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)

1. We investigated some neurochemical properties of a novel benzamide, YM-43611, [(S)-N-(1-benzyl-3-pyrrolidinyl)-5-chloro-4-cyclopropylcarbonylamino+ ++-2- methoxybenzamide] in comparison with putative D2-like receptor antagonists using both rat and human cloned dopamine D2-like receptors in vitro. 2. Receptor binding studies revealed that YM-43611 had appropriately potent affinities for both rat and human D2-like receptors, with moderate selectivity for D3 receptors and high selectivity for D4 receptors over D2 receptors (Ki values (nM) for rat receptors: D2, 165; D3, 35.5; D4, 1.85, and for human receptors: D2, 42.9; D3, 11.2; D4, 2.10). 3. YM-43611 displayed weak or negligible affinity for other neurotransmitter receptors, namely D1, D5, alpha(1), alpha(2), beta, 5-HT1A, 5-HT2A, 5-HT3, H1, M1 and M2 receptors. 4. Dopamine stimulated low-Km GTPase activity on membranes from Chinese hamster ovary (CHO) cells expressing the human D2-like receptor subtype. This response to dopamine of low-Km GTPase activity was inhibited by use of putative D2-like receptor antagonists. YM-43611 showed a moderate selectivity for D3 receptors (Ki = 45.5 nM) and a high selectivity for D4 receptors (Ki = 3.28 nM) over D2 receptors (Ki = 70.6 nM). 5. Dopamine inhibited forskolin-stimulated adenylate cyclase in intact CHO cells expressing the human D2-like receptor subtype. YM-43611 shifted the inhibition curve of dopamine on respective D2-like receptor subtype-mediated cyclic AMP formation to the right in a parallel fashion, showing a pA2 value of 7.42 (38.1 nM) for D2 receptors, a pKB value of 8.06 (8.68 nM) for D3 receptors, and a pA2 value of 8.42 (3.77 nM) for D4 receptors. 6. YM-43611 but not the other D2-like receptor antagonists exhibited good selectivity with respect to dual antagonism for D3 and D4 receptors in both receptor binding and functional assays. 7. These results indicate that YM-43611 is a novel D2-like receptor antagonist with high potency and selectivity for both D3 and D4 receptors. YM-43611 is therefore expected to be valuable in exploration of the physiological role of D3 and D4 receptors.
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PMID:In vitro pharmacological profile of YM-43611, a novel D2-like receptor antagonist with high affinity and selectivity for dopamine D3 and D4 receptors. 873 69

1. Chinese hamster ovary (CHO) cells have been reported to be devoid of 5-HT receptors and have frequently been used as hosts for the expression of cloned 5-HT receptors. Unexpectedly, 5-HT was found to induce profound inhibition of forskolin-stimulated cyclic AMP production in these cells and the aim of this study was to classify the 5-HT receptor involved. 2. In CHO(dhfr-) cells 5-HT was a potent agonist and caused 80-100% inhibition of forskolin stimulated cyclic AMP production. A study using several 5-HT1 receptor agonists revealed the following potencies (p[A50]): RU24969 (9.09 +/- 0.17) > 5-carboxamidotryptamine (8.86 +/- 0.20) > 5-HT (8.07 +/- 0.05) > CP-93,129 (7.74 +/- 0.10) > sumatriptan (5.93 +/- 0.04). All five agonists achieved a similar maximum effect. Irreversible receptor alkylation studies yielded a pKA estimate of 7.04 +/- 0.34 for 5-HT. 3. The 5-HT1A/1B antagonist, (+/-)-cyanopindolol (4-100 nM), caused parallel rightward shifts of the 5-HT concentration-effect curve with no change in asymptote. Schild analysis yielded a pKB estimate of 8.69 +/- 0.09 (Schild slope 1.13 +/- 0.10). (+/-)-Cyanopindolol actually behaved as a partial agonist with an intrinsic activity of 0.2-0.5 and a p[A50] of 8.55. 4. 5-HT (0.01-10 microM) also elicited a concentration-dependent increase in intracellular [Ca2+] in CHO(dhfr-) cells thus demonstrating that dual coupling is not a phenomenon restricted to systems in which there is overexpression of transfected receptors. 5. This agonist and antagonist profile is consistent with the presence of a 5-HT1B receptor. 8-OH-DPAT (1 microM) and renzapride (3 microM) were without effect on forskolin-stimulated cyclic AMP production and ketanserin (0.3 microM) did not antagonize the inhibition produced by 5-HT, thus excluding the involvement of 5-HT1A, 5-HT4, and 5-HT2 receptors. 6. The possibility that expression of a 5-HT1B receptor was associated with the dhfr- mutation was excluded since RU24969, 5-HT and CP-93,129 were also potent agonists in unmutated, CHO-K1 cells: p[A50] 9.03 +/- 0.03, 8.34 +/- 0.05, 7.69 +/- 0.07 respectively, and (+/-)-cyanopindolol (0.1 microM) shifted the 5-HT curve to the right and yielded a pA2 estimate of 8.70 +/- 0.06. 7. Little or no specific binding of [3H]-5-HT (0.1-200 nM) or of the high affinity ligand [125I]-iodocyanopindolol (0.01-3 nM) to CHO(dhfr-) cell membranes could be detected. 5-HT also failed to elicit any increase in the binding of [35S]-GTP gamma S to CHO membranes. 8. In conclusion, cultured CHO cells express 5-HT1B receptors which are negatively coupled to adenylyl cyclase and positively coupled to increases in intracellular calcium. The absence of radioligand binding was unexpected in view of the high potency of 5-HT and the partial agonist activity of the normally 'silent' competitive antagonist, (+/-)-cyanopindolol. This implies very efficient receptor-effector coupling of a low density of 5-HT1B receptors. Clearly, the absence of detectable radioligand binding cannot be assumed to mean the absence of receptors capable of eliciting a significant functional response.
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PMID:Characterization of a 5-HT1B receptor on CHO cells: functional responses in the absence of radioligand binding. 888 5

Inhibition of forskolin-stimulated cyclic AMP accumulation was measured in two stable HeLa cell lines HA6 and HA7 expressing different levels of recombinant human 5-HT1A receptors. These cells were studied previously to characterize another second messenger system activated by 5-HT1A receptors, i.e. calcium mobilization. The pharmacological characterization of the inhibition of cyclic AMP accumulation was made using agonists (5-HT, 8-OH-DPAT, buspirone, MDL 73005) and putative antagonists (SDZ 216-525, NAN-190, WAY-100135, pindolol, propranolol, WAY 100635). It is shown that 5-HT, 8-OH-DPAT, buspirone, MDL 73005 behaved as full (or nearly full) and potent agonists, whereas SDZ 216-525, NAN-190 and WAY-100135 displayed a limited (and similar) degree of intrinsic activity at human 5-HT1A receptors; on the other hand pindolol, propranolol and WAY 100635 behaved as "silent" antagonists. The effects were quantitatively and qualitatively very similar in both cells lines for all drugs tested, suggesting that the coupling between 5-HT1A receptors and inhibition of cyclic AMP accumulation in HeLa cells is very tight. There were, however, significant variations in both the level of agonism and the potency of a number of compounds when calcium mobilization and the inhibition of cyclic AMP accumulation were compared. Especially in HA7 cells which express lower receptor levels, a number of drugs failed to display agonism (e.g. buspirone or MDL 73005), whereas in HA6 cells they acted as partial agonists. Together, the data show that functional responses mediated by the same receptor can vary rather dramatically depending on receptor density and/or on the effector system involved. Interestingly, 5-HT1A receptor-mediated inhibition of adenylate cyclase activity measured in calf hippocampal membranes shows very similar degrees of potency and intrinsic activity for a number of compounds that have been tested on the inhibition of cyclic AMP accumulation in HeLa cells, suggesting that the very tight coupling observed in the recombinant system may apply to native 5-HT1A receptors.
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PMID:Inhibition of cAMP accumulation via recombinant human serotonin 5-HT1A receptors: considerations on receptor effector coupling across systems. 922 66

1. Previous studies have shown that flupirtine, a centrally acting, non-opioid analgesic agent, also exhibits neuroprotective activity in focal cerebral ischaemia in mice and reduces apoptosis induced by NMDA, gp 120 of HIV, prior protein fragment or lead acetate as well as necrosis induced by glutamate or NMDA in cell culture. To study the potential mechanism of the neuroprotective action of flupirtine, we investigated whether flupirtine is able to modulate potassium or NMDA-induced currents in rat cultured hippocampal neurones by use of the whole-cell configuration of the patch-clamp technique. 2. We demonstrated that 1 microM flupirtine activated an inwardly rectifying potassium current (K(ir)) in hippocampal neurones (deltaI=-39+/-18 pA at -130 mV; n=10). This effect was dose-dependent (EC50=0.6 microM). The reversal potential for K(ir) was in agreement with the potassium equilibrium potential predicted from the Nernst equation showing that K(ir) was predominantly carried by K+. Furthermore, the induced current was blocked completely by Ba2+ (1 mM), an effect typical for K(ir). 3. The activation of K(ir) by flupirtine was largely prevented by pretreatment of the cells with pertussis toxin (PTX) indicating the involvement of a PTX-sensitive G-protein in the transduction mechanism (deltaI=-3+/-6 pA at -130 mV; n=8). Inclusion of cyclic AMP in the intracellular solution completely abolished the activation of K(ir) (n=7). 4. The selective alpha2-adrenoceptor antagonist SKF-86466 (10 microM), the selective 5-HT1A antagonist NAN 190 as well as the selective GABA(B) antagonist 2-hydroxysaclofen (10 microM) failed to block the flupirtine effect on the inward rectifier. 5. Flupirtine (1 microM) could not change the current induced by 50 microM NMDA. 6. These results show that in cultured hippocampal neurones flupirtine activates an inwardly rectifying potassium current and that a PTX-sensitive G-protein is involved in the transduction mechanism.
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PMID:Influence of flupirtine on a G-protein coupled inwardly rectifying potassium current in hippocampal neurones. 942 Dec 79

Our previous study has demonstrated that astrocytes derived from the rat frontal cortex contain 5-hydroxytryptamine (5-HT)7 receptors positively coupled to adenylyl cyclase. In this study, we observed a desensitization of 5-HT7 receptors induced by a treatment with agonists (0.1, 1, and 10 muM, 0.5 to 3.5 h). Maximum responses, but not the EC50 values, in the concentration-response curve of 5-HT-induced cyclic AMP formation were decreased after pretreatment with 5-HT. Pretreatment with 5-carboxamidotryptamine (5-CT) elicited a potent desensitization of 5-HT-induced cyclic AMP formation. Neither 2-methyl-5-HT nor alpha-methyl-5-HT caused the desensitization. When the astrocytes were treated with isoproterenol, N-ethylcarboxamidoadenosine, and dibutyryl cyclic AMP (all of which increase intracellular cyclic AMP levels), 5-HT-induced cyclic AMP responses were not affected. Conversely, adenylyl cyclase activity mediated by either isoproterenol or N-ethylcarboxamidoadenosine was attenuated by pretreatment with each of these agonists, but not 5-HT. In addition, our study showed that the administration of 5-HT, 5-CT, and 8-hydroxy-2-(di-n-propylamino)tetralin to the astrocytes stimulated cyclic AMP formation both in the presence and absence of forskolin, whereas in neuron-rich cultures of the frontal cortex, these agonists did not change basal cyclic AMP levels and decreased forskolin-stimulated cyclic AMP formation. Neurons may predominantly contain 5-HT1A receptors that are negatively coupled to adenylyl cyclase. These results suggest that 5-HT7 receptors are highly expressed in astrocytes but not in neuronal cells, and that pretreatment with their agonists results in a homologous desensitization of the receptors.
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PMID:Agonist-induced desensitization of adenylyl cyclase activity mediated by 5-hydroxytryptamine7 receptors in rat frontocortical astrocytes. 951 51

F 11440 (4-methyl-2-[4-(4-(pyrimidin-2-yl)-piperazino)-butyl]-2H, 4H-1,2,4-triazin-3,5-dione) was the outcome of a research effort guided by the hypothesis that the magnitude of the intrinsic activity of agonists at 5-HT1A receptors determines the magnitude of their antidepressant and anxiolytic-like effects. The affinity of F 11440 for 5-HT1A binding sites (pKi, 8.33) was higher than that of buspirone (pKi, 7.50), and somewhat lower than that of flesinoxan (pKi, 8.91). In vivo, F 11440 was 4- to 20-fold more potent than flesinoxan, and 30- to 60-fold more potent than buspirone, in exerting 5-HT1A agonist activity at pre- and postsynaptic receptors in rats (measured by, for example, its ability to decrease hippocampal extracellular serotonin (5-HT) levels and to increase plasma corticosterone levels, respectively). F 11440 did not have detectable antidopaminergic activity (unlike buspirone, which inhibited all of the directly observable behavioral effects of methylphenidate in rats), showed no evidence of antihistaminergic activity (unlike flesinoxan, which protected against the effects of a histamine aerosol in guinea pigs), and had a 70-fold separation between its 5-HT1A agonist and alpha-1 adrenergic antagonist properties (measured as the ability to inhibit the methoxamineinduced increase in blood pressure in rats), unlike flesinoxan, which showed a <3-fold separation. In HeLa cells expressing human 5-HT1A receptors, F 11440 decreased the forskolin-induced increase in AMP, and, based on its maximal effect, was found to have an intrinsic activity of 1.0 relative to that of 5-HT, which was significantly higher than that of buspirone (0.49), ipsapirone (0.46) and flesinoxan (0.93). Consistent with the aforementioned hypothesis, F 11440 produced anxiolytic- and antidepressant-like effects in animal models (i.e., increased punished responding in a pigeon conflict procedure and decreased immobility in a rat forced swimming test, respectively) that were more substantial than those of buspirone, ipsapirone and flesinoxan. Thus, F 11440, shown here to be a potent, selective, high efficacy 5-HT1A receptor agonist, appears to have the potential to exert marked anxiolytic and antidepressant activity in humans.
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PMID:F 11440, a potent, selective, high efficacy 5-HT1A receptor agonist with marked anxiolytic and antidepressant potential. 976 47

We have used a combination of sequence comparisons, computer-based modeling and site-directed mutagenesis to investigate the molecular interactions involved in ligand binding and signal transduction of the human 5-HT1B receptor. Two amino acid residues, S212 in transmembrane region (TM) V and F331 in TM VI, were replaced by alanines. These amino acids are conserved in many G protein-coupled receptors and therefore likely to be important for receptor function. The mutant receptors were expressed in Chinese hamster ovary cells. The 5-HT-like agonist 5-carboxamido-tryptamine (5-CT) bound with 15-fold lower affinity to the S212A mutant as compared to wild-type receptor and the antagonist methiothepin bound with 17-fold lower affinity to the F331A mutant. No reduction in the affinity of 5-HT was seen for the S212A mutant, although an equivalent mutation in the 5-HT1A receptor resulted in a 100-fold reduction of 5-HT binding. The inhibition of forskolin-stimulated cyclic AMP production by 5-HT was significantly reduced in cells expressing the F331A mutant, even though the endogenous ligand 5-HT bound with somewhat increased affinity. Methiothepin acted as an inverse agonist and increased the forskolin-stimulated cyclic AMP production at both the wild-type receptor and the mutants, and the effect was stronger on the F331A mutant. These results suggest that F331 is involved in the conformational changes necessary for signal transduction.
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PMID:Mutagenesis of the human 5-HT1B receptor: differences from the closely related 5-HT1A receptor and the role of residue F331 in signal transduction. 987 59

Pindolol-insensitive [3H]-5-hydroxytryptamine ([3H]-5-HT) binding to rat hypothalamic membranes was pharmacologically and functionally characterized to resolve whether this procedure selectively labels 5-HT7 receptors. Consistent with a previous report, 3 microM and not 100 nM pindolol was required to occupy fully 5-HT1A and 5-HT1B receptors. Remaining [3H]-5-HT binding was saturable (KD, 1.59+/-0.21 nM; Bmax, 53.8+/-3.1 fmol x mg protein(-1)). Displacement of [3H]-5-HT with metergoline and 5-CT revealed shallow Hill slopes (<0.5) but seven other compounds had slopes >0.8 and pKi values and the rank order of affinity were significantly correlated (r = 0.81 and 0.93, respectively) with published [3H]-5-HT binding to rat recombinant 5-HT7 receptors. In the presence of pindolol, 5-HT-enhanced accumulation of [32P]-cyclic AMP was unaffected by the 5-HT4 antagonist RS39604 (0.1 microM) or the 5-ht6 antagonist Ro 04-6790 (1 microM) but significantly attenuated by mesulergine (250 nM), ritanserin (450 nM) or methiothepin (200 nM) which have high affinity for the 5-HT7 receptor. Intracerebroventricular pretreatment with the serotonergic neurotoxin 5,7-dihydroxytryptamine, 5,7-DHT, elevated the [3H]-5-HT Bmax 2 fold, indicating that the hypothalamic 5-HT7 receptor is post-synaptic to 5-HT nerve terminals and regulated by synaptic 5-HT levels. These results suggest that, in the presence of 3 microM pindolol, [3H]-5-HT selectively labels hypothalamic binding sites consistent with functional 5-HT7 receptors.
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PMID:Pindolol-insensitive [3H]-5-hydroxytryptamine binding in the rat hypothalamus; identity with 5-hydroxytryptamine7 receptors. 1036 78

F 11356 (4-[4-[2-(2-aminoethyl)-1H-indol-5-yloxyl]acetyl]piperazinyl-1-yl] ben zonitrile) was designed to take advantage of the superior potency and efficacy characteristics of 5-hydroxytryptamine (5-HT) compared with tryptamine at 5-HT1B/1D receptors. F 11356 has subnanomolar affinity for cloned human and nonhuman 5-HT1B and 5-HT1D receptors, and its affinity for 5-HT1A and other 5-HT receptors, including the 5-ht1F subtype, is 50-fold lower and micromolar, respectively. In C6 cells expressing human 5-HT1B or human 5-HT1D receptors, F 11356 was the most potent compound in inhibiting forskolin-induced cyclic AMP formation (pD2 = 8.9 and 9.6), and in contrast to tryptamine and derivatives, it produced maximal enhancement of [35S]guanosine-5'-O-(3-thio)triphosphate-specific binding equivalent to 5-HT. F 11356 was equipotent to 5-HT (pD2 = 7.1 versus 7.2) and more potent than tryptamine derivatives in contracting rabbit isolated saphenous vein. In isolated guinea pig trigeminal ganglion neurons, F 11356 was more potent (pD2 = 7.3 versus 6.7) and induced greater increases in outward hyperpolarizing Ca2+-dependent K+ current than sumatriptan. In anesthetized pigs, F 11356 elicited highly cranioselective, more potent (from 0.16 microgram/kg i.v.) and greater carotid vasoconstriction than tryptamine derivatives. Decreases in carotid blood flow were observed in conscious dogs from 0.63 mg/kg oral F 11356 in the absence of changes in heart rate or behavior. Oral activity was confirmed when hypothermic responses were elicited in guinea pigs (ED50 = 1.6 mg/kg), suggesting that F 11356 also accesses the brain. F 11356 thus is a selective, high-potency agonist at 5-HT1B/1D receptors, which distinguishes itself from tryptamine and derivatives in exerting high intrinsic activity at these receptors in vascular and neuronal models relevant to migraine.
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PMID:F 11356, a novel 5-hydroxytryptamine (5-HT) derivative with potent, selective, and unique high intrinsic activity at 5-HT1B/1D receptors in models relevant to migraine. 1038 63

Although the subtypes of serotonin 5-HT1 receptors have distinct structure and pharmacology, it has not been clear if they also exhibit differences in coupling to cellular signals. We have sought to compare directly the coupling of 5-HT1A and 5-HT1B receptors to adenylyl cyclase and to the mitogen-activated protein kinase ERK2 (extracellular signal-regulated kinase-2). We found that 5-HT1B receptors couple better to activation of ERK2 and inhibition of adenylyl cyclase than do 5-HT1A receptors. 5-HT stimulated a maximal fourfold increase in ERK2 activity in nontransfected cells that express endogenous 5-HT1B receptors at a very low density and a maximal 13-fold increase in transfected cells expressing 230 fmol of 5-HT1B receptor/mg of membrane protein. In contrast, activation of 5-HT1A receptors stimulated only a 2.8-fold maximal activation of ERK2 in transfected cells expressing receptors at 300 fmol/mg of membrane protein but did stimulate a 12-fold increase in activity in cells expressing receptors at 3,000 fmol/mg of membrane protein. Similarly, 5-HT1A, but not 5-HT1B, receptors were found to cause significant inhibition of forskolin-stimulated cyclic AMP accumulation only when expressed at high densities. These findings demonstrate that although both 5-HT1A and 5-HT1B receptors have been shown to couple to G proteins of the Gi class, they exhibit differences in coupling to ERK2 and adenylyl cyclase.
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PMID:Differential coupling of serotonin 5-HT1A and 5-HT1B receptors to activation of ERK2 and inhibition of adenylyl cyclase in transfected CHO cells. 1038 67


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