bluuebunny/crossref_metadata_2025_split huggingface dataset:
Block by gabapentin of the facilitation of glutamate release from rat trigeminal nucleus following activation of protein kinase C or adenylyl cyclase
Authors: Maneuf Yannick P , McKnight Alexander T 
Published: January 2005

The effect of activation of protein kinase C (PKC) or adenylyl cyclase on release of glutamate has been investigated in a perfused slice preparation from the rat caudal trigeminal nucleus. Stimulation of PKC by phorbol 12‐myristate 13‐acetate (PMA) produced a concentration‐dependent increase in K+‐evoked release of [2H]‐glutamate (maximum increase 45%, EC50 11.8 nM), but in the presence of gabapentin (30 μM) the facilitation of release was blocked. The adenylyl cyclase activator forskolin (FSK) also induced a concentration‐dependent increase in K+‐evoked release of [3H]‐glutamate (maximum increase 36%, EC50 2.4 μM), and again this facilitatory effect was blocked by gabapentin (30 μM). We suggest that these results may be of relevance to the antihyperalgesic properties of gabapentin, in conditions where concomitant release of substance P and CGRP produces activation of PKC and adenylyl cyclase respectively.British Journal of Pharmacology (2001) 134, 237–240; doi:10.1038/sj.bjp.0704227
[125I‐His9]‐Ghrelin, a novel radioligand for localizing GHS orphan receptors in human and rat tissue; up‐regulation of receptors with atherosclerosis
Authors: Katugampola Sidath D , Pallikaros Zakos , Davenport Anthony P 
Published: January 2005

Ghrelin is the recently identified endogenous ligand for the cloned growth hormone secretagogue receptor (GHS‐R). We have characterized for the first time the binding of human [125I‐His9]‐ghrelin to normal human and rat tissue and demonstrated expression of this ‘orphan’ receptor that has previously been predicted to exist from mRNA. Furthermore, we have discovered that [125I‐His9]‐ghrelin density is significantly increased in atherosclerosis.
[125I‐His9]‐Ghrelin bound to non‐diseased human heart (left ventricle) with an association rate constant (kobs) of 0.16±0.004 min−1, a dissociation rate constant of 0.068±0.0005 min−1 (kinetically derived KD of 0.1 nM; n=5 individuals±s.e.mean), a KD of 0.43±0.08 nM and Bmax of 7.8±0.9 fmol mg−1 protein (n=6 individual±s.e.mean).
Specific [125I‐His9]‐ghrelin binding was to the human vasculature including aorta, coronary, pulmonary, arcuate arteries in the kidney and saphenous veins. In rat tissues, binding sites were also localized to the vasculature in peripheral tissues as well as the granular layer of the cerebellum in the CNS.
[125I‐His9]‐Ghrelin binding was significantly up‐regulated (3 – 4 fold) in both atherosclerotic coronary arteries and saphenous vein grafts with advanced intimal thickening, compared with normal vessels (P<0.05).
Our results suggest that the native receptor for [125I‐His9]‐ghrelin may be widely distributed in the human cardiovascular system. Furthermore, changes in the density of this proposed ghrelin receptor implicates this new transmitter system in the development of atherosclerosis and may therefore represent a novel therapeutic target in the treatment of cardiovascular disease.

British Journal of Pharmacology (2001) 134, 143–149; doi:10.1038/sj.bjp.0704228
The mechanisms involved in the long‐lasting neuroprotective effect of fluoxetine against MDMA (‘ecstasy’)‐induced degeneration of 5‐HT nerve endings in rat brain
Authors: Sanchez V , Camarero J , Esteban B , Peter M J , Green A R , Colado M I 
Published: January 2005

It has been reported that co‐administration of fluoxetine with 3,4‐methylenedioxymethamphetamine (MDMA, ‘ecstasy’) prevents MDMA‐induced degeneration of 5‐HT nerve endings in rat brain. The mechanisms involved have now been investigated.
MDMA (15 mg kg−1, i.p.) administration produced a neurotoxic loss of 5‐HT and 5‐hydroxyindoleacetic acid (5‐HIAA) in cortex, hippocampus and striatum and a reduction in cortical [3H]‐paroxetine binding 7 days later. Fluoxetine (10 mg kg−1, i.p., ×2, 60 min apart) administered concurrently with MDMA or given 2 and 4 days earlier provided complete protection, and significant protection when given 7 days earlier. Fluvoxamine (15 mg kg−1, i.p., ×2, 60 min apart) only produced neuroprotection when administered concurrently.
Fluoxetine (10 mg kg−1, ×2) markedly increased the KD and reduced the Bmax of cortical [3H]‐paroxetine binding 2 and 4 days later. The Bmax was still decreased 7 days later, but the KD was unchanged. [3H]‐Paroxetine binding characteristics were unchanged 24 h after fluvoxamine (15 mg kg−1, ×2).
A significant cerebral concentration of fluoxetine plus norfluoxetine was detected over the 7 days following fluoxetine administration. The fluvoxamine concentration had decreased markedly by 24 h.
Pretreatment with fluoxetine (10 mg kg−1, ×2) failed to alter cerebral MDMA accumulation compared to saline pretreated controls.
Neither fluoxetine or fluvoxamine altered MDMA‐induced acute hyperthermia.
These data demonstrate that fluoxetine produces long‐lasting protection against MDMA‐induced neurodegeneration, an effect apparently related to the presence of the drug and its active metabolite inhibiting the 5‐HT transporter. Fluoxetine does not alter the metabolism of MDMA or its rate of cerebral accumulation.

British Journal of Pharmacology (2001) 134, 46–57; doi:10.1038/sj.bjp.0704230
Adenosine A2A receptor antagonists are potential antidepressants: evidence based on pharmacology and A2A receptor knockout mice
Authors: Yacoubi Malika El , Ledent Catherine , Parmentier Marc , Bertorelli Rosalia , Ongini Ennio , Costentin Jean , Vaugeois Jean‐Marie 
Published: January 2005

Adenosine, an ubiquitous neuromodulator, and its analogues have been shown to produce ‘depressant’ effects in animal models believed to be relevant to depressive disorders, while adenosine receptor antagonists have been found to reverse adenosine‐mediated ‘depressant’ effect.
We have designed studies to assess whether adenosine A2A receptor antagonists, or genetic inactivation of the receptor would be effective in established screening procedures, such as tail suspension and forced swim tests, which are predictive of clinical antidepressant activity.
Adenosine A2A receptor knockout mice were found to be less sensitive to ‘depressant’ challenges than their wildtype littermates. Consistently, the adenosine A2A receptor blockers SCH 58261 (1 – 10 mg kg−1, i.p.) and KW 6002 (0.1 – 10 mg kg−1, p.o.) reduced the total immobility time in the tail suspension test.
The efficacy of adenosine A2A receptor antagonists in reducing immobility time in the tail suspension test was confirmed and extended in two groups of mice. Specifically, SCH 58261 (1 – 10 mg kg−1) and ZM 241385 (15 – 60 mg kg−1) were effective in mice previously screened for having high immobility time, while SCH 58261 at 10 mg kg−1 reduced immobility of mice that were selectively bred for their spontaneous ‘helplessness’ in this assay.
Additional experiments were carried out using the forced swim test. SCH 58261 at 10 mg kg−1 reduced the immobility time by 61%, while KW 6002 decreased the total immobility time at the doses of 1 and 10 mg kg−1 by 75 and 79%, respectively.
Administration of the dopamine D2 receptor antagonist haloperidol (50 – 200 μg kg−1 i.p.) prevented the antidepressant‐like effects elicited by SCH 58261 (10 mg kg−1 i.p.) in forced swim test whereas it left unaltered its stimulant motor effects.
In conclusion, these data support the hypothesis that A2A receptor antagonists prolong escape‐directed behaviour in two screening tests for antidepressants. Altogether the results support the hypothesis that blockade of the adenosine A2A receptor might be an interesting target for the development of effective antidepressant agents.

British Journal of Pharmacology (2001) 134, 68–77; doi:10.1038/sj.bjp.0704240
Real‐time analysis of dopamine: antagonist interactions at recombinant human D2long receptor upon modulation of its activation state
Authors: Pauwels Petrus J , Tardif Stéphanie , Wurch Thierry , Colpaert Francis C 
Published: January 2005

Antipsychotic drugs may mediate their therapeutic effects not only by preventing the binding of dopamine but also by decreasing the propensity of the dopamine receptor to assume an active R* state. Ligand‐mediated activation and blockade of the recombinant human D2long receptor was investigated in CHO‐K1 cells upon modulation of its R* state.
Both the Ala371Lys (A371K) and Thr372Arg (T372R) D2long receptor mutants could be activated in a ligand‐dependent manner via a chimeric Gαq/o protein, and more efficaciously so than with the promiscuous Gα15 protein.
Dopamine and partial agonists (Emax: lisuride>>(+)‐UH 232≃bromerguride) displayed dissimilar Ca2+ kinetic properties at wild‐type and mutant receptors. A371K and T372R D2long receptor mutants demonstrated an attenuated and enhanced maximal response to these partial agonists, respectively.
Dopamine antagonists were unable to block the transient high‐magnitude Ca2+ phase at the wild‐type D2long receptor upon simultaneous exposure to antagonist and dopamine, while full blockade of the low‐magnitude Ca2+ phase did occur at a later time (onset‐time: haloperidol<bromerguride<(+)‐butaclamol). A similar, though more efficacious, antagonist profile was also found at the A371K mutant receptor. Conversely, the blockade of the low‐magnitude Ca2+ phase was attenuated (haloperidol) or almost absent [(+)‐butaclamol and bromerguride] at the T372R mutant receptor.
In conclusion, mutagenesis of the Ala371 and Thr372 positions affects in an opposite way the ligand‐dependent activation and blockade of the D2long receptor. The observed attenuation of dopamine‐mediated Ca2+ signal generation with different decay‐times may underlie distinct properties of the dopaminergic ligands.

British Journal of Pharmacology (2001) 134, 88–97; doi:10.1038/sj.bjp.0704243
The plasma protein extravasation induced by adenosine and its analogues in the rat dorsal skin: evidence for the involvement of capsaicin sensitive primary afferent neurones and mast cells
Authors: Esquisatto Laura C M , Costa Soraia K P , Camargo Enilton A , Ribela Maria T C P , Brain Susan D , Nucci Gilberto de , Antunes Edson 
Published: January 2005

The contribution of sensory neurons and mast cells to the oedema evoked by adenosine A1 (N6‐cyclopentyladenosine, CPA, 3 – 30 nmol site−1), A2 (5′N‐ethylcarboxamidoadenosine, NECA, 1 – 10 nmol site−1) and A3 receptor agonists (N6‐[3‐iodobenzyl]‐N‐methyl‐5′‐carboxiamidoadenosine, IB‐MECA, 0.01 – 3 nmol site−1) was investigated in the rat skin microvasculature, by the extravascular accumulation of intravenously‐injected (i.v.) 125I‐albumin.
Intradermal (i.d.) injection of adenosine and analogues induced increased microvascular permeability in a dose‐dependent manner (IB‐MECA > NECA > CPA > adenosine). The non‐selective adenosine receptor antagonist theophylline (5 – 50 nmol site−1) markedly inhibited adenosine, CPA or NECA but not IB‐MECA‐induced plasma extravasation. The A1 receptor antagonist 1,3‐dipropyl‐8‐cyclopentylxanthine (DPCPX, 0.3 – 3 μmol kg−1, i.v.) significantly reduced CPA‐induced plasma extravasation whereas responses to adenosine, NECA or IB‐MECA were unchanged. The A2 receptor antagonist 3,7‐dymethyl‐1‐proprargylxanthine (DMPX, 0.5 – 50 nmol site−1) significantly reduced NECA‐induced plasma extravasation without affecting responses to adenosine, CPA and IB‐MECA.
The tachykinin NK1 receptor antagonist (S)‐1‐[2‐[3‐(3,4‐dichlorphenyl)‐1 (3‐isopropoxyphenylacetyl) piperidin‐3‐yl] ethyl]‐4‐phenyl‐1 azaniabicyclo [2.2.2]octane chloride (SR140333), but not the NK2 receptor antagonist (S)‐N‐methyl‐N[4‐acetylamino‐4‐phenyl piperidino)‐2‐(3,4‐dichlorophenyl)butyl]‐benzamide (SR48968), significantly inhibited the plasma extravasation evoked by higher doses of adenosine (100 nmol site−1), CPA (100 nmol site−1), NECA (1 nmol site−1) and IB‐MECA (0.1 – 1 nmol site−1). In rats treated with capsaicin to destroy sensory neurons, the response to higher doses of adenosine, CPA and NECA, but not IB‐MECA, was significantly inhibited.
The effects of adenosine and analogues were largely inhibited by histamine and 5‐hydroxytryptamine (5‐HT) antagonists and by compound 48/80 pretreatment.
In conclusion, our results provide evidence that adenosine A1 and A2, but not A3, receptor agonists may function as cutaneous neurogenic pro‐inflammatory mediators; acting via microvascular permeability‐increasing mechanisms that can, depending on dose of agonist and purine receptor under study, involve the tachykinin NK1 receptor and mast cell amines.

British Journal of Pharmacology (2001) 134, 108–115; doi:10.1038/sj.bjp.0704245
Influence of aldosterone on collagen synthesis and proliferation of rat cardiac fibroblasts
Authors: Rombouts Krista , Wielant Annemie , Hellemans Karine , Schuppan Detlef , Geerts Albert 
Published: January 2005

Previous in vivo studies in men and experimental animal models have shown that hyperaldosteronemia is correlated with cardiac fibrosis due to increased total collagen synthesis. As yet, it is unclear whether aldosterone has direct pro‐fibrogenic effect on cardiac fibroblasts, the fibrogenic effector cell in the myocardium, and if so which procollagens specifically are synthesized at higher rates.
The present study aims at establishing whether de novo collagen synthesis by cardiac fibroblasts is enhanced following exposure for 2×24 h to pharmacological (10−7 – 10−8 M), near‐physiological (10−9 M) or physiological (10−10 – 10−11 M) aldosterone concentrations. During the last 24 h, cells were metabolically labelled with [35S]‐methionine/[35S]‐cysteine. Labelled procollagens were immunoprecipitated quantitatively using antibodies against specific procollagens. Contrary to expectations, 10−7 M aldosterone inhibited significantly de novo synthesis of procollagens type I and IV (−35% and −42%, respectively). For procollagen type III, only a tendency towards inhibition was observed. At lower concentrations of aldosterone (10−8 – 10−10 M), synthesis of procollagens type I, III or IV was unaffected.
Cellular DNA synthesis under influence of aldosterone was evaluated by measuring BrdU incorporation. Cells were treated with aldosterone, while BrdU was added during the last 16 h of treatment. Aldosterone had no demonstrable effect on cellular proliferation.
Reverse transcription‐polymerase chain reaction (RT – PCR) clearly demonstrated the presence of mineralocorticoid receptor mRNA in cardiac fibroblasts.
In spite of the expression of the mineralocorticoid receptor by cultured cardiac fibroblasts, the pro‐fibrogenic effect of aldosterone as observed in vivo, is not likely to be due to a direct effect of this hormone in cardiac fibroblasts.

British Journal of Pharmacology (2001) 134, 224–232; doi:10.1038/sj.bjp.0704247
Pharmacological modulation of monovalent cation currents through the epithelial Ca2+ channel ECaC1
Authors: Nilius Bernd , Prenen Jean , Vennekens Rudi , Hoenderop Joost G J , Bindels René J M , Droogmans Guy 
Published: January 2005

The recent identification of the epithelial Ca2+ channel, ECaC1, represents a major step forward in our knowledge of renal Ca2+ handling. ECaC1 constitutes the rate‐limiting apical Ca2+ entry mechanism of active, transcellular Ca2+ reabsorption. This unique highly selective Ca2+ channel shares a low but significant homology with transient receptor potential (TRP) channels and vanilloid receptors (VR).
We have studied the pharmacological modulation of currents through ECaC1 heterologously expressed in HEK 293 cells. Monovalent cation currents were measured by use of the whole cell patch clamp technique in cells dialysed with 10 mM BAPTA or 10 mM EGTA to prevent the fast Ca2+ dependent inactivation of ECaC1.
Several modulators were tested, including inorganic cations, putative store‐operated Ca2+ entry (SOC) blockers, the vanilloid receptor (VR‐1) blocker capsazepine, protein tyrosine kinase blockers, calmodulin antagonists and ruthenium red.
Ruthenium red and econazole appeared to be the most effective inhibitors of currents through ECaC1, with IC50 values of 111 nM and 1.3 μM, respectively, whereas the selective SOC inhibitor, SKF96365, was nearly ineffective.
The divalent cation current block profile for ECaC1 is Pb2+=Cu2+>Zn2+>Co2+>Fe2+ with IC50 values between 1 and approximately 10 μM.
In conclusion, ECaC activity is effectively inhibited by various compounds including ruthenium red, antimycotic drugs and divalent cations, which might be useful tools for pharmacological manipulation and several disorders related to Ca2+ homeostasis could benefit from such developments.

British Journal of Pharmacology (2001) 134, 453–462; doi:10.1038/sj.bjp.0704272
Common mechanisms of inhibition for the Na+/glucose (hSGLT1) and Na+/Cl−/GABA (hGAT1) cotransporters
Authors: Hirayama Bruce A , Díez‐Sampedro Ana , Wright Ernest M 
Published: January 2005

Electrophysiological methods were used to investigate the interaction of inhibitors with the human Na+/glucose (hSGLT1) and Na+/Cl−/GABA (hGAT1) cotransporters. Inhibitor constants were estimated from both inhibition of substrate‐dependent current and inhibitor‐induced changes in cotransporter conformation.
The competitive, non‐transported inhibitors are substrate derivatives with inhibition constants from 200 nM (phlorizin) to 17 mM (esculin) for hSGLT1, and 300 nM (SKF89976A) to 10 mM (baclofen) for hGAT1. At least for hSGLT1, values determined using either method were proportional over 5‐orders of magnitude.
Correlation of inhibition to structure of the inhibitors resulted in a pharmacophore for glycoside binding to hSGLT1: the aglycone is coplanar with the pyranose ring, and binds to a hydrophobic/aromatic surface of at least 7×12Å. Important hydrogen bond interactions occur at five positions bordering this surface.
In both hSGLT1 and hGAT1 the data suggests that there is a large, hydrophobic inhibitor binding site ∼8Å from the substrate binding site. This suggests an architectural similarity between hSGLT1 and hGAT1. There is also structural similarity between non‐competitive and competitive inhibitors, e.g., phloretin is the aglycone of phlorizin (hSGLT1) and nortriptyline resembles SKF89976A without nipecotic acid (hGAT1).
Our studies establish that measurement of the effect of inhibitors on presteady state currents is a valid non‐radioactive method for the determination of inhibitor binding constants. Furthermore, analysis of the presteady state currents provide novel insights into partial reactions of the transport cycle and mode of action of the inhibitors.

British Journal of Pharmacology (2001) 134, 484–495; doi:10.1038/sj.bjp.0704274
Assessment of agonism at G‐protein coupled receptors by phosphatidic acid and lysophosphatidic acid in human embryonic kidney 293 cells
Authors: Alderton Forbes , Sambi Balwinder , Tate Rothwelle , Pyne Nigel J , Pyne Susan 
Published: January 2005

Several different molecular species of phosphatidic acid (PA) bind to a G‐protein coupled receptor (GPCR) to induce activation of the p42/p44 mitogen‐activated protein kinase (p42/p44 MAPK) pathway in HEK 293 cells. PA is active at low nanomolar concentrations and the response is sensitive to pertussis toxin (which uncouples GPCRs from Gi/o). The de‐acylated product of PA, lysophosphatidic acid (LPA), which binds to members of the endothelial differentiation gene (EDG) family of receptors also stimulated p42/p44 MAPK in a pertussis toxin sensitive manner, but with an ∼100 – 1000 fold lower potency compared with the different molecular species of PA. RT – PCR using gene‐specific primers showed that HEK 293 cells express EDG2 and PSP24, the latter being a lipid binding GPCR out with the EDG cluster. We conclude that PA is a novel high potency GPCR agonist.British Journal of Pharmacology (2001) 134, 6–9; doi:10.1038/sj.bjp.0704278
Effects of local cytochalasin D delivery on smooth muscle cell migration and on collar‐induced intimal hyperplasia in the rabbit carotid artery
Authors: Bruijns Richard H J , Bult Hidde 
Published: January 2005

Smooth muscle cell (SMC) migration has been implicated in neointima formation after angioplasty. Therefore, we investigated whether cytochalasin D, a fungal metabolite that inhibits actin filament formation, suppressed SMC migration and collar‐induced intimal hyperplasia in the rabbit carotid artery.
To establish effective concentrations, contractions of carotid artery rings to phenylephrine were determined after incubation with cytochalasin D (10−8 – 10−6 M) for 30 min or 3 days. In vitro cell migration was studied using carotid artery explants and a modified Boyden chamber with SMCs isolated from the rabbit aorta. The in vivo effect was tested after infusion of 10−8 – 10−4 M cytochalasin D into collars placed around the left carotid artery; collars placed around the right artery served as controls.
Contractions to phenylephrine decreased after 30 min or 3 days exposure to 10−7 and 10−6 M cytochalasin D; the effect was partly reversible. These concentrations also inhibited cellular outgrowth and SMC migration in the in vitro assays.
Immunohistochemistry showed that local delivery of 10−5 or 10−4 M cytochalasin D for 2 weeks suppressed collar‐induced α‐SMC actin expression in the intima by 68% and 84% respectively. However, the cross‐sectional area of the intima was not reduced due to an influx of T‐lymphocytes and macrophages.
It is concluded that cytochalasin D suppressed SMC contractility and migration in vitro. Although perivascular infusion of cytochalasin D inhibited collar‐induced SMC migration from media to intima in vivo as well, the intimal hyperplasia was not reduced due to concomitant development of an inflammatory response.

British Journal of Pharmacology (2001) 134, 473–483; doi:10.1038/sj.bjp.0704281
Role of multidrug resistance protein 2 (MRP2) in glutathione‐bimane efflux from Caco‐2 and rat renal proximal tubule cells
Authors: Terlouw Sylvie A , Masereeuw Rosalinde , Van Den Broek Petra H H , Notenboom Sylvia , Russel Frans G M 
Published: January 2005

The multidrug resistance protein 2 (MRP2) has been shown to play an important role in the transport of glutathione conjugates in the liver. Its importance in renal excretion, however, is still uncertain and other organic anion transporters may be involved. The objective of the present study was to characterize glutathione conjugate efflux from rat kidney proximal tubule cells (PTC), and to determine the contribution of Mrp2.
We used isolated PTC in suspension, as well as grown to monolayer density. For comparison, transport characteristics were also determined in the human intestinal epithelial cell line Caco‐2, an established model to study MRP2‐mediated transport. The cells were loaded with monochlorobimane (MCB) at 10°C. MCB enters the cells by simple diffusion and is conjugated with glutathione to form the fluorescent glutathione‐bimane (GS‐B).
In primary cultures of rat PTC, no indications for a transporter‐mediated mechanism were found. The efflux of GS‐B from Caco‐2 cells and freshly isolated PTC was time‐ and temperature‐dependent. Furthermore, GS‐B transport in both models was inhibited by chlorodinitrobenzene (CDNB), with an inhibitory constant of 46.8±0.9 μM in freshly isolated PTC. In Caco‐2 cells, the inhibitory potency of CDNB was approximately 20 fold higher. Finally, efflux of GS‐B from freshly isolated PTC from Mrp2‐deficient (TR−) rats was studied. As compared to normal rat PTC, transport characteristics were not different.
We conclude that in freshly isolated rat PTC glutathione conjugate excretion is mediated by other organic anion transporters rather than by Mrp2.

British Journal of Pharmacology (2001) 134, 931–938; doi:10.1038/sj.bjp.0704284