. A weak link with an odds ratio of 1.3 has been found between the T102C polymorphism and schizophrenia. This polymorphism has also been studied in relation to suicide attempts, with a study finding excess of the C/C genotypes among the suicide attempters. A number of other studies were devoted to finding an association of the gene with schizophrenia, with diverging results.
These individual studies may, however, not give a full picture: A review from 2007 looking at the effect of different SNPs reported in separate studies stated that "genetic association studies [of HTR2A gene variants with psychiatric disorders] report conflicting and generally negative results" with no involvement, small or a not replicated role for the genetic variant of the gene.
One study has found that genetic variations between individuals in the HTR2A gene may to some extent account for the difference in outcome of antidepressant treatment, so that patients suffering from major depressive disorder and treated with Citalopram may benefit more than others if they have one particular genotype. In this study 768 single nucleotide polymorphism (SNP) across 68 genes were investigated and a SNP—termed rs7997012—in the second intron of the HTR2A gene showed significant association with treatment outcome.
The 5-HT2A receptors may be imaged with PET-scanners using the fluorine-18-altanserin and MDL 100,907 radioligands that binds to the neuroreceptor, e.g., one study reported a reduced binding of altanserin particularly in the hippocampus in patients with major depressive disorder. Another PET study reported increased altanserin binding in the caudate nuclei in obsessive compulsive disorder patients compared to a healthy control group.
Patients with Tourette's syndrome have also been scanned and the study found an increased binding of altanserin for patients compared to healthy controls. The altanserin uptake decreases with age reflecting a loss of specific 5-HT2A receptors with age. A study has also found a positive correlation among healthy subjects between altanserin binding and the personality trait neuroticism as measured by the NEO PI-R personality questionnaire.
Role in virus endocytosis
5-HT2A may be a necessary receptor for clathrin mediated endocytosis of the human polyoma virus called JC virus, the causative agent of progressive multifocal leukoencephalopathy (PML), that enters cells such as oligodendrocytes, astrocytes, B lymphocytes, and kidney epithelial cells. These cells need to express both the alpha 2-6–linked sialic acid component of the 5-HT2A receptor in order to endocytose JCV.
- "Human PubMed Reference:".
- "Mouse PubMed Reference:".
- Cook EH, Fletcher KE, Wainwright M, Marks N, Yan SY, Leventhal BL (August 1994). "Primary structure of the human platelet serotonin 5-HT2A receptor: identify with frontal cortex serotonin 5-HT2A receptor". Journal of Neurochemistry. 63 (2): 465–9. doi:10.1046/j.1471-4159.1994.63020465.x. PMID 8035173.
- Martin P, Waters N, Schmidt CJ, Carlsson A, Carlsson ML (1998). "Rodent data and general hypothesis: antipsychotic action exerted through 5-HT2A receptor antagonism is dependent on increased serotonergic tone". Journal of Neural Transmission. 105 (4–5): 365–96. doi:10.1007/s007020050064. PMID 9720968.
- Elphick GF, Querbes W, Jordan JA, Gee GV, Eash S, Manley K, Dugan A, Stanifer M, Bhatnagar A, Kroeze WK, Roth BL, Atwood WJ (November 2004). "The human polyomavirus, JCV, uses serotonin receptors to infect cells". Science. 306 (5700): 1380–3. doi:10.1126/science.1103492. PMID 15550673.
- Eison AS, Mullins UL (1996). "Regulation of central 5-HT2A receptors: a review of in vivo studies". Behavioural Brain Research. 73 (1–2): 177–81. doi:10.1016/0166-4328(96)00092-7. PMID 8788498.
- Sanders-Bush E, Mayer SE (2006). "Chapter 11: 5-Hydroxytryptamine (Serotonin): Receptor Agonists and Antagonists". In Brunton LL, Lazo JS, Parker K. Goodman & Gilman's the Pharmacological Basis of Therapeutics (11th ed.). New York: McGraw-Hill. ISBN 0-07-142280-3.
- George J. Siegel; R. Wayne Albers (2005). Basic neurochemistry: molecular, cellular, and medical aspects. 1 (7th ed.). Academic Press. p. 241. ISBN 0-12-088397-X.
- Hoyer D, Hannon JP, Martin GR (April 2002). "Molecular, pharmacological and functional diversity of 5-HT receptors". Pharmacology, Biochemistry, and Behavior. 71 (4): 533–54. doi:10.1016/S0091-3057(01)00746-8. PMID 11888546.
- Aghajanian GK, Marek GJ (April 1999). "Serotonin, via 5-HT2A receptors, increases EPSCs in layer V pyramidal cells of prefrontal cortex by an asynchronous mode of glutamate release". Brain Research. 825 (1–2): 161–71. doi:10.1016/S0006-8993(99)01224-X. PMID 10216183.
- Marek GJ, Wright RA, Gewirtz JC, Schoepp DD (2001). "A major role for thalamocortical afferents in serotonergic hallucinogen receptor function in the rat neocortex". Neuroscience. 105 (2): 379–92. doi:10.1016/S0306-4522(01)00199-3. PMID 11672605.
- Bortolozzi A, Díaz-Mataix L, Scorza MC, Celada P, Artigas F (December 2005). "The activation of 5-HT receptors in prefrontal cortex enhances dopaminergic activity". Journal of Neurochemistry. 95 (6): 1597–607. doi:10.1111/j.1471-4159.2005.03485.x. PMID 16277612.
- Amargós-Bosch M, Bortolozzi A, Puig MV, Serrats J, Adell A, Celada P, Toth M, Mengod G, Artigas F (March 2004). "Co-expression and in vivo interaction of serotonin1A and serotonin2A receptors in pyramidal neurons of prefrontal cortex". Cerebral Cortex. 14 (3): 281–99. doi:10.1093/cercor/bhg128. PMID 14754868.
- Feng J, Cai X, Zhao J, Yan Z (September 2001). "Serotonin receptors modulate GABA(A) receptor channels through activation of anchored protein kinase C in prefrontal cortical neurons". The Journal of Neuroscience. 21 (17): 6502–11. PMID 11517239.
- Marek GJ (June 2009). "Activation of adenosine(1) (A(1)) receptors suppresses head shakes induced by a serotonergic hallucinogen in rats". Neuropharmacology. 56 (8): 1082–7. doi:10.1016/j.neuropharm.2009.03.005. PMC . PMID 19324062.
- Zhang C, Marek GJ (January 2008). "AMPA receptor involvement in 5-hydroxytryptamine2A receptor-mediated pre-frontal cortical excitatory synaptic currents and DOI-induced head shakes". Progress in Neuro-Psychopharmacology & Biological Psychiatry. 32 (1): 62–71. doi:10.1016/j.pnpbp.2007.07.009. PMID 17728034.
- Gewirtz JC, Marek GJ (November 2000). "Behavioral evidence for interactions between a hallucinogenic drug and group II metabotropic glutamate receptors". Neuropsychopharmacology. 23 (5): 569–76. doi:10.1016/S0893-133X(00)00136-6. PMID 11027922.
- Marek GJ, Zhang C (September 2008). "Activation of metabotropic glutamate 5 (mGlu5) receptors induces spontaneous excitatory synaptic currents in layer V pyramidal cells of the rat prefrontal cortex". Neuroscience Letters. 442 (3): 239–43. doi:10.1016/j.neulet.2008.06.083. PMC . PMID 18621097.
- Lambe EK, Liu RJ, Aghajanian GK (November 2007). "Schizophrenia, hypocretin (orexin), and the thalamocortical activating system". Schizophrenia Bulletin. 33 (6): 1284–90. doi:10.1093/schbul/sbm088. PMC . PMID 17656637.
- Liu RJ, Aghajanian GK (January 2008). "Stress blunts serotonin- and hypocretin-evoked EPSCs in prefrontal cortex: role of corticosterone-mediated apical dendritic atrophy". Proceedings of the National Academy of Sciences of the United States of America. 105 (1): 359–64. doi:10.1073/pnas.0706679105. PMC . PMID 18172209.
- Geurts FJ, De Schutter E, Timmermans JP (June 2002). "Localization of 5-HT2A, 5-HT3, 5-HT5A and 5-HT7 receptor-like immunoreactivity in the rat cerebellum". Journal of Chemical Neuroanatomy. 24 (1): 65–74. doi:10.1016/S0891-0618(02)00020-0. PMID 12084412.
- Maeshima T, Shutoh F, Hamada S, Senzaki K, Hamaguchi-Hamada K, Ito R, Okado N (August 1998). "Serotonin2A receptor-like immunoreactivity in rat cerebellar Purkinje cells". Neuroscience Letters. 252 (1): 72–4. doi:10.1016/S0304-3940(98)00546-1. PMID 9756362.
- Maeshima T, Shiga T, Ito R, Okado N (December 2004). "Expression of serotonin2A receptors in Purkinje cells of the developing rat cerebellum". Neuroscience Research. 50 (4): 411–7. doi:10.1016/j.neures.2004.08.010. PMID 15567478.
- Dürk T, Panther E, Müller T, Sorichter S, Ferrari D, Pizzirani C, Di Virgilio F, Myrtek D, Norgauer J, Idzko M (May 2005). "5-Hydroxytryptamine modulates cytokine and chemokine production in LPS-primed human monocytes via stimulation of different 5-HTR subtypes". International Immunology. 17 (5): 599–606. doi:10.1093/intimm/dxh242. PMID 15802305.
- Urban JD, Clarke WP, von Zastrow M, Nichols DE, Kobilka B, Weinstein H, Javitch JA, Roth BL, Christopoulos A, Sexton PM, Miller KJ, Spedding M, Mailman RB (January 2007). "Functional selectivity and classical concepts of quantitative pharmacology". The Journal of Pharmacology and Experimental Therapeutics. 320 (1): 1–13. doi:10.1124/jpet.106.104463. PMID 16803859.
- Yu B, Becnel J, Zerfaoui M, Rohatgi R, Boulares AH, Nichols CD (November 2008). "Serotonin 5-hydroxytryptamine(2A) receptor activation suppresses tumor necrosis factor-alpha-induced inflammation with extraordinary potency". The Journal of Pharmacology and Experimental Therapeutics. 327 (2): 316–23. doi:10.1124/jpet.108.143461. PMID 18708586.
- Nau F, Yu B, Martin D, Nichols CD (2013). "Serotonin 5-HT2A receptor activation blocks TNF-α mediated inflammation in vivo". PloS One. 8 (10): e75426. doi:10.1371/journal.pone.0075426. PMC . PMID 24098382.
- Van de Kar LD, Javed A, Zhang Y, Serres F, Raap DK, Gray TS (May 2001). "5-HT2A receptors stimulate ACTH, corticosterone, oxytocin, renin, and prolactin release and activate hypothalamic CRF and oxytocin-expressing cells". The Journal of Neuroscience. 21 (10): 3572–9. PMID 11331386.
- Zhang Y, Damjanoska KJ, Carrasco GA, Dudas B, D'Souza DN, Tetzlaff J, Garcia F, Hanley NR, Scripathirathan K, Petersen BR, Gray TS, Battaglia G, Muma NA, Van de Kar LD (November 2002). "Evidence that 5-HT2A receptors in the hypothalamic paraventricular nucleus mediate neuroendocrine responses to (-)DOI". The Journal of Neuroscience. 22 (21): 9635–42. PMID 12417689.
- Harvey JA (2003). "Role of the serotonin 5-HT(2A) receptor in learning". Learning & Memory. 10 (5): 355–62. doi:10.1101/lm.60803. PMC . PMID 14557608.
- Williams GV, Rao SG, Goldman-Rakic PS (April 2002). "The physiological role of 5-HT2A receptors in working memory". The Journal of Neuroscience. 22 (7): 2843–54. PMID 11923449.
- Nichols DE (February 2004). "Hallucinogens". Pharmacology & Therapeutics. 101 (2): 131–81. doi:10.1016/j.pharmthera.2003.11.002. PMID 14761703.
- Blaazer AR, Smid P, Kruse CG (September 2008). "Structure-activity relationships of phenylalkylamines as agonist ligands for 5-HT(2A) receptors". ChemMedChem. 3 (9): 1299–309. doi:10.1002/cmdc.200800133. PMID 18666267.
- Moreno JL, Muguruza C, Umali A, Mortillo S, Holloway T, Pilar-Cuéllar F, Mocci G, Seto J, Callado LF, Neve RL, Milligan G, Sealfon SC, López-Giménez JF, Meana JJ, Benson DL, González-Maeso J (December 2012). "Identification of three residues essential for 5-hydroxytryptamine 2A-metabotropic glutamate 2 (5-HT2A·mGlu2) receptor heteromerization and its psychoactive behavioral function". The Journal of Biological Chemistry. 287 (53): 44301–19. doi:10.1074/jbc.M112.413161. PMC . PMID 23129762.
- González-Maeso J, Ang RL, Yuen T, Chan P, Weisstaub NV, López-Giménez JF, Zhou M, Okawa Y, Callado LF, Milligan G, Gingrich JA, Filizola M, Meana JJ, Sealfon SC (March 2008). "Identification of a serotonin/glutamate receptor complex implicated in psychosis". Nature. 452 (7183): 93–7. doi:10.1038/nature06612. PMC . PMID 18297054.
- Moreno JL, Holloway T, Albizu L, Sealfon SC, González-Maeso J (April 2011). "Metabotropic glutamate mGlu2 receptor is necessary for the pharmacological and behavioral effects induced by hallucinogenic 5-HT2A receptor agonists". Neuroscience Letters. 493 (3): 76–9. doi:10.1016/j.neulet.2011.01.046. PMC . PMID 21276828.
- Wingen M, Kuypers KP, Ramaekers JG (February 2007). "The role of 5-HT1a and 5-HT2A receptors in attention and motor control: a mechanistic study in healthy volunteers". Psychopharmacology. 190 (3): 391–400. doi:10.1007/s00213-006-0614-x. PMID 17124621.
- Wingen M, Kuypers KP, Ramaekers JG (July 2007). "Selective verbal and spatial memory impairment after 5-HT1A and 5-HT2A receptor blockade in healthy volunteers pre-treated with an SSRI". Journal of Psychopharmacology. 21 (5): 477–85. doi:10.1177/0269881106072506. PMID 17092965.
- Braden MR, Parrish JC, Naylor JC, Nichols DE (December 2006). "Molecular interaction of serotonin 5-HT2A receptor residues Phe339(6.51) and Phe340(6.52) with superpotent N-benzyl phenethylamine agonists". Molecular Pharmacology. 70 (6): 1956–64. doi:10.1124/mol.106.028720. PMID 17000863.
- Prabhakaran J, Solingapuram Sai KK, Zanderigo F, Rubin-Falcone H, Jorgensen MJ, Kaplan JR, Tooke KI, Mintz A, Mann JJ, Kumar JS. In vivo evaluation of [18F]FECIMBI-36, an agonist 5-HT2A/2C receptor PET radioligand in nonhuman primate. Bioorg Med Chem Lett. 2017 Jan 1;27(1):21-23. doi: 10.1016/j.bmcl.2016.11.043. PMID 27889455
- Canal, Clint E.; Morgan, Drake (July 2012). "Head-twitch response in rodents induced by the hallucinogen 2,5-dimethoxy-4-iodoamphetamine: a comprehensive history, a re-evaluation of mechanisms, and its utility as a model". Drug Testing and Analysis. 4 (7–8): 556–576. doi:10.1002/dta.1333. PMC . PMID 22517680.
- McLean TH, Parrish JC, Braden MR, Marona-Lewicka D, Gallardo-Godoy A, Nichols DE (September 2006). "1-Aminomethylbenzocycloalkanes: conformationally restricted hallucinogenic phenethylamine analogues as functionally selective 5-HT2A receptor agonists". Journal of Medicinal Chemistry. 49 (19): 5794–803. doi:10.1021/jm060656o. PMID 16970404.
- Chambers JJ, Kurrasch-Orbaugh DM, Parker MA, Nichols DE (March 2001). "Enantiospecific synthesis and pharmacological evaluation of a series of super-potent, conformationally restricted 5-HT(2A/2C) receptor agonists". Journal of Medicinal Chemistry. 44 (6): 1003–10. doi:10.1021/jm000491y. PMID 11300881.
- Ennis MD, Hoffman RL, Ghazal NB, Olson RM, Knauer CS, Chio CL, Hyslop DK, Campbell JE, Fitzgerald LW, Nichols NF, Svensson KA, McCall RB, Haber CL, Kagey ML, Dinh DM (July 2003). "2,3,4,5-tetrahydro- and 2,3,4,5,11,11a-hexahydro-1H-[1,4]diazepino[1,7-a]indoles: new templates for 5-HT(2C) agonists". Bioorganic & Medicinal Chemistry Letters. 13 (14): 2369–72. doi:10.1016/S0960-894X(03)00403-7. PMID 12824036.
- Martin Hansen PhD. Design and Synthesis of Selective Serotonin Receptor Agonists for Positron Emission Tomography Imaging of the Brain. University of Copenhagen, 2011.
- Juncosa JI, Hansen M, Bonner LA, Cueva JP, Maglathlin R, McCorvy JD, Marona-Lewicka D, Lill MA, Nichols DE (January 2013). "Extensive rigid analogue design maps the binding conformation of potent N-benzylphenethylamine 5-HT2A serotonin receptor agonist ligands". ACS Chemical Neuroscience. 4 (1): 96–109. doi:10.1021/cn3000668.
- Gatch MB, Kozlenkov A, Huang RQ, Yang W, Nguyen JD, González-Maeso J, Rice KC, France CP, Dillon GH, Forster MJ, Schetz JA (November 2013). "The HIV antiretroviral drug efavirenz has LSD-like properties". Neuropsychopharmacology. 38 (12): 2373–84. doi:10.1038/npp.2013.135. PMC . PMID 23702798.
- Janowsky A, Eshleman AJ, Johnson RA, Wolfrum KM, Hinrichs DJ, Yang J, Zabriskie TM, Smilkstein MJ, Riscoe MK (July 2014). "Mefloquine and psychotomimetics share neurotransmitter receptor and transporter interactions in vitro". Psychopharmacology. 231 (14): 2771–83. doi:10.1007/s00213-014-3446-0. PMC . PMID 24488404.
- Egan CT, Herrick-Davis K, Miller K, Glennon RA, Teitler M (April 1998). "Agonist activity of LSD and lisuride at cloned 5HT2A and 5HT2C receptors". Psychopharmacology. 136 (4): 409–14. doi:10.1007/s002130050585. PMID 9600588.
- Hofmann C, Penner U, Dorow R, Pertz HH, Jähnichen S, Horowski R, Latté KP, Palla D, Schurad B (2006). "Lisuride, a dopamine receptor agonist with 5-HT2B receptor antagonist properties: absence of cardiac valvulopathy adverse drug reaction reports supports the concept of a crucial role for 5-HT2B receptor agonism in cardiac valvular fibrosis". Clinical Neuropharmacology. 29 (2): 80–6. doi:10.1097/00002826-200603000-00005. PMID 16614540.
- Sharif NA, McLaughlin MA, Kelly CR (February 2007). "AL-34662: a potent, selective, and efficacious ocular hypotensive serotonin-2 receptor agonist". Journal of Ocular Pharmacology and Therapeutics. 23 (1): 1–13. doi:10.1089/jop.2006.0093. PMID 17341144.
- May JA, Dantanarayana AP, Zinke PW, McLaughlin MA, Sharif NA (January 2006). "1-((S)-2-aminopropyl)-1H-indazol-6-ol: a potent peripherally acting 5-HT2 receptor agonist with ocular hypotensive activity". Journal of Medicinal Chemistry. 49 (1): 318–28. doi:10.1021/jm050663x. PMID 16392816.
- Rang HP (2003). Pharmacology. Edinburgh: Churchill Livingstone. ISBN 0-443-07145-4. Page 187
- Shireman BT, Dvorak CA, Rudolph DA, Bonaventure P, Nepomuceno D, Dvorak L, Miller KL, Lovenberg TW, Carruthers NI (March 2008). "2-Alkyl-4-aryl-pyrimidine fused heterocycles as selective 5-HT2A antagonists". Bioorganic & Medicinal Chemistry Letters. 18 (6): 2103–8. doi:10.1016/j.bmcl.2008.01.090. PMID 18282705.
- Westkaemper RB, Runyon SP, Bondarev ML, Savage JE, Roth BL, Glennon RA (September 1999). "9-(Aminomethyl)-9,10-dihydroanthracene is a novel and unlikely 5-HT2A receptor antagonist". European Journal of Pharmacology. 380 (1): R5–7. doi:10.1016/S0014-2999(99)00525-7. PMID 10513561.
- Westkaemper RB, Glennon RA (June 2002). "Application of ligand SAR, receptor modeling and receptor mutagenesis to the discovery and development of a new class of 5-HT(2A) ligands". Current Topics in Medicinal Chemistry. 2 (6): 575–98. doi:10.2174/1568026023393741. PMID 12052195.
- Peddi S, Roth BL, Glennon RA, Westkaemper RB (December 2003). "Spiro[9,10-dihydroanthracene]-9,3'-pyrrolidine-a structurally unique tetracyclic 5-HT2A receptor antagonist". European Journal of Pharmacology. 482 (1–3): 335–7. doi:10.1016/j.ejphar.2003.09.059. PMID 14660041.
- Runyon SP, Mosier PD, Roth BL, Glennon RA, Westkaemper RB (November 2008). "Potential modes of interaction of 9-aminomethyl-9,10-dihydroanthracene (AMDA) derivatives with the 5-HT2A receptor: a ligand structure-affinity relationship, receptor mutagenesis and receptor modeling investigation". Journal of Medicinal Chemistry. 51 (21): 6808–28. doi:10.1021/jm800771x. PMC . PMID 18847250.
- Wilson KJ, van Niel MB, Cooper L, Bloomfield D, O'Connor D, Fish LR, MacLeod AM (May 2007). "2,5-Disubstituted pyridines: the discovery of a novel series of 5-HT2A ligands". Bioorganic & Medicinal Chemistry Letters. 17 (9): 2643–8. doi:10.1016/j.bmcl.2007.01.098. PMID 17314044.
- Weiner DM, Burstein ES, Nash N, Croston GE, Currier EA, Vanover KE, Harvey SC, Donohue E, Hansen HC, Andersson CM, Spalding TA, Gibson DF, Krebs-Thomson K, Powell SB, Geyer MA, Hacksell U, Brann MR (October 2001). "5-hydroxytryptamine2A receptor inverse agonists as antipsychotics". The Journal of Pharmacology and Experimental Therapeutics. 299 (1): 268–76. PMID 11561089.
- Vanover KE, Harvey SC, Son T, Bradley SR, Kold H, Makhay M, Veinbergs I, Spalding TA, Weiner DM, Andersson CM, Tolf BR, Brann MR, Hacksell U, Davis RE (September 2004). "Pharmacological characterization of AC-90179 [2-(4-methoxyphenyl)-N-(4-methyl-benzyl)-N-(1-methyl-piperidin-4-yl)-acetamide hydrochloride]: a selective serotonin 2A receptor inverse agonist". The Journal of Pharmacology and Experimental Therapeutics. 310 (3): 943–51. doi:10.1124/jpet.104.066688. PMID 15102927.
- Rosenberg R, Seiden DJ, Hull SG, Erman M, Schwartz H, Anderson C, Prosser W, Shanahan W, Sanchez M, Chuang E, Roth T (December 2008). "APD125, a selective serotonin 5-HT(2A) receptor inverse agonist, significantly improves sleep maintenance in primary insomnia". Sleep. 31 (12): 1663–71. PMC . PMID 19090322.
- Vanover KE, Weiner DM, Makhay M, Veinbergs I, Gardell LR, Lameh J, Del Tredici AL, Piu F, Schiffer HH, Ott TR, Burstein ES, Uldam AK, Thygesen MB, Schlienger N, Andersson CM, Son TY, Harvey SC, Powell SB, Geyer MA, Tolf BR, Brann MR, Davis RE (May 2006). "Pharmacological and behavioral profile of N-(4-fluorophenylmethyl)-N-(1-methylpiperidin-4-yl)-N'-(4-(2-methylpropyloxy)phenylmethyl) carbamide (2R,3R)-dihydroxybutanedioate (2:1) (ACP-103), a novel 5-hydroxytryptamine(2A) receptor inverse agonist". The Journal of Pharmacology and Experimental Therapeutics. 317 (2): 910–8. doi:10.1124/jpet.105.097006. PMID 16469866.
- Gardell LR, Vanover KE, Pounds L, Johnson RW, Barido R, Anderson GT, Veinbergs I, Dyssegaard A, Brunmark P, Tabatabaei A, Davis RE, Brann MR, Hacksell U, Bonhaus DW (August 2007). "ACP-103, a 5-hydroxytryptamine 2A receptor inverse agonist, improves the antipsychotic efficacy and side-effect profile of haloperidol and risperidone in experimental models". The Journal of Pharmacology and Experimental Therapeutics. 322 (2): 862–70. doi:10.1124/jpet.107.121715. PMID 17519387.
- Vanover KE, Betz AJ, Weber SM, Bibbiani F, Kielaite A, Weiner DM, Davis RE, Chase TN, Salamone JD (October 2008). "A 5-HT2A receptor inverse agonist, ACP-103, reduces tremor in a rat model and levodopa-induced dyskinesias in a monkey model". Pharmacology, Biochemistry, and Behavior. 90 (4): 540–4. doi:10.1016/j.pbb.2008.04.010. PMC . PMID 18534670.
- Abbas A, Roth BL (December 2008). "Pimavanserin tartrate: a 5-HT2A inverse agonist with potential for treating various neuropsychiatric disorders". Expert Opinion on Pharmacotherapy. 9 (18): 3251–9. doi:10.1517/14656560802532707. PMID 19040345.
- Moya PR, Berg KA, Gutiérrez-Hernandez MA, Sáez-Briones P, Reyes-Parada M, Cassels BK, Clarke WP (June 2007). "Functional selectivity of hallucinogenic phenethylamine and phenylisopropylamine derivatives at human 5-hydroxytryptamine (5-HT)2A and 5-HT2C receptors". The Journal of Pharmacology and Experimental Therapeutics. 321 (3): 1054–61. doi:10.1124/jpet.106.117507. PMID 17337633.
- González-Maeso J, Weisstaub NV, Zhou M, Chan P, Ivic L, Ang R, Lira A, Bradley-Moore M, Ge Y, Zhou Q, Sealfon SC, Gingrich JA (February 2007). "Hallucinogens recruit specific cortical 5-HT(2A) receptor-mediated signaling pathways to affect behavior". Neuron. 53 (3): 439–52. doi:10.1016/j.neuron.2007.01.008. PMID 17270739.
- Cussac D, Boutet-Robinet E, Ailhaud MC, Newman-Tancredi A, Martel JC, Danty N, Rauly-Lestienne I (October 2008). "Agonist-directed trafficking of signalling at serotonin 5-HT2A, 5-HT2B and 5-HT2C-VSV receptors mediated Gq/11 activation and calcium mobilisation in CHO cells". European Journal of Pharmacology. 594 (1–3): 32–8. doi:10.1016/j.ejphar.2008.07.040. PMID 18703043.
- Schmid CL, Raehal KM, Bohn LM (January 2008). "Agonist-directed signaling of the serotonin 2A receptor depends on beta-arrestin-2 interactions in vivo". Proceedings of the National Academy of Sciences of the United States of America. 105 (3): 1079–84. doi:10.1073/pnas.0708862105. PMC . PMID 18195357.
- Abbas A, Roth BL (January 2008). "Arresting serotonin". Proceedings of the National Academy of Sciences of the United States of America. 105 (3): 831–2. doi:10.1073/pnas.0711335105. PMC . PMID 18195368.
- Parker MA, Kurrasch DM, Nichols DE (April 2008). "The role of lipophilicity in determining binding affinity and functional activity for 5-HT2A receptor ligands". Bioorganic & Medicinal Chemistry. 16 (8): 4661–9. doi:10.1016/j.bmc.2008.02.033. PMC . PMID 18296055.
- "OSIRIS search results. Gene: HTR2A". Supplementary material to article
- Chambers JJ, Kurrasch-Orbaugh DM, Parker MA, Nichols DE (March 2001). "Enantiospecific synthesis and pharmacological evaluation of a series of super-potent, conformationally restricted 5-HT(2A/2C) receptor agonists". Journal of Medicinal Chemistry. 44 (6): 1003–10. doi:10.1021/jm000491y. PMID 11300881.
- Chee IS, Lee SW, Kim JL, Wang SK, Shin YO, Shin SC, Lee YH, Hwang HM, Lim MR (September 2001). "5-HT2A receptor gene promoter polymorphism -1438A/G and bipolar disorder". Psychiatric Genetics. 11 (3): 111–4. doi:10.1097/00041444-200109000-00001. PMID 11702051.
- Choi MJ, Lee HJ, Lee HJ, Ham BJ, Cha JH, Ryu SH, Lee MS (2004). "Association between major depressive disorder and the -1438A/G polymorphism of the serotonin 2A receptor gene". Neuropsychobiology. 49 (1): 38–41. doi:10.1159/000075337. PMID 14730199.
- Williams J, Spurlock G, McGuffin P, Mallet J, Nöthen MM, Gill M, Aschauer H, Nylander PO, Macciardi F, Owen MJ (May 1996). "Association between schizophrenia and T102C polymorphism of the 5-hydroxytryptamine type 2a-receptor gene. European Multicentre Association Study of Schizophrenia (EMASS) Group". Lancet. 347 (9011): 1294–6. doi:10.1016/s0140-6736(96)90939-3. PMID 8622505.
- Vaquero-Lorenzo C, Baca-Garcia E, Diaz-Hernandez M, Perez-Rodriguez MM, Fernandez-Navarro P, Giner L, Carballo JJ, Saiz-Ruiz J, Fernandez-Piqueras J, Baldomero EB, de Leon J, Oquendo MA (July 2008). "Association study of two polymorphisms of the serotonin-2A receptor gene and suicide attempts". American Journal of Medical Genetics Part B. 147B (5): 645–9. doi:10.1002/ajmg.b.30642. PMID 18163387.
- Gene Overview of All Published Schizophrenia-Association Studies for HTR2A - SzGene database at Schizophrenia Research Forum.
- Serretti A, Drago A, De Ronchi D (2007). "HTR2A gene variants and psychiatric disorders: a review of current literature and selection of SNPs for future studies". Current Medicinal Chemistry. 14 (19): 2053–69. doi:10.2174/092986707781368450. PMID 17691947.
- McMahon FJ, Buervenich S, Charney D, Lipsky R, Rush AJ, Wilson AF, Sorant AJ, Papanicolaou GJ, Laje G, Fava M, Trivedi MH, Wisniewski SR, Manji H (May 2006). "Variation in the gene encoding the serotonin 2A receptor is associated with outcome of antidepressant treatment". American Journal of Human Genetics. 78 (5): 804–14. doi:10.1086/503820. PMC . PMID 16642436.
- Laje G, Paddock S, Manji H, Rush AJ, Wilson AF, Charney D, McMahon FJ (October 2007). "Genetic markers of suicidal ideation emerging during citalopram treatment of major depression". The American Journal of Psychiatry. 164 (10): 1530–8. doi:10.1176/appi.ajp.2007.06122018. PMID 17898344.
- Laje G, McMahon FJ (December 2007). "The pharmacogenetics of major depression: past, present, and future". Biological Psychiatry. 62 (11): 1205–7. doi:10.1016/j.biopsych.2007.09.016. PMID 17949692.
- Smith AK, Dimulescu I, Falkenberg VR, Narasimhan S, Heim C, Vernon SD, Rajeevan MS (February 2008). "Genetic evaluation of the serotonergic system in chronic fatigue syndrome". Psychoneuroendocrinology. 33 (2): 188–97. doi:10.1016/j.psyneuen.2007.11.001. PMID 18079067.
- Lemaire C, Cantineau R, Guillaume M, Plenevaux A, Christiaens L (December 1991). "Fluorine-18-altanserin: a radioligand for the study of serotonin receptors with PET: radiolabeling and in vivo biologic behavior in rats". Journal of Nuclear Medicine. 32 (12): 2266–72. PMID 1744713.
- Lundkvist C, Halldin C, Ginovart N, Nyberg S, Swahn CG, Carr AA, Brunner F, Farde L (1996). "[11C]MDL 100907, a radioligland for selective imaging of 5-HT(2A) receptors with positron emission tomography". Life Sciences. 58 (10): PL 187–92. doi:10.1016/0024-3205(96)00013-6. PMID 8602111.
- Mintun MA, Sheline YI, Moerlein SM, Vlassenko AG, Huang Y, Snyder AZ (February 2004). "Decreased hippocampal 5-HT2A receptor binding in major depressive disorder: in vivo measurement with [18F]altanserin positron emission tomography". Biological Psychiatry. 55 (3): 217–24. doi:10.1016/j.biopsych.2003.08.015. PMID 14744461.
- Adams KH, Hansen ES, Pinborg LH, Hasselbalch SG, Svarer C, Holm S, Bolwig TG, Knudsen GM (September 2005). "Patients with obsessive-compulsive disorder have increased 5-HT2A receptor binding in the caudate nuclei". The International Journal of Neuropsychopharmacology. 8 (3): 391–401. doi:10.1017/S1461145705005055. PMID 15801987.
- Haugbøl S, Pinborg LH, Regeur L, Hansen ES, Bolwig TG, Nielsen FA, Svarer C, Skovgaard LT, Knudsen GM (April 2007). "Cerebral 5-HT2A receptor binding is increased in patients with Tourette's syndrome". The International Journal of Neuropsychopharmacology. 10 (2): 245–52. doi:10.1017/S1461145706006559. PMID 16945163.
- Rosier A, Dupont P, Peuskens J, Bormans G, Vandenberghe R, Maes M, de Groot T, Schiepers C, Verbruggen A, Mortelmans L (November 1996). "Visualisation of loss of 5-HT2A receptors with age in healthy volunteers using [18F]altanserin and positron emission tomographic imaging". Psychiatry Research. 68 (1): 11–22. doi:10.1016/S0925-4927(96)02806-5. PMID 9027929.
- Meltzer CC, Smith G, Price JC, Reynolds CF, Mathis CA, Greer P, Lopresti B, Mintun MA, Pollock BG, Ben-Eliezer D, Cantwell MN, Kaye W, DeKosky ST (November 1998). "Reduced binding of [18F]altanserin to serotonin type 2A receptors in aging: persistence of effect after partial volume correction". Brain Research. 813 (1): 167–71. doi:10.1016/S0006-8993(98)00909-3. PMID 9824691.
- Adams KH, Pinborg LH, Svarer C, Hasselbalch SG, Holm S, Haugbøl S, Madsen K, Frøkjaer V, Martiny L, Paulson OB, Knudsen GM (March 2004). "A database of [(18)F]-altanserin binding to 5-HT(2A) receptors in normal volunteers: normative data and relationship to physiological and demographic variables". NeuroImage. 21 (3): 1105–13. doi:10.1016/j.neuroimage.2003.10.046. PMID 15006678.
- Frokjaer VG, Mortensen EL, Nielsen FA, Haugbol S, Pinborg LH, Adams KH, Svarer C, Hasselbalch SG, Holm S, Paulson OB, Knudsen GM (March 2008). "Frontolimbic serotonin 2A receptor binding in healthy subjects is associated with personality risk factors for affective disorder". Biological Psychiatry. 63 (6): 569–76. doi:10.1016/j.biopsych.2007.07.009. PMID 17884017.
- Perez-Aguilar JM, Shan J, LeVine MV, Khelashvili G, Weinstein H (November 2014). "A functional selectivity mechanism at the serotonin-2A GPCR involves ligand-dependent conformations of intracellular loop 2". Journal of the American Chemical Society. 136 (45): 16044–54. doi:10.1021/ja508394x. PMC . PMID 25314362.