bluuebunny/crossref_metadata_2025 huggingface dataset:
[Nphe1]‐Nociceptin (1‐13)‐NH2, a nociceptin receptor antagonist, reverses nociceptin‐induced spatial memory impairments in the Morris water maze task in rats
Authors: Redrobe J P , Calo G , Guerrini R , Regoli D , Quirion R
Published: January 2005

The present study was undertaken to investigate the effects of the novel nociceptin receptor antagonist, [Nphe1]‐Nociceptin (1‐13)‐NH2 (bilateral intrahippocampal injection, 50 nmole rat−1) on purported nociceptin‐induced (bilateral intrahippocampal injection, 5 nmole rat−1) deficits in spatial learning in the rat Morris water maze task. In addition, experiments were performed in an ‘open field’ to investigate possible peptide‐induced changes in exploratory behaviour.

Nociceptin significantly impaired the ability of the animal to locate the hidden platform throughout training (P<0.001 versus control group).

Pretreatment with [Nphe1]‐Nociceptin (1‐13)‐NH2 significantly blocked nociceptin‐induced impairment of spatial learning (P<0.001 versus nociceptin group).

A probe trial revealed that vehicle‐treated animals spent more time in the quadrant that had previously contained the hidden platform, whereas nociceptin‐treated animals did not spend more time in any one quadrant.

Learning impairments were not attributable to non‐specific deficits in motor performance or change in exploratory behaviour.

Taken together, our results reveal that [Nphe1]‐Nociceptin (1‐13)‐NH2 represents an effective and useful in vivo antagonist at the nociceptin receptors involved in learning and memory.

British Journal of Pharmacology (2000) 131, 1379–1384; doi:10.1038/sj.bjp.0703724
Partial to complete antagonism by putative antagonists at the wild‐type α2C‐adrenoceptor based on kinetic analyses of agonist : antagonist interactions
Authors: Pauwels Petrus J , Colpaert Francis C
Published: January 2005

Activation of the recombinant human α2C‐adrenoceptor (α2C AR) by (−)‐adrenaline in CHO‐K1 cells transiently co‐expressing a chimeric Gαq/i1 protein induced a rapid, transient Ca2+ response with a high‐magnitude followed by a low‐magnitude phase which continued throughout the recorded time period (15 min).

Activation of the α2C AR by various α2 AR agonists revealed the following rank order of high‐magnitude Ca2+ response [Emax (%) versus 10 μM (−)‐adrenaline]: UK 14304 (102±4)=talipexole (101±3)=(−)‐adrenaline (100)=d‐medetomidine (98±1)>oxymetazoline (81±4)⋍clonidine (75±5).

The methoxy‐ (RX 821002) and ethoxy‐derivatives (RX 811059) of idazoxan and the dexefaroxan analogue atipamezole were fully effective as antagonists of both the high‐ and the low‐magnitude Ca2+ response. However, though acting as full antagonists of the high‐magnitude response, the further putative α2 AR antagonists idazoxan (27%), SKF 86466 (29%) and dexefaroxan (59%) reversed the low‐magnitude response only partially.

In conclusion, kinetic analyses of agonist : antagonist interactions at the α2C AR demonstrate a wide spectrum of partial to complete antagonism of the low‐magnitude Ca2+ response for structurally related α2 AR ligands.

British Journal of Pharmacology (2000) 131, 1385–1390; doi:10.1038/sj.bjp.0703726
Human renal mesangial cells are a target for the anti‐inflammatory action of 9‐cis retinoic acid
Authors: Manzano V Moreno , Muñoz J C Sepúlveda , Jiménez J Rodriguez , Puyol M Rodriguez , Puyol D Rodriguez , Kitamura M , Cazaña F J Lucio
Published: January 2005

Mesangial cells play an active role in the inflammatory response to glomerular injury. We have studied in cultured human mesangial cells (CHMC) several effects of 9‐cis retinoic acid (9‐cRA), an activator of both retinoic acid receptors (RARs) and retinoid X receptors (RXRs).

9‐cRA inhibited foetal calf serum‐induced CHMC proliferation. It also prevented CHMC death induced by the inflammatory mediator H2O2. This preventive effect was not due to any increase in H2O2 catabolism and it persisted even when both catalase and glutathione synthesis were inhibited. Finally, 9‐cRA diminished monocyte adhesion to FCS‐stimulated CHMC. Interestingly, the retinoid also inhibited in FCS‐stimulated cells the protein expression of two mesangial adhesion molecules, fibronectin and osteopontin, but it did not modify the protein expression of intercellular adhesion molecule‐1 and vascular adhesion molecule‐1.

All major RARs and RXRs isotypes were expressed in CHMC regardless of the presence or absence of 9‐cRA. Transcripts to RAR‐α, RAR‐β and RXR‐α increased after incubation with 9‐cRA whereas RXR‐γ was inhibited, suggesting a major role for RARs and RXRs in 9‐cRA‐anti‐inflammatory effects.

9‐cRA was toxic only at 50 μM (a concentration 50–5000 times higher than required for the effects above). Cell death occurred by apoptosis, whose onset was associated with a pronounced increase in catalase activity and reduced glutathione content, being more effectively induced by all‐trans retinoic acid. Modulation of the oxidant/antioxidant balance failed to inhibit apoptosis.

We conclude that mesangial cells might be a target for the treatment of inflammatory glomerulopathies with 9‐cRA.

British Journal of Pharmacology (2000) 131, 1673–1683; doi:10.1038/sj.bjp.0703728
Enhanced contractile response to thrombin in the pregnant rat myometrium
Authors: Shintani Yoshinobu , Hirano Katsuya , Nishimura Junji , Nakano Hitoo , Kanaide Hideo
Published: January 2005

Thrombin causes various cellular events by activating protease‐activated receptors (PARs). Here, we showed, for the first time, that thrombin induced myometrial contraction. To determine the mechanism of thrombin‐induced myometrial contraction, we simultaneously measured intracellular Ca2+ concentration ([Ca2+]i) and tension of fura‐PE3‐loaded rat myometrium using front‐surface fluorimetry. The expression of thrombin receptor mRNA in the rat myometrium were determined by reverse transcription‐polymerase chain reaction analysis (RT–PCR analysis).

Thrombin (0.01–3 u ml−1) caused dose‐dependent increase in [Ca2+]i and tension in the rat myometrium, and this effect was greatly enhanced in the pregnant myometrium. PAR1‐activating peptide mimicked the effects of thrombin.

In Ca2+‐free PSS, thrombin induced no increase in [Ca2+]i and tension in the pregnant myometrium. Both diltiazem (10 μM) and SK‐F 96365 (10 μM) significantly inhibited the thrombin‐induced elevations of [Ca2+]i and tension, and their effects were additive.

RT–PCR analysis revealed an approximately 10 fold increase in the level of thrombin receptor mRNA in the pregnant myometrium compared to that obtained in the non‐pregnant myometrium.

In conclusion, the contractile response to thrombin was greatly enhanced in the pregnant myometrium, mainly due to the up‐regulation of thrombin receptor. We propose that initiation of a post‐parturitional myometrial contraction is one of the most important physiological roles of thrombin receptor.

British Journal of Pharmacology (2000) 131, 1619–1628; doi:10.1038/sj.bjp.0703729
Inhibition of human platelet aggregation by a novel S‐nitrosothiol is abolished by haemoglobin and red blood cells in vitro: implications for anti‐thrombotic therapy
Authors: Megson Ian L , Sogo Naoki , Mazzei Francesca A , Butler Anthony R , Walton John C , Webb David J
Published: January 2005

S‐Nitrosothiols are nitric oxide (NO) donor drugs that have been shown to inhibit platelet aggregation in platelet rich plasma (PRP) in vitro and to inhibit platelet activation in vivo. The aim of this study was to compare the platelet effects of a novel S‐nitrosated glyco‐amino acid, RIG200, with an established S‐nitrosothiol, S‐nitrosoglutathione (GSNO) in PRP, and to investigate the effects of cell‐free haemoglobin and red blood cells on S‐nitrosothiol‐mediated inhibition of platelet aggregation.

The effects of GSNO and RIG200 in collagen (2.5 μg ml−1)‐induced platelet aggregation in PRP and whole blood were investigated in vitro. Both compounds were found to be powerful inhibitors of aggregation in PRP, and RIG200 was significantly more potent (IC50=2.0 μM for GSNO and 0.8 μM for RIG200; P=0.04).

Neither compound inhibited aggregation in whole blood, even at concentrations of 100 μM. Red blood cell concentrations as low as 1% of the haematocrit, and cell‐free haemoglobin (2.5 μM), significantly reduced their inhibitory effects on platelets.

Experiments involving measurement of cyclic GMP levels, electrochemical detection of NO and electron paramagnetic resonance of haemoglobin in red blood cells, indicated that scavenging of NO generated from S‐nitrosothiols by haemoglobin was responsible for the lack of effect of S‐nitrosothiols on platelets in whole blood.

These studies suggest that scavenging of NO by haemoglobin in blood might limit the therapeutic application of S‐nitrosothiols as anti‐platelet agents.

British Journal of Pharmacology (2000) 131, 1391–1398; doi:10.1038/sj.bjp.0703731
Molecular impact of MinK on the enantiospecific block of IKs by chromanols
Authors: Lerche C , Seebohm G , Wagner C I , Scherer C R , Dehmelt L , Abitbol I , Gerlach U , Brendel J , Attali B , Busch A E
Published: January 2005

Slowly activating IKs (KCNQ1/MinK) channels were expressed in Xenopous oocytes and their sensitivity to chromanols was compared to homomeric KCNQ1 channels. To elucidate the contribution of the β‐subunit MinK on chromanol block, a formerly described chromanol HMR 1556 and its enantiomer S5557 were tested for enantio‐specificity in blocking IKs and KCNQ1 as shown for the single enantiomers of chromanol 293B. Both enantiomers blocked homomeric KCNQ1 channels to a lesser extent than heteromeric IKs channels. Furthermore, we expressed both WT and mutant MinK subunits to examine the involvement of particular MinK protein regions in channel block by chromanols. Through a broad variety of MinK deletion and point mutants, we could not identify amino acids or regions where sensitivity was abolished or strikingly diminished (>2.5 fold). This could indicate that MinK does not directly take part in chromanol binding but acts allosterically to facilitate drug binding to the principal subunit KCNQ1.

British Journal of Pharmacology (2000) 131, 1503–1506; doi:10.1038/sj.bjp.0703734
Thrombin causes endothelium‐dependent biphasic regulation of vascular tone in the porcine renal interlobar artery
Authors: Derkach Dmitry N , Ihara Eikichi , Hirano Katsuya , Nishimura Junji , Takahashi Shosuke , Kanaide Hideo
Published: January 2005

Using a method employing front‐surface fura‐2 fluorometry to measure the cytosolic Ca2+ concentration, [Ca2+]i, the mechanism of endothelium‐dependent regulation of vascular tone by thrombin was studied in porcine renal interlobar arterial strips.

At concentrations lower than 3 u ml−1, thrombin evoked only early transient relaxation, while at 3 u ml−1 and higher concentrations, thrombin caused an early relaxation and a subsequent transient contraction. Both thrombin‐induced relaxation and contraction were abolished by removing the endothelium. Similar biphasic responses were observed with a protease‐activated receptor‐1‐activating peptide.

Early relaxation was associated with a decrease in [Ca2+]i, while the transient contraction was not associated with a change in [Ca2+]i of smooth muscle cells.

A thromboxane A2 (TXA2)/prostaglandin H2 (PGH2) receptor antagonist (10−5 M ONO‐3708) completely inhibited the thrombin‐induced contraction, whereas a thromboxane A2 synthase inhibitor (10−5 M OKY‐046) only partly inhibited it.

When the thrombin‐induced contraction was inhibited by ONO‐3708, either pretreatment with Nω‐nitro‐L‐arginine methylester (L‐NAME) or an increase in the amount of external K+ to 40 mM did not abolish thrombin‐induced relaxation during phenylephrine‐induced sustained contraction. However, the combination of pretreatment with L‐NAME and an elevation of external K+ to 40 mM completely abolished the relaxation.

There was no significant difference in the concentration‐dependent effects of thrombin on the initial early relaxation between conditions in which the contractile components either were or were not inhibited.

Thrombin is thus considered to mainly activate protease‐activated receptor‐1 and cause a biphasic response, early relaxation and a transient contraction, in the porcine renal interlobar artery in an endothelium‐dependent manner. The thrombin‐induced endothelium‐dependent relaxation was mediated by nitric oxide and hyperpolarizing factors, while the contraction was mediated by TXA2 and PGH2.

British Journal of Pharmacology (2000) 131, 1635–1642; doi:10.1038/sj.bjp.0703737
Sarcoplasmic reticulum function and carnitine palmitoyltransferase‐1 inhibition during progression of heart failure
Authors: Rupp Heinz , Vetter Roland
Published: January 2005

Failing cardiac hypertrophy is associated with an inadequate sarcoplasmic reticulum (SR) function. The hypothesis was examined that pressure overloaded hearts fail to increase SR Ca2+ uptake rate proportionally to the hypertrophy and that carnitine palmitoyltransferase‐1 inhibition by etomoxir ((±)‐ethyl 2[6(4‐chlorophenoxy)hexyl] oxirane‐2‐carboxylate) can counteract this process.

Severe left ventricular pressure overload was induced in rats by constricting the ascending aorta for 8, 10, 14 and 28 weeks leading to cardiac hypertrophy (+62–+103% of sham‐operated rats) and pulmonary congestion. Homogenate oxalate‐facilitated SR Ca2+ uptake rate g wet wt−1 was reduced (P<0.05) by 29.9±1.8% irrespective of phospholamban phosphorylation (in the presence of catalytic subunit of protein kinase A) and inhibition of SR Ca2+ release channel by ruthenium red. SERCA2 protein level was reduced (P<0.05) by 30.4±0.8%.

SR Ca2+ uptake rate was inversely correlated (P<0.05) with left ventricular weight but was not affected by the occurrence of pulmonary congestion. Because SR Ca2+ uptake rate of whole ventricles was not reduced, a hypertrophy proportional dilution of SR Ca2+ uptake has to be inferred which precedes pulmonary congestion.

Treatment with etomoxir (15 mg kg body wt−1 day−1 for 10 weeks) did not affect left ventricular weight but decreased (P<0.05) the right ventricular hypertrophy related to pulmonary congestion. In parallel, SR Ca2+ uptake rate of left ventricle and myosin isozyme V1 were increased (P<0.05).

Etomoxir represents a candidate approach for prevention of heart failure by inducing a hypertrophy proportional increase in SR Ca2+ uptake rate.

British Journal of Pharmacology (2000) 131, 1748–1756; doi:10.1038/sj.bjp.0703741
Pharmacological characterization of the 5‐HT receptor‐mediated contraction in the mouse isolated ileum
Authors: Tuladhar B R , Womack M D , Naylor R J
Published: January 2005

The pharmacological characterization of a 5‐HT receptor‐mediated contractile response in the mouse isolated ileum is described.

In the presence of methysergide (1 μM), 5‐hydroxytryptamine (5‐HT, 0.3–100 μM) produced phasic concentration‐dependent contractions of segments of the mouse isolated ileum with a pEC50 value of 5.47±0.09.

The 5‐HT3 receptor selective agonists m‐chlorophenylbiguanide (0.3–100 μM, pEC50 5.81±0.04), 1‐phenylbiguanide (3–100 μM, pEC50 5.05±0.06) and 2‐methyl‐5‐HT (3–100 μM, pEC50 5.00±0.07) acted as full agonists to induce contractile responses. 5‐methoxytryptamine (0.1–100 μM), RS 67506 (0.1–100 μM) and α‐methyl‐5‐HT (0.1–100 μM) failed to mimic the 5‐HT responses.

The contractile response to 5‐HT was not antagonized by either 5‐HT2 receptor antagonists ritanserin (0.1 μM) or ketanserin (1 μM) nor the 5‐HT4 receptor antagonist SB 204070 (0.1 μM).

The 5‐HT3 receptor selective antagonists granisetron (0.3–1 nM), tropisetron (1–10 nM), ondansetron (10 nM–1 μM) and MDL 72222 (10 nM–1 μM) caused rightward displacement of the concentration‐response curves to 5‐HT. The lower concentrations of the antagonists caused approximate parallel rightward shifts of the concentration‐response curves to 5‐HT with apparent pKB values for granisetron (9.70±0.39), tropisetron (9.18±0.20), ondansetron (8.84±0.24) and MDL 72222 (8.65±0.35). But higher concentrations of antagonists resulted in a progressive reduction in the maximum responses.

The contractile response to 5‐HT was abolished by tetrodotoxin (0.3 μM); atropine (0.1 and 1 μM) decreased the maximum response of the 5‐HT concentration‐response curve by approximately 65%.

It is concluded that a neuronally located 5‐HT3 receptor mediates a contractile response to 5‐HT in the mouse ileum. The 5‐HT3 receptor in the mouse ileum has a different pharmacological profile to that reported for the guinea‐pig ileum.

British Journal of Pharmacology (2000) 131, 1716–1722; doi:10.1038/sj.bjp.0703747
Bradykinin regulation of salt transport across mouse inner medullary collecting duct epithelium involves activation of a Ca2+‐dependent Cl− conductance
Authors: Kose H , Boese S H , Glanville M , Gray M A , Brown C D A , Simmons N L
Published: January 2005

The mechanism by which bradykinin regulates renal epithelial salt transport has been investigated using a mouse inner medullary renal collecting duct cell‐line mIMCD‐K2.

Using fura‐2 loaded mIMCD‐K2 cells bradykinin (100 nM) has been shown to induce a transient increase in intracellular Ca2+ via activation of bradykinin B2 receptors localized to both the apical and basolateral epithelial cell surfaces.

In mIMCD‐K2 epithelial cell‐layers clamped in Ussing chambers, 100 nM bradykinin via apical and basolateral bradykinin B2 receptors stimulated a transient increase in inward short‐circuit current (Isc) of similar duration to the increase in intracellular Ca2+.

Replacements of the bathing solution Na+ by the impermeant cation, N‐methyl‐D‐glucamine and of Cl− and HCO3− by the impermeant anion gluconate at either the apical (no reduction) or basal bathing solutions (abolition of the response) are consistent with the bradykinin‐stimulated increase in inward Isc resulting from basal to apical Cl− (anion) secretion.

Using the slow whole cell configuration of the patch‐clamp technique, bradykinin was shown to activate a transient Cl− selective whole cell current which showed time‐dependent activation at positive membrane potentials and time‐dependent inactivation at negative membrane potentials. These currents were distinct from those activated by forskolin (CFTR), but identical to those activated by exogenous ATP and are therefore consistent with bradykinin activation of a Ca2+‐dependent Cl− conductance.

The molecular identity of the Ca2+‐dependent Cl− conductance has been investigated by an RT–PCR approach. Expression of an mRNA transcript with 96% identity to mCLCA1/2 was confirmed, however an additional but distinct mRNA transcript with only 81% of the identity to mCLCA1/2 was identified.

British Journal of Pharmacology (2000) 131, 1689–1699; doi:10.1038/sj.bjp.0703749
Inhibition of endotoxin‐induced vascular hyporeactivity by 4‐amino‐tetrahydrobiopterin
Authors: Gibraeil Hanan D , Dittrich Peter , Saleh Samira , Mayer Bernd
Published: January 2005

The 4‐amino analogue of tetrahydrobiopterin (4‐ABH4) is a potent pterin‐site inhibitor of nitric oxide synthases (NOS). Although 4‐ABH4 does not exhibit selectivity between purified NOS isoforms, a pronounced selectivity of the drug towards inducible NOS (iNOS) is apparent in intact cells. This work was carried out to investigate the potential iNOS selectivity of 4‐ABH4 in isolated pig pulmonary and coronary arteries.

Endothelium‐dependent relaxations of pig pulmonary and coronary artery strips to bradykinin or calcium ionophore A23187 were inhibited by 4‐ABH4 in a concentration‐dependent manner. Half‐maximal inhibition was observed at 60–65 μM (pulmonary artery) and 200–250 μM 4‐ABH4 (coronary artery).

Pig coronary artery strips precontracted with 0.1 μM 9, 11‐dideoxy‐9, 11‐methanoepoxy‐prosta‐glandin F2α (U46619) showed a time‐dependent relaxation (monitored for up to 18 h) upon incubation with 1 μg ml−1 lipopolysaccharide (LPS). Addition of 10 μM 4‐ABH4 1 h after LPS led to a pronounced inhibition of the LPS‐triggered relaxation, whereas the pterin antagonist had no effect when given4 h after LPS.

Incubation of pulmonary and coronary artery strips with 1 μg ml−1 LPS attenuated contractile responses to norepinephrine (1 μM) and U46619 (0.1 μM). This hyporeactivity of the blood vessels to vasoconstrictor agents was inhibited by 4‐ABH4 in a concentration‐dependent manner [IC50=17.5±5.9 μM (pulmonary artery) and 20.7±3 μM (coronary artery)]. The effect of 0.1 mM 4‐ABH4 was antagonized by coincubation with 0.1 mM sepiapterin, which is known to supply intracellular BH4 via a salvage pathway.

These results demonstrate that 4‐ABH4 is a fairly selective inhibitor of iNOS in an in vitro model of endotoxaemia, suggesting that this drug and/or related pterin‐site NOS inhibitors may be useful to increase blood pressure in severe infections associated with a loss of vascular responsiveness to constrictor agents caused by endotoxin‐triggered iNOS induction in the vasculature.

British Journal of Pharmacology (2000) 131, 1757–1765; doi:10.1038/sj.bjp.0703752
Effects of the PAF receptor antagonist UK74505 on local and remote reperfusion injuries following ischaemia of the superior mesenteric artery in the rat
Authors: Souza D G , Cara D C , Cassali G D , Coutinho S F , Silveira M R , Andrade S P , Poole S P , Teixeira M M
Published: January 2005

The effects of the long lasting and potent PAF receptor antagonist UK74505 were assessed on the local and remote injuries following ischaemia and reperfusion (I/R) of the superior mesenteric artery (SMA) in rats.

In a severe model of ischaemia (120 min) and reperfusion (120) injury, in addition to the local and remote increases in vascular permeability and neutrophil accumulation, there was significant tissue haemorrhage, blood neutropenia, systemic hypotension and elevated local and systemic TNF‐α levels.

Post‐ischaemic treatment with the selectin blocker fucoidin (10 mg kg−1) prevented neutrophil accumulation in tissue and, in consequence, all the local and systemic injuries following severe I/R.

Treatment with an optimal dose of UK74505 (1 mg kg−1) also reversed local and remote neutrophil accumulation, increases in vascular permeability and intestinal haemorrhage. UK74505 partially inhibited blood neutropenia and reperfusion‐induced hypotension.

Interestingly, both fucoidin and UK74505 prevented the local, but not systemic, increases of TNF‐α levels following severe I/R injury, demonstrating an important role of migrating cells for the local production of TNF‐α. However, the results do not support a role for PAF as an intermediate molecule in the production of systemic TNF‐α.

The beneficial effects of UK74505 and other PAF receptor antagonists in models of I/R injury in animals and the safety of UK74505 use in man warrant further investigations of the use of this drug as preventive measure for I/R injury in humans.

British Journal of Pharmacology (2000) 131, 1800–1808; doi:10.1038/sj.bjp.0703756
Local regulation of [3H]‐noradrenaline release from the isolated guinea‐pig right atrium by P2X‐receptors located on axon terminals
Authors: Sperlágh Beáta , Erdélyi Ferenc , Szabó Gábor , Vizi E Sylvester
Published: January 2005

In this study the regulation of cardiac sympathetic outflow by presynaptic P2X receptor‐gated ion channels was examined.

ATP (30 μM–1 mM) and other P2‐receptor agonists elicited [3H]‐noradrenaline ([3H]‐NA) outflow from the isolated guinea‐pig right atrium with the potency order of ATP>2‐methyl‐thioATP>α,β‐methylene‐ATP=ADP, whereas β,γ‐methylene‐L‐ATP was inactive.

Ca2+‐free conditions abolished both electrical field stimulation (EFS)‐ and ATP‐evoked release of tritium. Unlike from EFS‐induced outflow, ATP‐induced [3H]‐NA outflow was not reduced by ω‐Conotoxin‐GVIA (100 nM), Cd2+ (100 μM) and tetrodotoxin (1 μM).

The rapid extracellular decomposition of ATP was revealed by HPLC analysis. However, the effect of ATP to promote [3H]‐NA release was not prevented by 8‐cyclopentyl‐1,3‐dipropylxanthine (DPCPX, 250 nM), 3,7‐dimethyl‐1‐propargylxanthine (DMPX, 250 nM), or by reactive blue 2 (RB2, 10 μM), antagonists of A1‐, A2‐ and inhibitory P2 receptors.

Zn2+ (50 μM), the P2X‐receptor modulator potentiated, and P2X receptor antagonists, i.e. suramin (300 μM), pyridoxal‐phosphate‐6‐azophenyl‐2′,4′‐disulphonic acid (PPADS, 30 μM) and 2′‐o‐(trinitrophenyl)‐adenosine 5′‐triphosphate (TNP‐ATP, 30 μM) antagonized the ATP (1 mM)‐evoked response.

RT–PCR study revealed the expression of P2X2 and P2X3 receptor mRNAs in guinea‐pig superior cervical ganglion.

PPADS (30 μM) significantly reduced the EFS‐induced [3H]‐NA outflow in the presence DPCPX (250 nM) and RB2 (10 μM).

In summary a P2X‐type purinoceptor regulates noradrenaline release from the isolated right atrium of the guinea‐pig. The pharmacological profile of the receptor resemble to homo‐oligomeric P2X3 or hetero‐oligomeric P2X2/P2X3 complexes, and provide a new target to intervene on sympathetic neuroeffector transmission at the presynaptic site.

British Journal of Pharmacology (2000) 131, 1775–1783; doi:10.1038/sj.bjp.0703757
Selective phenylalkylamine block of IKr over other K+ currents in guinea‐pig ventricular myocytes
Authors: Jones Stephen E , Missan Sergey , Zhabyeyev Pavel , McDonald Terence F
Published: January 2005

Previous studies on verapamil and D600 have established that the Ca2+‐channel blockers also inhibit delayed‐rectifier K+ currents in cardiac tissues and myocytes. However, estimated IC50 values range over two to three orders of concentration, and it is unclear whether this reflects a high selectivity by one or both of the phenylalkylamines for particular K+ channels. The purpose of the present study was to determine the concentration‐dependent actions of verapamil and D600 on three defined cardiac K+ currents.

Guinea‐pig ventricular myocytes in the conventional whole‐cell configuration were bathed with normal Tyrode's or K+‐free solution, and pulsed from −80 mV for measurement of the effects of 0.01 μM to 3 mM verapamil and D600 on the inwardly‐rectifying K+ current (IKl) and the two delayed‐rectifier K+ currents, rapidly‐activating IKr and slowly‐activating IKs.

The phenylalkylamines inhibited both inward‐ and outward‐directed IKl. The IC50 values for outward IKl were approximately 220 μM.

Verapamil and D600 were approximately equipotent inhibitors of the delayed‐rectifier K+ currents. They inhibited IKr with IC50 near 3 μM, and IKs with IC50 280 μM. These results are discussed in relation to previous findings on K+ currents and to the clinical actions of the drugs.

British Journal of Pharmacology (2000) 131, 1809–1816; doi:10.1038/sj.bjp.0703758
Novel mechanism of blocking axonal Na+ channels by three macrocyclic polyamine analogues and two spider toxins
Authors: Yakehiro Masuhide , Furukawa Yasuo , Koike Tohru , Kimura Eiichi , Nakajima Terumi , Yamaoka Kaoru , Seyama Issei
Published: January 2005

The mechanism of Na+ channel block by three macrocyclic polyamine derivatives and two spider toxins was studied with voltage clamp and internal perfusion method in squid axons.

All these chemicals specifically block Na+ channels in the open state only from the internal surface, and do not affect K+ channels.

The blocking effect is enhanced as the depolarizing pulse becomes larger. Blocked channels are unable to shift to the inactivated state.

In the case of cyclam and guanidyl‐side armed cyclam (G‐cyclam), quick release of these chemicals from the binding sites is proven by the increase in the tail current and prolongation of the time course of the off gating current. On the other hand, in the presence of N‐4 and the spider toxins, their detachment was delayed significantly.

Molecular requirements for the block of Na+ channels by these molecules are the presence of positive charge and hydrophobicity.

British Journal of Pharmacology (2001) 132, 63–72; doi:10.1038/sj.bjp.0703765
Characterization of a novel mechanism accounting for the adverse cholinergic effects of the anticancer drug irinotecan
Authors: Blandizzi Corrado , De Paolis Barbara , Colucci Rocchina , Lazzeri Gloria , Baschiera Fabio , Del Tacca Mario
Published: January 2005

This study investigates the mechanisms accounting for the adverse cholinergic effects of the antitumour drug irinotecan. The activity of irinotecan and its active metabolite, 7‐ethyl‐10‐hydroxy‐camptothecin (SN‐38), was assayed in models suitable for pharmacological studies on cholinergic system.

Irinotecan moderately inhibited human or electric eel acetylcholinesterase activity, SN‐38 had no effect, whereas physostigmine blocked both the enzymes with high potency and efficacy.

Irinotecan and SN‐38 did not affect spontaneous or electrically‐induced contractile activity of human colonic muscle. Acetylcholine and dimethylphenylpiperazinium (DMPP) caused phasic contractions or relaxations, respectively. Physostigmine enhanced the motor responses elicited by electrical stimulation.

Although irinotecan and SN‐38 did not modify the basal contractile activity of guinea‐pig ileum longitudinal muscle strips, irinotecan 100 μM moderately enhanced cholinergic twitch contractions. Acetylcholine or DMPP caused phasic contractions, whereas physostigmine enhanced the twitch responses. Electrically‐induced [3H]‐acetylcholine release was reduced by irinotecan (100 μM) or physostigmine (0.1 μM).

Intravenous irinotecan stimulated gastric acid secretion in rats, but no effects were obtained with SN‐38, physostigmine or i.c.v. irinotecan. Hypersecretion induced by irinotecan was partly prevented by ondansetron, and unaffected by capsazepine. In the presence of atropine, vagotomy and systemic or vagal ablation of capsaicin‐sensitive afferent fibres, irinotecan did not stimulate gastric secretion.

The present results indicate that irinotecan and SN‐38 do not act as specific acetylcholinesterase blockers or acetylcholine receptor agonists. It is rather suggested that irinotecan promotes a parasympathetic discharge to peripheral organs, mediated by capsaicin‐sensitive vagal afferent fibres, and that serotonin 5‐HT3 receptors are implicated in the genesis of vago‐vagal reflex triggered by irinotecan.

British Journal of Pharmacology (2001) 132, 73–84; doi:10.1038/sj.bjp.0703766
Blockade of chloride channels reveals relaxations of rat small mesenteric arteries to raised potassium
Authors: Doughty Joanne M , Boyle John P , Langton Philip D
Published: January 2005

Raised extracellular K+ relaxes some arteries, and has been proposed as Endothelium‐Derived Hyperpolarizing Factor (EDHF). However, relaxation of rat small mesenteric arteries to K+ is highly variable. We have investigated the mechanism of K+‐induced dilatation and relaxation of pressurized arteries and arteries mounted for measurement of isometric force.

Raising [K+]o from 5.88 – 10.58 mM did not dilate or relax pressurized or isometric arteries. Relaxation to raised [K+]o was revealed in the presence of 5‐nitro‐2‐(3‐phenylpropylamino) benzoic acid (NPPB); this effect of NPPB was concentration‐dependent (IC50: 1.16 μM).

Relaxations to raised [K+]o in the presence of NPPB, were abolished by 30 μM Ba2+ or endothelial‐denudation. Acetycholine (10 μM) relaxed endothelium‐intact arteries in presence of raised [K+]o NPPB and Ba2+.

Relaxations to raised [K+]o were revealed in hyperosmotic superfusate (+60 mM sucrose). These relaxations were abolished by 30 μM Ba2+. In the presence of raised [K+]o, 60 mM sucrose and 30 μM Ba2+, 10 μM acetycholine still relaxed all arteries.

Fifty μM 18α‐glycyrrhetinic acid (18α‐GA), a gap junction inhibitor, depressed relaxations to both 10 μM acetylcholine and raised [K+]o, in the presence of 10 μM NPPB.

In summary, blockade of a volume‐sensitive Cl− conductance in small rat mesenteric arteries, using NPPB or hyperosmotic superfusion, reveals a endothelium‐dependent, Ba2+ sensitive dilatation or relaxation of rat mesenteric arteries to raised [K+]o. We conclude that inwardly rectifying potassium channels on the endothelium underlie relaxations to raised [K+]o in rat small mesenteric arteries.

British Journal of Pharmacology (2001) 132, 293–301; doi:10.1038/sj.bjp.0703769
Platelet‐derived growth factor causes endothelium‐independent relaxation of rabbit mesenteric artery via the release of a prostanoid
Authors: Yamawaki Hideyuki , Sato Koichi , Hori Masatoshi , Ozaki Hiroshi , Karaki Hideaki
Published: January 2005

Recent evidence has indicated that the mitogen platelet‐derived growth factor (PDGF) can act acutely to regulate arterial tone. In this study we demonstrate that the BB isoform of PDGF (PDGF‐BB) can cause endothelium‐independent relaxation of rabbit isolated mesenteric arteries.

In endothelium‐denuded arteries, PDGF‐BB (40 pM–8.0 nM) caused concentration‐dependent relaxation of noradrenaline‐induced tone. The relaxation to PDGF‐BB was abolished by a cyclo‐oxygenase inhibitor, indomethacin (10 μM) and by the PDGF receptor‐associated tyrosine kinase inhibitor, tyrphostin AG1295 (50 μM), but not by NG‐monomethyl‐L‐arginine (L‐NMMA, 200 μM), an inhibitor of nitric oxide (NO) synthase.

PDGF‐BB (4.0 nM) significantly increased the release of prostacyclin (PGI2) in endothelium‐denuded arteries. Exogenously applied iloprost (1 μM), a stable analogue of PGI2, relaxed the endothelium‐denuded artery. PDGF‐BB (4.0 nM) significantly increased the cyclic AMP content.

In the absence of Ca2+, PDGF‐BB (4.0 nM) failed to relax the artery, and the release of PGI2 was almost completely suppressed. In addition, the release of PGI2 by PDGF‐BB (4.0 nM) was significantly reduced in the presence of endothelium. The effect of endothelium was eliminated by L‐NMMA (200 μM) and PGI2 release increased.

These data indicate that in rabbit mesenteric arteries, PDGF‐BB can evoke endothelium‐independent relaxation by stimulating the synthesis of PGI2. The PDGF‐BB‐induced prostaglandin synthesis is dependent on both Ca2+ and tyrosine phosphorylation of the PDGF receptor, and is attenuated by endothelium‐derived NO.

British Journal of Pharmacology (2000) 131, 1546–1552; doi:10.1038/sj.bjp.0703771
Protective effects of a new stable, highly active SOD mimetic, M40401 in splanchnic artery occlusion and reperfusion
Authors: Cuzzocrea Salvatore , Mazzon Emanuela , Dugo Laura , Caputi Achille P , Aston Karl , Riley Dennis P , Salvemini Daniela
Published: January 2005

Splanchnic artery occlusion shock (SAO) causes an enhanced formation of reactive oxygen species (ROS), which contribute to the pathophysiology of shock. Here we have investigated the effects of M40401, a new S,S‐dimethyl substituted biscyclohexylpyridine Mn‐based superoxide dismutase mimetic (SODm, kcat=1.2×10+9 M−1 s−1 at pH=7.4), in rats subjected to SAO shock.

Treatment of rats with M40401 (applied at 0.25, 2.5 or 25 μg kg−1, 15 min prior to reperfusion), attenuated the mean arterial blood and the migration of polymorphonuclear cells (PMNs) caused by SAO‐shock. M40401 also attenuated the ileum injury (histology) as well as the increase in the tissue levels of myeloperoxidase (MPO) and malondialdehyde (MDA) caused by SAO shock in the ileum.

Immunohistochemical analysis for nitrotyrosine revealed a positive staining in ileum from SAO‐shocked rats. The degree of staining for nitrotyrosine was markedly reduced in tissue sections obtained from SAO‐shocked rats which had received M40401. Reperfused ileum tissue sections from SAO‐shocked rats showed positive staining for P‐selectin and for anti‐intercellular adhesion molecule (ICAM‐1) in the vascular endothelial cells. M40401 treatment markedly reduced the intensity and degree of P‐selectin and ICAM‐1 in tissue sections from SAO‐shocked rats. M40401 treatment significantly improved survival.

Additionally, the very high catalytic activity of this new mimetic (comparable to the native human Cu/Zn SOD enzyme and exceeding the activity of the human Mn SOD enzyme) translates into a very low dose (∼μg kg−1) required to afford protection in this SAO model of ischemia reperfusion injury.

Taken together, our results clearly demonstrate that M40401 treatment exerts a protective effect, and part of this effect may be due to inhibition of the expression of adhesion molecules and peroxynitrite‐related pathways with subsequent reduction of neutrophil‐mediated cellular injury.

British Journal of Pharmacology (2001) 132, 19–29; doi:10.1038/sj.bjp.0703775
Leukotriene C4 enhances the contraction of porcine tracheal smooth muscle through the activation of Y‐27632, a rho kinase inhibitor, sensitive pathway
Authors: Setoguchi Hidekazu , Nishimura Junji , Hirano Katsuya , Takahashi Shosuke , Kanaide Hideo
Published: January 2005

An unsaturated fatty acid, leukotriene C4 (LTC4), has a potent contractile effect on human airway smooth muscle, and has been implicated in the pathogenesis of human asthma. Using front‐surface fluorometry with fura‐PE3, the effect of LTC4 on the intracellular Ca2+ concentration ([Ca2+]i) and tension were investigated in porcine tracheal smooth muscle strips.

The application of LTC4 induced little or no contraction despite a small and transient increase in [Ca2+]i. In the presence of LTC4, however, the contractions evoked by high K+ depolarization or a low concentration of carbachol (CCh) were markedly enhanced without inducing any changes in the [Ca2+]i levels, thus indicating that LTC4 increases the Ca2+ responsiveness of the contractile apparatus. This LTC4‐induced increase in Ca2+ responsiveness could partly be reproduced in the permeabilized preparation of tracheal smooth muscle strips.

The LTC4‐induced enhancement of contraction was accompanied by an increase in myosin light chain (MLC) phosphorylation and was blocked by a rho kinase inhibitor (Y‐27632), but not by either a PKC inhibitor (calphostin C) or a tyrosine kinase inhibitor (genistein).

These results indicated that, in porcine tracheal smooth muscle, LTC4 enhances the contraction by increasing the Ca2+ responsiveness of the contractile apparatus in a MLC phosphorylation dependent manner, possibly through the activation of the rho‐rho kinase pathway.

British Journal of Pharmacology (2001) 132, 111–118; doi:10.1038/sj.bjp.0703780
Contralateral but not systemic administration of the κ‐opioid agonist U‐50,488H induces anti‐nociception in acute hindpaw inflammation in rats
Authors: Bileviciute‐Ljungar Indre , Spetea Mariana
Published: January 2005

The anti‐nociceptive effects of contralateral administration of κ‐opioid agonist U‐50,488H were investigated in rats.

Inflammation was induced by unilateral injection of 1% carrageenan into the right hindpaw. Prior to carrageenan injection, U‐50,488H or saline was administered into the left hindpaw. Withdrawal responses to mechanical and heat stimulation and oedema levels were evaluated at 3, 6 and 24 h post‐carrageenan injection.

The results showed that the inflammatory effect of 1% carrageenan peaked after 6 h with bilateral decreases in withdrawal latencies and ipsilateral oedema formation.

Contralateral treatment with 0.01, 0.05, 0.3 and 2 mg of U‐50,488H attenuated nociceptive reflexes to mechanical stimulation on the inflamed side at 6 h. The anti‐nociceptive effect of contralateral treatment was dose‐dependent at 3 and 24 h. The hindpaw withdrawal latencies to heat stimulation were prolonged at 3 and 24 h after contralateral treatment with 0.3 mg U‐50,488H. No effect on inflammatory oedema formation was observed, except for a decrease at 3 h after treatment with 2 mg of U‐50,488H.

Sciatic nerve denervation on the contralateral side abolished the anti‐nociceptive effects of U‐50,488H (0.3 and 2 mg). In contrast, contralateral injection of 1 mg morphine prolonged paw latencies in denervated rats.

Both co‐administration of the peripherally selective opioid antagonist naloxone methiodide with 0.3 mg U‐50,488H, and alternatively, systemic administration of 0.3 mg U‐50,488H reversed the anti‐nociceptive effects induced by contralateral injection of U‐50,488H.

Taken together, our findings indicate that the contralateral administration of U‐50,488H attenuates nociceptive behaviour resulting from acute inflammation. The effect is mediated via peripheral neuronal κ‐opioid receptors and, possibly, spinal cord mechanisms, suggesting a new treatment approach for acute inflammatory conditions.

British Journal of Pharmacology (2001) 132, 252–258; doi:10.1038/sj.bjp.0703782
Inhibition of volume‐regulated anion channels in cultured endothelial cells by the anti‐oestrogens clomiphene and nafoxidine
Authors: Maertens Chantal , Droogmans Guy , Chakraborty Prabir , Nilius Bernd
Published: January 2005

We have used the whole‐cell patch clamp technique to study the effect of the partial anti‐oestrogens clomiphene and nafoxidine, the pure anti‐oestrogens ICI 182,780 and RU 58,668 and the oestrogen β‐estradiol, on the volume‐regulated anion channel (VRAC) in cultured pulmonary artery endothelial (CPAE) cells.

In contrast to the pure anti‐oestrogens and β‐estradiol, clomiphene and nafoxidine potently inhibited the volume‐sensitive chloride current, ICl,swell, activated by challenging CPAE cells with a 25% hypotonic solution. For clomiphene, the estimated IC50 and Hill coefficient were 1.03±0.14 μM and 1.40±0.21 respectively. In the case of nafoxidine, these values were 1.61±0.29 μM and 1.24±0.19.

The inhibition induced by the pure enantiomers of clomiphene, zuclomiphene and enclomiphene, was not different from that of the racemic mixture, indicating that the interaction between clomiphene and VRAC is not stereoselective.

Clomiphene and nafoxidine inhibited proliferation of CPAE cells. Half‐maximal inhibition was found at 1.98±0.17 and 1.66±0.21 μM respectively, concentrations similar to those for half‐maximal block of VRAC.

In conclusion, the nonsteroidal partial anti‐oestrogens nafoxidine and clomiphene are potent inhibitors of volume‐regulated anion channels. The inhibition by clomiphene is not stereoselective and occurs at concentrations close to therapeutically relevant concentrations. Finally, both drugs inhibit the proliferation of endothelial cells.

British Journal of Pharmacology (2001) 132, 135–142; doi:10.1038/sj.bjp.0703786
Differential coupling of the human P2Y11 receptor to phospholipase C and adenylyl cyclase
Authors: Qi Ai‐Dong , Kennedy Charles , Harden T Kendall , Nicholas Robert A
Published: January 2005

The human P2Y11 (hP2Y11) receptor was stably expressed in two cell lines, 1321N1 human astrocytoma cells (1321N1‐hP2Y11) and Chinese hamster ovary cells (CHO‐hP2Y11), and its coupling to phospholipase C and adenylyl cyclase was assessed.

In 1321N1‐hP2Y11 cells, ATP promoted inositol phosphate (IP) accumulation with low μM potency (EC50=8.5±0.1 μM), whereas it was 15 fold less potent (130±10 μM) in evoking cyclic AMP production.

In CHO‐hP2Y11 cells, ATP promoted IP accumulation with slightly higher potency (EC50=3.6±1.3 μM) than in 1321N1‐hP2Y11 cells, but it was still 15 fold less potent in promoting cyclic AMP accumulation (EC50=62.4±15.6 μM) than for IP accumulation. Comparable differences in potencies for promoting the two second messenger responses were observed with other adenosine nucleotide analogues.

In 1321N1‐hP2Y11 and CHO‐hP2Y11 cells, down regulation of PKC by chronic treatment with phorbol ester decreased ATP‐promoted cyclic AMP accumulation by 60 – 80% (P<0.001) with no change in its potency. Likewise, chelation of intracellular Ca2+ decreased ATP‐promoted cyclic AMP accumulation by ∼45% in 1321N1‐hP2Y11 cells, whereas chelation had no effect on either the efficacy or potency of ATP in CHO‐hP2Y11 cells.

We conclude that coupling of hP2Y11 receptors to adenylyl cyclase in these cell lines is much weaker than coupling to phospholipase C, and that activation of PKC and intracellular Ca2+ mobilization as consequences of inositol lipid hydrolysis potentiates the capacity of ATP to increase cyclic AMP accumulation in both 1321N1‐hP2Y11 and CHO‐hP2Y11 cells.

British Journal of Pharmacology (2001) 132, 318–326; doi:10.1038/sj.bjp.0703788
Inhibition by glucocorticoids of the mast cell‐dependent weal and flare response in human skin in vivo
Authors: Cole Zoë A , Clough Geraldine F , Church Martin K
Published: January 2005

This study examines the relative contributions made by inhibition of mast cell degranulation, reduction of mast cell recruitment and maturation, and lowering the responsiveness of the vasculature to histamine, in the inhibition by glucocorticoids of the weal and flare in human skin.

One forearm of healthy human volunteers was treated for 24 h (n=6) or daily for 21 days (n=10) with 0.05% clobetasol propionate. The other arm served as control. Weal and flare responses were elicited by intradermal injection of 20 μl of 0.3 mM codeine. The areas of the responses were measured using scanning laser Doppler imaging. Microdialysis was used to assess histamine release. Mast cell numbers and tissue histamine content were assessed in 4‐mm punch biopsies. Histamine (20 μl of 1 μM i.d.) was used to assess the status of the vasculature.

No significant effects were seen at 24 h. At 21 days, clobetasol reduced the areas of the codeine‐induced weal and flare responses by 59 and 58% respectively (both P=0.006). Mast cell numbers were reduced by 47%, (P=0.014) and total tissue histamine content by 52% (P=0.006). Codeine‐induced histamine release was reduced by 44% (P=0.022). The weal, but not the flare, induced by histamine was significantly inhibited (P=0.019). Echography revealed a 15% thinning of the skin by clobetasol.

These results demonstrate that reduction of the weal and flare responses to codeine following clobetasol treatment, results primarily from reduced mast cell numbers and tissue histamine content rather than inhibition by corticosteroids of mast cell degranulation.

British Journal of Pharmacology (2001) 132, 286–292; doi:10.1038/sj.bjp.0703789
Pregabalin may represent a novel class of anxiolytic agents with a broad spectrum of activity
Authors: Field Mark J , Oles Ryszard J , Singh Lakhbir
Published: January 2005

The present study examines the effect of pregabalin (previously S‐Isobutylgaba and CI‐1008) in two distinct rat models of anxiety. Pregabalin binds with high affinity and selectivity to the α2δ subunit of voltage dependent calcium channels (VDCC). Its corresponding R‐enantiomer (R‐isobutylgaba) is approximately 10 fold weaker. Pregabalin dose‐dependently induced anxiolytic‐like effects in both the rat conflict test and elevated X‐maze with respective minimum effective doses (MED) of 3 and 10 mg kg−1. In contrast, R‐isobutylgaba only showed activity at the highest dose of 100 mg kg−1 in the conflict test. These data indicate that pregabalin may possess clinical utility as a novel anxiolytic agent and demonstrates the importance of the α2δ subunit of VDCC in the mediation of anxiety related behaviours.

British Journal of Pharmacology (2001) 132, 1–4; doi:10.1038/sj.bjp.0703794