bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of mefloquine on cardiac contractility and electrical activity in vivo, in isolated cardiac preparations, and in single ventricular myocytes
Authors: Coker Susan J , Batey Andrew J , Lightbown Ian D , Díaz Mary E , Eisner David A
Published: January 2005

To examine the possible cardiotoxicity of the antimalarial drug mefloquine, increasing doses (0.3–30 mg kg−1) were given i.v. to anaesthetized guinea‐pigs. Mefloquine did not alter ECG intervals significantly but gradually increased systolic blood pressure (at 3 mg kg−1) then had a depressor effect (at 10 mg kg−1). Death due to profound hypotension, probably resulting from cardiac contractile failure or AV block, occurred after either 10 mg kg−1 (2/6) or 30 mg kg−1 (4/6) mefloquine.

In isolated cardiac preparations mefloquine (3–100 μM) did not alter the effective refractory period but at the higher concentrations resting tension increased. Developed tension was reduced by 100 μM mefloquine in left atria (from 5.8±1.7 to 2.2±0.4 mN) whereas in papillary muscles although 30 μM mefloquine reduced developed tension (from 2.6±0.5 to 1.1±0.1 mN) subsequent addition of 100 μM caused a marked, but not sustained, positive inotropic effect (from 1.2±0.1 to 3.8±0.8 mN).

In single ventricular myocytes, mefloquine (10 μM) shortened action potential duration (e.g. APD90 from 285±29 to 141±12 ms) and reduced the amplitude of the systolic Ca2+ transient. These effects were accompanied by a decrease in the L‐type Ca2+ current.

These results indicate that the main adverse effect of mefloquine on the heart is a negative inotropic action. This action can be explained by blockade of L‐type Ca2+ channels.

British Journal of Pharmacology (2000) 129, 323–330; doi:10.1038/sj.bjp.0703060
Impaired relaxation of stomach smooth muscle in mice lacking cyclic GMP‐dependent protein kinase I
Authors: Ny Lars , Pfeifer Alexander , Aszòdi Attila , Ahmad Marianne , Alm Per , Hedlund Petter , Fässler Reinhard , Andersson Karl‐Erik
Published: January 2005

Guanosine 3′, 5′‐cyclic monophosphate (cyclic GMP)‐dependent kinase I (cGKI) is a major receptor for cyclic GMP in a variety of cells. Mice lacking cGKI exhibit multiple phenotypes, including severe defects in smooth muscle function. We have investigated the NO/cGMP‐ and vasoactive intestinal polypeptide (VIP)/adenosine 3′, 5′‐cyclic monophosphate (cyclic AMP)‐signalling pathways in the gastric fundus of wild type and cGKI‐deficient mice.

Using immunohistochemistry, similar staining patterns for NO‐synthase, cyclic GMP‐ and VIP‐immunoreactivities were found in wild type and cGKI‐deficient mice.

In isolated, endothelin‐1 (3 nM–3 μM)‐contracted, muscle strips from wild type mice, electrical field stimulation (1–16 Hz) caused a biphasic relaxation, one initial rapid, followed by a more slowly developing phase. In preparations from cGKI‐deficient mice only the slowly developing relaxation was observed.

The responses to the NO donor, SIN‐1 (10 nM–100 μM), and to 8‐Br‐cyclic GMP (10 nM–100 μM) were markedly impaired in strips from cGKI‐deficient mice, whereas the responses to VIP (0.1 nM–1 μM) and forskolin (0.1 nM–1 μM) were similar to those in wild type mice.

These results suggest that cGKI plays a central role in the NO/cGMP signalling cascade producing relaxation of mouse gastric fundus smooth muscle. Relaxant agents acting via the cyclic AMP‐pathway can exert their effects independently of cGKI.

British Journal of Pharmacology (2000) 129, 395–401; doi:10.1038/sj.bjp.0703061
Curcumin prevents adriamycin nephrotoxicity in rats
Authors: Venkatesan Narayanan , Punithavathi Durairaj , Arumugam Venkatesan
Published: January 2005

The present study investigated the effect of curcumin on adriamycin (ADR) nephrosis in rats. The results indicate that ADR‐induced kidney injury was remarkably prevented by treatment with curcumin. Treatment with curcumin markedly protected against ADR‐induced proteinuria, albuminuria, hypoalbuminaemia and hyperlipidaemia. Similarly, curcumin inhibited ADR‐induced increase in urinary excretion of N‐acetyl‐β‐D‐glucosaminidase (a marker of renal tubular injury), fibronectin and glycosaminoglycan and plasma cholesterol. Curcumin restored renal function in ADR rats, as judged by the increase in GFR. The data also demonstrated that curcumin protected against ADR‐induced renal injury by suppressing oxidative stress and increasing kidney glutathione content and glutathione peroxidase activity. In like manner, curcumin abolished ADR‐stimulated kidney microsomal and mitochondrial lipid peroxidation. These data suggest that administration of curcumin is a promising approach in the treatment of nephrosis caused by ADR.

British Journal of Pharmacology (2000) 129, 231–234; doi:10.1038/sj.bjp.0703067
Urothelium‐derived inhibitory factor(s) influences on detrusor muscle contractility in vitro
Authors: Hawthorn M H , Chapple C R , Cock M , Chess‐Williams R
Published: January 2005

The function of the bladder urothelium in modulating contractile responses of the underlying detrusor smooth muscle to muscarinic stimulation has been examined in the pig bladder. Saturation curves for [3H]‐QNB binding demonstrated a greater muscarinic receptor density in the urothelium than in the detrusor smooth muscle. The presence of an intact urothelium on isolated bladder strips inhibited contractions induced by carbachol but not KCl. Contractions of a urothelium‐denuded muscle strip were inhibited in the presence of a second bladder strip with an intact urothelium, but not if the second strip was denuded. The urothelium‐induced inhibition of contractions was not prevented in the presence of L‐NOARG, methylene blue, indomethacin, propranolol, suramin, TEA or apamin. The data suggest the presence of a diffusable, urothelium‐derived inhibitory factor, which could not be identified but appears to be neither nitric oxide, a cyclo‐oxygenase product, a catecholamine, adenosine, GABA nor an EDHF sensitive to apamin.

British Journal of Pharmacology (2000) 129, 416–419; doi:10.1038/sj.bjp.0703068
Characterization of prostanoid receptors mediating inhibition of histamine release from anti‐IgE‐activated rat peritoneal mast cells
Authors: Chan C L , Jones R L , Lau H Y A
Published: January 2005

Prostanoid receptors mediating inhibition of anti‐IgE induced histamine release from rat peritoneal mast cells have been characterized pharmacologically. PGD2 and the specific DP receptor agonists BW 245C and ZK 118182 were the most potent inhibitors with half‐maximal concentrations of 0.26, 0.06 and 0.02 μM respectively. The maximum inhibition attainable was 60–65% with 10−5 M BW 245C and ZK 118182.

Among several EP receptor agonists investigated, only PGE2 and the EP2/EP3 receptor agonist misoprostol induced significant inhibition (46.8±4.7% at 10−4 M and 18.7±6.8% at 10−5 M respectively). The IP receptor agonists cicaprost and iloprost were both less potent than the DP agonists in inhibiting histamine release (45.2±3.3% and 35.1±2.5% inhibition respectively at 10−5 M), whereas PGF2α and the TP receptor agonist U‐46619 were only marginally effective.

The EP4/TP receptor antagonist AH 23848 failed to affect the inhibitory actions of PGD2 or PGE2 even at 10−5 M, whereas the DP/EP1/EP2 receptor antagonist AH 6809 slightly enhanced the effect of PGD2 at 10−6 M.

At concentrations of 3×10−6 to 10−5 M, the putative DP receptor antagonist ZK 138357 dose‐dependently suppressed the inhibitory activities of the DP agonists, PGE2 and cicaprost. The antagonism of ZK 138357 against the DP receptor agonists appeared to be competitive with pA2 values of around six.

In conclusion, these data support our earlier proposal that an inhibitory DP receptor is the predominant prostanoid receptor in rat peritoneal mast cell. The properties of this receptor in relation to putative DP receptor subtypes reported in the literature are discussed.

British Journal of Pharmacology (2000) 129, 589–597; doi:10.1038/sj.bjp.0703072
A novel anionic conductance affects action potential duration in isolated rat ventricular myocytes
Authors: Spencer C Ian , Uchida Wataru , Kozlowski Roland Z
Published: January 2005

Effects of extracellular anions were studied in electrophysiological experiments on freshly isolated rat ventricular myocytes. Under current‐clamp, action potential duration (APD) was prolonged by reducing the extracellular Cl− concentration and shortened by replacement of extracellular Cl− with I−. Under voltage‐clamp, membrane potential steps or ramps evoked an anionic background current (IAB) carried by either Cl−, Br−, I− or NO3−. Activation of IAB was Ca2+‐ and cyclic AMP‐independent, and was unaffected by cell shrinkage. IAB was insensitive to stilbene and fenamate anion transport blockers at concentrations that inhibit Ca2+‐, cyclic AMP‐ and swelling‐activated Cl− currents in ventricular cells of other mammals. These results suggest that IAB may be carried by a novel class of Cl− channel. Correlation of anion substitution experiments on membrane current and action potentials revealed that IAB could play a major role in controlling rat ventricular APD. These findings have important implications for those studying cardiac Cl− channels as potential targets for novel antiarrythmic agents.

British Journal of Pharmacology (2000) 129, 235–238; doi:10.1038/sj.bjp.0703074
Somatostatin‐induced control of cytosolic free calcium in pituitary tumour cells
Authors: Petrucci Cristina , Cervia Davide , Buzzi Marco , Biondi Carla , Bagnoli Paola
Published: January 2005

In rat pituitary tumour cells (GC cells), spontaneous oscillations of the intracellular concentration of Ca2+ ([Ca2+]i) induce growth hormone (GH) secretion that is inhibited by octreotide, a somatostatin (SRIF) agonist which binds to SRIF subtype (sst) receptor 2. The effects of its functional activation on the control of [Ca2+]i were investigated using fluorimetric measurements of [Ca2+]i.

SRIF decreases the basal [Ca2+]i and the [Ca2+]i rise in response to forskolin (FSK) through the inhibition of L‐type voltage‐dependent Ca2+ channels.

Pretreatment with octreotide or with L‐Tyr8Cyanamid 154806, a sst2 receptor antagonist, abolishes the SRIF‐induced inhibition of [Ca2+]i. Octreotide is known to operate through agonist‐induced desensitization, while the antagonist operates through receptor blockade.

sst1 and sst2 receptor‐immunoreactivities (‐IRs) are localized to cell membranes. sst2, but not sst1 receptor‐IR, internalizes after cell exposure to octreotide.

SRIF‐induced inhibition of basal [Ca2+]i or FSK‐induced Ca2+ entry is blocked by pertussis toxin (PTX).

FSK‐induced cyclic AMP accumulation is only partially decreased by SRIF or octreotide, indicating that sst2 receptors are coupled to intracellular pathways other than adenylyl cyclase (AC) inhibition.

In the presence of H‐89, an inhibitor of cyclic AMP‐dependent protein kinase (PKA), SRIF‐induced inhibition of basal [Ca2+]i is still present, although reduced in amplitude.

SRIF inhibits [Ca2+]i by activating sst2 receptors. Inhibition of AC activity is only partly responsible for this effect, and other transduction pathways may be involved.

British Journal of Pharmacology (2000) 129, 471–484; doi:10.1038/sj.bjp.0703075
Evidence against potassium as an endothelium‐derived hyperpolarizing factor in rat mesenteric small arteries
Authors: Lacy Peter S , Pilkington Gemma , Hanvesakul Rajesh , Fish Helen J , Boyle John P , Thurston Herbert
Published: January 2005

Endothelium‐derived hyperpolarizing factor (EDHF) has recently been identified as potassium released from endothelial cells into the myo‐endothelial space. The present study was designed to test this hypothesis.

In rat small mesenteric arteries, mounted in a wire myograph, relaxation to acetylcholine or potassium was not significantly changed following incubation with oxadiazolo‐quinoxalin‐1‐one (ODQ, 4 μM) and indomethacin (10 μM, n=9).

Maximal relaxations to acetylcholine occurred in all arteries, were maintained and were significantly greater (P<0.01, n=9) than the transient relaxations to potassium, which only occurred in 30–40% of vessels.

Removal of the vascular endothelium abolished relaxant responses both to potassium and acetylcholine (P<0.005, n=9).

Compared with responses in 5.5 mM potassium PSS, relaxation responses to added potassium in arteries maintained in 1.5 mM potassium PSS were more marked and were not dependent on the presence of an intact endothelium (n=8).

Incubation with BaCl2 (50 μM) significantly inhibited the maximal relaxant response to potassium in the presence of an intact endothelium in 5.5 mM potassium PSS (P<0.05, n=4), but had no effect on relaxation of de‐endothelialized preparations in 1.5 mM potassium PSS (n=5).

Treatment with ouabain (0.1 mM) abolished the relaxant response to potassium in 1.5 mM potassium PSS (P<0.001, n=9), but only partly inhibited the maximal relaxant response to acetylcholine in 5.5 mM potassium PSS (P<0.01, n=5).

These data show that at physiological concentrations of potassium an intact endothelium is necessary for potassium‐induced relaxation in rat mesenteric arteries. Furthermore, the response to potassium is clearly different to that from acetylcholine, indicating that potassium does not mimic EDHF released by acetylcholine in these arteries.

British Journal of Pharmacology (2000) 129, 605–611; doi:10.1038/sj.bjp.0703076
Extracellular nucleotides activate the p38‐stress‐activated protein kinase cascade in glomerular mesangial cells
Authors: Huwiler Andrea , Wartmann Markus , Van Den Bosch Henk , Pfeilschifter Josef
Published: January 2005

Extracellular ATP and UTP have been reported to activate a nucleotide receptor (P2Y2‐receptor) that mediates arachidonic acid release with subsequent prostaglandin formation, a reaction critically depending on the activity of a cytosolic phospholipase A2. In addition, extracellular nucleotides trigger activation of the classical mitogen‐activated protein kinase (MAPK) cascade and cell proliferation as well as of the stress‐activated protein kinase (SAPK) cascade.

In this study, we report that ATP and UTP are also able to activate the p38‐MAPK pathway as measured by phosphorylation of the p38‐MAPK and its upstream activators MKK3/6, as well as phosphorylation of the transcription factor ATF2 in a immunocomplex‐kinase assay.

Time courses reveal that ATP and UTP induce a rapid and transient activation of the p38‐MAPK activity with a maximal activation after 5 min of stimulation which declined to control levels over the next 20 min.

A series of ATP and UPT analogues were tested for their ability to stimulate p38‐MAPK activity. UTP and ATP were very effective analogues to activate p38‐MAPK, whereas ADP and γ‐thio‐ATP had only moderate activating effects. 2‐Methyl‐thio‐ATP, βγ‐imido‐ATP, AMP, adenosine and UDP had no significant effects of p38‐MAPK activity. In addition, the extracellular nucleotide‐mediated effect on p38‐MAPK was almost completely blocked by 1 mM of suramin, a putative P2‐purinoceptor antagonist.

In summary, these results demonstrate for the first time that extracellular nucleotides are able to activate the MKK3/6‐ p38‐MAPK cascade most likely via the P2Y2‐receptor. Moreover, this finding implies that all three MAPK subtypes are signalling candidates for extracellular nucleotide‐stimulated cell responses.

British Journal of Pharmacology (2000) 129, 612–618; doi:10.1038/sj.bjp.0703077
The novel immunosuppressant SDZ‐RAD protects rat brain slices from cyclosporine‐induced reduction of high‐energy phosphates
Authors: Serkova Natalie , Litt Lawrence , Leibfritz Dieter , Hausen Bernard , Morris Randall E , James Thomas L , Benet Leslie Z , Christians Uwe
Published: January 2005

SDZ‐RAD, 40‐O‐(2‐hydroxyethyl)‐rapamycin, is a novel macrolide immunosuppressant. Because of its synergistic interaction, SDZ‐RAD is under clinical investigation as immunosuppressant in combination with cyclosporine after organ transplantation. Neurotoxicity is a critical side‐effect of cyclosporine.

We studied the effect of SDZ‐RAD and its combination with cyclosporine on high‐energy phosphates, phosphocreatine (PCr) and nucleoside triphosphates (NTP), in brain slices using 31P‐magnetic resonance spectroscopy (MRS).

Cyclosporine significantly reduced high‐energy phosphates after 2 h in a dose‐dependent manner (100 μg l−1: 93±3% of control (NTP), 91±3% (PCr); 500 μg l−1: 84±2% (NTP), 73±2 (PCr); 5000 μg l−1: 68±3% (NTP), 55±5% (PCr); n=6; P<0.02).

In contrast, after perfusion for 2 h, SDZ‐RAD (500 μg l−1 and 5000 μg l−1) significantly increased high‐energy phosphate concentrations in the brain slices (P<0.02). Even at the lowest concentration, SDZ‐RAD protected brain energy metabolism against cyclosporine toxicity: 100 μg l−1 SDZ‐RAD+5000 μg l−1 cyclosporine: 86±3% (NTP), 83±7% (PCr), n = 3, P<0.03 compared to cyclosporine alone. 5As evaluated using an algorithm based on Loewe isobolograms, the effects of SDZ‐RAD/ cyclosporine combinations on brain energy reduction were antagonistic. Both drugs were found in mitochondria using h.p.l.c‐MS analysis.

We conclude that cyclosporine inhibits mitochondrial high‐energy phosphate metabolism, which can be antagonized by SDZ‐RAD.

British Journal of Pharmacology (2000) 129, 485–492; doi:10.1038/sj.bjp.0703079
No contractile effect for 5‐HT1D and 5‐HT1F receptor agonists in human and bovine cerebral arteries: similarity with human coronary artery
Authors: Bouchelet Isabelle , Case Bruce , Olivier André , Hamel Edith
Published: January 2005

Using subtype‐selective 5‐HT1 receptor agonists and/or the 5‐HT1 receptor antagonist GR127935, we characterized in vitro the 5‐HT receptor that mediates the contraction of human and bovine cerebral arteries. Further, we investigated which sumatriptan‐sensitive receptors are present in human coronary artery by reverse‐transcriptase polymerase chain reaction (RT–PCR).

Agonists with affinity at the 5‐HT1B receptor, such as sumatriptan, alniditan and/or IS‐159, elicited dose‐dependent contraction in both human and bovine cerebral arteries. They behaved as full agonists at the sumatriptan‐sensitive 5‐HT1 receptors in both species. In contrast, PNU‐109291 and LY344864, selective agonists at 5‐HT1D and 5‐HT1F receptors, respectively, were devoid of any significant vasocontractile activity in cerebral arteries, or did not affect the sumatriptan‐induced vasocontraction. The rank order of agonist potency was similar in both species and could be summarized as 5‐HT=alniditan>sumatriptan=IS‐159>>>PNU‐109291=LY344864.

In bovine cerebral arteries, the 5‐HT1 receptor antagonist GR127935 dose‐dependently inhibited the vasoconstrictions elicited by both 5‐HT and sumatriptan, with respective pA2 values of 8.0 and 8.6.

RT–PCR studies in human coronary arteries showed a strong signal for the 5‐HT1B receptor while message for the 5‐HT1F receptor was weak and less frequently detected. Expression of 5‐HT1D receptor mRNA was not detected in any sample.

The present results demonstrate that the triptan‐induced contraction in brain vessels is mediated exclusively by the 5‐HT1B receptor, which is also present in a majority of human coronary arteries. These results suggest that selective 5‐HT1D and 5‐HT1F receptor agonists might represent new antimigraine drugs devoid of cerebro‐ and cardiovascular effects.

British Journal of Pharmacology (2000) 129, 501–508; doi:10.1038/sj.bjp.0703081
Antihyperglycemic action of isoferulic acid in streptozotocin‐induced diabetic rats
Authors: Liu I‐Min , Hsu Feng‐Lin , Chen Chieh‐Fu , Cheng Juei‐Tang
Published: January 2005

Wistar rats with streptozotocin‐induced diabetes (STZ‐diabetic rats), which is similar to human insulin‐dependent diabetic mellitus (IDDM), were employed to investigate the antihyperglycemic action of isoferulic acid.

A single intravenous injection of isoferulic acid decreased the plasma glucose in a dose‐dependent manner in the STZ‐diabetic rats. Repeated intravenous administration of STZ‐diabetic rats with isoferulic acid (5.0 mg kg−1) also resulted in the lowering of plasma glucose after one day.

Stimulatory effects of isoferulic acid on the glucose uptake and glycogen synthesis in soleus muscles isolated from STZ‐diabetic rats were also obtained indicating an increase of glucose utilization following isoferulic acid treatment which was not dependent on insulin.

The mRNA level of glucose transporter subtype 4 form (GLUT4) in soleus muscle was raised by isoferulic acid after repeated treatment for 1 day in STZ‐diabetic rats. Similar repeated treatment with isoferulic acid reversed the elevated mRNA level of phosphoenolpyruvate carboxykinase (PEPCK) in liver of STZ‐diabetic rats to the normal level. However, expression of GLUT4 and PEPCK genes in nondiabetic rats were not influenced by similar treatment with isoferulic acid.

These results suggest that isoferulic acid can inhibit hepatic gluconeogenesis and/or increase the glucose utilization in peripheral tissue to lower plasma glucose in diabetic rats lacking insulin.

British Journal of Pharmacology (2000) 129, 631–636; doi:10.1038/sj.bjp.0703082
Effects of some isoprostanes on the human umbilical artery in vitro
Authors: Oliveira L , Stallwood N A , Crankshaw D J
Published: January 2005

Cumulative concentration‐effect curves for the selective prostanoid TP receptor agonist U46619 and six isoprostanes were constructed in the human isolated umbilical artery.

All compounds except 8‐iso‐PGF3α produced concentration‐dependent contractions. The contractile response to the isoprostanes increased with each cumulative addition up to a point, after which subsequent addition reduced the contraction below the previous level. This [downturn] in the concentration‐effect curve did not occur with U46619.

The potencies of the compounds tested were as follows (pEC50±s.e.mean): U46619, 6.7±0.2; 8‐iso‐PGE2, 6.5±0.1; 8‐iso‐PGF2α, 5.8±0.2; 8‐iso‐PGE1, 5.4±0.1; 8‐iso‐PGF1α, 5.0±0.1; 8‐iso‐PGF2β> 4.8; 8‐iso‐PGF3α>> 4.8 (n=4–17). Neither 8‐iso‐PGF2β nor 8‐iso‐PGF3α at 44 μM had a significant effect on cumulative concentration‐effect curves to U46619.

The selective TP receptor antagonist GR32191 (0.1 μM) caused rightward shifts in the concentration‐effect curves to all the active compounds. pA2 values for GR32191 against U46619, 8‐iso‐PGE2, 8‐iso‐PGF2α, 8‐iso‐PGE1 were 7.6±0.2, 9±1, 8.2±0.3 and 7.7±0.3, respectively (n=4).

Neither Nω‐nitro‐L‐arginine methyl ester (100 μM) nor the selective DP receptor antagonist BW A868C (50 nM) affected the complex concentration‐effect curve to 8‐iso‐PGE2 (n=3).

Stable contractions to U46619 (1–3 μM) were unaffected by anandamide at concentrations up to 60 μM.

British Journal of Pharmacology (2000) 129, 509–514; doi:10.1038/sj.bjp.0703083
Mechanisms of 17 β‐oestradiol induced vasodilatation in isolated pressurized rat small arteries
Authors: Shaw Linda , Taggart Michael J , Austin Clare
Published: January 2005

The influence of 17 β‐oestradiol on pressurized isolated rat mesenteric and coronary small arteries was investigated.

17 β‐oestradiol caused rapid (t1.0<5 mins) concentration‐dependent relaxations of pre‐contracted pressurized (50 mmHg) isolated rat mesenteric and coronary arteries. Similar responses were observed in both vessel types. Significant relaxations were only observed at concentrations exceeding 3 μM.

The vasodilatory responses in both types of artery were unaffected by 10 μM L‐nitro arginine (L‐NNA) alone or in the presence of 10 μM indomethacin, inhibitors of nitric oxide and prostaglandin synthesis respectively. They were also unaffected by the pre‐contracting agent used i.e. high K+ or U46619 (a thromboxane analogue).

Neither the oestrogen receptor antagonist ICI 182,780 (10 μM) nor the protein synthesis inhibitor cycloheximide (100 μM) had any effect on the responses of mesenteric arteries to 17 β‐oestradiol.

17 α‐oestradiol had only a minor effect on mesenteric arterial diameter over a concentration range similar to the effective vasodilatory range for 17 β‐oestradiol.

Membrane impermeant 17 β‐oestradiol conjugated to bovine serum albumin (β‐oestradiol‐17hemisuccinate‐BSA) (E‐H‐BSA) resulted in a vasodilatation of pressurized arteries.

Wortmannin, an inhibitor of myosin light chain kinase, near maximally relaxed pressurized mesenteric arteries although the time course for the response was significantly slower than that for 17 β‐oestradiol.

These results taken together suggest that the acute effects of 17 β‐oestradiol on isolated pressurized arterial tone may be due to effects directly on the vascular smooth muscle via non‐genomic mechanisms that involve a stereospecific interaction at the plasma membrane.

British Journal of Pharmacology (2000) 129, 555–565; doi:10.1038/sj.bjp.0703084
Cholecystokinin‐8 enhances nerve growth factor synthesis and promotes recovery of capsaicin‐induced sensory deficit
Authors: Manni Luigi , Lundeberg Thomas , Tirassa Paola , Aloe Luigi
Published: January 2005

Alterations of nerve growth factor (NGF) expression have been demonstrated during peripheral nerve disease and the impaired expression or synthesis and transportation of NGF has been correlated with the pathogenesis of several peripheral neuropathies. Since exogenous NGF administration seems to cause undesired side‐effects, therapeutical strategies based on the regulation of endogenous synthesis of NGF could prove useful in the clinical treatment of these disorders.

The aim of the present study was to analyse the effects of exogenous peripheral administration of the neuropeptide cholecystokinin‐8 (CCK‐8) on endogenous NGF synthesis, NGF mRNA and distribution of peripheral neuropeptides which are known to be regulated by this neurotrophin.

To address these questions we studied the effects of capsaicin (CAPS) before and after the administration of CCK‐8 on NGF levels, NGF mRNA expression and localization, and the concentration of substance P (SP) and calcitonin gene‐related peptide (CGRP) in peripheral tissue

These studies demonstrate that administration of the CCK‐8 induces an increase of NGF protein and mRNA in peripheral tissue. NGF level in paw skin of CAPS/CCK‐8‐treated mice is 3 fold higher than in controls (1241±110 pg gr−1 of tissue wet weight versus 414±110 pg gr−1 of controls) and nearly 6 fold higher than in CAPS‐treated mice (1241±110 pg gr−1 versus 248±27 pg gr−1). The increase of NGF is correlated with the recovery of impaired nocifensive behaviour and with an overexpression of SP and CGRP.

The evidence that CCK‐8 promotes the recovery of sensory deficits suggests a potential clinical use for this neuropeptide in peripheral neuropathies.

British Journal of Pharmacology (2000) 129, 744–750; doi:10.1038/sj.bjp.0703088
Non‐prostanoid prostacyclin mimetics as neuronal stimulants in the rat: comparison of vagus nerve and NANC innervation of the colon
Authors: Rudd John A , Qian Yue‐ming , Tsui Kenneth K C , Jones Robert L
Published: January 2005

The spontaneous activity of the rat isolated colon is suppressed by prostacyclin analogues such as cicaprost (IC50=4.0 nM). Activation of prostanoid IP1‐receptors located on NANC inhibitory neurones is involved. However, several non‐prostanoids, which show medium to high IP1 agonist potency on platelet and vascular preparations, exhibit very weak inhibitory activity on the colon. The aim of the study was to investigate this discrepancy.

Firstly, we have demonstrated the very high depolarizing potency of cicaprost on the rat isolated vagus nerve (EC50=0.23 nM). Iloprost, taprostene and carbacyclin were 7.9, 66, and 81 fold less potent than cicaprost, indicating the presence of IP1 as opposed to IP2‐receptors. Three non‐prostanoid prostacyclin mimetics, BMY 45778, BMY 42393 and ONO‐1301, although much less potent than cicaprost (195, 990 and 1660 fold respectively), behaved as full agonists on the vagus nerve.

On re‐investigating the rat colon, we found that BMY 45778 (0.1–3 μM), BMY 42393 (3 μM) and ONO‐1301 (3 μM) behaved as specific IP1 partial agonists, but their actions required 30–60 min to reach steady‐state and only slowly reversed on washing. This profile contrasted sharply with the rapid and readily reversible contractions elicited by a related non‐prostanoid ONO‐AP‐324, which is an EP3‐receptor agonist.

The full versus partial agonism of the non‐prostanoid prostacyclin mimetics may be explained by the markedly different IP1 agonist sensitivities of the two rat neuronal preparations. However, the slow kinetics of the non‐prostanoids on the NANC system of the colon remain unexplained, and must be taken into account when characterizing neuronal IP‐receptors.

British Journal of Pharmacology (2000) 129, 782–790; doi:10.1038/sj.bjp.0703090
Changes in the cytosolic Ca2+ concentration and Ca2+‐sensitivity of the contractile apparatus during angiotensin II‐induced desensitization in the rabbit femoral artery
Authors: Ushio‐Fukai Masuko , Yamamoto Hiromichi , Toyofuku Kazuki , Nishimura Junji , Hirano Katsuya , Kanaide Hideo
Published: January 2005

To investigate the underlying mechanism for the angiotensin II‐induced desensitization of the contractile response during the prolonged stimulation of the vascular smooth muscle, we determined the effects of angiotensin‐II on (1) cytosolic Ca2+ concentration ([Ca2+]i) and tension using fura‐2‐loaded medial strips of the rabbit femoral artery, (2) 45Ca2+ influx in ring preparations, and (3) Ca2+‐sensitivity of the contractile apparatus in α‐toxin permeabilized preparations.

In the presence of extracellular Ca2+, high concentrations of angiotensin‐II elicited biphasic increases in [Ca2+]i and tension, which consisted of initial transient and subsequent lower and sustained phases.

The 45Ca2+ influx initially increased after the application of 10−6 M angiotensin‐II, and thereafter gradually decreased. At 20 min after the application, there was a discrepancy between the level of [Ca2+]i and the extent of 45Ca2+ influx.

The relationships between [Ca2+]i and tension suggested that the angiotensin‐II‐induced increase in the Ca2+‐sensitivity of the contractile apparatus was maintained during the desensitization of smooth muscle contraction.

When 10−6 M angiotensin‐II was applied during the sustained phase of contraction induced by 118 mm K+‐depolarization, at 10 min after the application, the [Ca2+]i levels were significantly lower and the tension levels were significantly higher than those prior to the application of angiotensin‐II.

In conclusion, the decrease in [Ca2+]i, which is partially due to the inhibition of the Ca2+ influx, is mainly responsible for the desensitization evoked by high concentrations of angiotensin‐II, and angiotensin‐II seems to activate additional mechanisms which inhibit Ca2+ signaling during prolonged stimulation.

British Journal of Pharmacology (2000) 129, 425–436; doi:10.1038/sj.bjp.0703092
The mechanism of the decrease in cytosolic Ca2+ concentrations induced by angiotensin II in the high K+‐depolarized rabbit femoral artery
Authors: Ushio‐Fukai Masuko , Yamamoto Hiromichi , Nishimura Junji , Hirano Katsuya , Kanaide Hideo
Published: January 2005

Using front‐surface fluorometry of fura‐2‐loaded strips, and measuring the transmembrane 45Ca2+ fluxes of ring preparations of the rabbit femoral artery, the mechanism underlying a sustained decrease in the cytosolic Ca2+ concentration ([Ca2+]i) induced by angiotensin II (AT‐II) was investigated.

The application of AT‐II during steady‐state 118 mM K+‐induced contractions caused a sustained decrease in [Ca2+]i following a rapid and transient increase in [Ca2+]i, while the tension was transiently enhanced.

When the intracellular Ca2+ stores were depleted by thapsigargin, the initial rapid and transient increase in [Ca2+]i was abolished, however, neither the sustained decrease in [Ca2+]i nor the enhancement of tension were affected.

Depolarization with 118 mM K+ physiological salt solution containing 1.25 mM Ba2+ induced a sustained increase in both the cytosolic Ba2+ concentration ([Ba2+]i) level and tension. However, the application of 10−6 M AT‐II during sustained Ba2+‐contractions was found to have no effect on [Ba2+]i, but it did enhance tension.

After thapsigargin treatment, AT‐II neither decreased nor increased the enhanced Ca2+ efflux rate induced by 118 mM K+‐depolarization, whereas AT‐II did increase the enhanced 45Ca2+ influx and the 45Ca2+ net uptake induced by 118 mM K+‐depolarization.

Pretreatment with calphostin‐C, partially, but significantly inhibited the decrease in [Ca2+]i induced by AT‐II.

These findings therefore suggest that AT‐II stimulates Ca2+ sequestration into the thapsigargin‐insensitive Ca2+ stores, and thus induces a decrease in [Ca2+]i in the high external K+‐stimulated rabbit femoral artery.

British Journal of Pharmacology (2000) 129, 437–447; doi:10.1038/sj.bjp.0703093
Involvement of kinins in hyperresponsiveness induced by platelet activating factor in the human nasal airway
Authors: Turner P J , Dear J W , Foreman J C
Published: January 2005

The aim of this study was to investigate the role of kinins in the development of nasal hyperresponsiveness induced by platelet activating factor (PAF) in normal human subjects.

Intranasal administration of PAF, 60 μg, induced an increased responsiveness to histamine, 200 μg per nostril, 6 h later. This effect was abolished by pretreatment with the bradykinin B2 receptor antagonists icatibant and [1‐adamantaneacetyl‐D‐Arg0,Hyp3,β‐(2‐thienyl)‐Ala5,8,D‐Phe7]‐bradykinin ([Ad]‐BK), both at 200 μg, every 2 h following PAF administration.

In a separate experiment, utilizing the same protocol, nasal lavage was used to measure the release of mediators into the nasal cavity following treatment with PAF. PAF increased the levels of eosinophil cationic protein (ECP) and kinin detected in the lavage samples, compared with a saline control. The levels of these mediators were reduced by pretreatment with either icatibant or [Ad]‐BK.

Administration of lyso‐PAF, 60 μg intranasally, did not cause a rise in kinin or ECP levels in nasal lavage fluid.

Exogenous bradykinin, 500 μg, or a saline control, applied topically to the nasal mucosa every 30 min for 2 h, failed to cause hyperresponsiveness to histamine.

We conclude that bradykinin itself does not cause hyperresponsiveness, but is involved in the hyperresponsiveness induced by PAF in the human nasal airway.

British Journal of Pharmacology (2000) 129, 525–532; doi:10.1038/sj.bjp.0703095
Differential response to chloroethylclonidine in blood vessels of normotensive and spontaneously hypertensive rats: role of α1D‐ and α1A‐adrenoceptors in contraction
Authors: Ibarra Maximiliano , Pardo J Pablo , López‐Guerrero J Javier , Villalobos‐Molina Rafael
Published: January 2005

The effects of chloroethylclonidine on α1‐adrenoceptor‐mediated contraction in endothelium‐denuded caudal arteries and aorta from normotensive Wistar and Wistar Kyoto (WKY), and from spontaneously hypertensive (SHR) rats were evaluated.

Chloroethylclonidine elicited concentration‐dependent contractions. Maximal contraction was similar in caudal arteries among strains (∼40% of noradrenaline effect). However, chloroethylclonidine elicited a higher contraction in aorta from SHR than from normotensive rats. In Wistar aorta chloroethylclonidine produced the smallest contractile response.

In SHR aorta, BMY 7378 and 5‐methylurapidil blocked chloroethylclonidine‐elicited contraction, while (+)‐cyclazocine did not inhibit it; while in caudal arteries, 5‐methylurapidil blocked chloroethylclonidine action; the other antagonists had no effect.

In chloroethylclonidine‐treated aorta noradrenaline elicited biphasic contraction‐response curves, indicating a high affinity (pD2, 8.5–7.5) chloroethylclonidine‐sensitive component and a low affinity (pD2, 6.3–5.2) chloroethylclonidine‐insensitive component. The high affinity component was blocked by chloroethylclonidine; while in caudal arteries noradrenaline elicited monophasic contraction‐response curves with pD2 values (6.5–5.7) similar to the low affinity component in aorta.

Chloroethylclonidine inhibition of noradrenaline response was greater in aorta than in caudal arteries. Chloroethylclonidine increased the EC50 values of noradrenaline ∼1000 fold in aorta and ∼10 fold in caudal arteries.

In SHR aorta BMY 7378 protected α1D‐adrenoceptors and in caudal arteries 5‐methylurapidil protected α1A‐adrenoceptors from chloroethylclonidine alkylation, allowing noradrenaline to elicit contraction.

These results show marked strain‐dependent differences in the ability of chloroethylclonidine to contract aorta; moreover, chloroethylclonidine stimulates α1D‐adrenoceptors in aorta and α1A‐adrenoceptors in caudal arteries. The higher contraction observed in aorta from SHR and WKY suggests an augmented number of α1D‐adrenoceptors in these strains.

British Journal of Pharmacology (2000) 129, 653–660; doi:10.1038/sj.bjp.0703097
The effects of heparin and related molecules upon the adhesion of human polymorphonuclear leucocytes to vascular endothelium in vitro
Authors: Lever Rebecca , Hoult J Robin S , Page Clive P
Published: January 2005

The effects of an unfractionated heparin preparation (Multiparin), a low molecular weight heparin preparation (Fragmin) and a selectively O‐desulphated derivative of heparin lacking anticoagulant activity, have been investigated for their effects on the adhesion of human polymorphonuclear leucocytes (PMNs) to cultured human umbilical vein endothelial cells (HUVECs) in vitro. The effect of poly‐L‐glutamic acid, a large, polyanionic molecule was also studied.

Unfractionated heparin (50–1000 U ml−1), the O‐desulphated derivative (0.3–6 mg ml−1) and the low molecular weight heparin (50 U–1000 U ml−1) all inhibited significantly the adhesion of 51Cr labelled PMNs to HUVECs stimulated with interleukin‐1β (IL‐1β; 10 U ml−1), bacterial lipopolysaccharide (LPS; 2.5 μg ml−1) or tumour necrosis factor‐α (TNF‐α; 125 U ml−1) for 6 h, whereas poly‐L‐glutamic acid had no effect. In addition, the three heparin preparations in the same concentration range inhibited significantly the adhesion of f‐met‐leu‐phe‐stimulated PMNs to resting HUVECs.

The effects of unfractionated heparin upon the expression of adhesion molecules intercellular adhesion molecule‐1 (ICAM‐1) and E‐selection were also investigated, as were the effects of unfractionated heparin upon adhesion of human PMNs to previously stimulated HUVECs. Heparin had little effect upon levels of expression of these adhesion molecules on stimulated HUVECs. However, a profound effect upon PMN adhesion to previously stimulated HUVECs was demonstrated using the same preparation, suggesting that inhibition of adhesion molecule expression is not a major component of the described inhibitory effects of heparin.

Pre‐incubation of PMNs with heparin followed by washing inhibited their adhesion to HUVECs, under different conditions of cellular activation, implying that heparin can bind to these cells and exert its anti‐adhesive effects even when not directly present in the system.

These observations would suggest that both heparin and a low molecular weight heparin are capable of inhibiting adhesion of human PMNs to endothelial cells, an effect not dependent solely upon the polyanionic nature of these molecules, nor dependent upon their ability to act as anticoagulants.

British Journal of Pharmacology (2000) 129, 533–540; doi:10.1038/sj.bjp.0703099
Isolation of the serotoninergic 5‐HT4(e) receptor from human heart and comparative analysis of its pharmacological profile in C6‐glial and CHO cell lines
Authors: Mialet Jeanne , Berque‐Bestel Isabelle , Eftekhari Pierre , Gastineau Monique , Giner Mireille , Dahmoune Yamina , Donzeau‐Gouge Patrick , Hoebeke Johan , Langlois Michel , Sicsic Sames , Fischmeister Rodolphe , Lezoualc'h Frank
Published: January 2005

RT–PCR technique was used to clone the human 5‐HT4(e) receptor (h5‐HT4(e)) from heart atrium. We showed that this h5‐HT4(e) receptor splice variant is restricted to brain and heart atrium.

Recombinant h5‐HT4(e) receptor was stably expressed in CHO and C6‐glial cell lines at 347 and 88 fmol mg−1 protein, respectively. Expression of h5‐HT4(e) receptors at the cell membrane was confirmed by immunoblotting.

The receptor binding profile, determined by competition with [3H]‐GR113808 of a number of 5‐HT4 ligands, was consistent with that previously reported for other 5‐HT4 receptor isoforms. Surprisingly, we found that the rank order of potencies (EC50) of 5‐HT4 agonists obtained from adenylyl cyclase functional assays was inversely correlated to their rank order of affinities (Ki) obtained from binding assays. Furthermore, EC50 values for 5‐HT, renzapride and cisapride were 2 fold lower in C6‐glial cells than in CHO cells.

ML10302 and renzapride behaved like partial agonists on the h5‐HT4(e) receptor. These results are in agreement with the reported low efficacy of the these two compounds on L‐type Ca2+ currents and myocyte contractility in human atrium.

A constitutive activity of the h5‐HT4(e) receptor was observed in CHO cells in the absence of any 5‐HT4 ligand and two 5‐HT4 antagonists, GR113808 and ML10375, behaved as inverse agonists.

These data show that the h5‐HT4(e) receptor has a pharmacological profile which is close to the native h5‐HT4 receptor in human atrium with a functional potency which is dependent on the cellular context in which the receptor is expressed.

British Journal of Pharmacology (2000) 129, 771–781; doi:10.1038/sj.bjp.0703101
Chlorotoxin does not inhibit volume‐regulated, calcium‐activated and cyclic AMP‐activated chloride channels
Authors: Maertens Chantal , Wei Lin , Tytgat Jan , Droogmans Guy , Nilius Bernd
Published: January 2005

It was the aim of this study to look for a high‐affinity and selective polypeptide toxin, which could serve as a probe for the volume‐regulated anion channel (VRAC) or the calcium‐activated chloride channel (CaCC). We have partially purified chlorotoxin, including new and homologous short chain insectotoxins, from the crude venom of Leiurus quinquestriatus quinquestriatus (Lqq) by means of gel filtration chromatography. Material eluting between 280 and 420 min, corresponding to fractions 15–21, was lyophilized and tested on VRAC and CaCC, using the whole‐cell patch‐clamp technique. We have also tested the commercially available chlorotoxin on VRAC, CaCC, the cystic fibrosis transmembrane conductance regulator (CFTR) and on the glioma specific chloride channel (GCC).

VRAC and the correspondent current, ICl,swell, was activated in Cultured Pulmonary Artery Endothelial (CPAE) cells by a 25% hypotonic solution. Neither of the fractions 16–21 significantly inhibited ICl,swell (n=4–5). Ca2+‐activated Cl− currents, ICl,Ca, activated by loading T84 cells via the patch pipette with 1 μM free Ca2+, were not inhibited by any of the tested fractions (15–21), (n=2–5).

Chlorotoxin (625 nM) did neither effect ICl,swell nor ICl,Ca (n=4–5). The CFTR channel, transiently transfected in COS cells and activated by a cocktail containing IBMX and forskolin, was not affected by 1.2 μM chlorotoxin (n=5). In addition, it did not affect currents through GCC.

We conclude that submicromolar concentrations of chlorotoxin do not block volume‐regulated, Ca2+‐activated and CFTR chloride channels and that it can not be classified as a general chloride channel toxin.

British Journal of Pharmacology (2000) 129, 791–801; doi:10.1038/sj.bjp.0703102
Wound collagen deposition in rats: effects of an NO‐NSAID and a selective COX‐2 inhibitor
Authors: Muscará Marcelo N , McKnight Webb , Asfaha Samuel , Wallace John L
Published: January 2005

Selective cyclo‐oxygenase (COX)‐2 inhibitors and nitric oxide‐releasing nonsteroidal anti‐inflammatory drugs (NSAIDs) exhibit reduced toxicity in the gastrointestinal tract, but may affect wound healing in other tissues. In this study, we have compared the effects of a selective COX‐2 inhibitor (celecoxib), a nitric‐oxide releasing derivative of naproxen (HCT‐3012) and naproxen in a model of wound collagen deposition in the rat.

Polyvinyl alcohol sponges were implanted subcutaneously in rats. The rats were treated daily for 5 days with the test drugs at equieffective anti‐inflammatory doses.

Naproxen (10 mg kg−1) significantly decreased (45%) collagen deposition at the wound site relative to the vehicle‐treated control group. In contrast, HCT‐3012 (14.5 mg kg−1) significantly increased (62%) collagen deposition, while celecoxib (10 mg kg−1) had no effect.

Naproxen and HCT‐3012 suppressed prostaglandin (PG) E2 levels at the wound site and whole blood thromboxane synthesis to similar degrees. Celecoxib had no significant effect on wound fluid PGE2 levels, but slightly reduced whole blood thromboxane synthesis (by 17%).

COX‐1 mRNA and protein were expressed in the wound exudate, the skin surrounding the wound and in normal skin. In contrast, COX‐2 mRNA, but not protein, was expressed in wound and normal skin.

These results demonstrate that HCT‐3012 can significantly enhance collagen deposition at a wound site, despite inhibiting prostaglandin synthesis to the same extent as the parent drug. Nitric oxide‐releasing NSAIDs may represent a safer alternative to standard NSAIDs for use as anti‐inflammatory and analgesic agents by post‐surgery patients.

British Journal of Pharmacology (2000) 129, 681–686; doi:10.1038/sj.bjp.0703112
Modulation of peristalsis by cannabinoid CB1 ligands in the isolated guinea‐pig ileum
Authors: Izzo Angelo A , Mascolo Nicola , Tonini Marcello , Capasso Francesco
Published: January 2005

The effect of cannabinoid drugs on peristalsis in the guinea‐pig ileum was studied. Peristalsis was induced by delivering fluid into the oral end of an isolated intestinal segment. Longitudinal muscle reflex contraction, threshold pressure and threshold volume to trigger peristalsis, compliance of the intestinal wall during the preparatory phase (a reflection of the resistance of the wall to distension) and maximal ejection pressure during the emptying phase of peristalsis were measured.

The cannabinoid agonists WIN 55,212‐2 (0.3–300 nM) and CP55,940 (0.3–300 nM) significantly decreased longitudinal muscle reflex contraction, compliance and maximal ejection pressure, while increased threshold pressure and volume to elicit peristalsis. These effects were not modified by the opioid antagonist naloxone (1 μM) and by the α‐adrenoceptor antagonist phentolamine (1 μM).

The inhibitory effect of both WIN 55,212‐2 and CP55,940 on intestinal peristalsis was antagonized by the cannabinoid CB1 receptor antagonist SR141716A (0.1 μM), but not by the cannabinoid CB2 receptor antagonist SR144528 (0.1 μM).

In absence of other drugs, the CB1 receptor antagonists SR141716A (0.01–1 μM) and AM281 (0.01–1 μM) slightly (approximatively 20%) but significantly increased maximal ejection pressure during the empty phase of peristalsis without modifying longitudinal muscle reflex contraction, threshold pressure, threshold volume to trigger peristalsis and compliance.

It is concluded that activation of CB1 receptors reduces peristalsis efficiency in the isolated guinea‐pig, and that the emptying phase of peristalsis could be tonically inhibited by the endogenous cannabinoid system.

British Journal of Pharmacology (2000) 129, 984–990; doi:10.1038/sj.bjp.0703116