The 5-HT₇ receptor is a member of the

GPCR 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 ...

superfamily of cell surface

receptors Receptor may refer to: *Sensory receptor, in physiology, any structure which, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and responds to a n ...

and is activated by the neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) The 5-HT₇ receptor is coupled to G_s (stimulates the production of the intracellular signaling molecule

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 ...

) and is expressed in a variety of human tissues, particularly in the brain, the gastrointestinal tract, and in various blood vessels. This receptor has been a drug development target for the treatment of several clinical disorders. The 5-HT₇ receptor is encoded by the ''HTR7''

gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

, which in humans is transcribed into 3 different splice variants.

Function

When the 5-HT₇ receptor is activated by serotonin, it sets off a cascade of events starting with release of the stimulatory

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 ...

G_s from the GPCR complex. G_s in turn activates

adenylate 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 ...

which increases

intracellular This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms. It is intended as introductory material for novices; for more specific and technical definitions ...

levels of the second messenger

. The 5-HT₇ receptor plays a role in smooth muscle relaxation within the

vasculature The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...

and in the gastrointestinal tract. The highest 5-HT₇ receptor densities are in the

thalamus The thalamus (from Greek θάλαμος, "chamber") is a large mass of gray matter located in the dorsal part of the diencephalon (a division of the forebrain). Nerve fibers project out of the thalamus to the cerebral cortex in all directions, ...

and

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 hypothalamu ...

, and it is present at higher densities also in the

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 system, ...

and

cortex Cortex or cortical may refer to: Biology * Cortex (anatomy), the outermost layer of an organ ** Cerebral cortex, the outer layer of the vertebrate cerebrum, part of which is the ''forebrain'' *** Motor cortex, the regions of the cerebral cortex i ...

. The 5-HT₇ receptor is involved in

thermoregulation Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...

, circadian rhythm, learning and

memory Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered ...

, and

sleep Sleep is a sedentary state of mind and body. It is characterized by altered consciousness, relatively inhibited sensory activity, reduced muscle activity and reduced interactions with surroundings. It is distinguished from wakefulness by a de ...

. Peripheral 5-HT₇ receptors are localized in enteric nerves; high levels of 5-HT₇ receptor-expressing mucosal nerve fibers were observed in the colon of patients with

irritable bowel syndrome Irritable bowel syndrome (IBS) is a "disorder of gut-brain interaction" characterized by a group of symptoms that commonly include abdominal pain and or abdominal bloating and changes in the consistency of bowel movements. These symptoms may ...

. An essential role of 5-HT₇ receptor in intestinal

hyperalgesia Hyperalgesia ( or ; 'hyper' from Greek ὑπέρ (huper, “over”), '-algesia' from Greek algos, ἄλγος (pain)) is an abnormally increased sensitivity to pain, which may be caused by damage to nociceptors or peripheral nerves and can ...

was demonstrated in mouse models with

visceral hypersensitivity Visceral pain is pain that results from the activation of nociceptors of the thoracic, pelvic, or abdominal viscera (organs). Visceral structures are highly sensitive to distension (stretch), ischemia and inflammation, but relatively insensitive t ...

, of which a novel 5-HT₇ receptor antagonist administered perorally reduced intestinal pain levels. It is also speculated that this receptor may be involved in mood regulation, suggesting that it may be a useful target in the treatment of depression.

Variants

Three splice variants have been identified in humans (designated h5-HT_7(a), h5-HT_7(b), and h5-HT_7(d)), which encode receptors that differ in their carboxy terminals. The h5-HT_7(a) is the full length receptor (445 amino acids), while the h5-HT_7(b) is truncated at amino acid 432 due to alternative splice donor site. The h5-HT_7(d) is a distinct isoform of the receptor: the retention of an exon cassette in the region encoding the carboxyl terminal results a 479-amino acid receptor with a c-terminus markedly different from the h5-HT_7(a). A 5-HT_7(c) splice variant is detectable in rat tissue but is not expressed in humans. Conversely, rats do not express a splice variant homologous to the h5-HT_7(d), as the rat 5-HT₇ gene lacks the exon necessary to encode this isoform. Drug binding affinities are similar across the three human splice variants; however, inverse agonist efficacies appear to differ between the splice variants.

Discovery

In 1983, evidence for a 5-HT₁-like receptor was first found. Ten years later, 5-HT₇ receptor was cloned and characterized. It has since become clear that the receptor described in 1983 is 5-HT₇.

Ligands

Numerous orthosteric ligands of moderate to high affinity are known. Signaling biased ligands were discovered and developed in 2018.

Agonists

Agonists 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 agon ...

mimic the effects of the endogenous ligand, which is serotonin at the 5-HT₇ receptor (↑cAMP). * 5-Carboxamidotryptamine (5-CT) * 5-methoxytryptamine (5-MT, 5-MeOT) *

8-OH-DPAT 8-OH-DPAT is a research chemical of the aminotetralin chemical class which was developed in the 1980s and has been widely used to study the function of the 5-HT1A receptor. It was one of the first major 5-HT1A receptor full agonists to be discove ...

(mixed 5-HT_1A/5-HT₇ agonist) *

Aripiprazole Aripiprazole, sold under the brand names Abilify and Aristada among others, is an atypical antipsychotic. It is primarily used in the treatment of schizophrenia and bipolar disorder. Other uses include as an add-on treatment in major depressiv ...

(weak

partial agonist In pharmacology, partial agonists are drugs that bind to and activate a given receptor, but have only partial efficacy at the receptor relative to a full agonist. They may also be considered ligands which display both agonistic and antagonis ...

) * AS-19 *

E-55888 E-55888 is a drug developed by Esteve, which acts as a potent and selective full agonist at the 5HT7 serotonin receptor, and is used for investigating the role of 5-HT7 receptors in the perception of pain. When administered by itself, E-55888 i ...

* E-57431 *

LP-12 LP-12 is a drug which acts as a potent agonist at the 5HT7 serotonin receptor, with very high selectivity over other tested receptor subtypes such as the serotonin 5-HT1A and 5-HT2A, and the dopamine D2 receptor. It has been used to research the ...

(4-(2-Diphenyl)-N-(1,2,3,4-tetrahydronaphthalen-1-yl)-1-piperazinehexanamide) *

LP-44 LP-44 is a drug which acts as a potent and selective agonist at the 5HT7 serotonin receptor. While LP-44 is less selective than the related compound LP-12, it has been more widely used in research and has been used to show the complex role of 5- ...

(4- -(Methylthio)phenylN-(1,2,3,4-tetrahydro-1-naphthalenyl)-1-piperazinehexanamide) *

LP-211 LP-211 is a drug which acts as a potent and selective agonist at the 5HT7 serotonin receptor 5-HT receptors, 5-hydroxytryptamine receptors, or serotonin receptors, are a group of G protein-coupled receptor and ligand-gated ion channels foun ...

* MSD-5a * ''N_ω''-Methylserotonin * ''N''-(1,2,3,4-Tetrahydronaphthalen-1-yl)-4-aryl-1-piperazinehexanamides (can function as either an agonist or antagonist depending on side chain substitution) *

N,N-Dimethyltryptamine ''N'',''N''-Dimethyltryptamine (DMT or ''N'',''N''-DMT, SPL026) is a substituted tryptamine that occurs in many plants and animals, including human beings, and which is both a derivative and a structural analog of tryptamine. It is used as ...

AGH-107 AGH-107 is a potent, selective, water-soluble and brain penetrant full agonist at the 5HT7 serotonin receptor. AGH-107 is one of the few examples of low-basicity aminergic receptor agonists, which may underlie its high selectivity over the re ...

(water soluble, brain penetrating full agonist) *

AH-494 AH-494 is a potent and selective, water-soluble full agonist at the 5HT7 serotonin receptor. It is a close derivative of the known chemical probe 5-Carboxamidotryptamine, as well as of the more lipophilic indole-imidazoles: AGH-107 and AGH-192 ...

(3-(1-ethyl-1H-imidazol-5-yl)-1H-indole-5-carboxamide) *

AGH-192 AGH-192 is a potent and selective, water soluble, orally bioavailable and brain penetrant full agonist at the 5HT7 serotonin receptor, derived from the older drug AGH-107. In animal tests it showed activity indicative of potential application ...

(orally bioavailable, water soluble, brain penetrating full agonist)

Antagonists

Neutral antagonists (also known as silent antagonists) bind the receptor and have no

intrinsic activity Intrinsic activity (IA) and efficacy refer to the relative ability of a drug- receptor complex to produce a maximum functional response. This must be distinguished from the affinity, which is a measure of the ability of the drug to bind to its mol ...

but will block the activity of agonists or inverse agonists.

Inverse agonists In pharmacology, an inverse agonist is a drug that binds to the same receptor as an agonist but induces a pharmacological response opposite to that of the agonist. A neutral antagonist has no activity in the absence of an agonist or inverse ...

inhibit the

constitutive activity In biochemistry and pharmacology, receptors are chemical structures, composed of protein, that receive and transduce signals that may be integrated into biological systems. These signals are typically chemical messengers which bind to a recepto ...

of the receptor, producing functional effects opposite to those of agonists (at the 5-HT₇ receptor: ↓cAMP). Neutral antagonists and inverse agonists are typically referred to collectively as "antagonists" and, in the case of the 5-HT₇ receptor, differentiation between neutral antagonists and inverse agonists is problematic due to differing levels of inverse agonist efficacy between receptor splice variants. For instance, mesulergine and metergoline are reported to be neutral antagonists at the h5-HT_7(a) and h5-HT_7(d) receptor isoforms but these drugs display marked inverse agonist effects at the h5-HT_7(b) splice variant. * 3--3-ethyl-6-fluoro-1,3-dihydro-2''H''-indol-2-one *

Amisulpride Amisulpride is an antiemetic and antipsychotic medication used at lower doses intravenously to prevent and treat postoperative nausea and vomiting; and at higher doses by mouth to treat schizophrenia and acute psychotic episodes. It is sold un ...

Amitriptyline Amitriptyline, sold under the brand name Elavil among others, is a tricyclic antidepressant primarily used to treat cyclic vomiting syndrome (CVS), major depressive disorder and a variety of pain syndromes from neuropathic pain to fibromyalgi ...

Amoxapine Amoxapine, sold under the brand name Asendin among others, is a tricyclic antidepressant (TCAs). It is the N-demethylated metabolite of loxapine. Amoxapine first received marketing approval in the United States in 1992 (approximately 30 to 40 ...

Brexpiprazole Brexpiprazole, sold under the brand name Rexulti among others, is an atypical antipsychotic. It is a dopamine D2 receptor partial agonist and has been described as a "serotonin–dopamine activity modulator" (SDAM). The drug was approved by th ...

Clomipramine Clomipramine, sold under the brand name Anafranil among others, is a tricyclic antidepressant (TCA). It is used for the treatment of obsessive–compulsive disorder, panic disorder, major depressive disorder, and chronic pain. It may increase th ...

Clozapine Clozapine is a psychiatric medication and is the first atypical antipsychotic (also called second-generation antipsychotic). It is primarily used to treat people with schizophrenia and schizoaffective disorders who have had an inadequate respo ...

* CYY1005 (a highly selective, orally active 5-HT7 antagonist) * DR-4485 * EGIS-12233 (mixed 5-HT₆/5-HT₇ antagonist) *

AVN-101 AVN-101, a close structural analogue of latrepirdine, is a selective 5-HT6 receptor antagonist which is under development by Avineuro Pharmaceuticals for the treatment of Alzheimer's disease and anxiety disorders. As of November 2013, it is i ...

(mixed 5-HT₆/5-HT₇ antagonist) *

Fluphenazine Fluphenazine, sold under the brand name Prolixin among others, is a high-potency typical antipsychotic medication. It is used in the treatment of chronic psychoses such as schizophrenia, and appears to be about equal in effectiveness to low-pote ...

Fluperlapine Fluperlapine (NB 106-689), also known as fluoroperlapine, is a morphanthridine (11''H''-dibenzo ,ezepine) atypical antipsychotic with additional antidepressant and sedative effects. It was first synthesized in 1979, and then subsequently studie ...

* ICI 169,369 *

Imipramine Imipramine, sold under the brand name Tofranil, among others, is a tricyclic antidepressant (TCA) mainly used in the treatment of depression. It is also effective in treating anxiety and panic disorder. The drug is also used to treat bedwetting. ...

* JNJ-18038683 *

Ketanserin Ketanserin ( INN, USAN, BAN) (brand name Sufrexal; former developmental code name R41468) is a drug used clinically as an antihypertensive agent and in scientific research to study the serotonin system; specifically, the 5-HT2 receptor family. I ...

Loxapine Loxapine, sold under the brand names Loxitane and Adasuve (''inhalation'' only) among others, is an antipsychotic medication used primarily in the treatment of schizophrenia. The medicine is a member of the dibenzoxazepine class and structural ...

Lurasidone Lurasidone, sold under the trade name Latuda among others, is an antipsychotic medication used to treat schizophrenia and bipolar disorder. It is taken by mouth. Common side effects include sleepiness, movement disorders, nausea, and diarrhea. ...

* LY-215,840 *

Maprotiline Maprotiline, sold under the brand name Ludiomil among others, is a tetracyclic antidepressant (TeCA) that is used in the treatment of depression. It may alternatively be classified as a tricyclic antidepressant (TCA), specifically a secondary am ...

Mesulergine Mesulergine () (developmental code name CU-32085) is a drug of the ergoline group which was never marketed. It acts on serotonin and dopamine receptors. Specifically, it is an agonist of dopamine D2-like receptors and serotonin 5-HT6 receptors ...

Methysergide Methysergide, sold under the brand names Deseril and Sansert, is a monoaminergic medication of the ergoline and lysergamide groups which is used in the prophylaxis and treatment of migraine and cluster headaches. It has been withdrawn from the ma ...

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 closely ...

Olanzapine Olanzapine (sold under the trade name Zyprexa among others) is an atypical antipsychotic primarily used to treat schizophrenia and bipolar disorder. For schizophrenia, it can be used for both new-onset disease and long-term maintenance. It is t ...

Pimozide Pimozide (sold under the brand name Orap) is an antipsychotic drug of the diphenylbutylpiperidine class. It was discovered at Janssen Pharmaceutica in 1963. It has a high potency compared to chlorpromazine (ratio 50-70:1). On a weight basis ...

* RA-7 (1-(2-diphenyl)piperazine) * Ritanserin * SB-258,719 * SB-258741 *

SB-269970 SB-269970 is a drug and research chemical developed by GlaxoSmithKline used in scientific studies. It is believed to act as a selective 5-HT7, 5-HT7 receptor (biochemistry), receptor Antagonist (pharmacology), antagonist (EC50 = 1.25 nM) (or poss ...

(highly 5-HT₇ selective) * SB-656104-A * SB-691673 *

Sertindole Sertindole, sold under the brand name Serdolect among others, is an antipsychotic medication. Sertindole was developed by the Danish pharmaceutical company Lundbeck and marketed under license by Abbott Labs. Like other atypical antipsychotics, i ...

Spiperone Spiperone (Spiroperidol; brand name: Spiropitan ( JP)) is a typical antipsychotic and research chemical belonging to the butyrophenone chemical class. It is licensed for clinical use in Japan as a treatment for schizophrenia. Additionally, spip ...

* Tenilapine *

TFMPP 3-Trifluoromethylphenylpiperazine (TFMPP) is a recreational drug Recreational drug use indicates the use of one or more psychoactive drugs to induce an altered state of consciousness either for pleasure or for some other casual purpose or pas ...

Vortioxetine Vortioxetine, sold under the brand names Trintellix and Brintellix among others, is a medication used to treat major depressive disorder. Effectiveness is viewed as similar to that of other antidepressants. It is taken by mouth. Common side e ...

Trifluoperazine Trifluoperazine, marketed under the brand name Stelazine among others, is a typical antipsychotic primarily used to treat schizophrenia. It may also be used short term in those with generalized anxiety disorder but is less preferred to benzodiaze ...

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 agitation ...

Zotepine Zotepine is an atypical antipsychotic drug indicated for acute and chronic schizophrenia. It has been used in Germany since 1990 (although it has been discontinued in Germany) and Japan since 1982. Zotepine is not approved for use in the United ...

Inactivating antagonists

Inactivating antagonists are non-competitive antagonists that render the receptor persistently insensitive to agonist, which resembles receptor desensitization. Inactivation of the 5-HT₇ receptor, however, does not arise from the classically described mechanisms of receptor desensitization via receptor phosphorylation, beta-arrestin recruitment, and receptor internalization. Inactivating antagonists all likely interact with the 5-HT₇ receptor in an irreversible/pseudo-irreversible manner, as is the case with sup>3Hisperidone. *

Bromocriptine Bromocriptine, originally marketed as Parlodel and subsequently under many brand names, is an ergoline derivative and dopamine agonist that is used in the treatment of pituitary tumors, Parkinson's disease, hyperprolactinaemia, neuroleptic ...

Lisuride Lisuride, sold under the brand name Dopergin among others, is a monoaminergic medication of the ergoline class which is used in the treatment of Parkinson's disease, migraine, and high prolactin levels. It is taken by mouth. Side effects of lis ...

Metergoline Metergoline (, ), also known as methergoline and sold under the brand names Contralac (veterinary) and Liserdol (clinical), is a monoaminergic medication of the ergoline group which is used as a prolactin inhibitor in the treatment of hyperprola ...

Methiothepin Metitepine (; developmental code names Ro 8-6837 (maleate), VUFB-6276 (mesylate)), also known as methiothepin, is a drug described as a " psychotropic agent" of the tricyclic group which was never marketed. It acts as a non-selective antagonis ...

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 ...

Risperidone Risperidone, sold under the brand name Risperdal among others, is an atypical antipsychotic used to treat schizophrenia and bipolar disorder. It is taken either by mouth or by injection (subcutaneous or intramuscular). The injectable versions ...

References

External links

* * {{DEFAULTSORT:5-Ht7 Receptor Serotonin receptors