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Query: UNIPROT:P08908 (5-HT1A)
 5,574 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The family of serotonin receptors consists of at least eight distinct subtypes, divided into four classes based on their pharmacological and functional characteristics. Here we report the cloning and expression in Swiss 3T3 cells of the human 5-HT2 and 5-HT1A receptor subtypes. Both genes encode functional receptors for 5-HT, that differ considerably in genomic structure, primary amino acid sequence, pharmacology and signal transduction. The 5-HT1A receptor transfectants displayed a single high affinity site for the agonist [3H](+/-)-8-hydroxy-2-(di-n-propylamino)tetralin HBr ([3H]8-OH-DPAT) and a pharmacological profile specific for the 5-HT1A receptor. In these transfectants, 5-HT mediated a dose-dependent inhibition of forskolin-stimulated cAMP levels. Cells expressing the 5-HT2 receptor exhibited high affinity binding for the antagonist [3H]ketanserin with a 5-HT2 receptor specific pharmacological profile. In these cells 5-HT activated phospholipase C in a dose-dependent manner. The 5-HT2 receptor displayed a genomic organization quite different from the 5-HT1A, 5-HT1B and 5-HT1D receptor subtypes. While these receptors are encoded by one single exon, the 5-HT2 receptor is encoded by three exons separated by two introns. The latter finding adds and additional molecular criterion for receptor classification.
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PMID:Genomic organization, coding sequence and functional expression of human 5-HT2 and 5-HT1A receptor genes. 133 Jun 47

Hormonal modulation of neurotransmission emerged as a concept from the recognition that adrenocortical steroids exert profound effects at the level of receptors, G-proteins and effector units. G-proteins, a family of guanine nucleotide binding regulatory components that couple neurotransmitter receptors to various types of intracellular effector systems, appear to be a key target of glucocorticoid (GC) action in the CNS. It is thought that Gs/Gi mediates stimulation/inhibition of adenylate cyclase (AC system), which forms cyclic AMP as second messenger, while receptors stimulating phospholipase C do so through Go to produce two second messengers, inositol 1,4,5-triphosphate and diacylglycerol (PI system). Recent evidence suggests that GC increase Gs alpha-and decrease Gi alpha-protein subunit expression without affecting Go alpha. Activation of central pre- and postsynaptic 5-HT1A receptors which are linked to the Gi-AC complex, induces hypothermia and ACTH/cortisol release in rodents and humans. Compared with controls, patients with a major depressive disorder exhibit increased basal cortisol secretion associated with decreased hypothermic and ACTH/cortisol responses. The attenuated neuroendocrine and thermoregulatory response to 5-HT1A receptor activation may reflect a GC-dependent feedback inhibition of the hypothalamic-pituitary-adrenal (HPA) system and subsensitivity of the presynaptic 5-HT1A-Gi-AC complex function. Differential regulation of 5-HT1A and 5-HT2 function leading to a relative 5-HT2-Go-PI complex supersensitivity may maintain HPA hyperactivity during the course of depression. These findings corroborate recent reports that GC, via GC-GC receptor (GR) complex activated promotion of gene transcription, modify the expression 5-HT1A-coupled Gi (but not 5-HT2-coupled Go) resulting in altered sensitivity of 5-HT1A-mediated signal transduction and further support the hypothesis of a differential regulation of 5-HT1A and 5-HT2 receptor function and a GC-GR/5-HT1A-G-protein--effector system-related abnormality in depression.
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PMID:The 5-HT receptor--G-protein--effector system complex in depression. I. Effect of glucocorticoids. 164 69

The cloned 5-HT1A receptor, stably expressed in HeLa cells, has been shown to mediate the effects of 5-hydroxytryptamine (5-HT) to inhibit cAMP formation and to stimulate the hydrolysis of phosphatidylinositol. Both responses were found to be pertussis toxin sensitive. We have examined these two responses in membranes derived from these cells and show that the 5-HT1A receptor can directly regulate the activity of adenylyl cyclase and phospholipase C in response to agonist. In order to examine whether the same or distinct guanine nucleotide-binding regulatory protein(s) (G protein) are involved in these two signal transduction pathways, we used anti-peptide antibodies recognizing the alpha-subunits of Gi1, Gi2, Gi3 as specific tools, since these pertussis toxin substrates are expressed in HeLa cells. These antibodies have previously been shown to prevent receptor-G protein coupling by binding to the regions of G proteins which are putatively involved in interaction with receptors. Our results indicate that the Gi proteins, but preferentially Gi3, mediate the effects of 5-HT both to inhibit adenylyl cyclase and to stimulate phospholipase C. These findings demonstrate that the same receptor interacting with the same G protein can regulate several distinct effector molecules.
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PMID:Dual coupling of the cloned 5-HT1A receptor to both adenylyl cyclase and phospholipase C is mediated via the same Gi protein. 178 5

IMR-32 and SK-N-MC cells were found to contain [3H]quinuclidinyl benzilate specific binding sites inhibited by pirenzepine in a manner suggesting the presence of both M1-type and M2-type muscarinic receptor recognition sites. Neither cell had detectable [3H]8-OH-DPAT binding sites. Carbachol stimulated the rate of inositol phospholipid breakdown in IMR-32 and SK-N-MC human neuroblastoma cells with an EC50 value of about 50 microM in both cases. Pirenzepine inhibited the carbachol (100 microM)-stimulated inositol phospholipid breakdown in both cells with Hill slopes of unity and IC50 values of 15 nM (IMR-32) and 12 nM (SK-N-MC). The 5-HT1A receptor agonist 8-OH-DPAT competitively inhibited carbachol-stimulated inositol phospholipid breakdown with pA2 values of 5.78 (IMR-32) and 5.61 (SK-N-MC). These values are consistent with the inhibitory potency of 8-OH-DPAT towards [3H]quinuclidinyl benzilate binding in these cells. The 5-HT agonists 5-MeODMT and buspirone at micromolar concentrations inhibited carbachol-stimulated breakdown in IMR-32 cells. The inhibition by 8-OH-DPAT and 5-MeODMT was not affected by preincubation with (-)alprenolol. 5-HT (10-100 microM) was without effect on either basal or carbachol-stimulated breakdown. It is concluded that IMR-32 and SK-N-MC neuroblastoma cells express muscarinic M1-type but not serotoninergic receptors coupled to phosphoinositide-specific phospholipase C. 8-OH-DPAT acts as a weak antagonist at these muscarinic receptors.
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PMID:Antagonism by 8-hydroxy-2(di-n-propylamino)tetraline and other serotonin agonists of muscarinic M1-type receptors coupled to inositol phospholipid breakdown in human IMR-32 and SK-N-MC neuroblastoma cells. 182 86

Serotonin 5-HT1A receptors have been reported to be negatively coupled to muscarinic receptor-stimulated phosphoinositide turnover in the rat hippocampus. In the present study, we have investigated further the pharmacological specificity of this negative control and attempted to elucidate the mechanism whereby 5-HT1A receptor activation inhibits the carbachol-stimulated phosphoinositide response in immature or adult rat hippocampal slices. Various 5-HT1A receptor agonists were found to inhibit carbachol (10 microM)-stimulated formation of total inositol phosphates in immature rat hippocampal slices with the following rank order of potency (IC50 values in nM): 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) (11) greater than ipsapirone (20) greater than gepirone (120) greater than RU 24969 (140) greater than buspirone (560) greater than 1-(m-trifluoromethylphenyl)piperazine (1,500) greater than methysergide (5,644); selective 5-HT1B, 5-HT2, and 5-HT3 receptor agonists were inactive. The potency of the 5-HT1A receptor agonists investigated as inhibitors of the carbachol response was well correlated (r = 0.92) with their potency as inhibitors of the forskolin-stimulated adenylate cyclase in guinea pig hippocampal membranes. 8-OH-DPAT (10 microM) fully inhibited the carbachol-stimulated formation of inositol di-, tris-, and tetrakisphosphate but only partially antagonized (-40%) inositol monophosphate production. The effect of 8-OH-DPAT on carbachol-stimulated phosphoinositide turnover was not prevented by addition of tetrodotoxin (1 microM), by prior destruction of serotonergic afferents, by experimental manipulations causing an increase in cyclic AMP levels (addition of 10 microM forskolin), or by changes in membrane potential (increase in K+ concentration or addition of tetraethylammonium). Prior intrahippocampal injection of pertussis toxin also failed to alter the ability of 8-OH-DPAT to inhibit the carbachol response. Carbachol-stimulated phosphoinositide turnover in immature rat hippocampal slices was inhibited by the protein kinase C activators phorbol 12-myristate 13-acetate (10 microM) and arachidonic acid (100 microM). Moreover, the inhibitory effect of 8-OH-DPAT on the carbachol response was blocked by 10 microM quinacrine (a phospholipase A2 inhibitor) but not by BW 755C (100 microM), a cyclooxygenase and lipoxygenase inhibitor. These results collectively suggest that 5-HT1A receptor activation inhibits carbachol-stimulated phosphoinositide turnover by stimulating a phospholipase A2 coupled to 5-HT1A receptors, leading to arachidonic acid release. Arachidonic acid could in turn activate a gamma-protein kinase C with as a consequence an inhibition of carbachol-stimulated phosphoinositide turnover. This inhibition may be the consequence of a phospholipase C phosphorylation and/or a direct effect on the muscarinic receptor.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Potential mechanisms involved in the negative coupling between serotonin 5-HT1A receptors and carbachol-stimulated phosphoinositide turnover in the rat hippocampus. 184 78

The 5-HT1 receptor family comprises five different pharmacologic subtypes, designated 5-HT1A, 5-HT1B, 5-HT1C, 5-HT1D, and 5-HT1E, whose common property is to bind 5-HT with nanomolar affinity. Recent investigations with molecular biology approaches led to the cloning and sequencing of 5-HT1A receptors in the rat and in the human, and of the 5-HT1C receptor in the rat. Although the 5-HT1A and 5-HT1C protein binding subunits exhibit the same structure with seven hydrophobic transmembrane domains, an extracellular N terminal and an intracellular C tail, their respective amino-acid sequences are markedly different. Indeed, a higher degree of sequence homology is found between the 5-HT1C and 5-HT2 receptors than between the former and 5-HT1A receptors, suggesting that the 5-HT1C subtype in fact belongs to the 5-HT2 class of central 5-HT receptors. All other 5-HT1 receptor subtypes are negatively coupled to adenylyl cyclase, whereas the 5-HT1C subtype, like 5-HT2 receptors, is positively coupled to phospholipase C. The respective regional distributions and regulatory properties, as well as pending questions regarding the ultrastructural localization, synthesis, mutual interactions, and axonal flow of 5-HT1 receptor subtypes, are also discussed.
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PMID:The main features of central 5-HT1 receptors. 207 71

The signal transduction pathways of the cloned human 5-HT1A receptor have been examined in two mammalian cell lines transiently (COS-7) or permanently (HeLa) expressing this receptor gene. In both systems, 5-hydroxytryptamine (5-HT, serotonin) mediated a marked inhibition of beta 2-adrenergic agonist-stimulated (80% inhibition in COS-7 cells) or forskolin-stimulated cAMP formation (up to 90% inhibition in HeLa cells). This serotonin effect (EC50 = 20 nM) could be competitively antagonized by metitepine and spiperone (Ki = 81 and 31 nM, respectively) and could also be blocked by pretreatment of cells with pertussis toxin. In both cell types, 5-HT failed to stimulate adenylyl cyclase through the expressed receptors. In HeLa cells, 5-HT also stimulated phospholipase C (approximately 40-75% stimulation of formation of inositol phosphates). Again, this effect was inhibited by metitepine. However, the EC50 of 5-HT was considerably higher (approximately 3.2 microM) than that found for inhibition of adenylyl cyclase. Both pathways were demonstrated to be similarly affected by pertussis toxin. These findings indicate that like the M2 and M3 muscarinic cholinergic receptors, the 5-HT1A receptor can couple to multiple transduction pathways with varying efficiencies via pertussis toxin-sensitive G-proteins. The lack of stimulation of cAMP formation by this 5-HT1A receptor may suggest the existence of another pharmacologically closely related receptor.
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PMID:Effector coupling mechanisms of the cloned 5-HT1A receptor. 254 39

The existence of two different functional receptors for 5-hydroxytryptamine (5-HT) was first proposed by Gaddum and Picarelli. Aided by the development of radioligand binding techniques, the heterogeneity of 5-HT receptors has become more apparent in the past ten years. There are three main types of 5-HT receptors: 5-HT1, 5-HT2 and 5-HT3. Moreover, 5-HT1 is heterogenous and can be divided into 5-HT1A, 5-HT1B, 5-HT1C and 5-HT1D subtypes. 5-HT1B is probably related to the 5-HT autoreceptor controlling 5-HT release. Multiple 5-HT receptors are differentially distributed throughout the brain, and the agonist-receptor interaction is altered by physical parameters and chemicals, suggesting that the receptors may be physiologically relevant. Three 5-HT receptor subtypes, 5-HT1A, 5-HT1C and 5-HT2, have been cloned. All three receptors contain approximately 450 amino acids arrayed as seven transmembrane domains. 5-HT1 and 5-HT1A are coupled to adenylate cyclase positively and negatively, respectively, while 5-HT1C and 5-HT2 are coupled positively to phospholipase C. 5-HT1A is also coupled to the opening of K+ channels in hippocampal pyramidal cells. A number of 5-HT-induced physiological responses have been shown to correlate with the 5-HT receptor subtypes. Based on a number of pharmacological studies, it seems likely that the mode of action of certain psychotropic drugs is closely related to the activity of central 5-HT receptors.
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PMID:[5-Hydroxytryptamine receptors]. 255 57

5-HT1a receptors in the hippocampus play a critical role in modulating limbic system output. The activity and level of 5-HT1a receptors are modulated by glucocorticoid levels. The present study was undertaken to test the hypothesis that glucocorticoids attenuate the transcriptional activity of the 5-HT1a receptor gene. Using in situ hybridization and RNase protection assays, we observed a substantial increase in 5-HT1a mRNA expression after adrenalectomy in the same hippocampal regions in which 5-HT1a binding sites are increased. This increase in 5-HT1a mRNA expression occurs as early as 1 h after adrenalectomy and precedes the increase in receptor binding sites. Further in situ hybridization analysis showed that 5-HT1a mRNA is increased within individual hippocampal cells after adrenalectomy. Administration of dexamethasone completely prevents the adrenalectomy-induced elevation in hippocampal 5-HT1a receptor mRNA. Nuclear run-on assays showed that the rate of transcription of 5-HT1a mRNA after adrenalectomy increased 70% above the rate from control preparations and could be reduced to basal levels by the administration of dexamethasone. Adrenalectomy did not cause an increase in functional coupling of 5-HT1a receptors to adenylyl cyclase or phospholipase C. These results suggest that transcription of hippocampal 5-HT1a receptor mRNA is under negative regulation by corticosteroid hormones.
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PMID:Transcriptional regulation of hippocampal 5-HT1a receptors by corticosteroid hormones. 776 98

Serotonin (5-HT) is a central neurotransmitter and a neuromodulator. This amine is involved in many physiological functions and pathological disorders. Most of its effects are mediated by specific 5-HT receptors. In the first part of this paper, the present knowledge of 5-HT receptors is reviewed in terms of both pharmacology and molecular biology. In the second part, the functional properties of 5-HT receptors are analyzed and their involvement in pathophysiological processes is discussed. Most 5-HT receptors belong to the G-protein-coupled receptor family (5-HT1, 5-HT2 and 5-HT4 receptors), whereas one is a member of the ligand-gated ion-channel receptor family (5-HT3 receptor). 5-HT1 receptors are characterized by their high affinity for 5-HT and comprise several subclasses. Most are negatively coupled to adenylate cyclase but the 5-HT1C subtype is linked to phospholipase C activation and resembles the 5-HT2 receptor. By contrast, the newly identified 5-HT4 receptor is positively coupled to adenylate cyclase. Most 5-HT receptors have now been cloned, but their physiological roles are not completely understood. Better knowledge of 5-HT receptors has already led to the development of new drugs, such as buspirone, a 5-HT1A partial agonist devoid of benzodiazepine-like properties for the treatment of generalized anxiety. Anxiolytic properties have also been reported for 5-HT2 and 5-HT3 receptor antagonists. A new and potent anti-migrainous drug, sumatriptan, has recently been selected among compounds obtained by research on the 5-HT1D receptor. This key receptor controls the release of monoamines, amino acids and peptides, and new drugs are expected in the near future. The therapeutic potential of 5-HT3 antagonists is impressive, as these compounds have potent antiemetic, promnesic and antipsychotic properties in various animal models. Two such drugs have already been marketed for the prevention of radiation-induced emesis (ondansetron and granisetron) and are more potent than the antidopaminergic drugs. Many other data suggest that 5-HT receptors might be involved in other illnesses. Some drugs are in the development phase but identification of the relevant receptor is often difficult. Furthermore, the lak of specific ligands for some receptors clearly hinders functional correlations.
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PMID:[Central serotonin receptors. Principal fundamental and functional aspects. Therapeutic applications]. 780 Oct 37


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