UNIPROT:P08908 - FACTA Search

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)

In the presence of a 30 nM prazosin mask, [3H]-2-(2,6-dimethoxyphenoxyethyl) aminomethyl-1,4-benzodioxane ([3H]WB4101) can selectively label 5-HT1 serotonin receptors. Serotonin exhibits high affinity (Ki = 2.5 nM) and monophasic competition for [3H] WB4101 binding in cerebral cortex. Furthermore, we have found a significant correlation (r = 0.96) between the affinities of a number of serotonergic and nonserotonergic compounds at [3H]WB4101-binding sites in the presence of 30 nM prazosin and [3H] lysergic acid diethylamide ([3H]LSD)-labeled 5-HT1 serotonin receptors in homogenates of rat cerebral cortex. Despite similar pharmacological profiles, distribution studies indicate that, in the presence of 5 mM MgSO4, the Bmax of [3H]WB4101 is significantly lower than the Bmax of [3H]LSD in various brain regions. WB4101 competition for [3H] LSD-labeled 5-HT1 receptors fits best to a computer-derived model assuming two binding sites, with the KH for WB4101 being similar to the KD of [3H]WB4101 binding derived from saturation experiments. This suggests that [3H]WB4101 labels only one of the subtypes of the 5-HT1 serotonin receptors labeled by [3H]LSD. Interestingly, the selective 5-HT1A serotonin receptor antagonist, spiperone, and the selective 5-HT1A agonist, 8-hydroxy-2-(di-n-propylamino) tetraline, exhibit high affinity and monophasic competition for [3H]WB4101 but compete for multiple [3H]LSD 5-HT1 binding sites. These data indicate that [3H]WB4101 selectively labels the 5-HT1A serotonin receptor, whereas [3H] LSD appears to label both the 5-HT1A and the 5-HT1B serotonin receptor subtypes. The divalent cations, Mn2+, Mg2+, and Ca2+ were found to markedly increase the affinity and Bmax of [3H]WB4101 binding in cerebral cortex. Conversely, the guanine nucleotides guanylylimidodiphosphate and GTP, but not the adenosine nucleotide ATP, markedly reduce the Bmax of [3H]WB4101 binding. These characteristics are typical of agonists interacting with receptors which modulate cellular function via a guanine nucleotide-regulatory subunit.
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PMID:[3H]WB4101 labels the 5-HT1A serotonin receptor subtype in rat brain. Guanine nucleotide and divalent cation sensitivity. 286 62

Drug interactions with 5-HT1 (5-hydroxytryptamine type 1) binding site subtypes were analyzed in rat frontal cortex. 8-Hydroxy-N,N-dipropyl-2-aminotetralin (8-OH-DPAT) displays high affinity (Ki 3.3 +/- 1 nM) for 29 +/- 3% of total [3H]5-HT binding in rat frontal cortex and low affinity (Ki 9,300 +/- 1,000) for 71 +/- 4% of the remaining 5-HT1 sites. Therefore, non-5-HT1A binding in rat frontal cortex was defined as specific [3H]5-HT binding observed in the presence of 100 nM 8-OH-DPAT. 5-Methoxy 3-(1,2,3,6-tetrahydro-4-pyridinyl) 1 H indole (RU 24969), 1-(m-trifluoromethylphenyl)piperazine (TFMPP), mianserin, and methysergide produce shallow competition curves of [3H]5-HT binding from non-5-HT1A sites. Addition of 10(-3) M GTP does not increase the apparent Hill slopes of these competition curves. Computer-assisted iterative curve fitting suggests that these drugs can discriminate two distinct subpopulations of non-5-HT1A binding sites, each representing approximately 35% of the total [3H]5-HT binding in the rat frontal cortex. All three 5-HT1 binding site subtypes display nanomolar affinity for 5-HT and 5-methoxytryptamine. A homogeneous population of 5-HT1A sites can be directly labeled using [3H]8-OH-DPAT. These sites display nanomolar affinity for 8-OH-DPAT, WB 4101, RU 24969, 2-(4-[4-(2-pyrimidinyl)-1-piperazinyl] butyl)-1,2-benzisothiazol-3-(2H)one-1, 1-dioxidehydrochloride (TVX Q 7821), 5-methoxydimethyltryptamine, and d-lysergic acid diethylamide. The potencies of RU 24969, TFMPP, and quipazine for [3H]5-HT binding are increased by addition of 100 nM 8-OH-DPAT and 3,000 nM mianserin to the [3H]5-HT binding assay. Moreover, the drugs have apparent Hill slopes near 1 under these conditions. This subpopulation of total [3H]5-HT binding is designated 5-HT1B. By contrast, methysergide and mianserin become more potent inhibitors of residual [3H]5-HT binding to non-5-HT1A sites in the presence of 100 nM 8-OH-DPAT and 10 nM RU 24969. The drug competition curves under these conditions have apparent Hill slopes of near unity and these sites are designated 5-HT1C. Drug competition studies using a series of 24 agents reveals that each 5-HT1 subtype site has a unique pharmacological profile. These results suggest that radioligand studies can be used to differentiate three distinct subpopulations of 5-HT1 binding sites labeled by [3H]5-HT in rat frontal cortex.
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PMID:Pharmacological differentiation and characterization of 5-HT1A, 5-HT1B, and 5-HT1C binding sites in rat frontal cortex. 294 38

[3H]Spiroxatrine was examined as a potential ligand for the labeling of 5-HT1A sites in the rat hippocampus. Analysis of the binding of [3H]spiroxatrine in the absence and presence of varying concentrations of three monoamine neurotransmitters revealed that serotonin (5-HT) had high affinity (IC50 = 20.7 nM for the [3H]spiroxatrine binding sites, consistent with the labeling of 5-HT1 sites, while dopamine and norepinephrine had very low affinity (IC50 = 57600 nM and greater than 10(-4) M respectively). Saturation studies of the binding of [3H]spiroxatrine revealed a single population of sites with a Kd = 2.21 nM. Further pharmacologic characterization with the 5-HT1A ligands 8-hydroxy-2-(di-n-propylamino)tetralin, ipsapirone, and WB4101 and the butyrophenone compounds spiperone and haloperidol gave results that were consistent with [3H]spiroxatrine labeling 5-HT1A sites. This ligand produced stable, reproducible binding with a good ratio of specific to nonspecific binding. The binding of [3H]spiroxatrine was sensitive to GTP, suggesting that this ligand may act as an agonist. This was supported by the finding that spiroxatrine inhibits forskolin-stimulated adenylate cyclase activity (a proposed 5-HT1A receptor model) in the rat hippocampus. Since [3H]spiroxatrine is structurally distinct from other currently available radioligands for the 5-HT1A site, it should provide new information about the properties of this putative serotonergic receptor.
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PMID:[3H]spiroxatrine labels a serotonin1A-like site in the rat hippocampus. 295 59

Spiroxatrine has been reported to be a 5-HT1A serotonin receptor antagonist. Therefore [3H]spiroxatrine was synthesized and its 5-HT1A receptor binding properties in homogenates of rat hippocampal membranes were characterized with the expectation that it would be the first 5-HT1A antagonist radioligand. [3H]8-Hydroxydipropylaminotetralin [( 3H]8-OH-DPAT), a well-characterized 5-HT1A agonist radioligand, was studied in parallel for comparative purposes. Scatchard analyses of saturation studies of [3H]spiroxatrine and [3H]8-OH-DPAT binding produced KD values of 0.9 nM and 1.8 nM, with Bmax values of 424 and 360 fmol/mg protein, respectively. A highly significant correlation (r = 0.98; p less than 0.001) exists between Ki values obtained for a series of drugs in competing for [3H]-spiroxatrine and [3H]8-OH-DPAT binding. Of special interest was the observation that 5-HT1A agonists such as serotonin, 8-OH-DPAT, and ipsapirone competed with equal high affinities for [3H]spiroxatrine or [3H]8-OH-DPAT-labelled 5-HT1A receptors. [3H]Spiroxatrine and [3H]8-OH-DPAT binding to 5-HT1A receptors was inhibited by guanosine 5'-(beta,gamma-imido)triphosphate (a nonhydrolyzable analog of GTP) in a concentration-dependent manner whereas adenosine 5'-(beta,gamma-imido)triphosphate (a nonhydrolyzable analog of ATP) had no effect. The similarities in the 5-HT1A receptor radiolabelling properties of [3H]spiroxatrine and [3H]8-OH-DPAT, i.e., the high affinities of agonists and the guanyl nucleotide sensitivity, indicate that [3H]spiroxatrine has "agonist-like" binding properties in its interaction with the 5-HT1A receptor.
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PMID:[3H]spiroxatrine: a 5-HT1A radioligand with agonist binding properties. 296 50

The ability of 5-hydroxytryptamine (5-HT) and the 5-HT1A selective agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) to modulate adenylate cyclase activity was measured in rat hippocampus. In vitro ADP ribosylation of GTP-binding proteins by pertussis toxin in this tissue abolished both 5-HT- and 8-OH-DPAT-induced inhibition of forskolin-stimulated adenylate cyclase activity. These findings indicate that 5-HT1A receptors are linked a pertussis-sensitive Gi protein in rat hippocampus.
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PMID:5-Hydroxytryptamine1A receptors are linked to a Gi-adenylate cyclase complex in rat hippocampus. 297 52

The two 3H-labeled agonists [3H]8-hydroxy-2-(di-n-propylamino) tetralin ([3H]8-OH-DPAT) and [3H]serotonin ([3H]5-HT) have been used to examine the effects of physico-chemical parameters and modulatory agents on the high affinity 5-HT receptor binding sites in various regions of the rat central nervous system. Sites labeled by [3H]8-OH-DPAT and [3H]5-HT were differentially sensitive to changes in incubation temperature and pH, such that the optimal interaction of [3H]8-OH-DPAT with specific sites in the striatum was at 30 degrees C and pH 7.4, whereas [3H]5-HT sites in the same region were most easily labeled at 2-23 degrees C and pH 8.2. Micromolar concentrations of Mn2+ enhanced [3H]5-HT binding but inhibited markedly [3H]8-OH-DPAT binding to striatal membranes. In contrast, both [3H]5-HT and [3H]8-OH-DPAT binding were increased by the cation in hippocampal membranes. Conversely, GTP reduced the binding of either ligand in the hippocampus but affected only [3H]5-HT binding in the striatum. Furthermore, N-ethylmaleimide inhibited equally [3H]5-HT and [3H]8-OH-DPAT binding to hippocampal membranes, but was markedly less potent against [3H]8-OH-DPAT binding to striatal membranes. These results led to the definition of assay conditions for studying separately [3H]8-OH-DPAT binding to "hippocampal-like" (HL) and "striatal-like" (SL) sites. [3H]8-OH-DPAT HL binding sites were particularly abundant in the hippocampus, septum and cerebral cortex, and exhibited pharmacological properties typical of the postsynaptic 5-HT1A subsites previously characterized with [3H]5-HT as the ligand. The regional distribution of [3H]8-OH-DPAT SL binding sites was strikingly different from that of HL sites, but similar to that of serotoninergic terminals identified by their capacity to take up [3H]5-HT. The selective lesion by 5,7-dihydroxytryptamine of serotoninergic projections induced a marked loss of [3H]8-OH-DPAT SL binding sites in the striatum and the cerebral cortex, indicating that these sites were located presynaptically. In contrast, [3H]5-HT binding sites remained unchanged in lesioned rats, which confirmed further their exclusive postsynaptic location in brain.
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PMID:Differentiation of pre- and post-synaptic high affinity serotonin receptor binding sites using physico-chemical parameters and modifying agents. 301 81

In vitro intracellular recording techniques in the rat brain slice preparation demonstrate that both serotonin (5-HT) and baclofen (a GABAB-receptor agonist) inhibit 5-HT neurons in the dorsal raphe nucleus by inducing a hyperpolarization of membrane potential and a decrease in apparent input resistance (Rin). Similar to previous results with 5-HT, baclofen-mediated inhibition of 5-HT neurons also shows an apparent reversal potential (Erev) of approximately -90 mV, consistent with mediation by K channels. In slices from rats that had previously received a local injection of pertussis toxin (0.5 microgram) immediately rostral to the dorsal raphe nucleus, there was a virtually complete blockade of inhibition induced by both the serotonin autoreceptor and the GABAB-receptor. Intracellular injection of the stable GTP analog (guanosine-5'-O-(3-thiotriphosphate); GTP gamma S) mimicked the actions of both 5-HT and baclofen. The inhibitory actions of GTP gamma S were not additive with those of either 5-HT or baclofen, suggesting they share some common effector system. The stable cAMP analog (8-bromo-adenosine-3',5'-cyclic monophosphate (8-Br-cAMP] had no effect on membrane potential or apparent input resistance and did not block the inhibitory actions mediated by 5-HT or baclofen. The local injection of pertussis toxin (0.5 microgram) caused a far greater blockade of 5-HT and baclofen-mediated inhibition than the intracerebroventricular (i.c.v.) injection of pertussis toxin (1.0 micrograms). In parallel sets of animals with i.c.v. and local injections, we measured the pertussis toxin-mediated ADP-ribosylation of G proteins in membranes prepared from dorsal raphe nucleus. These biochemical studies showed that sensitivities to 5-HT and baclofen correlated with the concentration of remaining non-ADP-ribosylated G proteins following in vivo pertussis toxin injection. In summary, these results provide evidence for the role of a G protein(s) in the mediation of the cAMP-independent increase in potassium conductance in 5-HT neurons of dorsal raphe nucleus induced by both 5-HT1A- and GABAB-receptors.
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PMID:Evidence for G protein mediation of serotonin- and GABAB-induced hyperpolarization of rat dorsal raphe neurons. 313 62

The sulfhydryl reagents p-chloromercuribenzoate and N-ethylmaleimide (NEM) inactivate high affinity [3H]serotonin [( 3H]5-HT) binding to bovine and rat brain membranes in a concentration-dependent manner. In both species, 15-25% of total specific high affinity [3H]5-HT binding is relatively insensitive to NEM. This study examines the NEM sensitivity of the various high affinity [3H]5-HT binding subtypes, using selective ligands, tissues, and pharmacological masks to study each subtype. Reconstitution of NEM-inactivated binding by addition of GTP-binding proteins (G proteins, Gi and Go) is also described. Agonist binding to 5-HT1A, 5-HT1B, and 5-HT1D sites in rat brain and to 5-HT1A and 5-HT1D sites in bovine brain is sensitive to NEM. Binding of [3H]dihydroergotamine and [125I]iodocyanopindolol, both of which are weak partial agonists to 5-HT1B sites is relatively insensitive to NEM. Binding of [3H]5-HT to 5-HT1C sites in rat and bovine brain and choroid plexus is relatively insensitive to NEM. In the presence of spiperone to mask binding of 5-HT2 sites, binding of antagonist [( 3H]mesulergine) to 5-HT1C sites is also insensitive to NEM. Likewise, binding of the agonist [3H]4-bromo-2,5-dimethoxyphenylisopropylamine and of the antagonist [3H]ketanserin to 5-HT2 sites is not inhibited by NEM treatment of membranes. These findings suggest that agonist binding to 5-HT1A, 5-HT1B, and 5-HT1D sites is sensitive to NEM alkylation. Binding of neither agonist nor antagonist to 5-HT1C and 5-HT2 sites is sensitive to NEM. Inability of high concentrations of a variety of ligands to protect the sensitive binding sites against NEM inactivation indicates that the critical sulfhydryl group(s) are not located in the ligand binding domain of the NEM-sensitive binding sites. When membranes are treated with NEM, displacement of [125I]iodocyanopindolol by 5-HT is no longer sensitive to 5'-guanylyl imidodiphosphate (Gpp(NH)p). Gpp(NH)p sensitivity of agonist displacement of 5-HT1B binding to NEM-treated membranes is restored by addition of purified guanine nucleotide binding proteins (Gi plus Go). In addition, NEM-inactivated binding to 5-HT1A and 5-HT1D sites can be restored by addition of Gi plus Go. These data suggest that NEM exerts its effects on 5-HT1A, 5-HT1B, and 5-HT1D binding sites by inactivating the G protein(s) associated with the 5-HT receptor subtypes.
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PMID:Differential inactivation and G protein reconstitution of subtypes of [3H]5-hydroxytryptamine binding sites in brain. 313 89

Radioligand binding studies were performed to characterize serotonin 5-HT1D receptors in postmortem human prefrontal cortex and caudate homogenates. [3H]5-HT binding, in the presence of pindolol (to block 5-HT1A and 5-HT1B receptors) and mesulergine (to block 5-HT1C receptors), was specific, saturable, reversible, and of high affinity. Scatchard analyses of [3H]5-HT-labeled 5-HT1D sites in human prefrontal cortex produced a KD value of 4.2 nM and Bmax of 126 fmol/mg protein. In competition experiments, 8-hydroxydipropylaminotetralin, trifluoromethylphenylpiperazine, mesulergine, 4-bromo-2,5-dimethoxyphenylisopropylamine, and ICS 205-930 had low affinity for [3H]5-HT-labeled 5-HT1D sites, indicating that the pharmacology of the 5-HT1D site is distinct from that of previously identified 5-HT1A, 5-HT1B, 5-HT1C, 5-HT2, and 5-HT3 sites. 5-HT1D sites in human brain have a similar pharmacology to the 5-HT1D sites previously identified in rat, porcine and bovine brains. Guanyl nucleotides, guanosine 5'-O-(3-thiotriphosphate) (GTP-gamma-S) and guanosine 5'-(beta, gamma-imido)-triphosphate (Gpp(NH)p), modulated the binding of [3H]5-HT to 5-HT1D sites, whereas adenyl nucleotides had no effect. These findings are supportive of the presence of serotonin 5-HT1D receptors in human prefrontal cortex and caudate which appear to be coupled to a GTP binding protein.
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PMID:Serotonin 5-HT1D receptors in human prefrontal cortex and caudate: interaction with a GTP binding protein. 314 89

The specific binding of [3H]8-hydroxy-2-(di-n-propylamino)tetralin ([ 3H]8-OH-DPAT) to 5-hydroxytryptamine (5-HT)-related sites was investigated in several regions of the rat brain. Marked differences were observed in the characteristics of binding to membranes from hippocampus, striatum, and cerebral cortex. Hippocampal sites exhibited the highest affinity (KD approximately 2 nM) followed by the cerebral cortex (KD approximately 6 nM) and the striatum (KD approximately 10 nM). Ascorbic acid inhibited specific [3H]8-OH-DPAT binding in all three regions but millimolar concentrations of Ca2+, Mg2+, and Mn2+ enhanced specific binding to hippocampal membranes, whereas only Mn2+ increased it in the cerebral cortex and all three cations inhibited specific binding to striatal membranes. Guanine nucleotides (0.1 mM GDP, GTP) inhibited binding to hippocampal and cortical membranes only. As intracerebral 5,7-dihydroxytryptamine markedly decreased [3H]8-OH-DPAT binding sites in the striatum, but not in the hippocampus, the striatal sites appear to be on serotoninergic afferent fibers. In contrast, in the hippocampus the sites appear to be on postsynaptic 5-HT target cells, as local injection of kainic acid decreased their density. Both types of sites appear to be present in the cerebral cortex. The postsynaptic hippocampal [3H]8-OH-DPAT binding sites are probably identical to the 5-HT1A subsites, but the relationship between the presynaptic binding sites and the presynaptic autoreceptors controlling 5-HT release deserves further investigation.
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PMID:[3H]8-hydroxy-2-(di-n-propylamino)tetralin binding to pre- and postsynaptic 5-hydroxytryptamine sites in various regions of the rat brain. 315 80

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