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Query: UMLS:C0027819 (neuroblastoma)
 27,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Effects of (R)-N-(quinuclidin-3-yl)-2-(1-methyl-1 H-indol-3-yl)-2-oxo-acetamide (RS-056812-198) on 5-HT3 receptors have been investigated in whole-cell voltage-clamped N1E-115 mouse neuroblastoma cells and on 5-HT3 receptors composed of either long (5-HT3R-Al) or short (5-HT3R-AS) subunits expressed in Xenopus laevis oocytes. In N1E-115 cells RS-056812-198 evokes small transient inward currents, which are completely and reversibly inhibited by the selective 5-HT3 receptor antagonist MDL 72222 and cross-desensitizes with the 5-hydroxytryptamine (5-HT)-evoked current. The concentration-effect curve of RS-056812-198 yields an EC50 of 18 nM and a maximum amplitude of 15% of the maximum 5-HT-evoked current. In contrast to its effects on N1E-115 cells, RS-056812-198 does not evoke an ion current on cloned 5-HT3 receptors expressed in Xenopus oocytes, but acts as an antagonist. For 5-HT3R-A1 receptors, the IC50 of RS-056812-198 is 0.4 nM. The results show that (I) RS-056812-198 is a high-affinity partial agonist on 5-HT3 receptors in N1E-115 cells, thus providing a valuable tool to study agonist-receptor interaction in more detail: (2) 5-HT3 receptors on N1E-115 cells differ from the homo-oligomeric 5-HT3 receptors expressed in Xenopus oocytes. Whether the difference is caused by differences in protein processing in the two preparations or by expression of additional, yet unidentified subunits in N1E-115 cells and consequent formation of hetero-oligomeric 5-HT3 receptors remains to be determined.
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PMID:RS-056812-198: partial agonist on native and antagonist on cloned 5-HT3 receptors. 909 92

Potentiation of the 5-HT3 receptor-mediated ion current in mouse N1E-115 neuroblastoma cells by 5-hydroxyindole (5-OHi) and three analogues (5-aminoindole, catechol and indole) was examined using whole-cell voltage clamp and single channel patch clamp techniques. The substances tested enhanced the amplitude of the maximum 5-HT-evoked ion current by 12-30%. The rank order (at 1 mM) to potentiate the 5-HT-induced current was: 5-OHi approximately 5-aminoindole approximately catechol > indole. The concentration-effect curve of 5-HT was shifted leftwards by 1 mM 5-OHi, resulting in a two-fold increase of the apparent affinity of 5-HT from 1.4 microM to 0.7 microM, without affecting the Hill coefficient. The time constant of reversal of activation of the 5-HT-induced ion current upon washout of the agonist was delayed by 1 mM 5-OHi from 4.0 sec to 12.8 sec. 5-HT3 receptor-gated single channel events in cell-attached patches in the presence and absence of 1 mM 5-OHi were indistinguishable, apart from a slight increase in the event frequency. The results suggest that 5-OHi and analogues potentiate the 5-HT3 receptor-mediated ion current by delaying agonist dissociation and thereby increase the probability of channel opening. From the increased apparent affinity of 5-HT and the non-surmountability of the potentiating effect, it is concluded that 5-OHi and analogues are allosteric modulators of 5-HT3 receptors.
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PMID:Allosteric potentiation of the 5-HT3 receptor-mediated ion current in N1E-115 neuroblastoma cells by 5-hydroxyindole and analogues. 922 90

The effects of a range of phenothiazines were examined on 5-hydroxytryptamine3 (5-HT3) receptors in membranes from NIE-115 neuroblastoma cells using radioligand binding. Chlorpromazine, fluphenazine, perphenazine, trifluoperazine and prochlorperazine inhibited specific binding of both the 5-HT3 receptor antagonist [3H]GR65630 and agonist [3H]meta-chlorophenylbiguanide (mCPBG), with Ki values ranging from 0.4 to 3.9 microM. The mode of action of chlorpromazine was further examined using photoaffinity labelling in the presence and absence of 5-HT. Saturation radioligand binding data with both [3H]GR65630 and [3H]mCPBG showed that photoaffinity labelling with chlorpromazine (1 microM) caused a decrease in the maximum number of binding sites observed (35% and 28% for agonist and antagonist, respectively). This decrease was not observed when the membranes were incubated in the presence of 5-HT. The results demonstrate a direct interaction of a range of phenothiazines at the 5-HT3 receptor binding site.
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PMID:Radioligand binding and photoaffinity labelling studies show a direct interaction of phenothiazines at 5-HT3 receptors. 922 92

A fast solution exchange system (Dilger and Brett, 1990; Biophysics Journal 57: 723-731) with an exchange rate < 1 msec was used to study 5-HT3 (5-HT; 5-hydroxytryptamine) receptor-mediated currents in superfused outside-out patches of N1E-115 mouse neuroblastoma cells. At negative membrane potentials, 5-HT induced inward currents in a concentration-dependent manner (IC50 = 3.8 microM, Hill coefficient = 1.8). The mean peak current at a near-maximally effective 5-HT concentration of 30 microM was 20.6 pA. The 5-HT3 receptor antagonist ondansetron (0.3 nM) reversibly inhibited the 5-HT (30 microM) signal by approximately 50%. The currents induced during application of 30 microM 5-HT for 2 sec were characterized by inward rectification, a monophasic onset (tau ON = 37.5 msec) and, after reaching a peak, a monophasic decay (desensitization; tau OFF = 391 msec). Onset and decay were slower at lower 5-HT concentrations. The recovery of fully desensitized patches required a washout period of 45 sec. Pentobarbital inhibited 5-HT-induced (30 microM) currents in a concentration-dependent manner. The maximally obtainable inhibition with a given pentobarbital concentration was reached already when it was exclusively coapplied with 5-HT (IC50 = 135 microM. Hill coefficient = -0.7), since additional preexposure for at least 45 sec did not alter the concentration-response curve of pentobarbital. In conclusion, outside-out patches of N1E-115 cells are suitable to study the kinetic properties of 5-HT3 receptor channels. The results obtained in this model with pentobarbital are compatible with the suggestion that the inhibitory action of pentobarbital on 5-HT3 receptors is dependent on the agonist-activated (open) channel.
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PMID:5-HT3 receptors in outside-out patches of N1E-115 neuroblastoma cells: basic properties and effects of pentobarbital. 922 91

A complete understanding of how excitatory ligand-gated ion channels regulate intracellular Ca2+ in nerve cells remains to be elucidated. Laser-scanning confocal microscopy was used here to measure Ca2+ changes in the neuroblastoma x glioma hybrid cell line NG108-15, employed as a model nerve cell line, upon activation by the 5-HT3 receptor, a serotonin-activated ligand-gated ion channel. Addition of the 5-HT3 agonist 1-m-(chlorophenyl)-biguanide (mCPBG) induced increases in [Ca2+]i in both the cytoplasm and the nuclei of the NG108-15 cells. Using high-time resolution line scanning, no delay was evident between the mCPBG-induced rise in cytosolic [Ca2+]i and the rise in nuclear [Ca2+]i. The agonist-induced responses were completely blocked by addition of EGTA to chelate external Ca2+ and by addition of the 5-HT3 receptor antagonist tropisetron or the L-type Ca2+ channel blocker nitrendipine. Caffeine, but not thapsigargin, treatment significantly reduced the mCPBG-induced responses in the nucleus and the cytoplasm, both to the same extent. We conclude that, upon 5-HT3 receptor activation, Ca2+ enters the cells through voltage-gated Ca2+ channels and then triggers the release of Ca2+ from ryanodine-sensitive intracellular stores, greatly amplifying the increases in Ca2+ in the cytoplasm and the nucleus.
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PMID:5-HT3 receptors induce rises in cytosolic and nuclear calcium in NG108-15 cells via calcium-induced calcium release. 944 42

1. 5-HT3 receptor-mediated ion current was recorded from NCB-20 neuroblastoma cells using the whole-cell patch-clamp technique. Rapid drug superfusion was used to study the mechanism of alcohol potentiation of 5-HT3 receptor function and to analyse effects of alcohols on receptor-channel kinetics in detail. 2. Trichloroethanol (TCEt) increased in a dose-dependent way the initial slope, 20-80% rise time and measured desensitization rate of the current induced by low concentrations (1-2 microM) of 5-HT. Ethanol (EtOH) and butanol (ButOH) had similar effects on the 5-HT3 receptor-induced current. 3. TCEt and ButOH decreased the measured desensitization rate of current induced by 10 microM 5-HT, a maximally effective concentration of agonist. These alcohols also increased the relative amplitude of steady state to peak current induced by 2 or 10 microM 5-HT, indicating a possible decrease in the intrinsic rate of desensitization. 4. TCEt also decreased the deactivation rate of the current activated by 2 microM 5-HT after a short pulse of agonist application. 5. Current sweeps generated by 1 microM 5-HT in the presence or absence of 10 mM TCEt or 100 mM EtOH were well fitted using a modified standard kinetic model derived from the nicotinic acetylcholine receptor. This analysis indicated that potentiation by alcohols could be accounted for by increases in the association rate constant coupled with decreases in the dissociation and desensitization rate constants. 6. This study suggests that alcohols potentiate 5-HT3 receptor-mediated current by both increasing the rate of channel activation and stabilizing the open state by decreasing the rates of channel deactivation and desensitization.
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PMID:Alcohols potentiate the function of 5-HT3 receptor-channels on NCB-20 neuroblastoma cells by favouring and stabilizing the open channel state. 951 97

Direct effects of the enantiomers of the classical dopamine receptor ligand apomorphine on 5-HT3 receptors were examined in NIE-115 neuroblastoma cells in whole-cell voltage clamp mode. R(-)-apomorphine (R(-)APO; 3-300 microM) evokes a small, transient inward ion current. At 30 microM, R(-)APO induces its maximum inward current, which is approximately 3% of the amplitude of the inward current induced by 10 microM 5-HT. The R(-)APO-induced current is completely and reversibly inhibited after superfusion of 50 nM of the selective 5-HT3 receptor antagonist MDL 72222 and after desensitization of the 5-HT3 receptors by 10 microM 5-HT. The results indicate that R(-)APO is a partial agonist at the 5-HT3 receptor. R(-)APO (30 microM) evokes a depolarization of the membrane potential with an amplitude which is 26% of the 10 microM 5-HT-induced depolarization. In addition, the 5-HT-induced depolarization is reduced (from 29 to 15 mV) after prolonged exposure of the cell to R(-)APO. S(+)-apomorphine (S(+)APO; 3-300 microM) does not evoke an ion current. Instead, S(+)APO antagonizes the 5-HT3 receptor with an IC50 of 32 microM. The combined results indicate that enantiomers of apomorphine act directly on 5-HT3 receptors, and suggest that the in vivo effects of apomorphine are partially attributable to a direct interaction with 5-HT3 receptors.
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PMID:Agonist and antagonist effects of apomorphine enantiomers on 5-HT3 receptors. 968 Feb 51

The patch-clamp technique was applied in out-side-out patches of N1E-115 mouse neuroblastoma cells to investigate the effects of ifenprodil [(+/-) erythreo-ifenprodil tartratel, a drug with neuroprotective properties in cerebral ischemia, on the inward currents through 5-HT3 receptor channels. A high time resolution was achieved by using a rapid solution exchange system (exchange rate <1 ms). Ifenprodil inhibited the peak currents evoked by 30 microM 5-HT in a concentration-dependent but voltage-independent manner. The effect was most potent when ifenprodil was continuously applied to the patches 45 s before and during the 2-s administration of 5-HT (IC50=16 microM) and it was only slightly less potent when it was applied during the 45 s prior to 5-HT only (IC50=29 microM). When applied in this manner, ifenprodil also produced a concentration-dependent increase of the onset time constant (tauON) of the 5-HT (30 microM)-induced currents. When the drug was exclusively co-applied with 5-HT, ifenprodil was least potent in inhibiting the peak currents (IC50=98 microM), and it had no effect on the current onset kinetics. All protocols of ifenprodil application accelerated current inactivation as reflected by a decrease of the current inactivation time constant (tauOFF). All effects of ifenprodil were reversible after washout periods of 2-5 min. In conclusion, the potency of ifenprodil in inhibiting the inward current through 5-HT3 receptor channels is strongly dependent on the application protocol: presence of the drug before the agonist-induced activation of the 5-HT3 receptor channels is necessary for a relatively potent inhibition of the 5-HT-induced peak current and is a prerequisite for the prolongation of tauON; in addition, a weak but fast inhibitory effect on the current amplitude and decay constant of the 5-HT-induced current was revealed by the experiments in which ifenprodil was exclusively present during exposure to 5-HT. Three alternatives compatible with the components of the ifenprodil effect have been discussed: (1) different effects of the two enantiomers, (2) action via two different mechanisms, and (3) operation via a single mechanism only.
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PMID:Inhibition of 5-HT3 receptor cation channels by ifenprodil in excised patches of N1E-115 cells. 974 98

The nonsteroidal antioestrogen tamoxifen has been shown to block a number of voltage-gated cation-selective channels but its effect on ligand-gated cation-selective channels has not been studied. We have investigated the action of tamoxifen and the related derivative toremifene on ligand-gated cationic nicotinic acetylcholine and 5-HT3 receptor channels. Tamoxifen and toremifene both inhibited cationic currents of adult-type human muscle nicotinic acetylcholine receptors expressed in Xenopus oocytes with similar IC50 values of 1.2 +/- 0.03 microM (nH = 0.84 +/- 0.02) and 1.2 +/- 0.1 microM (nH = 1.1 +/- 0.1), respectively. Tamoxifen could also block native 5-HT3 receptors in NG108-15 neuroblastoma/glioma hybrid cells with IC50 = 0.81 +/- 0.15 microM and nH of 1.3 +/- 0.3. The characteristics of block by tamoxifen at the 5-HT3 receptor were voltage- and use-independent. The inhibition of the 5-HT-evoked currents were not overcome by increasing concentrations of 5-HT consistent with a noncompetitive mechanism of block.
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PMID:Inhibition of ligand-gated cation-selective channels by tamoxifen. 975 28

Human embryonic kidney (HEK) 293 cells were stably transfected with the cDNA encoding the short splice variant of the mouse 5-HT3 receptor (m5-HT3A(b); isolated by RT-PCR from NG108-15 cells) and its pharmacological properties were compared with those of the native 5-HT3 receptor of the mouse neuroblastoma cell line N1E-115. The m5-HT3A(b) receptor of N1E-115 cells differs from that isolated from NG108-15 cells by one amino acid (Val instead of Ile) at position 52 of the amino acid sequence. Both radioligand binding studies with the selective 5-HT3 receptor antagonist [3H]GR65630 (3-(5-methyl-1H-imidazol-4-yl)-1-(1-methyl-1H-indol-3-yl)-1-propanone) and functional experiments by measurement of [14C]guanidinium influx evoked by 5-HT in the absence and presence of 10 microM substance P were carried out. Binding of [3H]GR65630 to the recombinant receptor in HEK 293 cells and the native receptor in N1E-115 cells was specific and of high affinity (Kd 4.4 and 3.0 nM, respectively) and characterized by Bmax values of 875 and 1414 fmol/mg protein, respectively. At 10 nM [3H]GR65630, specific binding was inhibited by the selective 5-HT3 receptor antagonist ondansetron (Ki 11 and 42 nM, respectively) and by 5-HT (Ki 294 and 563 nM, respectively). In the transfected HEK 293 cells, 5-HT induced an influx of [14C]guanidinium both in the absence (pEC50 5.7) and presence of substance P (pEC50 6.6,) which was counteracted by 0.3 microM ondansetron; in the N1E-115 cells, 5-HT also evoked [14C]guanidinium influx in the absence (pEC50 6.0) and presence of substance P (pEC50 6.0). Both in transfected HEK 293 cells and in N1E-115 cells, the 5-HT receptor ligand RS-056812-198 ((R)-N-(quinuclidin-3-yl)-2-(1-methyl-1 H-indol-3-yl)-2-oxo-acetamide; in the presence of substance P) induced an influx of [14C]guanidinium (pEC50 9.8 and 8.7, respectively) with a maximum of about 70 and 30% of the maximum response to 5-HT, respectively. 5-HT (in the presence of substance P)-induced [14C]guanidinium influx was inhibited by the imidazoline BDF 6143 (4-chloro-2(2-imidazolin-2-ylamino)-isoindoline; pIC50 4.9 and 5.3, respectively) and by the sigma-site ligand (+/-)-ifenprodil (pIC50 5.0 and 5.2, respectively). In conclusion, most of the drugs exhibited practically identical properties at both the recombinant m5-HT3A(b) receptor in HEK 293 cells and the native m5-HT3 receptor of N1E-115 cells. However, the recombinant receptor had a higher affinity for ondansetron, and the potency of 5-HT in inducing cation influx through the recombinant, but not through the native receptor, was increased by substance P. RS-056812-198 was a 10-fold more potent partial agonist at the recombinant than at the native receptor. These differences may be due to cell-specific post-translational modifications of the 5-HT3 receptor protein in the two cell lines, to the expression of other subunits in addition to the m5-HT3A(b) receptor in N1E-115 cells and/or to the difference in the amino acid sequence at position 52 of the short splice variants of the m5-HT3 receptors expressed in the two cell lines.
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PMID:Pharmacological differences and similarities between the native mouse 5-HT3 receptor in N1E-115 cells and a cloned short splice variant of the mouse 5-HT3 receptor expressed in HEK 293 cells. 1054 22


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