Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P08908 (5-HT1A)
 5,574 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human serotonin [5-hydroxytryptamine (5-HT)1A] receptors have been transfected in NIH-3T3 cells, and their pharmacology and coupling to adenylyl cyclase have been analyzed. Three cellular preparations were used, 1) monoclonal cell lines (clones 6, 2B, and 4B), expressing 45, 280, and 500 fmol of 5-HT1A receptors/mg of protein, respectively; 2) clones 6, 2B, and 4B in which the concentration of 5-HT1A receptors was increased after stimulation of the glucocorticoid-inducible promoter with dexamethasone; and 3) polyclonal cell lines that expressed an increasing amount of 5-HT1A receptor as a function of cell passage. The transfected 5-HT1A receptors inhibited basal, forskolin-stimulated, and isoproterenol-stimulated adenylyl cyclase. The inhibition was dependent on the receptor density expressed, increasing from 60% at low density (45 fmol/mg) to 90% at a density higher than 280 fmol/mg. The pharmacology of the 5-HT1A receptor was studied, with particular attention being paid to the behavior of some agonists. These pharmacological characteristics are similar to those of 5-HT1A receptors in hippocampus but different from those of 5-HT1A in cerebral cortex. Analysis of the potencies and efficacies of the full agonist 5-HT and the partial agonist ipsapirone, as a function of receptor density in the three cellular populations used, revealed that 1) the efficacies of the full and partial agonists increased with the receptor density; 2) the EC50 values of the full and partial agonists were not shifted to the left when the receptor density was increased (based on the increase in efficacy and considering the classical pharmacological models of receptor-drug action, a 9-10-fold shift was expected); and 3) the ratio between the efficacies of the full agonist 5-HT and the partial agonist ipsapirone was not modified when the receptor concentration was increased or when the GTP-binding protein availability was decreased. The results indicate that neither the classical nor the operational model of drug-receptor action can be used to describe the coupling of 5-HT1A receptors to adenylyl cyclase in transfected NIH-3T3 cells. One of the explanations could be that 5-HT1A receptors and GTP-binding proteins are coupled in functional domains (almost precoupled), rather than distributed in homogeneous compartments in which they are free to diffuse.
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PMID:Transfection of human 5-hydroxytryptamine1A receptors in NIH-3T3 fibroblasts: effects of increasing receptor density on the coupling of 5-hydroxytryptamine1A receptors to adenylyl cyclase. 161 16

NAN-190 has been reported to be a 5-HT1A antagonist in drug discrimination studies. In order to determine if the effect of NAN-190 was directly due to competitive inhibition at 5-HT1A receptors, 5-HT1A-mediated inhibition of adenylyl cyclase in hippocampal membranes was investigated. NAN-190 (10(-10)-10(-5) M), by itself, was found to have no effect on forskolin-stimulated adenylyl cyclase. NAN-190, however, did shift the 5-carboxamidotryptamine (a 5-HT1A agonist) log-concentration inhibition curve to the right in a concentration-dependent manner, typical of competitive antagonism. Schild analysis revealed a KB of 1.9 nM for NAN-190. Thus, NAN-190 appeared to be a potent competitive 5-HT1A antagonist using the in vitro adenylyl cyclase system. [3H]NAN-190 was synthesized and its 5-HT1A receptor binding properties were characterized and compared with the 5-HT1A agonist radioligand, [3H]8-hydroxy-2-(di-n-propylamino)tetralin ([3H]8-OH-DPAT). The 5-HT1A agonists, serotonin (5-HT) and 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) competed with equal affinities regardless of the radioligand used to label the 5-HT1A receptors. [3H]NAN-190 and [3H]8-OH-DPAT labeled the same number of sites in rat hippocampus, striatum and frontal cortex. Guanosine-5'-O-(3-thio)triphosphate (GTP gamma S) and 5-guanylyl-imidodiphosphate (GppNHp), non-hydrolyzable analogs of GTP, inhibited specific [3H]NAN-190 binding. Adenosine-5'-O-(3-thio)triphosphate (ATP gamma S) and 5-adenylyl-imidodiphosphate (AppNHp) were ineffective. This guanylyl nucleotide-specific effect is generally associated with agonist radioligand binding to a GTP-binding protein coupled receptor. However, [3H]8-OH-DPAT was far more sensitive than [3H]NAN-190 to the Bmax reducing effects of GTP and GTp gamma S. We propose that the test for a reduction in Bmax by non-hydrolyzable guanylyl nucleotides may be more sensitive than other tests for quantifying agonist activity and may demonstrate that NAN-190 has low intrinsic activity. In summary, NAN-190 displayed antagonist-like properties in functional models of 5-HT1A receptor activity and possibly partial agonist-like properties in radioligand binding experiments.
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PMID:NAN-190: agonist and antagonist interactions with brain 5-HT1A receptors. 228 13

Serotonin (5-hydroxytryptamine; 5-HT) and its analogs activate adenylate cyclase in membrane particles from neuroblastoma NCB.20 cells. Low concentrations of GTP (EC50 = 60 nM) were required for activation by serotonin. Guanosine 5'-O-(2-thiodiphosphate) inhibited serotonin-activated cyclase in these cells. The nonhydrolyzable GTP analogs guanosine 5'-O-(3-thiotriphosphate) (EC50 = 3 nM) and guanylyl-imidodiphosphate (EC50 = 100 nM) substituted for GTP in potentiating serotonin activation. Pretreatment of the cells with cholera toxin potentiated enzyme activation by serotonin, whereas pertussis toxin was found to have little effect, indicating the involvement of the alpha subunit of a stimulatory GTP-binding protein in enzyme activation. Homologous desensitization of the serotonin-stimulated adenylate cyclase was demonstrated in membranes prepared from intact cells pretreated with serotonin. Cell membrane particles that were desensitized to serotonin were still responsive to beta-adrenergic agonists and to prostaglandin E1. Evidence is presented indicating that serotonin stimulation of adenylate cyclase is mediated by receptors that are distinct from other positively coupled receptors (beta-adrenergic, histamine, and prostacyclin). Equilibrium binding analysis with [3H]serotonin, [3H]lysergic acid diethylamide, and [3H]dihydroergotamine suggested that the site density was below the level of detection of binding of these radioligands. The pharmacological characteristics of the serotonin-activated cyclases were analyzed in order to compare these serotonin receptors with the family of different receptor subtypes. Correlation analysis between the potencies of different agonists and antagonists at the cyclase in these cells and their reported relative potencies for different serotonin receptor subtypes showed no correlation with the 5-HT1A, 5HT1B, 5HT1D, 5-HT2, and 5-HT3 receptors. On the other hand, the analysis showed that the NCB.20 serotonin receptors are similar but not identical to the rat and pig brain 5-HT1C receptors and to the serotonin receptors coupled to adenylate cyclase in the trematodes Schistosoma mansoni and Fasciola hepatica. The results point to a novel serotonin receptor which has a low density in these cells.
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PMID:Serotonin receptor-mediated activation of adenylate cyclase in the neuroblastoma NCB.20: a novel 5-hydroxytryptamine receptor. 233 46

The inhibition of forskolin-stimulated adenylate cyclase activity by 5-hydroxytryptamine (5-HT) receptor agonists was measured in rat hippocampal membranes isolated from animals treated with vehicle or islet-activating protein (IAP; pertussis toxin). In vehicle-treated animals, 5-HT, 8-hydroxy-2-(di-n-propylamino)tetralin, buspirone, and gepirone were potent in inhibiting forskolin-stimulated adenylate cyclase activity with EC50 values of 60, 76, 376, and 530 nM, respectively. IAP treatment reduced by 30-55% the 5-HT1A agonist inhibition of adenylate cyclase activity via 5-HT1A receptors. The data indicate that the inhibitory guanine nucleotide-binding protein or Go (a similar GTP-binding protein of unknown function purified from brain) mediates the 5-HT1A agonist inhibition of hippocampal adenylate cyclase.
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PMID:Pertussis toxin attenuates 5-hydroxytryptamine1A receptor-mediated inhibition of forskolin-stimulated adenylate cyclase activity in rat hippocampal membranes. 252 68

Serotonin (5-hydroxytryptamine, 5-HT) inhibited the formation of cAMP promoted by vasoactive intestinal polypeptide, plus forskolin, in mouse hippocampal and cortical neurons in primary culture. The rank order of potencies of classical 5-HT1 agonists in inhibiting cAMP formation in hippocampal neurons was 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) greater than 5-carboxamidotryptamine (5-CT) greater than d-lysergic acid diethylamide greater than 5-HT greater than 5-methoxy-N,N-dimethyltryptamine (5-MeO-N,N-DMT) greater than RU 24969 greater than ipsapirone greater than bufotenine greater than buspirone [half-maximal efficacy (EC50) = 7, 18, 30, 52, 90, 102, 100, 110, and 128 nM, respectively]. All the tryptamine derivatives substituted in position 5 of the indol were potent agonists [5-HT, 5-CT, 5-MeO-N,N-DMT, 5-methoxytryptamine, and bufotenine], whereas tryptamine, N-methyltryptamine, and N,N-dimethyltryptamine were poor agonists. The most potent antagonists tested were spiperone, (+/-)-pindolol, (+/-)-cyanopindolol, WB4101, and methiothepin, the affinity of spiperone for this receptor being 22 nM. In contrast, ketanserin, a specific 5-HT2 antagonist, and 5-HT3-selective drugs (ICS 205 930 and MDL 72222) were very weak in antagonizing the 5-HT-inhibited cAMP formation. The pharmacological profiles of 5-HT receptors mediating the inhibition of cAMP formation indicate that these receptors correspond to the 5-HT1A-binding site subtypes. Experiments with the Bordetella pertussis toxin indicate that the 5-HT1A receptor mediating inhibition of cAMP production involves a pertussis toxin-sensitive GTP-binding protein. In the absence of VIP, cAMP formation could be stimulated through a 5-HT receptor, but the specific 5-HT1A agonists, 8-OH-DPAT and RU 24969 did not stimulate cAMP production. These results suggest that in mouse embryonic hippocampal neurons, the 5-HT1A receptors, which are negatively coupled to adenylate cyclase, are distinct from the receptor positively coupled to this enzyme. The pharmacological characterization of the 5-HT receptor negatively coupled to adenylate cyclase in mouse embryonic cortical neurons indicates that it differs from the 5-HT1A receptor found in hippocampal neurons. Its main differences with the 5-HT1A receptor in hippocampal neurons are as follows: 1) 8-OH-DPAT was only a poor partial agonist in cortical neurons, whereas it was the best full agonist in hippocampal neurons; and 2) metergoline and methysergide as well as the anxiolytic drugs, ipsapirone and buspirone, which were potent agonists in hippocampal neurons, were competitive antagonists in cortical neurons.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Pharmacology of 5-hydroxytryptamine-1A receptors which inhibit cAMP production in hippocampal and cortical neurons in primary culture. 282 13

GTP hydrolyzing activity was assayed by measuring the amount of 32P(i) released from 0.3 microM [gamma-32P]GTP in the membranes prepared from rat brain. 5-Hydroxytryptamine (5-HT) stimulated the high-affinity GTPase activity in hippocampus, but not in striatum, in a concentration-dependent manner with an EC50 value of 18 nM and maximal percent stimulation of 13.9%. This response was mimicked by (+/-)-8-hydroxy-2-(di-n-propylamino)tetralin [(+/-)-8-OH-DPAT], but not by (+/-)-1-(2,5-dimethoxy-4-iodophyenyl)-2-aminopropane [(+/-)-DOI]. These results suggest that 5-HT-stimulated high-affinity GTPase activity of the GTP-binding protein(s) is mediated via 5-HT1A receptor subtype in the rat hippocampus.
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PMID:5-HT1A receptor-mediated activation of high-affinity GTPase in rat hippocampal membranes. 777 84

5-Hydroxytryptamine (5-HT) is a mitogen for selected cell types. We have reported that 5-HT is an autocrine growth factor for functioning human pancreatic carcinoid (BON) cells; autocrine growth effect is transmitted by 5-HT1A but not 5-HT1C/2 receptors, activation of which decreases cyclic AMP production through a pertussis toxin-sensitive inhibitory GTP-binding protein. In this study, the effect of 5-HT3 receptor antagonist, ondansetron, on BON was examined. Ondansetron did not affect growth of BON cells and also affected neither stimulation of phosphatidylinositol hydrolysis or inhibition of cyclic AMP production evoked by 5-HT in BON cells. Ondansetron, however, inhibited mobilization of intracellular calcium evoked by 5-HT. Present findings suggest that BON cells possess 5-HT3 receptors, but their roles in pancreatic carcinoid cells are still unknown.
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PMID:Effect of 5-HT3 receptor antagonist (ondansetron) on functioning human pancreatic carcinoid cells. 825 12

Agonists for GTP-binding protein (G protein)-coupled receptors are thought to bind with high affinity to the complex of receptor and G protein. Nonhydrolyzable GTP analogs have been shown to disrupt this complex and reduce the binding affinity for many agonists. Antagonists are thought to bind to the receptor whether or not it is coupled to the G protein, and therefore binding remains unchanged in the presence of GTP analogs. The binding of the serotonin 5-hydroxytryptamine (5-HT)2 receptor agonists serotonin (5-HT) and 4-bromo-2,5-dimethoxyphenylisopropylamine is not affected by the presence of GTP analogs when the cloned 5-HT2 receptor is expressed in the 293 human embryonic kidney cell line. The same receptor expressed in mouse NIH3T3 cells is partially sensitive to GTP analogs. Both cell lines have similar proportions of agonist and antagonist binding sites, and agonist stimulation of both cell lines leads to a robust increase in phosphoinositide hydrolysis. Differences in GTP metabolism in 293 cells is not likely to be the cause of the observed difference in inhibition of agonist binding, because the cloned 5-HT1A serotonin receptor expressed in these cells is sensitive to GTP analogs. The GTP-insensitive agonist binding is best explained by the existence of a G protein-receptor complex in 293 cells that is not sensitive to GTP analogs. Such a G protein-receptor complex may explain the fraction of agonist binding in the brain that is not sensitive to GTP analogs.
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PMID:High affinity agonist binding to cloned 5-hydroxytryptamine2 receptors is not sensitive to GTP analogs. 831 23

The ionic channels and signal transduction pathways underlying the 5-hydroxytryptamine (5-HT)-induced hyperpolarization in neurons of the rat dorsolateral septal nucleus (DLSN) were examined by using intracellular and voltage-clamp recording techniques. Application of 5-HT (1-50 microM) caused a hyperpolarizing response associated with a decreased membrane resistance in DLSN neurons. The hyperpolarization induced by 5-HT was blocked by Ba2+ (1 mM) but not by tetraethylammonium (TEA, 3 mM), glibenclamide (100 microM) and extracellular Cs+ (2 mM). 8-Hydroxy-di-n-propylamino tetralin (8-OH-DPAT; 3 microM), a selective agonist for the 5-HT1A receptor, mimicked 5-HT in producing the hyperpolarization. The 5-HT hyperpolarization was blocked by NAN-190 (5 microM), a 5-HT1A receptor antagonist. CP93129 (100 microM), a 5-HT1B receptor agonist, and L-694-247 (100 microM), a 5-HT1B/1D receptor agonist, also produced hyperpolarizing responses. The order of agonist potency was 8-OH-DPAT >> CP93129 > or = L-694-247. (+/-)-2,5-Dimethoxy-4-iodoamphetamine hydrochloride (DOI, 100 microM), a 5-HT2 receptor agonist, and RS67333 (100 microM), a 5-HT4 receptor agonist, caused no hyperpolarizing response. The voltage-clamp study showed that 5-HT caused an outward current (I5-HT) in a concentration-dependent manner. I5-HT was associated with an increased membrane conductance. I5-HT reversed the polarity at the equilibrium potential for K+ calculated by the Nernst equation. I5-HT showed inward rectification at membrane potentials more negative than-70 mV. Ba2+ (100 microM) blocked the inward rectifier K+ current induced by 5-HT. I5-HT was irreversibly depressed by intracellular application of guanosine 5'-O-(3-thiotriphosphate)(GTP-gamma S) but not by guanosine 5'-O-(2-thiodiphosphate) (GDP beta S). These results suggest that in rat DLSN neurons activation of 5-HT1A receptors causes a hyperpolarizing response by activating mainly the inward rectifier K+ channels through a GTP-binding protein.
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PMID:Effects of 5-hydroxytryptamine on neuronal activities in the rat dorsolateral septal nucleus. 991 16

1. The basolateral amygdala (ABL) nuclei contribute to the process of anxiety. GABAergic transmission is critical in these nuclei and serotonergic inputs from dorsal raphe nuclei also significantly regulate GABA release. In mechanically dissociated rat ABL neurons, spontaneous miniature inhibitory postsynaptic currents (mIPSCs) arising from attached GABAergic presynaptic nerve terminals were recorded with the nystatin-perforated patch method and pharmacological isolation. 2. 5-HT reversibly reduced the GABAergic mIPSC frequency without affecting the mean amplitude. The serotonergic effect was mimicked by the 5-HT1A specific agonist 8-OH DPAT (8-hydroxy-2-(di-n-propylamino)tetralin) and blocked by the 5-HT1A antagonist spiperone. 3. The GTP-binding protein inhibitor N-ethylmaleimide removed the serotonergic inhibition of mIPSC frequency. In either K+-free or Ca2+-free external solution, 5-HT could inhibit mIPSC frequency. 4. High K+ stimulation increased mIPSC frequency and 8-OH DPAT inhibited this increase even in the presence of Cd2+. 5. Forskolin, an activator of adenylyl cyclase (AC), significantly increased synaptic GABA release frequency. Pretreatment with forskolin prevented the serotonergic inhibition of mIPSC frequency in both the standard and high K+ external solution. 6. Ruthenium Red (RR), an agent facilitating the secretory process in a Ca2+-independent manner, increased synaptic GABA release. 5-HT also suppressed RR-facilitated mIPSC frequency. 7. We conclude that 5-HT inhibits GABAergic mIPSCs by inactivating the AC-cAMP signal transduction pathway via a G-protein-coupled 5-HT1A receptor and this intracellular pathway directly acts on the GABA-releasing process independent of K+ and Ca2+ channels in the presynaptic nerve terminals.
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PMID:Presynaptic serotonergic inhibition of GABAergic synaptic transmission in mechanically dissociated rat basolateral amygdala neurons. 1038 97


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