bluuebunny/crossref_metadata_2025 huggingface dataset:
Cardiovascular profile of the calcium sensitizer EMD 57033 in open‐chest anaesthetized pigs with regionally stunned myocardium
Authors: De Zeeuw Sandra , Trines Serge A I P , Krams Rob , Verdouw Pieter D , Duncker Dirk J
Published: January 2005

Ca2+ sensitizers enhance systolic function, but may impair relaxation in vitro; these effects may differ in stunned and normal myocardium. We therefore studied the effect of EMD 57033 on systolic and diastolic function of normal and stunned porcine myocardium in vivo.

Myocardial stunning by 15 min coronary occlusion and 30 min reperfusion abolished systolic shortening (SS) (baseline 13±1%) and decreased end‐systolic elastance (Ees) from 67±7 to 47±5 mmHg mm−1 (both P<0.05). Maximum rate of fall of myocardial elastance (dE/dtmin) decreased from −850±100 to −320±30 mmHg mm−1 s−1, while the time constant τe of the decay of elastance increased from 58±3 to 68±6 ms (both P<0.05). End‐diastolic elastance (Eed) was unchanged although the zero pressure intercept (L0,ed) had increased.

In the stunned region, EMD 57033 (0.2 mg kg−1 min−1 for 60 min, i.v., n=7) increased SS to 19±2%, Ees to 287±40 mmHg mm−1, dE/dtmin to −3630±640 mmHg mm−1 s−1 and decreased τe to 50±3 ms, while Eed remained unchanged. In the normal region, EMD 57033 increased SS from 14±2 to 18±3%, Ees from 59±4 to 263±23 mmHg mm−1, dE/dtmin from −480±70 to −2280±700 mmHg mm−1 s−1 and decreased τe from 91±12 to 61±3 ms (all P<0.05), while Eed remained unchanged. These responses were minimally affected by adrenoceptor blockade (n=7). Vehicle (n=7) had no effect on either region.

EMD 57033 increased cardiac output (up to 27±8%) and LVdP/dtmax (86±19%). Mean aortic pressure decreased (19±7%) due to systemic vasodilation that was not amenable to blockade of adrenoceptors or NO synthesis.

In conclusion, EMD 57033 restored systolic and diastolic function of stunned myocardium, and produced similar improvements in systolic and diastolic function in normal myocardium.

British Journal of Pharmacology (2000) 129, 1413–1422; doi:10.1038/sj.bjp.0703231
Comparison of the activity and disposition of the novel cholesterol absorption inhibitor, SCH58235, and its glucuronide, SCH60663
Authors: Van Heek Margaret , Farley Constance , Compton Douglas S , Hoos Lizbeth , Alton Kevin B , Sybertz Edmund J , Davis Harry R
Published: January 2005

Previous studies described the metabolism‐based discovery of a potent, selective inhibitor of intestinal absorption of cholesterol, SCH58235 (Ezetimibe). Here we demonstrate that the phenolic glucuronide (SCH60663) of SCH58235, was more potent at inhibiting cholesterol absorption in rats than SCH58235, when administered by the intraduodenal route.

To understand the increased potency of the glucuronide, the metabolism and distribution of SCH58235 and SCH60663 were studied in bile duct‐cannulated rats.

One minute after intraduodenal delivery of SCH58235, significant levels of compound were detected in portal plasma; >95% was glucuronidated, indicating that the intestine was metabolizing SCH58235 to its glucuronide. When intraduodenally delivered as SCH58235, the compound was glucuronidated, moved through the intestinal wall, into portal plasma, through the liver, and into bile. However, when delivered as SCH60663, >95% of the compound remained in the intestinal lumen and wall, which may explain its increased potency. Significant inhibition of cholesterol absorption and glucuronidation of SCH58235 occurred when SCH58235 was intravenously injected into bile duct‐cannulated rats. Autoradiographic analysis demonstrated that drug related material was located throughout the intestinal villi, but concentrated in the villus tip.

These data indicate that (a) SCH58235 is rapidly metabolized in the intestine to its glucuronide; (b) once glucuronidated, the dose is excreted in the bile, thereby delivering drug related material back to the site of action and (c) the glucuronide is more potent than the parent possibly because it localizes to the intestine. Taken together, these data may explain the potency of SCH58235 in the rat (ID50=0.0015 mg kg−1) and rhesus monkey (ID50=0.0005 mg kg−1).

British Journal of Pharmacology (2000) 129, 1748–1754; doi:10.1038/sj.bjp.0703235
The in vivo pharmacological profile of CS‐747, a novel antiplatelet agent with platelet ADP receptor antagonist properties
Authors: Sugidachi Atsuhiro , Asai Fumitoshi , Ogawa Taketoshi , Inoue Teruhiko , Koike Hiroyuki
Published: January 2005

CS‐747 is a novel antiplatelet agent that generates an active metabolite, R‐99224, in vivo. CS‐747 itself was totally inactive in vitro. This study examined in vivo pharmacological profiles of CS‐747 after single oral administration to rats.

Orally administered CS‐747 (0.3–10 mg kg−1) partially but significantly decreased [3H]‐2‐methylthio‐ADP binding to rat platelets. CS‐747 (3 mg kg−1, p.o.) treatment neutralized ADP‐induced decreases of cyclic AMP concentrations induced by prostaglandin E1, suggesting that metabolites of CS‐747 interfere with Gi‐linked P2T receptor.

CS‐747 (0.3 and 3 mg kg−1, p.o.) markedly inhibited ex vivo washed platelet aggregation in response to ADP but not to thrombin. CS‐747 also exhibited a marked inhibition of ADP‐induced ex vivo platelet aggregation in PRP with a rapid onset (<0.5 h) and long duration (>3 days) of action (ED50 at 4 h=1.2 mg kg−1).

R‐99224 (IC50=45 μM) inhibited in vitro PRP aggregation in a concentration‐related manner.

CS‐747 prevented thrombus formation in a dose‐related manner with an ED50 value of 0.68 mg kg−1. CS‐747 was more potent than clopidogrel (6.2 mg kg−1) and ticlopidine (>300 mg kg−1).

CS‐747, clopidogrel, and ticlopidine prolonged the bleeding time. The order of potency of these agents in this activity was the same as that in antiaggregatory and antithrombotic activities.

These findings indicate that CS‐747 is an orally active and a potent antiplatelet and antithrombotic agent with a rapid onset and long duration of action, and warrants clinical evaluations of the agent.

British Journal of Pharmacology (2000) 129, 1439–1446; doi:10.1038/sj.bjp.0703237
Identification of the cytochrome P450 enzymes involved in the metabolism of cisapride: in vitro studies of potential co‐medication interactions
Authors: Bohets H , Lavrijsen K , Hendrickx J , Van Houdt J , Van Genechten V , Verboven P , Meuldermans W , Heykants J
Published: January 2005

Cisapride is a prokinetic drug that is widely used to facilitate gastrointestinal tract motility.

Structurally, cisapride is a substituted piperidinyl benzamide that interacts with 5‐hydroxytryptamine‐4 receptors and which is largely without central depressant or antidopaminergic side‐effects.

The aims of this study were to investigate the metabolism of cisapride in human liver microsomes and to determine which cytochrome P‐450 (CYP) isoenzyme(s) are involved in cisapride biotransformation. Additionally, the effects of various drugs on the metabolism of cisapride were investigated.

The major in vitro metabolite of cisapride was formed by oxidative N‐dealkylation at the piperidine nitrogen, leading to the production of norcisapride.

By using competitive inhibition data, correlation studies and heterologous expression systems, it was demonstrated that CYP3A4 was the major CYP involved. CYP2A6 also contributed to the metabolism of cisapride, albeit to a much lesser extent.

The mean apparent Km against cisapride was 8.6±3.5 μM (n=3). The peak plasma levels of cisapride under normal clinical practice are approximately 0.17 μM; therefore it is unlikely that cisapride would inhibit the metabolism of co‐administered drugs.

In this in vitro study the inhibitory effects of 44 drugs were tested for any effect on cisapride biotransformation. In conclusion, 34 of the drugs are unlikely to have a clinically relevant interaction; however, the antidepressant nefazodone, the macrolide antibiotic troleandomycin, the HIV‐1 protease inhibitors ritonavir and indinavir and the calcium channel blocker mibefradil inhibited the metabolism of cisapride and these interactions are likely to be of clinical relevance. Furthermore, the antimycotics ketoconazole, miconazole, hydroxy‐itraconazole, itraconazole and fluconazole, when administered orally or intravenously, would inhibit cisapride metabolism.

British Journal of Pharmacology (2000) 129, 1655–1667; doi:10.1038/sj.bjp.0703246
Effect of heparin on antigen‐induced airway responses and pulmonary leukocyte accumulation in neonatally immunized rabbits
Authors: Preuss Janet M H , Page Clive P
Published: January 2005

The effect of single administrations of aerosolized heparin, low molecular weight heparin (LMWH) and the linear polyanionic molecule, polyglutamic acid (PGA) were examined on antigen‐induced airway hyperresponsiveness and leukocyte accumulation in neonatally immunized rabbits.

Adult litter‐matched NZW rabbits immunized within 24 h of birth with Alternaria tenuis antigen were treated with heparin, LMWH or PGA prior to or following antigen challenge (Alternaria tenuis). For each drug‐treated group, a parallel group of rabbits were treated with the appropriate vehicle. In all groups, airway responsiveness to inhaled histamine and bronchoalveolar lavage (BAL) was performed 24 h prior to and following antigen challenge.

Basal lung function in terms of resistance (RL) and dynamic compliance (Cdyn) and acute bronchoconstriction was unaltered by pre‐treatment with heparin, LMWH or PGA compared to their respective vehicles 24 h prior to or following antigen challenge.

In vehicle‐treated animals, airway hyperresponsiveness to inhaled histamine was indicated by an increase in the maximal responses of the cumulative concentration‐effect curves to histamine and reductions in RLPC50 and CdynPC35 values 24 h following antigen challenge.

Heparin and LMWH given prior to antigen challenge significantly inhibited the development of airway hyperresponsiveness, whereas PGA did not. When given following antigen challenge, all three drugs failed to inhibit the development of airway hyperresponsiveness.

Eosinophil and neutrophil cell numbers in BAL fluid increased significantly 24 h following antigen challenge. Heparin, LMWH and PGA failed to inhibit the increase in cell numbers following antigen challenge whether given prior to or following antigen challenge.

British Journal of Pharmacology (2000) 129, 1585–1596; doi:10.1038/sj.bjp.0703247
Neuropeptide Y regulates intracellular calcium through different signalling pathways linked to a Y1‐receptor in rat mesenteric small arteries
Authors: Prieto Dolores , Buus Carsten L , Mulvany Michael J , Nilsson Holger
Published: January 2005

Simultaneous measurements of intracellular calcium concentration ([Ca2+]i) and tension were performed to clarify whether the mechanisms which cause the neuropeptide Y (NPY)‐elicited contraction and potentiation of noradrenaline contractions, and the NPY inhibition of forskolin responses are linked to a single or different NPY receptor(s) in rat mesenteric small arteries.

In resting arteries, NPY moderately elevated [Ca2+]i and tension. These effects were antagonized by the selective Y1 receptor antagonist, (R)‐N2‐(diphenacetyl)‐N‐[(4‐hydroxyphenyl)methyl]‐D‐arginineamide (BIBP 3226) (apparent pKB values of 8.54±0.25 and 8.27±0.17, respectively).

NPY (0.1 μM) caused a near 3 fold increase in sensitivity to noradrenaline but did not significantly modify the tension‐[Ca2+]i relationship for this agonist. BIBP 3226 competitively antagonized the contractile response to NPY in arteries submaximally preconstricted with noradrenaline (pA2 7.87±0.20).

In arteries activated by vasopressin, the adenylyl cyclase activator forskolin (3 μM) induced a maximum relaxation and a return of [Ca2+]i to resting levels. NPY completely inhibited these effects. The contractile responses to NPY in arteries maximally relaxed with either sodium nitroprusside (SNP) or nifedipine were not significantly higher than those evoked by the peptide at resting tension, in contrast to the contractions to NPY in forskolin‐relaxed arteries. BIBP 3226 competitively antagonized the contraction to NPY in forskolin‐relaxed arteries with a pA2 of 7.92±0.29.

Electrical field stimulation (EFS) at 8–32 Hz caused large contractions in arteries relaxed with either forskolin or noradrenaline in the presence of phentolamine. These responses to EFS were inhibited by BIBP 3226. Similar EFS in resting, non‐activated arteries did not produce any response.

The present results suggest that different intracellular pathways are linked to a single NPY Y1 receptor in intact rat mesenteric small arteries, and provide little support for involvement of other postjunctional NPY receptors in the contractile responses to NPY. Neurally released NPY also seems to act through Y1 receptors, and may serve primarily as an inhibitor of vasodilatation.

British Journal of Pharmacology (2000) 129, 1689–1699; doi:10.1038/sj.bjp.0703256
Allosteric modulators affect the efficacy of partial agonists for recombinant GABAA receptors
Authors: Maksay Gábor , Thompson Sally A , Wafford Keith A
Published: January 2005

Different α subunits of human γ‐aminobutyric acid type A (GABAA) receptors were transiently expressed together with β3 and γ2 subunits in Xenopus oocytes to examine the interactions of various GABAA agonists and representative allosteric modulators. Chloride currents elicited by agonists were measured using two electrode voltage clamp electrophysiology.

Where compounds behaved as full agonists, i.e. GABA on all subtypes and 4,5,6,7‐tetrahydroisoxazolo [5,4‐c]pyridin‐3‐ol (THIP) on α2β3γ2 GABAA receptors, agonist concentration‐response curves were shifted to the left by the benzodiazepine full agonist chlordiazepoxide and the anticonvulsant loreclezole, or to the right by the inverse agonist 6,7‐dimethoxy‐4‐ethyl‐β‐carboline‐3‐carboxylic acid methyl ester (DMCM), with no effect on the maximal currents (Imax).

In contrast, maximal responses for different partial GABAA agonists on all benzodiazepine‐sensitive αxβ3γ2 GABAA receptors were enhanced by chlordiazepoxide. Imax values for piperidine‐4‐sulphonic acid (P4S) on α1β3γ2, THIP on α3β3γ2, and 5‐(4‐piperidyl)isothiazol‐3‐ol (thio‐4‐PIOL) on α2β3γ2 and α5β3γ2 GABAA receptors were increased by chlordiazepoxide, while that for P4S on α1β3γ2 receptors was decreased by DMCM.

The Imax values for partial agonists were also enhanced by pentobarbitone, the neurosteroid allopregnanolone and loreclezole irrespective of receptor subtype or the nature of the partial agonist.

In the light of models of ligand‐gated ion channel receptor activation we suggest two possible mechanisms of action for the effects of allosteric modulators on partial agonist receptor activation: either selective modulation of agonist affinity for the open/closed state, or direct modulation of the gating process itself.

British Journal of Pharmacology (2000) 129, 1794–1800; doi:10.1038/sj.bjp.0703259
Mepyramine but not cimetidine or clobenpropit blocks pertussis toxin‐induced histamine sensitization in rats
Authors: Vleeming W , Hendriksen C F M , Van De Kuil A , Van Den Hout J W E , De Wildt D J
Published: January 2005

The effects of pertussis toxin (PT) and the role of histaminergic H1, H2 and H3 receptor blockade on the actions of histamine on blood pressure, heart rate, blood gas values, and mortality were studied in anaesthetized rats.

Four days after treatment with PT, histamine dose‐dependently decreased mean arterial blood pressure (MAP) and PT enhanced the histamine‐induced decrease in MAP. In the PT but not in the inactivated PT (IPT) or saline treated group three out of six animals died after the highest dose of histamine (300 mg kg−1, i.v.)

In order to determine the type of histamine receptor that mediates HS, 4 days after PT the selective antagonists mepyramine (H1), cimetidine (H2) and clobenpropit (H3) were administered 20 min before the challenge with histamine. Mepyramine completely inhibited both the enhanced histamine‐induced decrease in MAP and mortality brought about by PT. Cimetidine and clobenpropit had no protective effects, but rather enhanced the histamine‐induced mortality elicited by PT.

The present study shows that PT caused HS in rats which is primarily mediated via H1 and secondarily via H2 and H3 receptors. These results are considered to be a first step in the elucidation of the mechanism(s) of the HS test used in the quality control of acellular pertussis vaccine.

British Journal of Pharmacology (2000) 129, 1801–1807; doi:10.1038/sj.bjp.0703263
Characterization and distribution of prolactin releasing peptide (PrRP) binding sites in the rat – evidence for a novel binding site subtype in cardiac and skeletal muscle
Authors: Satoh Fumitoshi , Smith David M , Gardiner James V , Mahmoodi Mehdi , Murphy Kevin G , Ghatei Mohammad A , Bloom Stephen R
Published: January 2005

Prolactin releasing peptide (PrRP) was recently purified from bovine hypothalamus and binds to the orphan receptor, UHR‐1. We examined the distribution and kinetics of 125I‐PrRP binding in rat tissues together with molecular characterization by chemical cross‐linking and Northern blotting.

In this study 125I‐PrRP binding showed specificity and rapid association and dissociation.

Specific binding was found in membranes from rat tissues including brain (hypothalamus, medulla oblongata and cerebellum), pituitary, heart, soleus muscle, adipose tissue, kidney, adrenal gland, testis and small intestine. In hypothalamus, pituitary, heart and soleus competition analysis indicated only one class of binding site in each tissue. Binding affinity for PrRP (IC50) and binding site density (Bmax) respectively were 5.2±0.9 nM and 674±97 fmol mg protein−1 in hypothalamus (n=5), 1.4±0.6 nM and 541±126 fmol mg protein−1 in pituitary (n=3), 6.6±0.7 nM and 628±74 fmol mg protein−1 in heart (n=4) and 9.8±0.9 nM and 677±121 fmol mg protein−1 in soleus muscle (n=4).

Analysis of 125I‐PrRP‐binding site complexes by chemical cross‐linking showed a binding site Mr of 69,000 in hypothalamus and 41,000 in heart and soleus.

Northern analysis of polyA+ RNA from hypothalamus showed a 4.2 kb band as expected for UHR‐1, but heart and soleus showed a 4.8 kb band.

Taken together these results indicate that there may be different subtypes of PrRP binding sites in rat tissues which may differ from UHR‐1.

British Journal of Pharmacology (2000) 129, 1787–1793; doi:10.1038/sj.bjp.0703266
In vitro and in vivo effects of kinin B1 and B2 receptor agonists and antagonists in inbred control and cardiomyopathic hamsters
Authors: Hallé S , Gobeil F , Ouellette J , Lambert C , Regoli D
Published: January 2005

The aims of this study were to examine the possible alterations occurring in the effects of kinins on isolated aortae of inbred control (CHF 148) and cardiomyopathic (CHF 146) hamsters of 150–175 and 350–375 days of age.

Bradykinin (BK) and desArg9BK contracted isolated aortae (with or without endothelium) of hamsters of both strains and ages. After tissue equilibration (90 min), responses elicited by both kinin agonists were stable over the time of experiments. The patterns of isometric contractions of BK and desArg9BK were however found to be different; desArg9BK had a slower onset and a longer duration of action than BK.

Potencies (pEC50 values) of BK in all groups of hamsters were significantly increased by preincubating the tissues with captopril (10−5 M).

No differences in the pEC50 values and the Emax values for BK or desArg9BK were seen between isolated vessels from inbred control and cardiomyopathic hamsters.

The myotropic effect of BK was inhibited by the selective non peptide antagonist, FR 173657 (pIC50 7.25±0.12 at the bradykinin B2 receptor subtype (B2 receptor)). Those of desArg9BK, at the bradykinin B1 receptor subtype (B1 receptor) were abolished by either R 715 (pIC50 of 7.55±0.05; αE=0), Lys[Leu8]desArg9BK (pIC50 of 7.21±0.01; αE=0.22) or [Leu8]desArg9BK (pIC50 of 7.25±0.02; αE=0.18).

FR 173657 had no agonistic activity, exerted a non competitive type of antagonism and was poorly reversible (lasting more than 5 h) from B2 receptor. In vivo, FR 173657 (given per os at 1 and 5 mg kg−1, 1 h before the experiment) antagonized the acute hypotensive effect of BK in anaesthetized hamsters.

It is concluded that aging and/or the presence of a congenital cardiovascular disorder in hamsters are not associated with changes in the in vitro aortic responses to either BK or desArg9BK.

British Journal of Pharmacology (2000) 129, 1641–1648; doi:10.1038/sj.bjp.0703269
Exogenous cholecystokinin‐8 reduces vagal efferent nerve activity in rats through CCKA receptors
Authors: Bucinskaite Violeta , Kurosawa Mieko , Lundeberg Thomas
Published: January 2005

It has been proposed that the vagus nerve plays a role in mediating cholecystokinin‐8 (CCK‐8) effect on such gastric functions as motility, emptying and gastric acid secretion. To examine the contribution of the efferent pathways in realizing these effects, efferent mass activity in the ventral gastric vagal nerve in Sprague‐Dawley rats was recorded.

Intravenous infusion of CCK‐8 (0.1–1 nmol) suppressed the efferent activity. The effect of CCK‐8 was significantly reduced in animals with total subdiaphragmatic vagotomy in comparison to those with partial vagotomy.

Intravenous infusion of CCKA receptor antagonist L‐364,718 (1–100×10−6 g) blocked the response of vagal efferent activity to 0.1 nmol CCK‐8, but the CCKB receptor antagonist L‐365,260 (1–100×10−6 g) did not in the conditions of either partial or total vagotomy.

Intracisternal infusion of L‐364,718 (1×10−6 g) blocked the response of vagal efferent activity to 0.1 nmol CCK‐8 i.v.

Infusion of exogenous CCK‐8 did not affect the activity of supradiaphragmatic vagal afferents.

The results suggest that the effect of systemically administered CCK‐8 on vagal efferent activity is mediated by both peripherally (subdiaphragmatically) and centrally localized CCKA receptors.

British Journal of Pharmacology (2000) 129, 1649–1654; doi:10.1038/sj.bjp.0703270
Characterization of the ATPase released during sympathetic nerve stimulation of the guinea‐pig isolated vas deferens
Authors: Westfall T D , Sarkar S , Ramphir N , Westfall D P , Sneddon P , Kennedy C
Published: January 2005

The release of ATPase activity evoked by electrical field stimulation (EFS) (8 Hz, 25 s) was investigated in several tissues in which adenosine 5′‐triphosphate (ATP) acts as a neurotransmitter.

Superfusate collected during EFS of sympathetic nerves of the guinea‐pig, rat and mouse isolated vas deferens and parasympathetic nerves of the guinea‐pig isolated urinary bladder contained ATPase activity. ATP breakdown was fastest in superfusate collected from the guinea‐pig isolated vas deferens. However, EFS of the enteric nerves of the guinea‐pig isolated taenia coli did not release any detectable ATPase.

The ATPase released from the guinea‐pig isolated vas deferens metabolized ATP at similar rates at incubation temperatures of 37°C and 20°C. Lineweaver–Burke analysis of the initial rates of ATP hydrolysis gave a KM of 39 μM and a Vmax of 1039 pmol ATP metabolized min−1 ml−1 superfusate.

6‐N,N‐diethyl‐D‐β,γ‐dibromomethyleneATP (ARL 67156), pyridoxalphosphate‐6‐azophenyl‐2′,4′‐disulphonic acid (PPADS) and pyridoxal‐5′‐phosphate (P‐5‐P) all inhibited the ATPase activity in a concentration‐dependent manner with a potency order of ARL 67156=PPADS>P‐5‐P.

In conclusion, EFS of several tissues in which ATP is a neurotransmitter causes the release of an ATPase and activity is greatest in the guinea‐pig vas deferens. The enzyme has pharmacological and kinetic characteristics that are similar to ectonucleoside triphosphate diphosphohydrolases.

British Journal of Pharmacology (2000) 129, 1684–1688; doi:10.1038/sj.bjp.0703271
Central injection of nitric oxide synthase inhibitors increases peripheral interleukin‐6 and serum amyloid A: involvement of adrenaline from adrenal medulla
Authors: Song Dong‐Keun , Im Yeong‐Bin , Jung Jun‐Sub , Yan Ji‐Jing , Huh Sung‐Oh , Suh Hong‐Won , Kim Yung‐Hi
Published: January 2005

Accumulating evidence suggests that plasma levels of interleukin‐6 (IL‐6), a major cytokine stimulating the synthesis of acute phase proteins, are intimately regulated by the central nervous system (CNS).

In the present study, effects of intracerebroventricular (i.c.v) injection of NG‐nitro‐L‐arginine methyl ester (L‐NAME) or 7‐nitroindazole, nitric oxide synthase (NOS) inhibitors, on plasma IL‐6 levels and peripheral IL‐6 mRNA expression were examined in mice.

L‐NAME (0.1–2 μg per mouse i.c.v.) and 7‐nitroindazole (0.2–2 μg per mouse i.c.v.) induced a dose‐dependent increase in plasma IL‐6 levels and a subsequent increase in circulating serum amyloid A, a liver acute‐phase protein. In contrast, an intraperitoneal (i.p.) injection of L‐NAME up to the dose of 25 μg per mouse had no effect.

Pretreatment with yohimbine (α2‐adrenergic antagonist; 1 mg kg−1 i.p.), or ICI‐118,551 (β2‐adrenergic antagonist; 2 mg kg−1 i.p.), but not with prazosin (α1‐adrenergic antagonist; 1 mg kg−1 i.p.), nor betaxolol (β1‐adrenergic antagonist; 2 mg kg−1 i.p.), significantly inhibited the central L‐NAME‐induced plasma IL‐6 levels.

I.c.v. (50 μg per mouse) or i.p. (100 mg kg−1) pretreatment with 6‐hydroxydopamine had no effect on central L‐NAME‐induced plasma IL‐6 levels. However, intrathecal (i.t.) pretreatment with 6‐hydroxydopamine (20 μg per mouse) markedly inhibited central L‐NAME‐induced plasma IL‐6 levels. Both yohimbine (1.5 μg per mouse i.t.) and ICI‐118,551 (1.5 μg per mouse i.t.) were effective in inhibition of central L‐NAME‐induced plasma IL‐6 levels.

There was an elevation of base‐line plasma IL‐6 levels in adrenalectomized animals. The adrenalectomy‐enhanced levels were not further increased by central L‐NAME.

L‐NAME (2 μg per mouse i.c.v.) induced an increase in IL‐6 mRNA expression in liver, spleen, and lymph node.

These results suggest that NOS activity in the brain tonically down‐regulates peripheral IL‐6 by inhibiting adrenaline release from the adrenal medulla.

British Journal of Pharmacology (2000) 130, 41–48; doi:10.1038/sj.bjp.0703273
Peroxynitrite‐mediated release of arachidonic acid from PC12 cells
Authors: Guidarelli Andrea , Palomba Letizia , Cantoni Orazio
Published: January 2005

A short term exposure of PC12 cells to a concentration of tert‐butylhydroperoxide (tB‐OOH) causing peroxynitrite‐dependent DNA damage and cytotoxiticity promoted a release of arachidonic acid (AA) that was sensitive to phospholipase A2 (PLA2) inhibitors and insensitive to phospholipase C or diacylglycerol lipase inhibitors. The extent of AA release was also mitigated by nitric oxide synthase (NOS) inhibitors and peroxynitrite scavengers. Low levels (10 μM) of authentic peroxynitrite restored the release of AA mediated by tB‐OOH in NOS‐inhibited cells whereas concentrations of peroxynitrite of 20 μM, or higher, effectively stimulated a PLA2 inhibitor‐sensitive release of AA also in the absence of additional treatments. These results are consistent with the possibility that endogenous as well as exogenous peroxynitrite promotes activation of PLA2.

British Journal of Pharmacology (2000) 129, 1539–1542; doi:10.1038/sj.bjp.0703275
Neurokinin B‐ and specific tachykinin NK3 receptor agonists‐induced airway hyperresponsiveness in the guinea‐pig
Authors: Daoui Samira , Naline Emmanuel , Lagente Vincent , Emonds‐Alt Xavier , Advenier Charles
Published: January 2005

The aim of this study was to determine whether neurokinin B (NKB) or specific agonists of tachykinin NK3 receptors, [MePhe7]NKB and senktide, were able to induce airway hyperresponsiveness in guinea‐pigs. The effects of these compounds were compared to those of substance P (SP), neurokinin A (NKA) and the preferential tachykinin NK1 ([Sar9, Met(02)11]SP) or NK2 ([βAla8]NKA (4‐10)) receptor agonists.

In guinea‐pigs pretreated with phosphoramidon (10−4 M aerosol for 10 min) and salbutamol (8.7×10−3 M for 10 min), all tachykinins administrated by aerosol (3×10−7 to 10−4 M) induced airway hyperresponsiveness 24 h later, displayed by an exaggerated response to the bronchoconstrictor effect of acetylcholine (i.v.). The rank order of potency was: [βAla8]NKA (4‐10)>NKA=NKB=senktide=[MePhe7]NKB=[Sar9,Met(02)11]SP>SP.

Airway hyperresponsiveness induced by [MePhe7]NKB was prevented by the tachykinin NK3 (SR 142801) and NK2 (SR 48968) receptor antagonists.

Bronchoconstriction induced by tachykinins administered by aerosol was also determined. SP, NKA, NKB and the tachykinin NK1 and NK2 receptor agonist induced bronchoconstriction. The rank order of potency was: NKA=[βAla8]NKA (4‐10)>NKB=SP=[Sar9,Met(02)11]SP. Under similar conditions, and for concentrations which induce airway hyperresponsiveness, senktide and [MePhe7]NKB failed to induce bronchoconstriction.

It is concluded that tachykinin NK3‐receptor stimulation can induce airway hyperresponsiveness and that this effect is not related to the ability of tachykinins to induce bronchoconstriction.

British Journal of Pharmacology (2000) 130, 49–56; doi:10.1038/sj.bjp.0703278
Inhibitory mechanism of tranilast in human coronary artery smooth muscle cells proliferation, due to blockade of PDGF‐BB‐receptors
Authors: Watanabe Shinji , Matsuda Akihisa , Suzuki Yasuhiro , Kondo Kazunao , Ikeda Yasuhiko , Hashimoto Hisakuni , Umemura Kazuo
Published: January 2005

We have previously reported that tranilast, an anti‐allergic drug, prevented the experimental intimal thickening in the rat and mouse femoral arteries and its effect may be exerted through the inhibition of vascular smooth muscle cell proliferation. However, its inhibitory mechanism has yet to be understood.

In this study, we investigated the inhibitory effect of tranilast on platelet‐derived growth factor BB‐homodimer (PDGF‐BB) mediated signal transduction pathways in cultured human coronary artery smooth muscle cells (CASMCs).

Growth responses to PDGF‐BB were measured by [3H]‐thymidine incorporation or cell counting. Activation of DNA synthesis and augmentation of cell proliferation stimulated by PDGF‐BB in quiescent cultures of CASMCs were inhibited by tranilast in a concentration‐dependent manner.

Western blot analysis of lysates from CASMCs with an anti‐activated mitogen‐activated protein (MAP) kinase antibody revealed that tranilast (10–300 μM) inhibited MAP kinase activation by PDGF‐BB in a concentration‐dependent manner. Tranilast also reduced PDGF‐BB‐stimulated tyrosine phosphorylation of a 180 kDa band, corresponding in mass to the PDGF β‐receptor, as shown by immunoblots using an anti‐phosphotyrosine antibody.

Receptor‐binding study with [125I]‐PDGF‐BB on CASMCs showed that tranilast (10–1000 μM) inhibited the specific binding of PDGF‐BB to cell surface receptors in a concentration‐dependent manner. Scatchard analysis revealed that pretreatment with 300 μM tranilast decreased the maximum binding capacity (Bmax) from 27.6 to 18.0 fmol 106 cells−1 without affecting binding affinity (Kd∼0.15 nM), indicating a non‐competitive inhibition of the receptor binding.

These results suggest that the suppression of human CASMC growth by tranilast might be at least partly due to blockade of PDGF‐BB‐receptor binding.

British Journal of Pharmacology (2000) 130, 307–314; doi:10.1038/sj.bjp.0703285
The role of nitric oxide in the responses of the ovine digital artery to vasoactive agents and modification of these responses by endotoxin and cytokines
Authors: Pawson P , Reid J , Nolan A M
Published: January 2005

Laminitis, an important cause of lameness in domestic ungulates, occurs as a result of altered digital perfusion. Endotoxin and cytokines may mediate the vascular derangements observed through alterations in nitric oxide production. In this study, the vascular responses of the isolated ovine digital artery were examined and the influence of endotoxin and cytokines investigated.

Neither removal of the endothelium nor incubation with NG‐nitro‐L‐arginine methyl ester (L‐NAME, 300 μM) altered the response to phenylephrine (PE, 1 nMto 300 μM). Indomethacin (10 μM) decreased PE log EC50from −6.22±0.08 to −6.55±0.07. Acetylcholine (1 nMto 1 mM) and bradykinin (BK, 100 pMto 3 μM) induced endothelium‐dependent relaxation. Bradykinin‐induced relaxation was reduced byL‐NAME, Emaxfalling from −61.7±7.4 to −34.0±2.1%. Addition of indomethacin further reduced BK Emaxto −9.6±2.8%. Sodium nitroprusside (1 nMto 300 μM) produced endothelium‐independent relaxation that was unaffected byL‐NAME or indomethacin.

Following a 6 h incubation with endotoxin (3 μg ml−1), arterial responses to PE and BK did not differ from polymyxin B‐treated controls (10 μg ml−1). Arteries incubated for 6 h with interferon‐γ (IFN‐γ, 10 ng ml−1) and tumour necrosis factor‐α (TNF‐α, 5 ng ml−1) exhibited greater relaxation to BK (Emax−50.0±5.1%) than polymyxin B‐treated controls (Emax−33.1±4.0%), but did not differ in their response to PE.

Prolonged incubation (16 h) with endotoxin (3 μg ml−1) did not alter the response to PE, however incubation with IFN‐γ (10 ng ml−1), TNF‐α (5 ng ml−1) and interleukin‐1β (20 ng ml−1) for 16 h increased PE log EC50from −6.44±0.09 to −6.10±0.11.

Nitric oxide is an important mediator of endothelium‐dependent relaxation in ovine digital arteries but does not modulate PE‐induced vasoconstriction. Incubation with cytokines decreased the sensitivity of digital arteries to PE.

British Journal of Pharmacology(2000)130, 109–117; doi:10.1038/sj.bjp.0703286
In vivo effects of the 5‐HT6 antagonist SB‐271046 on striatal and frontal cortex extracellular concentrations of noradrenaline, dopamine, 5‐HT, glutamate and aspartate
Authors: Dawson L A , Nguyen H Q , Li P
Published: January 2005

Although the 5‐HT6 receptor subtype was identified some 5 years ago, very little is known about its function within the brain. Here we demonstrate, for the first time, the neurochemical effects of a selective 5‐HT6 receptor ligand. Using in vivo microdialysis in the freely moving rat, we evaluated the effects of the selective 5‐HT6 receptor antagonist SB‐271046 by simultaneous measurement of 5‐hydroxytryptamine (5‐HT), dopamine (DA), noradrenaline (NA), glutamate and aspartate from the striatum and frontal cortex. SB‐271046 did not alter basal levels of 5‐HT, DA and NA in either brain region. Similarly, there was no change basal levels of either of the excitatory amino acids within the striatum. In contrast, administration of SB‐271046 (10 mg kg−1 s.c.) produced a significant (P<0.05), tetrodotoxin‐dependent, increase in extracellular levels of both glutamate and aspartate within the frontal cortex, reaching maximum values of 375.4±82.3 and 215.3±62.1% of preinjection values, respectively.

British Journal of Pharmacology (2000) 130, 23–26; doi:10.1038/sj.bjp.0703288
Rapid desensitization of the TRH receptor and persistent desensitization of its constitutively active mutant
Authors: Zaltsman Ilona , Grimberg Hagit , Lupu‐Meiri Monica , Lifschitz Ilana , Oron Yoram
Published: January 2005

We studied rapid desensitization of the thyrotropin‐releasing hormone receptor (TRH‐R) or the m1‐muscarinic receptor (m1‐R) to a short challenge of threshold TRH concentration and persistent desensitization due to constitutive activity of a mutant TRH‐R.

Xenopus oocytes expressing TRH‐Rs and/or m1‐Rs were challenged for 15 s with threshold concentrations of TRH ([TRH]) and then immediately with supraoptimal [TRH] or acetylcholine ([ACh]). The threshold challenge caused desensitization of 50–57% of responses to subsequent supraoptimal stimulation with TRH or ACh.

The homologous desensitization was reversible within 60 s after removal of the agonist.

The protein kinase C (PKC) inhibitor, chelerythrine, inhibited the control responses by 30–40%, without affecting the desensitized responses. Chelerythrine or the phosphatase inhibitor, okadaic acid, had little effect on the kinetics of resensitization, indicating limited involvement of PKC.

In oocytes coexpressing wild type TRH‐Rs or m1‐Rs with a constitutively active TRH‐R mutant (C335Stop TRH‐R), a persistent desensitization (33–57%) of the responses to TRH or ACh was observed. Additionally, there was a complete loss of the rapid desensitization induced by threshold [TRH].

Chlorodiazepoxide (CDE), a competitive binding antagonist of TRH‐Rs and an inverse agonist of C335Stop TRH‐Rs, abolished the persistent desensitization induced by C335Stop TRH‐Rs and enabled the rapid desensitization, conferring the wild type phenotype on C335Stop TRH‐Rs. Chelerythrine had qualitatively the same effect as CDE.

In conclusion, unlike the rapid desensitization, the persistent desensitization caused by the constitutively active C335Stop TRH‐Rs is largely mediated by PKC. It abrogates, however, the rapid desensitization, suggesting a common mechanistic step(s).

British Journal of Pharmacology (2000) 130, 315–320; doi:10.1038/sj.bjp.0703291
Characterization of the binding of two novel glycine site antagonists to cloned NMDA receptors: evidence for two pharmacological classes of antagonists
Authors: Chopra Bela , Chazot Paul L , Stephenson F Anne
Published: January 2005

The potency of two novel glycine site antagonists, GV150,526A and GV196,771A, was assessed by their ability to inhibit the binding of [3H]‐MDL105,519 to cell homogenates prepared from mammalian cells transfected with either NR1‐1a, NR1‐2a, NR1‐1a/NR2A, NR1‐1a/NR2B, NR1‐1a/NR2C or NR1‐1a/NR2D NMDA receptor clones.

The inhibition constants (Kis) for GV150,526A displacement of [3H]‐MDL105,519 binding to either NR1‐1a or NR1‐2a expressed alone were not significantly different and were best fit by a one‐site binding model. GV150,526A inhibition to NR1‐1a/NR2 combinations was best fit by a two‐site model with the NR1‐1a/NR2C having an approximate 2–4 fold lower affinity compared to other NR1‐1a/NR2 receptors.

The Kis for GV196,771A displacement of [3H]‐MDL105,519 binding to NR1‐1a, NR1‐2a and all NR1‐1a/NR2 combinations was best fit by a two‐site binding model. There was no significant difference between the Kis for the binding to NR1‐1a and NR1‐2a; NR1‐1a/NR2A receptors had an approximate 4 fold lower affinity for GV196,771A compared to other NR1‐1a/NR2 combinations.

The Kis for both GV150,526A and GV196,771A for the inhibition of [3H]‐MDL105,519 binding to membranes prepared from adult rat forebrain were determined and compared to the values obtained for binding to cloned NMDA receptors.

The Kis for a series of glycine site ligands with diverse chemical structures were also determined for the inhibition of [3H]‐MDL105,519 binding to NR1‐1a/NR2A receptors. L689,560 displayed similar binding characteristics to GV150,526A.

It is suggested that glycine site antagonists may be divided into two classes based on their ability to distinguish between NR1 and NR1/NR2 receptors with respect to binding curve characteristics.

British Journal of Pharmacology (2000) 130, 65–72; doi:10.1038/sj.bjp.0703298
The phosphatidylinositol 4‐kinase inhibitor phenylarsine oxide blocks evoked neurotransmitter release by reducing calcium entry through N‐type calcium channels
Authors: Searl T J , Silinsky E M
Published: January 2005

The effects of the phosphatidylinositol 4‐kinase inhibitor, phenylarsine oxide (PAO), on acetylcholine (ACh) release and on prejunctional Ca2+ currents were studied at the frog neuromuscular junction using electrophysiological recording techniques.

Application of PAO (30 μM) increased both spontaneous ACh release reflected as miniature end‐plate potential (mepp) frequencies and evoked ACh release reflected as end‐plate potential (epp) amplitudes with a similar time course.

Following the initial increase in epp amplitudes produced by PAO, epps slowly declined and were eventually abolished after approximately 20 min. However, mepp frequencies remained elevated over this time period.

PAO (30 μM) also inhibited the perineural voltage change associated with Ca2+ currents through N‐type Ca2+ channels (prejunctional Ca2+ currents) at motor nerve endings. Addition of British anti‐lewisite (BAL, 1 mM), an inactivator of PAO, partially reversed both the inhibition of epps and the inhibition of the prejunctional Ca2+ current.

The effects of PAO on N‐type Ca2+ channels were investigated more directly using the whole cell patch clamp technique on acutely dissociated sympathetic neurons. Application of PAO (30–40 μM) to these neurons decreased the voltage‐activated calcium currents through N‐type Ca2+ channels, an effect that was partially reversible by BAL.

In combination, these results suggest that inhibition of neurotransmitter release by PAO occurs as a consequence of the inhibition of Ca2+ entry via N‐type calcium channels. The relationship between the effects of PAO on N‐type Ca2+ channels in motor nerve endings and in neuronal soma is discussed.

British Journal of Pharmacology (2000) 130, 418–424; doi:10.1038/sj.bjp.0703299
Evidence for a M1 muscarinic receptor on the endothelium of human pulmonary veins
Authors: Walch Laurence , Gascard Jean‐Pierre , Dulmet Elisabeth , Brink Charles , Norel Xavier
Published: January 2005

To characterize the muscarinic receptors on human pulmonary veins associated with the acetylcholine (ACh)‐induced relaxation, isolated venous and arterial preparations were pre‐contracted with noradrenaline (10 μM) and were subsequently challenged with ACh in the absence or presence of selective muscarinic antagonists.

ACh relaxed venous preparations derived from human lung with a pD2 value of 5.82±0.09 (n=16). In venous preparations where the endothelium had been removed, the ACh relaxations were abolished (n=4). ACh relaxed arterial preparations with a pD2 value of 7.06±0.14 (n=5).

Atropine (1 μM), the non selective antagonist for muscarinic receptors, inhibited ACh‐induced relaxations in human pulmonary veins. The affinity value (pKB value) for atropine was: 8.64±0.10 (n=5). The selective muscarinic antagonists (darifenacin (M3), himbacine (M2,M4), methoctramine (M2) and pFHHSiD (M1,M3)) also inhibited ACh‐induced relaxations in venous preparations. The pKB values obtained for these antagonists were not those predicted for the involvement of M2–5 receptors in the ACh‐induced relaxation in human pulmonary veins.

The pKB value for darifenacin (1 μM) was significantly greater in human pulmonary arterial (8.63±0.14) than in venous (7.41±0.20) preparations derived from three lung samples.

In human pulmonary veins, the pKB values for pirenzepine (0.5 and 1 μM), a selective antagonist for M1 receptors, were: 7.89±0.24 (n=7) and 8.18±0.22 (n=5), respectively. In the venous preparations, the pKB values derived from the functional studies with all the different muscarinic antagonists used were correlated (r=0.89; P=0.04; slope=0.78) with the affinity values (pKi values) previously published for human cloned m1 receptors in CHO cells.

These results suggest that the relaxations induced by ACh are due to the activation of M1 receptors on endothelial cells in isolated human pulmonary veins.

British Journal of Pharmacology (2000) 130, 73–78; doi:10.1038/sj.bjp.0703301
Modulation of 3H‐noradrenaline release by presynaptic opioid, cannabinoid and bradykinin receptors and β‐adrenoceptors in mouse tissues
Authors: Trendelenburg A U , Cox S L , Schelb V , Klebroff W , Khairallah L , Starke K
Published: January 2005

Release‐modulating opioid and cannabinoid (CB) receptors, β‐adrenoceptors and bradykinin receptors at noradrenergic axons were studied in mouse tissues (occipito‐parietal cortex, heart atria, vas deferens and spleen) preincubated with 3H‐noradrenaline.

Experiments using the OP1 receptor‐selective agonists DPDPE and DSLET, the OP2‐selective agonists U50488H and U69593, the OP3‐selective agonist DAMGO, the ORL1 receptor‐selective agonist nociceptin, and a number of selective antagonists showed that the noradrenergic axons innervating the occipito‐parietal cortex possess release‐inhibiting OP3 and ORL1 receptors, those innervating atria OP1, ORL1 and possibly OP3 receptors, and those innervating the vas deferens all four opioid receptor types.

Experiments using the non‐selective CB agonists WIN 55,212‐2 and CP 55,940 and the CB1‐selective antagonist SR 141716A indicated that the noradrenergic axons of the vas deferens possess release‐inhibiting CB1 receptors. Presynaptic CB receptors were not found in the occipito‐parietal cortex, in atria or in the spleen.

Experiments using the non‐selective β‐adrenoceptor agonist isoprenaline and the β2‐selective agonist salbutamol, as well as subtype‐selective antagonists, demonstrated the occurrence of release‐enhancing β2‐adrenoceptors at the sympathetic axons of atria and the spleen, but demonstrated their absence in the occipito‐parietal cortex and the vas deferens.

Experiments with bradykinin and the B2‐selective antagonist Hoe 140 showed the operation of release‐enhancing B2 receptors at the sympathetic axons of atria, the vas deferens and the spleen, but showed their absence in the occipito‐parietal cortex.

The experiments document a number of new presynaptic receptor locations. They confirm and extend the existence of marked tissue and species differences in presynaptic receptors at noradrenergic neurons.

British Journal of Pharmacology (2000) 130, 321–330; doi:10.1038/sj.bjp.0703305
Induced desensitization of the insulinotropic effects of antidiabetic drugs, BTS 67 582 and tolbutamide
Authors: McClenaghan Neville H , Ball Andrew J , Flatt Peter R
Published: January 2005

Acute and chronic mechanisms of action of novel insulinotropic antidiabetic drug, BTS 67 582 (1,1‐dimethyl‐2‐(2‐morpholinophenyl)guanidine fumarate), were examined in the stable cultured BRIN‐BD11 cell line.

BTS 67 582 (100–400 μM) stimulated a concentration‐dependent increase (P<0.01) in insulin release at both non‐stimulatory (1.1 mM) and stimulatory (8.4 mM) glucose.

Long‐term exposure (3–18 h) to 100 μM BTS 67 582 in culture time‐dependently decreased subsequent responsiveness to acute challenge with 200 μM BTS 67 582 or 200 μM tolbutamide at 12–18 h (P<0.001). Similarly 3–18 h culture with the sulphonylurea, tolbutamide (100 μM), also effectively suppressed subsequent insulinotropic responses to both BTS 67 582 and tolbutamide.

Culture with 100 μM BTS 67 582 or 100 μM tolbutamide did not affect basal insulin secretion, cellular insulin content, or cell viability and exerted no influence on the secretory responsiveness to 200 μM of the imidazoline, efaroxan.

While 18 h BTS 67 582 culture did not affect the insulin‐releasing actions (P<0.001) of 16.7 mM glucose, 10 mM arginine, 30 mM KCl, 25 μM forskolin or 10 nM phorbol‐12‐myristate 13‐acetate (PMA), significant inhibition (P<0.001) of the insulinotropic effects of 10 mM 2‐ketoisocaproic acid (KIC) and 10 mM alanine were observed.

These data suggest that BTS 67 582 shares a common signalling pathway to sulphonylurea but not imidazoline drugs. Desensitization of drug action may provide an important approach to dissect sites of action of novel and established insulinotropic antidiabetic agents.

British Journal of Pharmacology (2000) 130, 478–484; doi:10.1038/sj.bjp.0703306