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)

Binding characteristics of a radioiodinated serotonin-1A (5-HT1A) receptor antagonist, 4-(2'-methoxy-phenyl)-1-[2'-(n-2"-pyridinyl)-p- iodobenzamido]-ethyl-piperazine ([125I]p-MPPI) were evaluated using in vitro homogenate binding and autoradiographic techniques in rat brains. [125I]p-MPPI displayed a Kd value of 0.32 +/- 0.04 nM (in the presence of MgCl2) and a Bmax value of 315 +/- 60 fmol/mg of protein in rat hippocampal homogenates. The number of 5-HT1A receptors labeled by [125I]p-MPPI was 40% higher than that labeled by trans-8-hydroxy-2-(N-n-propyl-N-3'-iodo-2'- propenyl)aminotetralin ([125I]R(+)8-OH-PIPAT) (225 +/- 47 fmol/mg of protein), a radioiodinated 5-HT1A agonist. The magnesium ion showed an inhibitory effect on [125I]p-MPPI binding but increased the specific binding of [125I]R(+)8-OH-PIPAT. A significant increase in Bmax values in the presence of guanyl nucleotides was observed for [125I]p-MPPI (control, 307 +/- 35 fmol/mg of protein; with GTP, 345 +/- 30 fmol/mg of protein; with guanylyl-imidodiphosphate, 362 +/- 35 fmol/mg of protein); however, both guanyl nucleotides significantly reduced the Bmax values measured by [125I]R(+)8-OH-PIPAT (control, 213 +/- 50 fmol/mg of protein; with GTP, 133 +/- 20 fmol/mg of protein; with guanylyl-imidodiphosphate, 108 +/- 20 fmol/mg of protein). The binding characteristics of [125I]p-MPPI for 5-HT1A receptors suggest that p-MPPI is an antagonist for 5-HT1A receptors. In vitro autoradiographic studies in rat brain sections with [125I]p-MPPI showed specific labeling of areas rich in 5-HT1A receptors and the regional distribution closely matched those labeled by [125I]R(+)8-OH-PIPAT.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:4-(2'-Methoxy-phenyl)-1-[2'-(n-2"-pyridinyl)-p-iodobenzamido]-ethyl- piperazine ([125I]p-MPPI) as a new selective radioligand of serotonin-1A sites in rat brain: in vitro binding and autoradiographic studies. 781 60

A potential 5-HT1A receptor antagonist, p-MPPI, 4-(2'-methoxy-)phenyl-1-[2'-(n-2"-pyridinyl)-p-iodobenzamido-]ethy l- piperazine, was developed. The [125I]p-MPPI demonstrated high affinity and selectivity toward 5-HT1A receptors; Kd = 0.36 nM and Bmax = 264 fmol/mg of protein in rat hippocampal membrane homogenates. The binding is not sensitive to GTP (300 microM) or Gpp(NH)p (100 microM). In forskolin-stimulated adenylyl cyclase assay using rat hippocampus, p-MPPI (up to 10 microM) showed no agonist activity as compared to that of (+/-)-8-OH-DPAT. At 100 nM it completely antagonized the inhibition of forskolin-stimulated adenylyl cyclase activity produced by 100 nM of (+/-)-8-OH-DPAT. This potential 5-HT1A antagonist may provide a powerful tool for studies of the pharmacology of the 5-HT1A receptor system.
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PMID:A potential 5-HT1A receptor antagonist: p-MPPI. 796 12

In developing selective ligands for dopamine D2 and D3 receptors, several iodinated 2-aminotetralins and 3-amino-1-benzopyrans, trans-7-hydroxy-2-[N-(3'-iodo-2'- propenyl)amino]tetralin (1), trans-monohydroxy-2-[N-propyl-N-(3'-iodo-2'-propenyl)amino]tetralin (7-, 5-, and 6-OH-PIPAT) (2, 3, and 4), and trans-monohydroxy-3,4-dihydro-3-[N-propyl-N-(3'-iodo-2'- propenyl)-amino]-2H-1-benzopyran (6- and 8-OH-benzopyrans) (5 and 6), were prepared. These compounds were evaluated for their binding profiles in several membrane preparations: Spodoptera frugiperda (Sf9) cells expressing dopamine D2 (non-GTP coupled, low-affinity states) and D3 receptors, HEK293 cells expressing dopamine D2 receptors in high-affinity states (D2H), rat hippocampal homogenates for 5-HT1A receptors, and cerebellar homogenates for sigma receptors. The mono-N-alkylated 2-aminotetralin, 1, displayed high sigma binding (Ki = 1.68 nM) with a moderate D3 binding (Ki = 30.2 nM). Derivatives with one N-propyl and one N-(3'-iodo-2'-propeny) group generally displayed high to moderate affinity to D3 receptors (Ki = 2.90, 1.85, 0.99, 2.20, 31.4, and 6.69 nM for 7-OH-DPAT [7-hydroxy-2-(N,N-di-n-propylamino)tetralin], 2, 3, 4, 5, and 6, respectively). It is interesting to note that all of the active D3 ligands also displayed comparable binding to the high affinity states of D2 receptors in HEK293 cells (Ki = 6.6, 3.6, 9.7, and 10.8 nM for 2, 3, 4, and 6, respectively). Among all of the tetralin derivatives tested, 5-OH-PIPAT, 3, showed the highest binding affinity to D3 receptors (Ki = 0.99 nM) and better selectivity (KiD2H/KiD3, KiD2/KiD3, Ki5-HT1A/KiD3 and Ki sigma/KiD3 = 3.64, 327, 48.4, and 1250 nM, respectively), making it the best ligand for studying dopamine D2H and D3 receptors.
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PMID:Iodinated 2-aminotetralins and 3-amino-1-benzopyrans: ligands for dopamine D2 and D3 receptors. 799 Jan 23

1. 5-Hydroxytryptamine (5-HT) has been shown to induce contraction of tracheal smooth muscle. However, the mechanisms of action of 5-HT are not known. We therefore investigated the effects of 5-HT on phospholipase C (PLC)-mediated phosphoinositide (PI) hydrolysis and its regulation in canine cultured tracheal smooth muscle cells (TSMCs) labelled with [3H]-inositol. 5-HT-induced inositol phosphates (IPs) accumulation was time- and dose-dependent with a half-maximal response (EC50) and a maximal response at 0.38 +/- 0.05 and 10 microM, respectively. 2. Ketanserin and mianserin (10 and 100 nM), 5-HT2 receptor antagonists, were equipotent in blocking the 5-HT-induced IPs accumulation with pKB values of 8.46 and 8.21, respectively. In contrast, the dose-response curves of 5-HT-induced IPs accumulation were not shifted until the concentrations of NAN-190 and metoclopramide (5-HT1A and 5-HT3 receptor antagonists, respectively) were increased up to 10 microM. 3. Pretreatment of TSMCs with pertussis toxin or cholera toxin did not inhibit the 5-HT-induced IPs accumulation, but partially inhibited the AlF(4-)-induced IPs response. 4. Stimulation of IPs accumulation by 5-HT required the presence of external Ca2+ and was blocked by EGTA. The addition of Ca2+ (3-620 nM) to digitonin-permeabilized TSMCs directly stimulated IPs accumulation. A further Ca(2+)-dependent increase in IPs accumulation was obtained by inclusion of either guanosine 5'-O-(3-thiotriphoshate) (GTP gamma S) or 5-HT. The combination of GTP gamma S and 5-HT elicited an additive effect on IPs accumulation. 5. Treatment with phorbol 12-myristate 13-acetate (PMA, 1 microM, 30 min) abolished the 5-HT-induced IPs accumulation. The concentrations of PMA that gave a half-maximal and maximal inhibition of 5-HT-induced IPs accumulation were 2.2 +/- 0.4 nM and 1 microM, n = 3, respectively. The protein kinase C (PKC) activator, 4 alpha-phorbol 12,13-didecanoate, at 1 microM, did not influence this response. The inhibitory effect of PMA was reversed by staurosporine, a PKC inhibitor, suggesting that the inhibitory effect of PMA is mediated through the activation of PKC. 6. The site of this inhibition was further investigated by examining the effect of PMA on AlF(4-)-induced IPs accumulation in canine TSMCs. AlF(4-)-stimulated IPs accumulation was inhibited by PMA treatment, suggesting that the effect of PMA is distal to the 5-HT receptor. 7. Acetylcholine-induced IPs accumulation was completely inhibited by atropine, but not affected by ketanserin or mianserin, suggesting that 5-HT-induced IPs accumulation is not due to release of acetylcholine.8. These results demonstrate that 5-HT directly stimulates PLC-mediated PI hydrolysis via a pertussis toxin- and cholera toxin-insensitive GTP binding protein in canine TSMCs and that this coupling process is negatively regulated by PKC. 5-HT2 receptors may be predominantly mediating IPs accumulation and presumably IP-induced Ca2+ release may function as the transducing mechanism for 5-HT stimulated contraction of tracheal smooth muscle.
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PMID:5-Hydroxytryptamine receptor-mediated phosphoinositide hydrolysis in canine cultured tracheal smooth muscle cells. 801 56

We have previously isolated the rat serotonin (5-HT)1A receptor gene (G21Y2) and now report the expression and characterization of this receptor. The BamHI/Xbal fragment of this gene was cloned into Rc/RSV and stably transfected into HeLa cells by the calcium phosphate method. For determination of specific 5-HT1A receptor binding, [3H]8OH-DPAT was used as the radioligand and incubated with HeLa cell membranes. The cells expressed specific and saturable binding of [3H]8OH-DPAT with a Kd value of 0.3 nM and a Bmax value of 2 pmol/mg protein. GTP (50 microM) added to the incubation mixture increased the Kd value to 3 nM indicating that the expressed receptor is coupled to a G protein. The specific binding was inhibited by selective 5-HT1A partial agonists, such as buspirone, ipsapirone, gepirone, tandospirone, zalospirone and SUN8399 with Ki values of 1-30nM, whereas other neurotropic drugs except for spiperone (Ki = 46 nM) and nemonapride (Ki = 2.3 nM) were effective only at concentrations of more than 100 microM. The potencies of these compounds to inhibit [3H]8OH-DPAT from its specific binding sites were similar to their affinities determined in rat hippocampus binding studies. These data suggest that the expressed receptor is a 5-HT1A-type similar to 5-HT1A receptors in the rat hippocampus.
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PMID:Characterization of a cloned rat serotonin 5-HT1A receptor expressed in the HeLa cell line. 809 15

Plasma membranes from Chinese hamster ovary (CHO) cells transfected with the serotonin 5-HT1A receptor have been incubated with full or partial receptor agonists and the photoreactive GTP analog, 4-azidoanilido-[alpha-32P]-GTP ([32P]-AA-GTP), to characterize the resulting receptor-G-protein interactions. Subsequent solubilization and immunoprecipitation of the membranes with anti-G(i)alpha-2 or anti-G(i)alpha-3 immunoglobulins revealed that full and partial agonists produce concentration-dependent labeling of the respective G-proteins with [32P]-AA-GTP. Full agonists of the 5-HT1A receptor [serotonin 5-hydroxytryptamine (5-HT) and 8-hydroxy-2-(di-n-propylamino)tetraline (8-OH-DPAT)] produced a 7-12-fold increase in the labeling of G(i)alpha-2 and G(i)alpha-3, whereas partial agonists (rauwolscine and ipsapirone) produced a smaller incorporation (2-5-fold) of [32P]-AA-GTP by the same G-proteins. The concentration of agonist producing half-maximal binding of [32P]-AA-GTP by G(i)alpha-3 [5-HT, 48 +/- 1 nM; 8-OH-DPAT, 28 +/- 1 nM; ipsapirone, 22 +/- 6 nM] compared to G(i)alpha-2 [5-HT, 124 +/- 38 nM; 8-OH-DPAT, 40 +/- 1 nM, ipsapirone, 82 +/- 7 nM] was lower with all agonists except rauwolscine, where the EC50's were similar (G(i)alpha-2, 604 +/- 145 nM; Gi alpha-3, 708 +/- 130 nM).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Selective activation of inhibitory G-protein alpha-subunits by partial agonists of the human 5-HT1A receptor. 815 46

Insect cell expression systems are used to characterize signaling components such as G protein-coupled receptors. As such, one must know whether endogenous G proteins couple to non-native receptors. We examined G protein linkages after infection of Sporodoptera frugiperda (Sf9) cells with a baculovirus encoding the 5-HT1A receptor. Receptor expression was confirmed by immunoblot. Some of the receptors were functional, showing guanine nucleotide-sensitive binding to the specific agonist ligand [3H]8-hydroxy-2-(di-n-propylamino)-1,2,3,4-tetranaphthalene). Peak expression (approximately 150 fmol/mg of membrane protein) was attained approximately 72-96 h post-infection. 5-HT-increased covalent binding of [32P]GTP-azidoanilide to a 40 kDa band, which was identified as a G protein by nucleotide blocking, Mg2+ dependence, and immunoblot and immunoprecipitation studies. The band comigrated with 1) pertussis toxin substrate(s), and 2) a band recognized by two G(o) alpha antisera and one common to heterotrimeric G protein alpha-subunits, but not by sera specific for Gs alpha or G(i) alpha. Labeled species could be precipitated with a G(o) alpha antiserum. 5-HT-increased labeling of the band was prevented by preincubation with pertussis toxin. These studies suggest that the 5-HT1A receptor couples effectively to native insect cell G(o)-like proteins.
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PMID:Human 5-HT1A receptor expressed in insect cells activates endogenous G(o)-like G protein(s). 817 13

The effects of 5-HT1A antagonists spiperone, methiothepin and BMY 7378 on [3H]-8-OH-DPAT binding were determined in vitro and ex vivo in rat hippocampus CA3 membrane preparations, and ex vivo in tissue sections of CA1 and CA3 subfields using quantitative autoradiography. In CA3 membranes from rats sacrificed 1 h or 24 h after administration of 5 mg/kg i.p. spiperone or methiothepin, no decrease in [3H]-8-OH-DPAT Bmax values approached statistical significance. Autoradiograms from identically treated rats showed significant increases in Kd values in both CA1 and CA3 hippocampal subfields 24 h but not 1 h after administration of the drugs, while no changes were observed in the dorsal raphe at either time. In vitro co-incubation of membranes with spiperone (200 or 500 nM) or methiothepin (500 nM) resulted in significant decreases in both affinity and Bmax values. In contrast, co-incubation with BMY 7378 (5 nM) increased only Kd values. GTP gamma S produced a concentration-dependent inhibition of specific [3H]8-OH-DPAT binding. At 0.1 mM of GTP gamma S, Kd values were increased three-fold and Bmax values were significantly decreased. When membranes were co-incubated with GTP gamma S and spiperone or BMY 7378, Kd values increased further. Moreover, the effects of spiperone and GTP gamma S on Bmax values were additive. It is concluded that BMY 7378 acts as a competitive antagonist at hippocampal post-synaptic 5-HT1A receptors, whereas spiperone and methiothepin exert their delayed antagonistic effects at these receptors through a non-competitive mechanism of action, possibly affecting the coupling of the receptors to their Gi/o proteins.
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PMID:Delayed effects of spiperone on serotonin1A receptors in the dorsal hippocampus of rats. 829 25

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 effect 5-HT1A receptor activation on the temperature dependence of HVA calcium channel currents has been studied in acutely isolated DR neurones, using barium as the charge carrier. 8-OH-DPAT caused a reduction in the temperature dependence of the peak current amplitude. However the most dramatic effect of 8-OH-DPAT was a large reduction in Q10 for the current activation rate. This also occurred with direct G-protein activation using GTP gamma S. In the presence of GTP gamma S, current activation became bi-exponential, rather than mono-exponential as in the control situation. The time constants of both components were significantly slower than the controls, and the Q10 for both components was significantly lower. GDP beta S had no effect on the temperature dependence or kinetics of activation of HVA current. Depolarizing prepulses applied prior to test pulses were able to reverse the action of 8-OH-DPAT on the Q10 of the activation rate. When prepulses were applied to cells containing GTP gamma S, the activation rate Q10 was similar to control values. We postulate that the highly significant reduction in activation rate Q10, seen with both 8-OH-DPAT and GTP gamma S, is as a result of a change in the mechanism underlying activation of HVA channels on depolarization. Contrary to previous models of calcium current modulation our results show that the mechanisms responsible for slowed activation by transmitters and facilitation of the residual current by depolarizing prepulses have little in common. We present a new model of transmitter modulation of HVA current, consistent with a mechanistic approach to channel subunit structure.
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PMID:The modulation of calcium channel currents recorded from adult rat dorsal raphe neurones by 5-HT1A receptor or direct G-protein activation. 860 96

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