bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitric oxide and the haemodynamic profile of endotoxin shock in the conscious mouse
Authors: Rees D D , Monkhouse J E , Cambridge D , Moncada S 
Published: January 2005

The release of cytokines following administration of endotoxin and the contribution of nitric oxide (NO) to the subsequent haemodynamic profile were investigated in the conscious mouse.
Administration of endotoxin (E. Coli, 026:B6, 12.5 mg kg−1, i.v.) elevated the concentration of tumour necrosis factor‐α (TNF‐α) in the plasma within 0.5 h, reaching a maximum at 2 h and returning to control concentrations by 4 h. In addition, the concentration of interleukin‐6 (IL‐6) in the plasma was also elevated within 1 h, reaching a maximum at 3 h and remaining elevated throughout the 12 h of study.
Endotoxin (12.5 mg kg−1, i.v.) induced the expression of a Ca2+‐independent (inducible) NO synthase in the mouse heart and elevated the concentrations of nitrite and nitrate in the plasma within 4 h, reaching a maximum at 12 h. This was accompanied by a progressive fall in blood pressure over the same period.
The vasopressor effect of noradrenaline (0.5–4 μg kg−1 min−1, i.v.) administered as a continuous infusion was significantly attenuated 7 h after endotoxin (12.5 mg kg−1, i.v).
The NO synthase inhibitor NG‐monomethyl‐L‐arginine HCl (L‐NMMA; 1–10 mg kg−1, i.v. bolus) reversed the fall in blood pressure when administered 7 h after endotoxin (12.5 mg kg−1, i.v.).
In an attempt to maintain a constant blood concentration, L‐NMMA was administered as a continuous infusion (10 mg kg−1 h−1, i.v.), beginning 4 h after a lower dose of endotoxin (6 mg kg−1, i.v.). Such treatment prevented the fall in blood pressure and the elevation of nitrite and nitrate in the plasma throughout the 18 h of observation.
The fall in blood pressure following endotoxin (3 mg kg−1, i.v.) was significantly reduced throughout the 18 h of observation in homozygous mutant mice lacking the inducible NO synthase.
In summary, we have developed a model of endotoxin shock in the conscious mouse in which an overproduction of NO by the inducible NO synthase is associated with the haemodynamic disturbances. This model, which exhibits many of the characteristics of septic shock in man, will enable the study of the pathology of this condition in more detail and aid the investigation of potential therapeutic agents both as prophylactics and, more importantly, as treatments.
Gabapentin potentiation of the antiepileptic efficacy of vigabatrin in an in vitro model of epilepsy
Authors: Lücke A , Mußhoff U , Köhling R , Osterfeld M , Mayer T , Wolf P , Schütte W , Speckmann E‐J 
Published: January 2005

An enhancement of promoted release of γ‐aminobutyric acid (GABA) and a change in GABA‐metabolism have been suggested as mechanisms of action of gabapentin. Vigabatrin is supposed to act mainly via inhibition of GABA‐transaminase but it also interferes with GABA‐release and GABA‐uptake. On the basis of these mechanisms of action, a pharmacodynamic interaction of the two antiepileptic drugs could be supposed which might be of relevance in the sense of a rational polypharmacy.
To address the aforementioned hypothesis, experiments were carried out on hippocampal slices (n=107) of guinea‐pigs (n=70). Epileptiform field potentials (e.f.p.) were induced by omission of magnesium from the bath solution and recorded in the stratum pyramidale of the CA3 region. Gabapentin (30–600 μM; 5.1–102.72 μg ml−1), vigabatrin (50–200 μM, 6.45–25.8 μg ml−1) and the GABAA‐receptor antagonist bicuculline (100 μM) were added to the bath solution for 3 h.
Gabapentin, in concentrations up to 600 μM, failed to decrease the repetition rate or duration of e.f.p. (n=19). However, vigabatrin, evoked a dose‐dependent reduction of the repetition rate of e.f.p. For a concentration of 100 μM (12.9 μg ml−1) there was a reduction down to 48±5% (mean±s.e.mean) of the initial value within 3 h (n=11). With simultaneous administration of vigabatrin (100 μM) and gabapentin (60 μM) for 3 h (n=15), the repetition rate of e.f.p. decreased down to 8±3%, which is significantly different from the values obtained after administration of 100 μM vigabatrin alone (P<0.0001). Both, the antiepileptic effect of vigabatrin alone and the enhancement by gabapentin were blocked by the GABAA‐receptor antagonist bicuculline (100 μM, n=16).
These results demonstrate that gabapentin is able to augment the antiepileptic effects of vigabatrin significantly. It is possible that a change in the GABA‐release machinery is induced by vigabatrin which then can be augmented by gabapentin.
P2Y1‐receptors in human platelets which are pharmacologically distinct from P2YADP‐receptors
Authors: Fagura M S , Dainty I A , McKay G D , Kirk I P , Humphries R G , Robertson M J , Dougall I G , Leff P 
Published: January 2005

In the present study we have classified the receptor(s) mediating increases in intracellular calcium concentration ([Ca2+]i) in human washed platelets and compared the pharmacological profile obtained with that observed in Jurkat cells, stably transfected with a bovine P2Y1‐receptor.
The P2Y1‐receptor antagonist, adenosine‐3′‐phosphate‐5′‐phosphate (A3P5P), competitively antagonized agonist responses in both Jurkat cells, and in platelets with similar affinities (pKB of 5.8 and 6.0, respectively).
The selective P2YADP antagonist, AR‐C66096, exhibited partial agonism in the Jurkat cells with an affinity (pKA) of 4.9. This value is consistent with its known P2Y1‐receptor activity. In platelets, AR‐C66096 at a concentration (0.1 μM) approximately 100 fold greater than its known P2YADP receptor affinity, had no effect on ADP‐induced increases in [Ca2+]i.
The ability of adenine nucleotide analogues to elevate [Ca2+]i in the Jurkat cells was also determined. The rank order of agonist potency (p[A]50) was: 2‐MeSADP (8.3)>2‐ClATP (7.8)>ADP (7.5)=2‐MeSATP (7.4)>ATPγS (6.5)>ATP (6.2), with ATP appearing to be a partial agonist.
The same rank order of potency was observed when similar experiments were performed in platelets. However, the absolute potencies of all the agonists and the intrinsic activities of both ATPγS and ATP were lower in platelets.
The operational model of agonism was used to test whether the agonist concentration‐effect profiles obtained in these two cell types could be explained on the basis of differences in receptor reserve. The analysis indicated that the data obtained in platelets closely resembled that predicted for a low density or poorly coupled P2Y1‐receptor system.
The hypothesis that the observed partial agonist behaviour of ATP was the result of receptor activation by contaminating ADP with concomitant receptor blockade by ATP, was tested in the platelet system. This hypothesis was supported by a theoretical analysis, which yielded an affinity value for ATP similar to that obtained previously at P2Y1‐receptors.
In summary, the results of this study indicate that human washed platelets contain P2Y1‐receptors which mediate increases in [Ca2+]i and that this receptor population is pharmacologically distinct from P2YADP‐receptors.
G‐protein activation at 5‐HT1A receptors by the 5‐ht1F ligand LY334370 in guinea‐pig brain sections and recombinant cell lines
Authors: Dupuis Delphine S , Colpaert Francis C , Pauwels Petrus J 
Published: January 2005

G‐protein activation by the 5‐ht1F receptor agonist 5‐(4‐fluorobenzoyl)amino‐3‐(1‐methylpiperidin‐4‐yl)‐1H‐indole fumarate (LY334370) was investigated by use of autoradiography of receptor‐activated G‐proteins in guinea‐pig brain sections and [35S]‐GTPγS binding responses in cell lines stably expressing human 5‐HT1A (h 5‐HT1A) receptors.
LY334370 (10 μM) caused little or no stimulation of [35S]‐GTPγS binding in guinea‐pig brain regions enriched in 5‐ht1F binding sites (e.g., claustrum, caudate/putamen and thalamic nuclei), as identified by labelling with 10 nM [3H]‐sumatriptan plus 10 nM 5‐carboxamidotryptamine (5‐CT).
Application of LY334370 (10 μM) to guinea‐pig brain sections resulted in an increase of [35S]‐GTPγS binding in hippocampus (123±17%), lateral septum (58±14%), dorsal raphe (57±10%), entorhinal (37±11%) and cingulate cortex (28±10%). This distribution fits with the G‐protein activation mediated by 5‐HT1A receptors as found with lisuride (10 μM), and labelling of 5‐HT1A receptors by 140 pM [125I]‐4‐(2′‐methoxy‐phenyl)‐1‐[2′‐(n‐2′′‐pyridinyl)‐p‐iodobenzamido]‐ethyl‐piperazine (p‐MPPI).
The LY334370‐mediated [35S]‐GTPγS response was antagonized by the selective, silent 5‐HT1A receptor antagonist N‐[2‐[4‐(2‐methoxyphenyl)1‐piperazinyl]ethyl]‐N‐(2‐pyridinyl)cyclohexanecarboxamide (WAY100635, 1 μM) in each of the brain structures investigated. The distribution pattern of the [35S]‐GTPγS binding response and the antagonist profile suggest that the LY334370‐induced response in guinea‐pig brain is mediated by 5‐HT1A receptors.
The maximal LY334370‐induced [35S]‐GTPγS binding response (83 to 94%) in membranes of recombinant C6‐glial/h 5‐HT1A and HeLa/h 5‐HT1A cells was close to that of 5‐HT, suggesting LY334370 to exert high intrinsic activity at h 5‐HT1A receptors.
In conclusion, in guinea‐pig brain sections and recombinant cell lines the 5‐ht1F receptor agonist LY334370 causes G‐protein activation that is mediated by 5‐HT1A receptors. Caution should be taken when employing this ligand as a putative selective 5‐ht1F agonist.
Modulation of cell adhesion molecule expression and function on human lung microvascular endothelial cells by inhibition of phosphodiesterases 3 and 4
Authors: Blease Kate , Burke‐Gaffney Anne , Hellewell Paul G 
Published: January 2005

Expression of cell adhesion molecules (CAM) on the lung microvascular endothelium is believed to play a key role in the recruitment of leukocytes in pulmonary inflammation. Moreover, regulation of CAM expression may be an important mechanism through which this inflammation may be controlled. Experimental evidence has suggested that combined phosphodiesterase (PDE) 3 and 4 inhibitors increase cyclic AMP levels within cells greater than inhibition of either isoenzyme alone. In the present study we assessed the effect of combinations of rolipram (PDE4 inhibitor), ORG 9935 (PDE3 inhibitor) and salbutamol (β‐agonist) on CAM expression and neutrophil or eosinophil adhesion to human lung microvascular endothelial cells (HLMVEC).
Tumour necrosis factor‐α (TNF‐α)‐induced intercellular adhesion molecule (ICAM)‐1, vascular cell adhesion molecule (VCAM)‐1 and E‐selectin expression were measured on HLMVEC monolayers at 6 h by a specific ELISA technique in the presence of different combinations of medium, rolipram, ORG 9935 and salbutamol.
Rolipram in combination with salbutamol, but neither agent alone, inhibited TNF‐α‐induced E‐selectin expression, whilst ICAM‐1 and VCAM‐1 expression were not affected. ORG 9935 had no significant effect on CAM expression alone. However, in combination with rolipram a syngergistic inhibition of VCAM‐1 and E‐selectin, but not ICAM‐1, expression was observed. No further inhibition was seen in the additional presence of salbutamol.
Neutrophil adhesion to TNF‐α‐stimulated (6 h) HLMVEC was mainly E‐selectin dependent in this model, as ENA2 an anti‐E‐selectin monoclonal antibody (mAb) abrogated neutrophil adhesion. Eosinophil adhesion was E‐selectin‐, ICAM‐1‐ and VCAM‐1‐dependent, as assessed by the inhibitory activity of ENA2 and the ability of a mAb to the ICAM‐1 ligand, CD18, and a mAb to the VCAM‐1 ligand, VLA4, to attenuate adhesion.
Rolipram in the presence of salbutamol or ORG 9935 significantly inhibited neutrophil adherence to TNF‐α‐stimulated HLMVEC. Eosinophil adherence to monolayers was inhibited only when HLMVEC were activated in the presence of rolipram and ORG 9935.
Collectively, the findings presented in this manuscript suggest that inhibition of PDE4 with appropriate activation of adenylate cyclase is sufficient to inhibit induction of E‐selectin expression on HLMVEC to a level that has functional consequences for neutrophil adhesion. In contrast, combined inhibition of PDE3 and 4 isoenzymes is necessary to inhibit VCAM‐1 and to have inhibitory effects on eosinophil adhesion to activated HLMVEC. Upregulation of ICAM‐1 expression on HLMVEC does not appear to be modulated by PDE3 and 4 inhibition. These data may have implications for the use of selective PDE4 inhibitors in lung inflammation.
Different effects of gadolinium on IKR, IKS and IK1 in guinea‐pig isolated ventricular myocytes
Authors: Pascarel C , Hongo K , Cazorla O , White E , Le Guennec J‐Y 
Published: January 2005

Using the whole cell configuration of the patch clamp technique, we studied the potential blocking effects of gadolinium (1 μM to 1 mM) on potassium currents: IKR, IKS and IK1. The study was performed on guinea‐pig isolated ventricular myocytes.
The background current, IK1 was insensitive to Gd3+. Thus, we found that no obvious screening of surface charges was visible with concentrations of Gd3+ up to 100 μM.
By use of three different protocols: tail currents fitting, analysis of envelope of tails and electrophysiological dissection, we found that IKR was the only component of IK that was sensitive to Gd3+. The sensitivity was apparently different depending on the protocol used.
Comparison of the results obtained with the different protocols revealed that the rapid component of IKR is more sensitive to Gd3+ than the slow one.
Of the different protocols used to distinguish between IKR and IKS, the electrophysiological dissection seems to be the more accurate.
Investigation of the actions and antagonist activity of some polyamine analogues in vivo
Authors: Doyle Karen M , Shaw Graham G 
Published: January 2005

The ability of three putative polyamine antagonists to antagonize behavioural changes induced by spermine was assessed.
Injection of an excitotoxic dose of spermine (100 μg, i.c.v.) in mice results in the development of a characteristic behavioural profile, which has two temporally distinct phases. The early events include clonic convulsions, and the later, more general excitation, includes tremor and culminates in the development of a fatal tonic convulsion.
Co‐administration of arcaine (25 μg, i.c.v.) potentiated the early phase effects after spermine injection, but antagonized the development of spermine‐induced tonic convulsions. A larger dose of arcaine (50 μg, i.c.v.) given alone resulted in the development of spermine‐like body tremor and convulsions. It therefore appears that arcaine is not a pure polyamine antagonist in vivo, but may be a partial agonist.
Similarly, 1,10‐diaminodecane appeared to act as a partial agonist in vivo, although it was less potent than arcaine.
In contrast, diethylenetriamine (DET) effectively inhibited the development of the early effects of spermine, but was ineffective against the spermine‐induced CNS excitation and tonic convulsions.
It is concluded that none of the putative polyamine antagonists tested behaved as effective polyamine antagonists in vivo, although each produced some antagonism.
Effect of inhibition of tyrosine phosphatases on voltage‐operated calcium channel currents in rabbit isolated ear artery cells
Authors: Wijetunge S , Lymn J S , Hughes A D 
Published: January 2005

The effect of increasing cellular tyrosine phosphorylation by inhibiting endogenous tyrosine phosphatases was examined on voltage‐operated calcium channel currents in vascular smooth muscle cells.
In single ear artery smooth muscle cells of the rabbit, studied by the whole cell voltage clamp technique, intracellular application of the tyrosine phosphatase inhibitors, sodium orthovanadate (100 μM) and peroxyvanadate (100 μM orthovanadate+1 mM H2O2) increased voltage‐operated calcium channel currents by 56% and 83%, respectively.
Bath application of two other membrane permeant tyrosine phosphatase inhibitors, phenylarsine oxide (100 μM) and dephostatin (50 μM) also increased voltage‐operated calcium channel currents by 48% and 52%, respectively.
The selective tyrosine kinase inhibitor, tyrphostin‐23 (100 μM) reduced calcium channel currents by 41%. Pre‐incubation with tyrphostin‐23 abolished the effects of peroxyvanadate, phenylarsine oxide and dephostatin on calcium channels.
Western blot analysis of rabbit ear artery cell lysates showed increased tyrosine phosphorylation of several endogenous proteins following treatment with peroxyvanadate.
These results indicate that a number of structurally dissimilar inhibitors of tyrosine phosphatases increase voltage‐operated calcium channel currents in arterial smooth muscle cells presumably due to increased tyrosine phosphorylation.
Inhibition of NMDA‐gated ion channels by the P2 purinoceptor antagonists suramin and reactive blue 2 in mouse hippocampal neurones
Authors: Peoples Robert W , Li Chaoying 
Published: January 2005

The action of suramin and reactive blue 2 on N‐methyl‐D‐aspartate (NMDA)‐activated ion current was studied in mouse hippocampal neurones in culture by use of whole‐cell patch‐clamp recording.
Suramin and reactive blue 2 inhibited steady‐state current activated by 25 μM NMDA with IC50 values of 68 and 11 μM, respectively.
Reactive blue 2 produced a gradual decline of NMDA‐activated current to a steady‐state, but this slow onset was not an indication of use‐dependence, as it could be eliminated by exposure to reactive blue 2 before NMDA application. In addition, NMDA‐activated current recovered completely from inhibition by reactive blue 2 in the absence of agonist.
The slow onset of inhibition by reactive blue 2 was not apparently due to an action at an intracellular site, as inclusion of 250 μM reactive blue 2 in the recording pipette did not alter inhibition by 25 μM reactive blue 2 applied externally.
Reactive blue 2 and suramin inhibited NMDA‐gated channels in a voltage‐independent manner.
Reactive blue 2, 25 μM, decreased the maximal response to NMDA from 1441 to 598 pA without changing its EC50. In contrast, 75 μM suramin increased the EC50 for NMDA from 13 to 35 μM, and decreased the maximal response to NMDA from 1822 to 1498 pA. Schild analysis of suramin inhibition of NMDA‐activated current yielded a nonlinear plot.
Both agents decreased the maximal response to glycine without altering its EC50.
Suramin and reactive blue 2 appear to inhibit NMDA receptor‐channels in a manner that is noncompetitive with respect to both NMDA and glycine. However, inhibition by suramin differed from that by reactive blue 2, in that suramin significantly increased the EC50 of NMDA.
Characterization of Ro 04‐6790 and Ro 63‐0563: potent and selective antagonists at human and rat 5‐HT6 receptors
Authors: Sleight Andrew J , Boess Frank G , Bös Michael , Levet‐Trafit Bernard , Riemer Claus , Bourson Anne 
Published: January 2005

This study describes the in vitro characterization of two potent and selective 5‐HT6 receptor antagonists at the rat and human recombinant 5‐HT6 receptor.
In binding assays with [3H]‐LSD, 4‐amino‐N‐(2,6 bis‐methylamino‐pyrimidin‐4‐yl)‐benzene sulphonamide (Ro 04‐6790) and 4‐amino‐N‐(2,6 bis‐methylamino‐pyridin‐4‐yl)‐benzene sulphonamide (Ro 63‐0563) had mean pKi values ±s.e.mean at the rat 5‐HT6 receptor of 7.35±0.04 and 7.83±0.01, respectively and pKi values at the human 5‐HT6 receptor of 7.26±0.06 and 7.91±0.02, respectively.
Both compounds were found to be over 100 fold selective for the 5‐HT6 receptor compared to 23 (Ro 04‐6790) and 69 (Ro 63‐0563) other receptor binding sites.
In functional studies, neither compound had any significant effect on basal levels of cyclicAMP accumulation in Hela cells stably expressing the human 5‐HT6 receptor, suggesting that the compounds are neither agonists nor inverse agonists at the 5‐HT6 receptor. However, both Ro 04‐6790 and Ro 63‐0563 behaved as competitive antagonists with mean ±s.e.mean pA2 values of 6.75±0.07 and 7.10±0.09, respectively.
In rats habituated to observation cages, Ro 04‐6790 produced a behavioural syndrome similar to that seen following treatment with antisense oligonucleotides designed to reduce the expression of 5‐HT6 receptors. This behavioural syndrome consisted of stretching, yawning and chewing.
Ro 04‐6790 and Ro 63‐0563 represent valuable pharmacological tools for the identification of 5‐HT6 receptors in natural tissues and the study of their physiological function.
Effects of the 5‐lipoxygenase activating protein inhibitor MK886 on voltage‐gated and Ca2+‐activated K+ currents in rat arterial myocytes
Authors: Smirnov Sergey V , Knock Greg A , Aaronson Philip I 
Published: January 2005

The effects on the voltage‐gated (IK) and Ca2+ activated (IK,Ca) K+ currents in rat arterial myocytes of the 5‐lipoxygenase activating protein (FLAP) inhibitor MK886, and its inactive analogue L583,916 were evaluated.
In rat pulmonary arterial myocytes (RPAMs), MK886 caused a concentration‐dependent reduction of the IK, with little obvious change in the kinetics of the current. Half maximal current block was observed at 75 nM MK886.
MK886 application led to a concentration‐dependent increase in the amplitude of the TEA‐sensitive IK,Ca current and single channel activity in RPAMs in whole cell and inside‐out configurations, respectively. The threshold concentration for this effect was approximately 300 nM and a maximal 4–5 fold increase was observed at 10 μM MK886. MK886 also increased IK,Ca in rat mesenteric arterial myocytes (RMAMs).
L538,916, an analogue of MK886 which does not block FLAP, had no effect on either IK or IK,Ca at a concentration of 10 μM.
Leukotriene C4 (100 nM) had no effect on either IK or IK,Ca in RPAMs. MK886 produced its usual increase in IK,Ca and also blocked IK, in the presence of leukotriene C4. Similarly, leukotriene E4 (100 nM) did not alter the amplitude of IK. Also, the nonselective leukotriene receptor antagonist ICI 198,615 (3 μM) did not affect IK in RPAMs, and did not affect the response to MK886.
Arachidonic acid (10 μM) enhanced IK,Ca in both RPAMs and RMAMs.
The results show that MK886 markedly affects both IK and IK,Ca in a manner similar to that of arachidonic acid and independent of the endogenous production of leukotrienes. It is therefore possible that MK886, which is thought to compete with arachidonic acid for its binding to FLAP, may similarly occupy arachidonic acid binding sites on these K+ channels, and mimic its effects. Alternatively, MK886 might act via non‐selective effects on other arachidonic acid metabolites which could modify K+ channel function.