bluuebunny/crossref_metadata_2025_split huggingface dataset:
h5‐HT1B receptor‐mediated constitutive Gαi3‐protein activation in stably transfected Chinese hamster ovary cells: an antibody capture assay reveals protean efficacy of 5‐HT
Authors: Newman‐Tancredi Adrian , Cussac Didier , Marini Laetitia , Touzard Manuelle , Millan Mark J 
Published: April 2003

Serotonin 5‐HT1B receptors couple to G‐proteins of the Gi/o family. However, their activation of specific G‐protein subtypes is poorly characterised. Using an innovative antibody capture/guanosine‐5′‐0‐(3‐[35S]thio)‐triphosphate ([35S]GTPγS) binding strategy, we characterised Gαi3 subunit activation by h5‐HT1B receptors stably expressed in Chinese hamster ovary (CHO) cells.
The agonists, 5‐HT, alniditan and BMS181,101, stimulated Gαi3, whereas methiothepin and SB224,289 behaved as inverse agonists. The selective 5‐HT1B receptor ligand, S18127, modestly stimulated Gαi3 and reversed the actions of both 5‐HT and methiothepin. S18127 (1 μM) also produced parallel, dextral shifts of the 5‐HT and methiothepin isotherms.
Isotopic dilution experiments ([35S]GTPγS versus GTPγS) revealed high‐affinity [35S]GTPγS binding to Gαi3 subunits in the absence of receptor ligands indicating constitutive activity. High‐affinity [35S]GTPγS binding was increased 2.8‐fold by 5‐HT with an increase in the affinity of GTPγS for Gαi3 subunits. In contrast, methiothepin halved the number of high‐affinity binding sites and decreased their affinity.
h5‐HT1B receptor‐mediated Gαi3 subunit activation was dependent on the concentration of NaCl. At 300 mM, 5‐HT stimulated [35S]GTPγS binding, basal Gαi3 activation was low and methiothepin was inactive. In contrast, at 10 mM NaCl, basal activity was enhanced and the inverse agonist activity of methiothepin was accentuated. Under these conditions, 5‐HT decreased Gαi3 activation.
In conclusion, at h5‐HT1B receptors expressed in CHO cells: (i) inverse agonist induced inhibition of Gαi3, and its reversal by S18127, reveals constitutive activation of this Gα subunit; (ii) constitutive Gαi3 activation can be quantified by isotopic dilution [35S]GTPγS binding and (iii) decreasing NaCl concentrations enhances Gαi3 activation and leads to protean agonist properties of 5‐HT: that is a switch to inhibition of Gαi3.

British Journal of Pharmacology (2003) 138, 1077–1084. doi:10.1038/sj.bjp.0705140
Activation of a glycine transporter on spinal cord neurons causes enhanced glutamate release in a mouse model of amyotrophic lateral sclerosis
Authors: Raiteri Luca , Paolucci Egle , Prisco Simona , Raiteri Maurizio , Bonanno Giambattista 
Published: April 2003

The release of [3H]D‐aspartate ([3H]D‐ASP) or [3H]GABA evoked by glycine from spinal cord synaptosomes was compared in mice expressing mutant human SOD1 with a Gly93 Ala substitution ([SOD1‐G93A(+)]), a transgenic model of amyotrophic lateral sclerosis, and in control mice. Mice expressing mutated SOD1 were killed at the advanced phase of the pathology, when they showed signs of ingestion disability, because of paralysis of the posterior limbs. In control mice glycine concentration‐dependently evoked [3H]D‐ASP and [3H]GABA release. Potentiation of the spontaneous release of both amino acids is likely to be mediated by activation of a glycine transporter, since the effects of glycine were counteracted by the glycine transporter blocker glycyldodecylamide but not by the glycine receptor antagonists strychnine and 5,7‐dichlorokynurenate. The glycine‐evoked release of [3H]D‐ASP, but not that of [3H]GABA, was significantly more pronounced in SOD1‐G93A(+) than in control animals.British Journal of Pharmacology (2003) 138, 1021–1025. doi:10.1038/sj.bjp.0705142
Differential effects of ascorbate on endothelium‐derived hyperpolarizing factor (EDHF)‐mediated vasodilatation in the bovine ciliary vascular bed and coronary artery
Authors: McNeish Alister J , Nelli Silvia , Wilson William S , Dowell Fiona J , Martin William 
Published: April 2003

The ability of ascorbate to inhibit endothelium‐derived hyperpolarizing factor (EDHF)‐mediated vasodilatation was compared in the bovine perfused ciliary vascular bed and isolated rings of coronary artery.
Acetylcholine‐induced, EDHF‐mediated vasodilatation of the ciliary circulation was blocked following inclusion of ascorbate (50 μM, 120 min) in the perfusion fluid. The blockade was highly selective since ascorbate had no effect on the vasodilator actions of the KATP channel opener, levcromakalim, nor on the tonic vasodepressor action of basally released nitric oxide.
The possibility that concentration of ascorbate by the ciliary body was a prerequisite for blockade to occur was ruled out, since EDHF was still blocked when the anterior and posterior chambers were continuously flushed with Krebs solution or when both the aqueous and vitreous humour were drained.
Ascorbate at 50 μM failed to affect bradykinin‐ or acetylcholine‐induced, EDHF‐mediated vasodilatation in rings of bovine coronary artery. Raising the concentration to 3 mM did produce blockade of EDHF, but this was nonselective, since vasodilator responses to endothelium‐derived nitric oxide were also inhibited.
Thus, ascorbate (50 μM) is not a universal blocker of EDHF. Whether its ability to block in the bovine ciliary circulation, but not in the coronary artery, is due to differences in the nature of EDHF at the two sites, differences in vessel size (resistance arterioles versus conduit artery), the presence or absence of flow, or to some other factor remains to be determined.

British Journal of Pharmacology (2003) 138, 1172–1180. doi:10.1038/sj.bjp.0705143
Mechanisms of hydrogen‐peroxide‐induced biphasic response in rat mesenteric artery
Authors: Gao Yu‐Jing , Hirota Simon , Zhang Da‐Wei , Janssen Luke J , Lee Robert M K W 
Published: April 2003

In phenylephrine (PHE) (1 μM)‐precontracted superior mesenteric arteries from adult rats, low concentration of hydrogen peroxide (H2O2, 10–100 μM) caused only contraction, while high concentration of H2O2 (0.3–1 mM) caused a biphasic response: a transient contraction followed by a relaxation response.
Endothelium removal did not affect the biphasic response. 7,7‐Dimethyl‐(5Z,8Z)‐eicosadienoic acid, diclofenac, furegrelate, or SQ 29548 greatly inhibited the contraction but did not affect the relaxation. 17‐Octadecynoic acid, eicosatriynoic acid, ICI 198615, SQ 22536, or ODQ did not inhibit the biphasic response.
KCl at 40 mM inhibited the relaxation response to H2O2 by 98±24%. 4‐Aminopyridine (4‐AP) inhibited while tetraethylammonium chloride (TEA), charybdotoxin, or glibenclamide attenuated the relaxation response. A combination of 4‐AP, TEA and glibenclamide mimicked the effects of 40 mM KCl. Iberiotoxin, apamin, or barium chloride did not inhibit the relaxation response.
H2O2 at 1 mM hyperpolarized membrane potential and reversibly augmented K+ current in smooth muscle cells of mesenteric artery. These effects of H2O2 were attenuated significantly by 4‐AP.
In summary, in PHE‐precontracted rat mesenteric artery: (1) the response to H2O2 shifted qualitatively from contraction to a biphasic response as H2O2 increased to 0.3 mM or higher; (2) the relaxation response is caused by the activation of K+ channels, with voltage‐dependent K+ channels playing a primary role; and the contraction is likely to be mediated by thromboxane A2; (3) the K+ channel activation by H2O2 is independent of phospholipase A2, cyclooxygenase, lipoxygenase, cytochrome P450 monooxygenase, adenylate or guanylate cyclase.

British Journal of Pharmacology (2003) 138, 1085–1092. doi:10.1038/sj.bjp.0705147
Structural requirements for novel willardiine derivatives acting as AMPA and kainate receptor antagonists
Authors: More Julia C A , Troop Helen M , Dolman Nigel P , Jane David E 
Published: April 2003

The natural product willardiine is an AMPA receptor agonist. We have examined the structural changes required to convert willardiine into an antagonist at AMPA and kainate receptors. Structure–activity analysis has been carried out to discover the structural features required to increase the potency and/or selectivity of the antagonists at AMPA or kainate receptors.
Reduction of the fast component of the dorsal root‐evoked ventral root potential (fDR‐VRP) has been used to investigate AMPA receptor antagonist activity. To examine antagonist activity at kainate receptors, the ability of compounds to depress kainate‐induced depolarisations of dorsal root fibres was assessed.
Blocking ionisation of the uracil ring by adding a methyl group to the N3 position was not sufficient to convert willardiine into an antagonist. However, willardiine derivatives with a side‐chain bearing a carboxylic acid group at the N3‐position of the uracil ring could antagonise AMPA and kainate receptors.
S stereochemistry was optimal for antagonism. When compounds with differing interacidic group chain lengths were compared, a group chain length of two methylene groups was preferable for AMPA receptor antagonism in the series of compounds bearing a carboxyalkyl side chain (UBP275, UBP277 and UBP279 reduced the fDR‐VRP with IC50 values of 287±41, 23.8±3.9 and 136±17 μM, respectively). For kainate receptor antagonism, two or three methylene groups were almost equally acceptable (UBP277 and UBP279 reduced dorsal root kainate responses with apparent KD values of 73.1±4.5 and 60.5±4.1 μM, respectively).
Adding an iodo group to the 5‐position of UBP277 and UBP282 enhanced activity at kainate receptors (UBP291 and UBP301 antagonised kainate responses on the dorsal root with apparent KD values of 9.83±1.62 and 5.94±0.63 μM, respectively).
The most useful antagonist identified in this study was UBP301, which was a potent and ∼30‐fold selective kainate receptor antagonist. UBP282 may also be of use in isolating a non‐GluR5‐mediated kainate response.

British Journal of Pharmacology (2003) 138, 1093–1100. doi:10.1038/sj.bjp.0705148
Oral nicorandil recaptures the waned protection from preconditioning in vivo
Authors: Iliodromitis Efstathios K , Cokkinos Philip , Zoga Anastasia , Steliou Ioulia , Vrettou Agathi R , Kremastinos Dimitrios Th 
Published: April 2003

Protection from preconditioning (PC) wanes and is eventually lost when multiple bouts of short ischemia or a prolonged reperfusion interval precedes the following sustained ischemia. The activation of mitochondrial KATP channels plays a pivotal role in the intracellular signaling of PC. We tested whether the KATP channel opener nicorandil (nic) preserves the given protection from PC in conditions where this benefit decays and is lost.
Eight groups of rabbits were divided into two equal series of experiments, one without nic (placebo) and one with nic treatment. Nic was given orally for 5 consecutive days in a dose of 5 mg kg−1 d−1. In a second step, four additional groups were treated with nic plus the KATP channel blocker 5HD and 1 additional control group with nitroglycerin only. All the animals were anesthetized and then subjected to 30 min of myocardial ischemia and 2 h of reperfusion with one of the following interventions before the sustained ischemia: Control groups to no intervention; 3PC groups to three cycles of 5‐min ischemia–10‐min reperfusion; 8PC groups to eight cycles of 5‐min ischemia – 10‐min reperfusion; and 3PC90 groups to the same interventions as the 3PC groups but with a prolonged (90 min) intervening reperfusion interval before the sustained ischemia. The infarcted and the risk areas were expressed in percent.
There was no significant change in infarct size between the placebo, the nic and the 5HD‐nic in the control groups (41.5±4.7, 43.9±7.1 and 48.7±6.4%) and 3PC groups (10.3±3.4, 12.2±3.9 and 12.6±4.5%). However, there was a significant decrease after nic treatment in groups 8PC (47.7±8.8% vs 13.0±2.6%, P<0.01) and 3PC90 (37.3±6.0% vs 14.2±2.4%, P<0.01), which was abrogated (38.2±4.7 and 42.7±4.4%, respectively, for 8PC and 3PC90 groups). Nitroglycerin had no effect on infarct size (39.1±3.1%, P=NS vs other controls).
Oral treatment with nic recaptures the waned protection of PC, both after repetitive bouts of short ischemia or after a prolonged reperfusion interval, preserving the initially obtained benefit. Nic by itself is insufficient to initiate PC in vivo.

British Journal of Pharmacology (2003) 138, 1101–1106. doi:10.1038/sj.bjp.0705149
Positive allosteric modulation of the human metabotropic glutamate receptor 4 (hmGluR4) by SIB‐1893 and MPEP
Authors: Mathiesen Jesper Mosolff , Svendsen Nannette , Bräuner‐Osborne Hans , Thomsen Christian , Ramirez M Teresa 
Published: April 2003

We have identified 2‐methyl‐6‐(2‐phenylethenyl)pyridine (SIB‐1893) and 2‐methyl‐6‐phenylethynyl pyridine hydrochloride (MPEP) as positive allosteric modulators for the hmGluR4. SIB‐1893 and MPEP enhanced the potency and efficacy of L‐2‐amino‐4‐phophonobutyrate (L‐AP4) in guanosine 5′‐O‐(3‐[35S]thiotriphosphate ([35S]GTPγS) binding and efficacy in cAMP studies. These effects were fully blocked by the mGluR4 competitive antagonist (RS)‐α‐cyclopropyl‐4‐phosphonophenylglycine (CPPG), indicating a dependency on receptor activation. Although SIB‐1893 and MPEP had no effects alone in GTPγS binding, effects were observed in the cell‐based cAMP assay due to media‐derived activation as indicated by CPPG inhibition. Positive modulation of the mGluR4 was a receptor‐specific effect since SIB‐1893 and MPEP had neither effects on mGluR2‐expressing cells nor on the parent BHK cell line. In [3H]L‐AP4 binding, a two‐fold decrease in KD but not in Bmax was observed with 100 μM SIB‐1893, whereas MPEP affected neither parameter. Finally, SIB‐1893 and MPEP failed to displace [3H]L‐AP4 binding. Taken together, these data identify positive allosteric modulators for the hmGluR4.British Journal of Pharmacology (2003) 138, 1026–1030. doi:10.1038/sj.bjp.0705159
Erythropoietin fosters both intrinsic and extrinsic neuronal protection through modulation of microglia, Akt1, Bad, and caspase‐mediated pathways
Authors: Chong Zhao Zhong , Kang Jing‐Qiong , Maiese Kenneth 
Published: April 2003

Erythropoietin (EPO) plays a significant role in the hematopoietic system, but the function of EPO as a neuroprotectant and anti‐inflammatory mediator requires further definition. We therefore examined the cellular mechanisms that mediate protection by EPO during free radical injury in primary neurons and cerebral microglia.
Neuronal injury was evaluated by trypan blue, DNA fragmentation, phosphatidylserine (PS) exposure, Akt1 phosphorylation, Bad phosphorylation, mitochondrial membrane potential, and cysteine protease activity. Microglial activation was assessed through proliferating cell nuclear antigen and PS receptor expression.
EPO provides intrinsic neuronal protection that is both necessary and sufficient to prevent acute genomic DNA destruction and subsequent membrane PS exposure, since protection by EPO is completely abolished by cotreatment with an anti‐EPO neutralizing antibody.
Extrinsic protection by EPO is offered through the inhibition of cerebral microglial activation and the suppression of microglial PS receptor expression for the prevention of neuronal phagocytosis. In regards to microglial chemotaxis, EPO modulates neuronal poptotic membrane PS exposure necessary for microglial activation primarily through the regulation of caspase 1.
EPO increases Akt1 activity, phosphorylates Bad, and maintains neuronal nuclear DNA integrity through the downstream modulation of mitochrondrial membrane potential, cytochrome c release, and caspase 1, 3, and 8‐like activities.
Elucidating the intrinsic and extrinsic protective pathways of EPO that mediate both neuronal integrity and inflammatory microglial activation may enhance the development of future therapies directed against acute neuronal injury.

British Journal of Pharmacology (2003) 138, 1107–1118. doi:10.1038/sj.bjp.0705161
Differences in troglitazone action on glucose metabolism in freshly isolated vs long‐term incubated rat skeletal muscle
Authors: Gras Florian , Brunmair Barbara , Roden Michael , Waldhäusl Werner , Fürnsinn Clemens 
Published: April 2003

Exposure of isolated skeletal muscle to troglitazone has resulted in inconsistent findings ranging from inhibition to stimulation of fuel oxidation and the glycogenic pathway. To better understand such variation in outcome, the present study used isolated rat soleus muscle strips to examine the interdependent influences of prolonged maintenance in vitro and of troglitazone exposure.
If freshly isolated muscle strips were exposed to troglitazone (1 μmol l−1) for 24 h, glucose oxidation was markedly reduced (−26±1%, P<0.0001), whereas glycogen synthesis remained unaffected (+9±7%, n.s.).
In contrast, extended exposure to troglitazone for 72 h increased both glucose oxidation (+65±28%, P<0.05) and glycogen synthesis (+46±11%, P<0.005), and a similar stimulatory effect was also observed in muscles exposed to troglitazone only during the last 24 h of their 72 h preincubation period (glucose oxidation: +61±15%, P<0.001; glycogen synthesis: +43±15%, P<0.01).
Troglitazone thus stimulated glucose utilization in long‐term incubated muscle independent of the duration of exposure (24 or 72 h), whereas it inhibited glucose utilization in freshly isolated muscle.
The observed differences in troglitazone action on freshly isolated vs long‐term incubated muscle suggest that findings on muscle tissue subject to prolonged maintenance in vitro cannot be extrapolated to native muscle in vivo.

British Journal of Pharmacology (2003) 138, 1140–1146. doi:10.1038/sj.bjp.0705162
Stress‐responsive JNK mitogen‐activated protein kinase mediates aspirin‐induced suppression of B16 melanoma cellular proliferation
Authors: Ordan Orly , Rotem Ronit , Jaspers Ilona , Flescher Eliezer 
Published: April 2003

Available anticancer drugs do not seem to modify the prognosis of metastatic melanoma. Salicylate and acetyl salicylic acid (aspirin) were found to suppress growth in a number of transformed cells, that is, prostate and colon. Therefore, we studied the direct effects of aspirin on metastatic B16 melanoma cells.
Aspirin at a plasma‐attainable and nontoxic level suppressed the proliferation of B16 cells.
Aspirin induced the activation of p38 and c‐Jun N‐terminal kinase (JNK) mitogen‐activated protein kinases.
Inhibition of JNK, but not p38, decreased the suppressive effect of aspirin upon the proliferation of B16 cells.
The aspirin‐induced reduction in B16 proliferation was cumulative over time.
Aspirin and the chemotherapeutic drug 1,3‐bis(2‐chloroethyl)‐1‐nitrosourea (BCNU) induced B16 cell death synergistically.
In addition to the murine B16 cell line, the proliferation of SK‐28 human melanoma cells was also suppressed by aspirin.
In conclusion, aspirin suppresses the proliferation of metastatic B16 cells in a JNK‐dependent mechanism.

British Journal of Pharmacology (2003) 138, 1156–1162. doi:10.1038/sj.bjp.0705163
Inhibition of EDHF by two new combinations of K+‐channel inhibitors in rat isolated mesenteric arteries
Authors: Hinton Jane M , Langton Philip D 
Published: April 2003

It is widely established that in rat mesenteric arteries, endothelium‐derived hyperpolarizing factor (EDHF)‐mediated relaxation evoked by acetylcholine is abolished by a combination of charybdotoxin plus apamin. 4‐Aminopyridine, an inhibitor of voltage‐gated (Kv) K+‐channels, in combination with apamin had moderate effects on the EDHF‐mediated relaxation. Maurotoxin (MTX), an inhibitor of Kv and intermediate‐conductance Ca2+‐activated K+‐channels (IK), had no effect on EDHF‐mediated relaxation. However, MTX in combination with apamin completely abolished EDHF‐mediated relaxation and endothelial cell hyperpolarization. The selective IK inhibitor 2‐(2‐chlorophenyl)‐2,2‐diphenyl acetonitrile (TRAM‐39) had no significant effect on EDHF‐mediated relaxation. EDHF‐mediated vasorelaxation and hyperpolarization was abolished by a combination of TRAM‐39 and apamin. These data demonstrate two new combinations of K+‐channel inhibitors for the investigation of EDHF. Furthermore, by using TRAM‐39, a potent selective inhibitor of IK channels, we provide the first direct evidence that abolition of EDHF requires the simultaneous presence of intermediate‐ and small‐conductance Ca2+‐activated K+‐channel inhibitors.British Journal of Pharmacology (2003) 138, 1031–1035. doi:10.1038/sj.bjp.0705171
Inhibition of G protein‐activated inwardly rectifying K+ channels by fluoxetine (Prozac)
Authors: Kobayashi Toru , Washiyama Kazuo , Ikeda Kazutaka 
Published: April 2003

The effects of fluoxetine, a commonly used antidepressant drug, on G protein‐activated inwardly rectifying K+ channels (GIRK, Kir3) were investigated using Xenopus oocyte expression assays.
In oocytes injected with mRNAs for GIRK1/GIRK2, GIRK2 or GIRK1/GIRK4 subunits, fluoxetine reversibly reduced inward currents through the basal GIRK activity. The inhibition by fluoxetine showed a concentration‐dependence, a weak voltage‐dependence and a slight time‐dependence with a predominant effect on the instantaneous current elicited by voltage pulses and followed by slight further inhibition. Furthermore, in oocytes expressing GIRK1/2 channels and the cloned Xenopus A1 adenosine receptor, GIRK current responses activated by the receptor were inhibited by fluoxetine. In contrast, ROMK1 and IRK1 channels in other Kir channel subfamilies were insensitive to fluoxetine.
The inhibitory effect on GIRK channels was not obtained by intracellularly applied fluoxetine, and not affected by extracellular pH, which changed the proportion of the uncharged to protonated fluoxetine, suggesting that fluoxetine inhibits GIRK channels from the extracellular side.
The GIRK currents induced by ethanol were also attenuated in the presence of fluoxetine.
We demonstrate that fluoxetine, at low micromolar concentrations, inhibits GIRK channels that play an important role in the inhibitory regulation of neuronal excitability in most brain regions and the heart rate through activation of various G‐protein‐coupled receptors. The present results suggest that inhibition of GIRK channels by fluoxetine may contribute to some of its therapeutic effects and adverse side effects, particularly seizures in overdose, observed in clinical practice.

British Journal of Pharmacology (2003) 138, 1119–1128. doi:10.1038/sj.bjp.0705172
Population dynamics of Lymnaea columella and its natural infection by Fasciola hepatica in the State of Minas Gerais, Brazil
Authors: Coelho L.H.L. , Lima W.S. 
Published: April 2003

AbstractStudies on the population dynamics and natural infection of Lymnaea columella by Fasciola hepatica were carried out from September 1999 to December 2000 in a low-lying area near Itajubá in the Brazilian State of Minas Gerais. A total of 626 snails were collected monthly at nine different sites, counted, and dissected to search for larvae of F. hepatica. The highest populations of L. columella were reached in October of 1999 and August of 2000, and the highest natural infection rates of snails by F. hepatica were reached in September 1999 (5.2%) and July 2000 (3.9%). The removal by farmers of aquatic plants from the drainage furrows caused a drastic reduction in this snail population.