bluuebunny/crossref_metadata_2025 huggingface dataset:
The effects of a novel sulphidopeptide leukotriene antagonist, BAY x7195, against elicited bronchoconstriction in the anaesthetized guinea‐pig
Authors: Francis H P , Patel U P , Thompson A M , Carpenter T G , Gardiner P J , Abram T S
Published: January 2005

The novel leukotriene antagonist Bay  x7195, has been evaluated against bronchoconstriction induced by leukotriene D4 (LTD4), the thromboxane A2 (TXA2) mimetic U46619, histamine and antigen, in the guinea‐pig in vivo by use of a modified Konzett‐Rössler preparation.

LTD4, given intravenously (i.v.) at 1 or 3 μg kg−1 in the presence of indomethacin and sotalol, caused a 50–70% maximal bronchoconstriction in most animals.

BAY x7195, given i.v., orally (p.o.), by aerosol or dry powder insufflation, in lactose, reduced LTD4‐induced bronchoconstriction dose‐dependently. The approximate ID50 values were 83 μg kg−1, 3 mg kg−1, 0.0003 % w/v for 20 breaths and 20 μg respectively.

The action of BAY x7195 (10 mg kg−1, p.o.) was long lasting, causing significant inhibition of the LTD4‐induced response (88% reduction) 8 h after dosing.

When given intravenously, in the presence of selected antagonists, BAY x7195 caused a dose‐related reduction in the antigen‐induced response, with an approximate ID50 of 2 mg kg−1.

At 3 mg kg−1, i.v., a dose which abolished the response to LTD4, BAY x7195 had no effect on U46619‐ or histamine‐induced bronchoconstriction.

BAY x7195 is a potent, selective and long acting antagonist of LTD4‐induced bronchoconstriction, in an anaesthetized, ventilated guinea‐pig model. It is therefore worthy of clinical evaluation in diseases believed to involve the sulphidopeptide leukotrienes, such as asthma.

British Journal of Pharmacology (1998) 123, 39–44; doi:10.1038/sj.bjp.0701580
Effects of long‐term treatment with trandolapril on sarcoplasmic reticulum function of cardiac muscle in rats with chronic heart failure following myocardial infarction
Authors: Yamaguchi Fuminari , Sanbe Atsushi , Takeo Satoshi
Published: January 2005

Calcium transport activity of isolated cardiac sarcoplasmic reticulum (SR) including Ca2+ uptake and release is decreased in animals with chronic heart failure (CHF) following myocardial infarction. The present study was undertaken to determine whether an angiotensin converting enzyme (ACE) inhibitor, trandolapril, improves cardiac sarcoplasmic reticular function in animals with CHF following myocardial infarction.

CHF was induced by left coronary artery ligation in rats, which resulted in an infarction of approximately 45% of the left ventricle. Aortic flow and cardiac output index were decreased, and left ventricular end‐diastolic pressure was increased 8 weeks after the operation, suggesting the development of CHF.

The developed force transients of cardiac skinned fibres of the rats with CHF were decreased when the skinned fibre was preloaded for 0.25–1 min with 10−5 M Ca2+ (48–88%) and when preloaded with 10−6 M Ca2+ and then exposed to 0.1–1 mM caffeine (45–93%).

The [3H]‐ryanodine‐binding activity in SR‐enriched fractions was reduced by 23% in the CHF group. These results suggest that the amount of Ca2+ released from SR is decreased due to a reduced rate of SR Ca2+ uptake and a downregulation of the SR Ca2+‐release channel.

Rats were treated orally with 3 mg kg−1 day−1 trandolapril from the 2nd to the 8th week after the coronary artery ligation. Treatment with trandolapril attenuated the reduction in aortic flow and cardiac output index and the increase in left ventricular end‐diastolic pressure, and improved the developed force transients of the skinned fibre of the animal with CHF without causing a reduction of infarct size. Treatment with trandolapril also attenuated the reduction in ryanodine receptor density in the viable left ventricle of the rat with CHF.

It is concluded that long‐term treatment with trandolapril attenuates cardiac SR dysfunction in rats with CHF and that the mechanism underlying this effect is, at least in part, attributed to prevention of downregulation of Ca2+ release channel.

British Journal of Pharmacology (1998) 123, 326–334; doi:10.1038/sj.bjp.0701592
Role of lipid peroxidation and the glutathione‐dependent antioxidant system in the impairment of endothelium‐dependent relaxations with age
Authors: Rodríguez‐Martínez M Angeles , Alonso M Jesús , Redondo Juliana , Salaíces Mercedes , Marín Jesús
Published: January 2005

Age‐related changes in the blood prooxidant‐antioxidant state, as well as its influence on the relaxant responses to acetylcholine (ACh) were studied in the tail artery from 6‐, 24‐ and 30‐month‐old Sprague‐Dawley (SD) rats.

Malondialdehyde (MDA) plasma levels increased 2 and 3 times in 24‐ and 30‐month‐old rats, respectively, when compared with 6‐month‐old rats (0.43±0.09 μM). This increase was accompanied by an induction of 6‐phosphogluconate dehydrogenase (6PG‐DH) and glutathione reductase (GR) activities in red blood cells from 24‐month‐old rats. In 30‐month‐old rats, a further induction of these enzymatic activities, as well as glucose‐6‐phosphate dehydrogenase (G6P‐DH) and glutathione peroxidase (GPx) activities was observed.

No differences with age were found in the concentration‐response curves to ACh in isolated tail artery segments from 6‐ and 24‐month‐old rats precontracted with 0.3 μM noradrenaline (NA). However, a decrease in sensitivity to ACh‐induced relaxation was observed in 30‐month‐old rats; EC30 values were 3.5 (1.3–8.0)×10−7 M and 18.1 (8.9–30.1)×10−7 M for 6‐ and 30‐month‐old rats, respectively. Moreover, a decrease in maximum ACh relaxation (10 μM) was found in 30‐month‐old rats in comparison with that obtained in 6‐month‐old rats (58.5±3.9% and 42.5±3.4% of previous NA contraction, respectively).

Incubation of tail artery segments with MDA (0.5, 1 or 10 μM) caused a reduction of ACh‐induced relaxations that was different in the three ages. Thus, the reduction of ACh‐induced relaxations became significant with 0.5 μM MDA in 6‐, with 1 μM MDA in 24‐, and with 10 μM MDA in 30‐month‐old rats. In addition, MDA did not cause a shift in the concentration‐response curve to ACh, but a decrease in the maximum response.

Superoxide dismutase (SOD; 150 u ml−1, a superoxide anion scavenger) reversed the inhibitory effect of MDA on ACh‐induced relaxations at all ages studied.

We conclude that: (1) ageing produces an increase in lipid peroxidation process, as indicated by the increase in MDA plasma levels, that is accompanied by an induction of lipid peroxide detoxification enzymes; (2) the changes in prooxidant‐antioxidant equilibrium with age contribute, at least partially, to the impairment of the relaxant responses evoked by ACh; and (3) the effect of MDA appears to be mediated by superoxide anion at all ages studied.

British Journal of Pharmacology (1998) 123, 113–121; doi:10.1038/sj.bjp.0701595
Effects of a hydroxylated metabolite of the β‐adrenoreceptor antagonist, carvedilol, on post‐ischaemic splanchnic tissue injury
Authors: Christopher Theodore A , Lopez Bernard L , Ma Xin‐Liang , Feuerstein Giora Z , Ruffolo Robert R , Yue Tian‐Li
Published: January 2005

Reactive oxygen species have been demonstrated to play a critical role in post‐ischaemic tissue injury. The present experiment was designed to evaluate the effects of SB 211475, a hydroxylated metabolite of the new β‐adrenoceptor antagonist, carvedilol, on rat splanchnic ischaemia (SI, 60 min) and reperfusion(R)‐induced shock and tissue injury.

Administration of SB 211475 two min before R attenuated SI/R injury in a dose‐dependent manner. At doses of 0.5 mg kg−1 and 1.0 mg kg−1, SB 211475 exerted significant anti‐shock and endothelial protective effects, characterized by prolonged survival times, increased survival rates, attenuated increases in tissue myeloperoxidase activity and haematocrits, and preserved endothelium‐dependent vasorelaxation.

Administration of 1 mg kg−1 carvedilol attenuated shock‐induced tissue injury and endothelial dysfunction. However, administration of 0.5 mg kg−1 carvedilol had no protective effects on post‐ischaemic tissue injury.

Previous studies have shown that SB 211475 has virtually no β‐blocking activity but possesses more potent antioxidant activity than carvedilol. In the present study, SB 211475 exerted more potent protective effects than the parent compound, suggesting that this metabolite of carvedilol is superior to carvedilol with regard to its protection against post‐ischaemia tissue injury.

British Journal of Pharmacology (1998) 123, 292–298; doi:10.1038/sj.bjp.0701598
Protective effects of mercaptoethylguanidine, a selective inhibitor of inducible nitric oxide synthase, in ligature‐induced periodontitis in the rat
Authors: Lohinai Zsolt , Benedek Péter , Fehér Erzsébet , Györfi Adrienn , Rosivall László , Fazekas Árpád , Salzman Andrew L. , Szabó Csaba
Published: January 2005

Excessive production of nitric oxide (NO), and the generation of peroxynitrite have been implicated in various proinflammatory conditions. In the present study, using mercaptoethylguanidine (MEG), a selective inhibitor of iNOS and a peroxynitrite scavenger, we investigated the role of iNOS and peroxynitrite in a rat model of periodontitis.

Periodontitis was produced in rat by a ligature of 2/0 braided silk placed around the cervix of the lower left 1st molar. Animals were then divided into two groups: one group of rats was treated with MEG (30 mg kg−1, i.p., 4 times per day for 8 days), animals in the other group received vehicle. At day 8, the gingivomucosal tissue encircling the mandibular 1st molars was removed on both sides from ligated and sham operated animals for inducible nitric oxide synthase (iNOS) activity assay and for immunocytochemistry with anti‐iNOS serum. Plasma extravasation was measured with the Evans blue technique. Alveolar bone loss was measured with a videomicroscopy.

Ligation caused a significant, more than 3 fold increase in the gingival iNOS activity, whereas it did not affect iNOS activity on the contralateral side, when compared to sham‐operated animals. Immunohistochemical analysis revealed iNOS‐positive macrophages, lymphocytes and PMNs in the connective tissue and immunoreactive basal layers of epithelium on side of the ligature, and only a few iNOS‐reactive connective tissue cells on the contralateral side. Ligation significantly increased Evans blue extravasation in gingivomucosal tissue and alveolar bone destruction compared to the contralateral side. MEG treatment significantly reduced the plasma extravasation and bone destruction.

The present results demonstrated that ligature‐induced periodontitis increases local NO production and that MEG treatment protects against the associated extravasation and bone destruction. Based on the present data, we propose that enhanced formation of NO and peroxynitrite plays a significant role in the pathogenesis of periodontitis.

British Journal of Pharmacology (1998) 123, 353–360; doi:10.1038/sj.bjp.0701604
Effects of the Aconitum alkaloid mesaconitine in rat hippocampal slices and the involvement of α‐ and β‐adrenoceptors
Authors: Ameri Angela
Published: January 2005

The effects of mesaconitine, the main alkaloid contained in Aconiti tuber, were investigated by use of extracellular recordings of stimulus‐evoked population spikes and field excitatory postsynaptic potentials (e.p.s.ps) in the CA1 region of rat hippocampal slices.

At a concentration of 10 nM, mesaconitine evoked excitations, which were manifested as an increase in the amplitude of the orthodromic spike and the appearance of multiple spikes following the first postsynaptic spike, without affecting the magnitude of paired‐pulse facilitation. The increase in spike amplitude was persistent and was not reversed by up to 90 min of washout. At concentrations of 30 and 100 nM, the alkaloid produced a biphasic effect, that is an excitation followed by an inhibition without having any effect upon the field e.p.s.p. At concentrations above 100 nM, mesaconitine suppressed the orthodromic population spike and the field e.p.s.p.

The excitatory effect was also observed when electrical stimulation was stopped completely during the application of mesaconitine (10 nM) and during the first 15 min of washout.

The enhancement of the population spike and the appearance of multiple spikes induced by mesaconitine (10–100 nM) were blocked by pretreatment with the β‐adrenoceptor antagonists propranolol (1 μM) and timolol (1 μM), whereas the inhibitory effect was blocked by the α‐adrenoceptor antagonists yohimbine (1 μM) and phentolamine (10 μM). However, when the β‐adrenoceptor antagonist timolol was added 10 min after the application of mesaconitine, it failed to block the long‐lasting enhancement of the spike amplitude and the appearance of multiple population spikes.

Application of the selective β‐adrenoceptor agonist isoprenaline (500 nM) to the hippocampal slices induced an increase in the amplitude of the orthodromic population spike and elicited 2–3 additional spikes. Mesaconitine (10 nM) did not further potentiate this enhancement of the spike amplitude when added after a 15 min pretreatment with isoprenaline.

Perfusion of forskolin, which directly activates adenylate cyclase, enhanced the population spike. Mesaconitine had no additional effect when applied after pretreatment with forskolin.

It is concluded that the excitatory effects evoked by lower concentrations of the plant alkaloid mesaconitine are mediated by stimulation of β‐adrenoceptors and the consequent activation of intracellular processes which lead to the long‐lasting changes in excitability.

British Journal of Pharmacology (1998) 123, 243–250; doi:10.1038/sj.bjp.0701608
Platelets, neutrophils, and vasoconstriction after arterial injury by angioplasty in pigs: effects of MK‐886, a leukotriene biosynthesis inhibitor
Authors: Provost Patrick , Borgeat Pierre , Merhi Yahye
Published: January 2005

Leukotrienes constitute a class of potent bioactive mediators known to play a pivotal role in inflammation. Since their biosynthesis has been shown to be enhanced by platelet‐neutrophil interactions, leukotrienes may be involved in these interactions and the arterial response to injury. Therefore, we investigated the effects of the selective leukotriene biosynthesis inhibitor 3‐[1‐(4‐chlorobenzyl)‐3‐t‐butyl‐thio‐5‐isopropylindol‐2‐yl]‐2,2‐dimethylpropanoic acid (MK‐886) on the acute thrombotic and vasomotor responses after arterial injury by angioplasty.

Carotid arterial injury was produced by balloon dilatation in control (molecusol vehicle; n=10) and treated (MK‐886, 10 mg kg−1, i.v.; n=9) pigs. The acute thrombotic reaction following deep arterial wall injury was quantified with 51Cr labelled platelets and 111In labelled neutrophils, and the vasomotor response was determined angiographically.

Platelet deposition at the site of deep arterial wall injury averaged 56.4±11.0×106 platelets cm−2 in the control group, and was significantly reduced to 18.2±3.8×106 platelets cm−2 (P<0.005) by treatment with MK‐886. Neutrophil deposition was also decreased by MK‐886, from 242.8±36.8 to 120.9±20.3×103 neutrophils cm−2 (P<0.01). MK‐886‐treated animals had a significant decrease in the postangioplasty vasoconstrictive response at the site of endothelial injury distally, from 37.5±3.1% in the control group to 13.5±2.5% (P<0.001).

The effects of MK‐886 were associated with a profound inhibition of ex vivo leukotriene B4 (LTB4) synthesis in blood stimulated by the calcium ionophore A23187 and a significant reduction of neutrophil aggregation in whole blood (P<0.01), whereas neutrophil superoxide anion production, serum thromboxane B2 and platelet aggregation in whole blood were not influenced.

The relevant effects of MK‐886 are primarily related to inhibition of neutrophil function and suggest an important modulatory role for leukotrienes in the pathophysiological response associated with platelet and neutrophil interactions following arterial injury in vivo.

British Journal of Pharmacology (1998) 123, 251–258; doi:10.1038/sj.bjp.0701611
Effect of L‐buthionine‐(S,R)‐sulphoximine, an inhibitor of γ‐glutamylcysteine synthetase on peroxynitrite‐ and endotoxic shock‐induced vascular failure
Authors: Cuzzocrea Salvatore , Zingarelli Basilia , O'Connor Michael , Salzman Andrew L. , Szabó Csaba
Published: January 2005

Peroxynitrite, a cytotoxic oxidant formed from the reaction of nitric oxide (NO) and superoxide is a mediator of cellular injury in ischaemia/reperfusion injury, shock and inflammation. Here we investigated whether L‐buthionine‐(S,R)‐sulphoximine (BSO), an inhibitor of γ‐glutamylcysteine synthetase, alters endothelial and vascular smooth muscle injury in response to peroxynitrite in vitro and during endotoxic shock in vivo.

In human umbilical vein endothelial cells and in rat aortic smooth muscle cells, BSO (1 mM, for 24 h) enhanced, whereas glutathione (3 mM) or glutathione ethyl ester (3 mM) attenuated the peroxynitrite (100–1000 μM)‐induced suppression of mitochondrial respiration (measured by the conversion of 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) to formazan), formation of nitrotyrosine (detected by Western blotting), protein oxidation (measured by detection of 2,4 dinitrophenylhydrazine‐reactive carbonyls), and DNA single strand breakage and activation of the nuclear enzyme poly (ADP‐ribose) synthetase (PARS) (measured by the incorporation of radiolabelled NAD+ into nuclear proteins and by the alkaline unwinding assay, respectively). Glutathione ethyl ester treatment reduced the BSO‐induced enhancement of peroxynitrite‐induced cytotoxicity.

In rat isolated thoracic aortic rings, BSO treatment (in vivo, at 1 g kg−1 intraperitoneally (i.p.) for 24 h) enhanced, whereas pretreatment with glutathione (in vitro, 3 mM) attenuated the peroxynitrite‐induced reduction of the contractions to noradrenaline, and the peroxynitrite‐induced impairment of the endothelium‐dependent relaxations to acetylcholine.

In BSO‐pretreated rats, treatment with bacterial lipopolysaccharide (LPS, 15 mg kg−1, i.p., for 6 h) caused a more pronounced vascular hyporeactivity and endothelial dysfunction ex vivo. BSO pretreatment also increased the degree of nitrotyrosine staining (detected by imunohistochemistry) in the aorta after LPS treatment.

In conclusion, our results demonstrate that L‐buthionine‐(S,R)‐sulphoximine, an inhibitor of γ‐glutamylcysteine synthetase enhances peroxynitrite‐ and endotoxic shock‐induced vascular failure. Based on these findings, we suggest that endogenous glutathione plays an important protective role against peroxynitrite‐ and LPS‐induced vascular injury.

British Journal of Pharmacology (1998) 123, 525–537; doi:10.1038/sj.bjp.0701612
Pharmacology of (S)‐homoquisqualic acid and (S)‐2‐amino‐5‐phosphonopentanoic acid [(S)‐AP5] at cloned metabotropic glutamate receptors
Authors: Bräuner‐Osborne Hans , Krogsgaard‐Larsen Povl
Published: January 2005

In this study we have determined the pharmacological profile of (S)‐quisqualic acid, (S)‐2‐amino‐4‐phosphonobutyric acid ((S)‐AP4) and their higher homologues (S)‐homoquisqualic acid, (S)‐2‐amino‐5‐phosphonopentanoic acid ((S)‐AP5), respectively, and (R)‐AP5 at subtypes of metabotropic (S)‐glutamic acid (mGlu) receptors expressed in Chinese hamster ovary cells.

(S)‐Quisqualic acid was a potent mGlu1/mGlu5 agonist (EC50 values of 1.1 μM and 0.055 μM, respectively) showing no activity at mGlu2 and weak agonism at mGlu4 (EC50∼1000 μM).

(S)‐Homoquisqualic acid displayed competitive antagonism at mGlu1 (KB=184 μM) and full agonism at mGlu5 (EC50=36 μM) and mGlu2 (EC50=23 μM), but was inactive at mGlu4.

(S)‐AP4 was a potent and selective mGlu4 agonist (EC50=0.91 μM) being inactive at mGlu1, mGlu2 and mGlu5 both as agonist and antagonist.

(S)‐AP5 displayed very weak agonist activity at mGlu4. At the mGlu2 receptor subtype (S)‐AP5 acted as a competitive antagonist (KB=205 μM), whereas the compound was inactive at mGlu1 and mGlu5. (R)‐AP5 was inactive at all mGlu receptor subtypes tested both as agonist and antagonist.

These studies demonstrate that incorporation of an additional carbon atom into the backbone of (S)‐glutamic acid and its analogues, to give the corresponding homologues, and replacement of the terminal carboxyl groups by isosteric acidic groups have profound effects on the pharmacological profiles at mGlu receptor subtypes. Furthermore, (S)‐homoquisqualic acid has been shown to be a potentially useful tool for differentiating mGlu1 and mGlu5.

British Journal of Pharmacology (1998) 123, 269–274; doi:10.1038/sj.bjp.0701616
Role of kinins in the endothelial protective effect of ischaemic preconditioning
Authors: Bouchard Jean‐François , Chouinard Jérôme , Lamontagne Daniel
Published: January 2005

The aim of this study was to assess whether the protective effect of ischaemic preconditioning on endothelial function in coronary arteries of the rat involves kinins.

Isolated hearts of the rat were exposed to a 30‐min low‐flow ischaemia (flow rate of 1 ml min−1) followed by 20‐min reperfusion, after which coronaries were precontracted with 0.1 μM U‐46619, and the response to the endothelium‐dependent vasodilator, 5‐hydroxytryptamine (5‐HT, 10 μM), compared to that of the endothelium‐independent vasodilator, sodium nitroprusside (SNP, 3 μM).

In untreated hearts, ischaemia‐reperfusion diminished selectively 5‐HT‐induced vasodilatation, compared with time‐matched sham hearts. The vasodilatation to SNP was unaffected after ischaemia‐reperfusion. Preconditioning (5 min of zero‐flow ischaemia followed by 10 min reperfusion) in untreated hearts preserved the vasodilatation produced by 5‐HT.

Blockade of B1 and B2 receptors with either 3 nM [Lys0, Leu8, des‐Arg9]‐bradykinin (LLDBK) or 10 nM Hoe 140 (icatibant), respectively, (started 15 min before ischaemic preconditioning or a corresponding sham period and stopped just before the 20‐min reperfusion period) had no effect on the vasodilatation produced by either 5‐HT or SNP in sham hearts. Pretreatment with Hoe 140 did not block the protective effect of ischaemic preconditioning on the 5‐HT vasodilatation. In contrast, LLDBK halved the protective effect of ischaemic preconditioning on endothelium‐dependent vasodilatation.

Perfusion with either bradykinin or des‐Arg9‐bradykinin (1 nM) 30 min before and lasting throughout the ischaemia protected the endothelium.

In conclusion, ischaemic preconditioning affords protection to the endothelial function in coronary resistance arteries of the rat partly by activation of B1 receptors. Although exogenous BK perfusion can protect the endothelium, B2 receptors do not play an important role in this protection in the rat isolated heart.

British Journal of Pharmacology (1998) 123, 413–420; doi:10.1038/sj.bjp.0701619
Effects of the enantiomers of R,S‐salbutamol on incompletely fused tetanic contractions of slow‐ and fast‐twitch skeletal muscles of the guinea‐pig
Authors: Prior Chris , Leonard Maureen B. , McCullough John R.
Published: January 2005

The effects of racemic R,S‐salbutamol, and its individual enantiomers have been studied on incompletely fused (sub‐tetanic) contractile responses of fast‐ and slow‐contracting isolated skeletal muscles of the guinea‐pig.

R,S‐salbutamol (2–4 μM) decreased the peak force of sub‐tetani in the slow‐contracting soleus muscle and increased the peak force of sub‐tetani in the fast‐contracting peroneus longus muscle. It also increased the force of the first twitch of sub‐tetani in both muscles. The decrease in the peak force of sub‐tetani in the soleus muscle was due to defusion of the individual twitches caused by a shortening of their time course.

The effects of 4 μM of the racemate on both fast‐ and slow‐contracting muscles were mimicked by 2 μM R‐salbutamol (levalbuterol). However, 2 μM S‐salbutamol was devoid of activity in both muscles.

We concluded that all the effects of R,S‐salbutamol on guinea‐pig skeletal muscles are due to the activity of the R‐enantiomer. Thus there is a common enantiomeric profile for the skeletal muscle and bronchorelaxant activity of the compound.

British Journal of Pharmacology (1998) 123, 558–564; doi:10.1038/sj.bjp.0701627
The inhibitory effect of propranolol on ATP‐sensitive potassium channels in neonatal rat heart
Authors: Xie Lai‐Hua , Takano Makoto , Noma Akinori
Published: January 2005

Whole cell and single channel recordings of ATP‐sensitive K+ current (IK,ATP) were carried out in ventricular myocytes isolated from neonatal rat hearts.

(±)‐Propranolol, a commonly used β‐blocker, inhibited the whole cell IK,ATP in a concentration‐dependent manner with a half‐maximal concentration (IC50) of 6.7±1.4 μM, whereas it blocked the inward rectifier K+ current (IK,1) only at much higher concentrations (IC50=102.4±20.2 μM). The inhibition was time‐ and voltage‐independent.

In the outside‐out patch configuration, (±)‐propranolol inhibited IK,ATP (IC50=9.8±2.9 μM) by decreasing the open probability of the channel without inducing additional noise in the open‐channel current or a decrease of single channel conductance. The single channel current of IK,1 was also blocked by (±)‐propranolol in the same way as IK,ATP.

(+)‐Propranolol, an optic isomer having no β‐blocking effect, inhibited IK,ATP (IC50=5.8±1.0 μM), whilst atenolol, a selective β1‐blocker had no effect. Neither GDPβS (1 mM) nor GTPγS (200 μM) included in the pipette solution modulated the inhibitory effect of (±)‐propranolol.

We concluded that the inhibitory effect of (±)‐propranolol was not via the β‐adrenergic signal transduction pathway, but by direct inhibition of IK,ATP channels.

British Journal of Pharmacology (1998) 123, 599–604; doi:10.1038/sj.bjp.0701630
Insulin‐releasing action of the novel antidiabetic agent BTS 67 582
Authors: McClenaghan Neville H. , Flatt Peter R. , Bailey Clifford J.
Published: January 2005

BTS 67 582 (1,1‐dimethyl‐2‐(2‐morpholinophenyl)guanidine fumarate) is a novel antidiabetic agent with a short‐acting insulin‐releasing effect. This study examined its mode of action in the clonal B‐cell line BRIN‐BD11.

BTS 67 582 increased insulin release from BRIN‐BD11 cells in a concentration‐dependent manner (10−8 to 10−4 M) at both non‐stimulating (1.1 mM) and stimulating (16.7 mM) concentrations of glucose.

BTS 67 582 (10−4 M) potentiated the insulin‐releasing effect of a depolarizing concentration of K+ (30 mM), whereas the K+ channel openers pinacidil (400 μM) and diazoxide (300 μM) inhibited BTS 67 582‐induced release.

Suppression of Ca+ channel activity with verapamil (20 μM) reduced the insulin‐releasing effect of BTS 67 582 (10−4 M).

BTS 67 582 (10−4 M) potentiated insulin release induced by amino acids (10 mM), and enhanced the combined stimulant effects of glucose plus either the fatty acid palmitate (10 mM), or agents which raise intracellular cyclic AMP concentrations (25 μM forskolin and 1 mM isobutylmethylxanthine), or the cholinoceptor agonist carbachol (100 μM).

Inhibition of glucose‐stimulated insulin release by adrenaline or noradrenaline (10 μM) was partially reversed by BTS 67 582 (10−4 M).

These data suggest that the insulin‐releasing effect of BTS 67 582 involves regulation of ATP‐sensitive K+ channel activity and Ca2+ influx, and that the drug augments the stimulant effects of nutrient insulin secretagogues and agents which enhance adenylate cyclase and phospholipase C. BTS 67 582 may also exert insulin‐releasing effects independently of ATP‐sensitive K+ channel activity.

British Journal of Pharmacology (1998) 123, 400–404; doi:10.1038/sj.bjp.0701631
Ipriflavone as an inhibitor of human cytochrome P450 enzymes
Authors: Monostory Katalin , Vereczkey László , Lévai Ferenc , Szatmári István
Published: January 2005

Reduction of theophylline metabolism and elimination were observed in a theophylline‐treated patient during ipriflavone administration. After withdrawal of ipriflavone, the serum theophylline level decreased to an extent similar to that found before administration of ipriflavone. The effects of ipriflavone and its major metabolites 7‐hydroxy‐isoflavone and 7‐(1‐carboxy‐ethoxy)‐isoflavone on cytochrome P450 activities were studied in vitro in human liver microsomes from three donors.

Ipriflavone and 7‐hydroxy‐isoflavone competitively inhibited phenacetin O‐deethylase and tolbutamide hydroxylase activity. The parent compound and its dealkylated metabolite were strong inhibitors exhibiting Ki values around 10–20 μM, while 7‐(1‐carboxy‐ethoxy)‐isoflavone had no effect on the cytochrome P450 activities investigated. 7‐Hydroxy‐isoflavone is the only one that influenced nifedipine oxidase activity. It competitively inhibited this activity with a Ki value of 129.5 μM.

The steady state concentrations of ipriflavone and 7‐hydroxy‐isoflavone in plasma of patients receiving 3×200 mg daily doses of ipriflavone for 48 weeks were found to be 0.33±0.32 μM and 1.44±0.77 μM, respectively.

The results indicate that the decrease in theophylline metabolism observed in a patient treated with ipriflavone may be due to a competitive interaction of ipriflavone or its metabolite, 7‐hydroxy‐isoflavone with CYP1A2. On the other hand, our in vitro findings predict some more interaction with CYP2C9.

British Journal of Pharmacology (1998) 123, 605–610; doi:10.1038/sj.bjp.0701633
State‐dependent NMDA receptor antagonism by Ro 8‐4304, a novel NR2B selective, non‐competitive, voltage‐independent antagonist
Authors: Kew James N C. , Trube Gerhard , Kemp John A.
Published: January 2005

Subunit‐selective blockade of N‐methyl‐D‐aspartate (NMDA) receptors provides a potentially attractive strategy for neuroprotection in the absence of undesirable side effects. Here, we describe a novel NR2B‐selective NMDA antagonist, 4‐{3‐[4‐(4‐fluoro‐phenyl)‐3,6‐dihydro‐2H‐pyridin‐1‐yl]‐2‐hydroxy‐propoxy}‐benzamide (Ro 8‐4304), which exhibits >100 fold higher affinity for recombinant NR1001/NR2B than NR1001/NR2A receptors.

Ro 8‐4304 is a voltage‐independent, non‐competitive antagonist of NMDA receptors in rat cultured cortical neurones and exhibits a state‐dependent mode of action similar to that described for ifenprodil.

The apparent affinity of Ro 8‐4304 for the NMDA receptor increased in an NMDA concentration‐dependent manner so that Ro 8‐4304 inhibited 10 and 100 μM NMDA responses with IC50s of 2.3 and 0.36 μM, respectively. Currents elicited by 1 μM NMDA were slightly potentiated in the presence of 10 μM Ro 8‐4304, and Ro 8‐4304 binding slowed the rate of glutamate dissociation from NMDA receptors.

These results were predicted by a reaction scheme in which Ro 8‐4304 exhibits a 14 and 23 fold higher affinity for the activated and desensitized states of the NMDA receptor, respectively, relative to the agonist‐unbound resting state. Additionally, Ro 8‐4304 binding resulted in a 3–4 fold increase in receptor affinity for glutamate site agonists.

Surprisingly, whilst exhibiting a similar affinity for NR2B‐containing NMDA receptors as ifenprodil, Ro 8‐4304 exhibited markedly faster kinetics of binding and unbinding to the NMDA receptor. This spectrum of kinetic behaviour reveals a further important feature of this emerging class of NR2B‐selective compounds.

British Journal of Pharmacology (1998) 123, 463–472; doi:10.1038/sj.bjp.0701634
Cyclothiazide and AMPA receptor desensitization: analyses from studies of AMPA‐induced release of [3H]‐noradrenaline from hippocampal slices
Authors: Cowen Michael S. , Beart Philip M.
Published: January 2005

Responses in brain produced by the activation of the α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionate (AMPA) subtype of ionotropic receptor for L‐glutamate are often rapidly desensitizing. AMPA‐induced desensitization and its characteristics, and the potentiating effect of cyclothiazide were investigated in vitro by analysing AMPA‐induced release of [3H]‐noradrenaline from prisms of rat hippocampus.

AMPA (1–1000 μM) stimulated the release of [3H]‐noradrenaline in a concentration‐dependent manner that was both calcium‐dependent and tetrodotoxin‐sensitive, and attenuated by the AMPA‐selective antagonists, NBQX (1 and 10 μM), LY 293558 (1 and 10 μM) and GYKI 52466 (10 and 30 μM).

By use of an experimental procedure with consecutive applications of AMPA (100 μM, 28 min apart), the second response was reduced, indicative of receptor desensitization, and was reversed by cyclothiazide in a concentration‐dependent manner (1–300 μM). The concentration‐response curve for AMPA‐induced release of [3H]‐noradrenaline was shifted leftwards, but the reversal by cyclothiazide of the desensitized response was partial and failed to reach the maximal response of the first stimulus.

Observations made with various schedules of cyclothiazide application indicated that the initial AMPA‐evoked response was already partially desensitized (150% potentiation by 100 μM cyclothiazide) and that the desensitization was not likely to be due to a time‐dependent diminution and was long‐lasting (second application of cyclothiazide was ineffective).

Co‐application of a number of drugs with actions on second messenger systems, in association with the second AMPA stimulus, revealed significant potentiation of the AMPA‐induced release of [3H]‐noradrenaline: forskolin (10 μM, +78%), Rp‐cAMPS (100 μM, +65%), Ro 31‐8220 (10 μM, + 163%) and thapsigargin (100 μM, +161%).

The AMPA receptor‐mediated response regulating the release of [3H]‐noradrenaline from rat hippocampal slices was desensitized and cyclothiazide acted to reverse partially the desensitization in a concentration‐dependent manner. Since the time‐course of desensitization was longer lasting than that noted in previous electrophysiological studies, multiple events may be involved in the down‐regulation of AMPA receptor activity including receptor phosphorylation and depletion of intracellular Ca2+ stores.

British Journal of Pharmacology (1998) 123, 473–480; doi:10.1038/sj.bjp.0701638
Transition of functional innervation in the developing porcine airway from nitrergic to catecholaminergic
Authors: Connellan D R. , Mitchell H W.
Published: January 2005

We determined the distribution and chemical nature of the inhibitory neurotransmitter(s) to the airway smooth muscle (ASM) before and after birth.

Relaxation responses to electrical field stimulation (EFS) were studied in isovolumic bronchial segments from foetal (approximately 100/115 days gestation) and adult (25 kg) pigs, and in isovolumic tracheal segments from the foetus, and tracheal smooth muscle strips from the adult pig. Preparations were conditioned in low doses of atropine (10−7 M) to reduce the effects of excitatory neurotransmission and then exposed to carbachol to produce submaximal muscle tone. Some studies were also carried out on bronchial segments from 4 week old pigs.

EFS (65 V, 2 ms, 5–20 Hz for 5 s) produced a TTX‐sensitive relaxation in epithelium‐intact and epithelium‐denuded preparations. In foetal bronchial and tracheal preparations, EFS‐induced relaxation was strongly inhibited by NG‐nitro‐L‐arginine (L‐NOARG, 10−6 to 10−4 M; P<0.01–0.001). However, in the adult, only relaxations of the trachea were inhibited by L‐NOARG; bronchi were resistant to L‐NOARG and also to N‐nitro‐L‐arginine methyl ester (L‐NAME, 10−4 M). The inhibitory actions of L‐NOARG (10−6 to 10−4 M) were substantially reversed by 10−2 M L‐arginine. Experiments with bronchial segments from 4 week old pigs showed partial inhibition of relaxations by L‐NOARG.

The L‐NOARG‐insensitive relaxations recorded in the adult bronchus were blocked by propranolol (10−6 M).

The onset of relaxation to EFS was more prompt and the rate of relaxation more rapid in foetal bronchi than in adult bronchi (P<0.0005). Maximum relaxation and recovery times were the same.

Foetal and adult bronchi were relaxed by sodium nitroprusside (SNP) with similar sensitivity and maximum effect. The rate of relaxation to SNP was not different in the two ages.

In the absence of atropine and carbachol, excitatory cholinergic responses to EFS (65 V, 2 ms, 5 Hz for 20 s) were not altered by L‐NOARG (10−4 M) or L‐NAME (10−4 M) in the adult bronchus but were modestly increased by L‐NOARG in the foetal bronchus (P<0.01).

The tracheobronchial tree appears functionally innervated by nitrergic input to the smooth muscle before birth. However, at or after 4 weeks of age the inhibitory neural input to the bronchi is catecholaminergic, but it remains nitrergic in the trachea. There is also a weak nitrergic pre‐ or postsynaptic inhibition of the effects of cholinergic neurotransmission in the foetal bronchus but not in the adult.

British Journal of Pharmacology (1998) 123, 712–718; doi:10.1038/sj.bjp.0701641
Identification of the L‐menthol binding site in guinea‐pig lung membranes
Authors: Wright C E. , Bowen W P. , Grattan T J. , Morice A H.
Published: January 2005

L‐Menthol inhibits both neurokinin A and capsaicin‐induced bronchoconstriction in the guinea‐pig and relaxes pre‐constricted guinea‐pig isolated bronchi. Structure‐activity relationships have been defined for the action of (−)‐menthol and related compounds on cold receptors, suggesting an action of L‐menthol at a pharmacological receptor. We have performed radioligand binding studies to characterize the binding sites for [3H]‐L‐menthol in whole cell membranes prepared from guinea‐pig lung tissue.

In kinetic studies, [3H]‐L‐menthol was found to bind rapidly and reversibly. Binding of [3H]‐L‐menthol to lung membranes was found to be time‐dependant becoming fully associated to its site within 40 min, and half‐maximum association occurred within 8 min (t1/2=8 min). [3H]‐L‐menthol was fully dissociated from its binding site within 8 min, (t1/2=2 min).

Inhibition studies presented a pharmacological profile of the ‘L‐menthol site’. Capsaicin, capsazepine, D‐menthol, eugenol, SCH23390 and camphor were all found to displace [3H]‐L‐menthol binding. In contrast WS3, noradrenaline, 5‐hydroxytryptamine, spiperone, flunarazine, bepridil and nicardipine were without effect.

We have identified a L‐menthol binding site in the guinea‐pig, which may represent a site common to a variety of compounds.

British Journal of Pharmacology (1998) 123, 481–486; doi:10.1038/sj.bjp.0701642
Effect of trimetazidine and verapamil on the cardiomyopathic hamster myosin phenotype
Authors: D'hahan Nathalie , Taouil Karima , Janmot Chantal , Morel Jean‐Emile
Published: January 2005

In this study we investigated whether long‐term trimetazidine (anti‐ischaemic drug) therapy alters the ventricular myosin heavy chain (MHC) isoform composition in a model of cardiomyopathy.

MHC isoforms were analysed in the native state by electrophoresis in a pyrophosphate buffer. Myosin isoform patterns were studied in cardiac muscle from cardiomyopathic hamsters (CMH) of the BIO 14 : 6 strain during the time course of the disease and compared with those of healthy golden hamsters (F1B). The correlation between myosin profile and Ca2+‐activated ATPase activity was determined from 220 days.

At the stage of insufficiency (350 days), CMH presented the most abnormal phenotype with 53% V1‐24% V3 compared to 79% V1‐7% V3 (P<0.001), in F1B. Trimetazidine was administered to cardiomyopathic hamsters from the early stage of active disease (30 days) to the congestive stages (220–350 days). Within 65 days, trimetazidine treatment, in CMH and F1B, reduced V1 to a low level (53% and 62%, respectively), which remained constant throughout the treatment. This level was similar to that in 220 and 350 days‐old untreated‐CMH. In sharp contrast, a standard calcium blocker, verapamil, administered to CMH in the same conditions resulted in a higher V1 (about 70%) and higher global myosin ATPase activity from 220 days.

Previous results in terms of hypertrophy and survival, compared to these results, suggest that verapamil and trimetazidine treatments reveal a disssociation between ventricular hypertrophy and isomyosin distribution. In addition, the shift in favour of V3 may not necessarily be an aggravating factor of the disease but an adaptative compensatory event.

British Journal of Pharmacology (1998) 123, 611–616; doi:10.1038/sj.bjp.0701643
Characterization of [3H]‐(2S,2′R,3′R)‐2‐(2′,3′‐dicarboxy‐ cyclopropyl)glycine ([3H]‐DCG IV) binding to metabotropic mGlu2 receptor‐transfected cell membranes
Authors: Cartmell Jayne , Adam Geo , Chaboz Sylvie , Henningsen Robert , Kemp John A. , Klingelschmidt Agnes , Metzler Veit , Monsma Frederick , Schaffhauser Hervé , Wichmann Jürgen , Mutel Vincent
Published: January 2005

The binding of the new selective group II metabotropic glutamate receptor radioligand, [3H]‐(2S,2′R,3′R)‐2‐(2′,3′‐dicarboxycyclopropyl)glycine ([3H]‐DCG IV), was characterized in rat mGlu2 receptor‐transfected CHO cell membranes.

[3H]‐DCG IV binding was pH‐dependent, but was not sensitive to temperature. Saturation analysis showed the presence of a single binding site, with a Kd value of 160 nM and a Bmax value of 10 pmol mg−1 protein. Binding was not sensitive to Na+‐dependent glutamate uptake blockers or Cl−‐dependent glutamate binding inhibitors. Furthermore, up to concentrations of 1 mM, the glutamate ionotropic receptor agonists, N‐methyl‐D‐aspartic acid (NMDA), (S)‐α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) and kainate, did not affect [3H]‐DCG IV binding.

Of the compounds observed to inhibit [3H]‐DCG IV binding, the most potent were the recently described selective group II agonist, (+)‐2‐aminobicyclo‐[3.1.0]hexane‐2,6‐dicarboxylate (LY 354740; Ki value 16 nM) and antagonist, 2‐amino‐2‐(2‐carboxycyclopropan‐1‐yl)‐3‐(dibenzopyran‐4‐yl) propanoic acid (LY 341495; Ki value 19 nM). As expected, for a G‐protein‐coupled receptor, guanosine‐5′‐O‐(3‐thiotriphosphate) (GTPγS) inhibited [3H]‐DCG IV binding in a concentration‐dependent manner, with an IC50 value of 12 nM.

A highly significant correlation was observed between the potencies of compounds able to inhibit [3H]‐DCG IV binding and potencies obtained for agonist activity in a GTPγ35S binding functional assay. In addition, these studies identified a number of compounds with previously unknown activity at mGlu2 receptors, including L(+)‐2‐amino‐3‐phosphonopropionic acid (L‐AP3), L(+)‐2‐amino‐5‐phosphonopentanoic acid (L‐AP5), 3‐((RS)‐2‐carboxypiperazin‐4‐yl)‐propyl‐1‐phosphonic acid (R‐CPP), N‐acetyl‐L‐aspartyl‐L‐glutamic acid (NAAG) and (RS)‐α‐methylserine‐O‐phosphate (MSOP).

British Journal of Pharmacology (1998) 123, 497–504; doi:10.1038/sj.bjp.0701647
Effects of rolipram on cyclic AMP levels in alveolar macrophages and lipopolysaccharide‐induced inflammation in mouse lung
Authors: Lucia Gonçalves de Moraes Vera , Singer Monique , Boris Vargaftig B. , Chignard Michel
Published: January 2005

Our previous work demonstrated that bacterial lipopolysaccharide (LPS), administered by aerosol, induced tumour necrosis factor (TNF‐α) synthesis leading to the infiltration of neutrophils into mice lungs. The treatment of animals with prostaglandin E2 or dibutyryl cyclic AMP impaired both processes. In this study, the target cell for LPS and the modulation by cyclic AMP of TNF‐α production and neutrophil recruitment were investigated.

One hour after inhalation of 2 ml of 0.3 mg ml−1 LPS, TNF‐α levels measured by an ELISA method increased in the bronchoalveolar lavage fluid (BALF) of BALB/c mice, reaching a maximal level 3 h after inhalation. The immunocytochemistry assay demonstrated that 1 h after inhalation, 21.2% of alveolar macrophages collected in the BALF were immunopositive for TNF‐α.

When mice were pretreated, i.p., with 20 mg kg−1 rolipram, a selective inhibitor of phosphodiesterase type 4, TNF‐α levels in the BALF were significantly reduced and only 7.3% of alveolar macrophages were immunopositive for TNF‐α.

Alveolar macrophages from rolipram‐treated mice collected 30 min after inhalation of LPS had a significant increase in the intracellular concentrations of cyclic AMP. This was accompanied by a marked reduction of TNF‐α levels in the BALF that were associated with a suppression of TNF‐α mRNA expression.

Systemic treatment with 20 mg kg−1 rolipram almost completely inhibited the LPS‐induced neutrophil recruitment, whereas it did not significantly reduce the recruitment induced by rmTNF‐α.

Our results indicate that alveolar macrophages may be the target cells for both the induction and control of the lung inflammatory response to LPS. They also suggest that systemic treatment with cyclic AMP‐elevating agents may be useful to control local inflammation resulting from inhalation of bacterial endotoxin.

British Journal of Pharmacology (1998) 123, 631–636; doi:10.1038/sj.bjp.0701649
Mechanisms of acute vasodilator response to bacterial lipopolysaccharide in the rat coronary microcirculation
Authors: Cannon Toby R. , Mann Giovanni E. , Baydoun Anwar R.
Published: January 2005

In this study the mechanisms of the acute vasodilator action of bacterial lipopolysaccharide (LPS) were investigated in the rat Langendorff perfused heart.

Infusion of LPS (5 μg ml−1) caused a rapid and sustained fall in coronary perfusion pressure (PP) of 59±4 mmHg (n=12) and a biphasic increase in NO levels determined in the coronary effluent by chemiluminescent detection. Both the fall in PP and the increase in NO release were completely abolished (n=3) by pretreatment of hearts with the NO synthase inhibitor L‐NAME (50 μM).

LPS‐induced vasodilatation was markedly attenuated to 5±4 mmHg (n=3) by pretreatment of hearts with the B2 kinin receptor antagonist Hoe‐140 (100 nM).

Vasodilator responses to LPS were also blocked by brief pretreatment with mepacrine (0.5 μM, n=3) or nordihydroguaiaretic acid (0.1 μM, n=4) and markedly attenuated by WEB 2086 (3 μM, n=4).

Thirty minutes pretreatment of hearts with dexamethasone (1 nM), but not progesterone (1 μM), significantly modified responses to LPS. The action of dexamethasone was time‐dependent, having no effect when applied either simultaneously with or pre‐perfused for 5 min before the administration of LPS but inhibiting the response to LPS by 91±1% (n=4) when pre‐perfused for 15 min. The inhibition caused by dexamethasone was blocked by 15 min pretreatment with the glucocorticoid receptor antagonist RU‐486 (100 nM) or by 2 min pre‐perfusion of a 1 : 200 dilution of LCPS1, a selective anti‐lipocortin 1 (LC1) neutralizing antibody.

Treatment with the protein synthesis inhibitor, cycloheximide (10 μM, for 15 min) selectively blunted LPS‐induced vasodilatation, reducing the latter to 3±5 mmHg (n=3), while having no effect on vasodilator responses to either bradykinin or sodium nitroprusside.

These results indicate that LPS‐induced vasodilatation in the rat heart is dependent on activation of kinin B2 receptors and synthesis of NO. In addition, phospholipase A2 (PLA2) is activated by LPS resulting in the release of platelet‐activating factor (PAF) and lipoxygenase but not cyclo‐oxygenase products. These effects are dependent on de novo synthesis of an intermediate protein which remains to be identified.

British Journal of Pharmacology (1998) 123, 637–644; doi:10.1038/sj.bjp.0701650