bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of tumour necrosis factor‐α on left ventricular function in the rat isolated perfused heart: possible mechanisms for a decline in cardiac function
Authors: Edmunds N J , Lal H , Woodward B
Published: January 2005

The cardiac depressant actions of TNF were investigated in the isolated perfused rat heart under constant flow (10 ml min−1) and constant pressure (70 mmHg) conditions, using a recirculating (50 ml) mode of perfusion.

Under constant flow conditions TNF (20 ng ml−1) caused an early (<25 min) decrease in left ventricular developed pressure (LVDP), which was maintained for 90 min (LVDP after 90 min: control vs TNF; 110±4 vs 82±10 mmHg, P<0.01).

The depression in cardiac function seen with TNF under constant flow conditions, was blocked by the ceramidase inhibitor N‐oleoylethanolamine (NOE), 1 μM, (LVDP after 90 min: TNF vs TNF with NOE; 82±10 vs 111±5 mmHg, P<0.05).

In hearts perfused at constant pressure, TNF caused a decrease in coronary flow rate (change in flow 20 min after TNF: control vs TNF; −3.0±0.9 vs −8.7±1.2 ml min−1, P<0.01). This was paralleled by a negative inotropic effect (change in LVDP 20 min after TNF: control vs TNF; −17±7 vs −46±6 mmHg, P<0.01). The decline in function was more rapid and more severe than that seen under conditions of constant flow.

These data indicate that cardiac function can be disrupted by TNF on two levels, firstly via a direct, ceramidase dependant negative inotropic effect, and secondly via an indirect coronary vasoconstriction.

British Journal of Pharmacology (1999) 126, 189–196; doi:10.1038/sj.bjp.0702294
Lack of interaction between nitric oxide and the redox modulatory site of the NMDA receptor
Authors: Aizenman Elias , Potthoff William K
Published: January 2005

The inhibitory effects of nitric oxide (NO) on N‐methyl‐D‐aspartate (NMDA) receptor function have been proposed to be mediated via the interaction of this gas with a redox‐sensitive thiol moiety on the receptor. Here, we evaluated this suggested mechanism by examining the actions of various NO donors on native neuronal receptors as well as in wild‐type and cysteine‐mutated recombinant NMDA receptors expressed in Chinese hamster ovary (CHO) cells.

The NO donor N‐ethyl‐2‐(1‐ethyl‐2‐hydroxy‐2‐nitrosohydraxino)ethanamine (NOC‐12; 100 μM) produced a rapid and readily reversible inhibition of whole‐cell currents induced by NMDA (30 μM) in cultured cortical neurons. The inhibition was apparent at all holding potentials, though a more pronounced block was observed at negative voltages. The effects of NOC‐12 disappeared when the donor was allowed to expire. A similar receptor block was observed with another NO‐releasing agent, S‐nitroso‐N‐acetylpenicillamine (SNAP; 1 mM).

The blocking effects of NO released by SNAP, 3‐morpholinosydnonimine (SIN‐1; 1 mM), and 3‐[2‐hydroxy‐1‐(1‐methylethyl)‐2‐nitrosohydrazino]‐1‐propanamine (NOC‐5; 100 μM) on currents mediated by recombinant NR1/NR2B receptors were virtually indistinguishable from those observed on native receptors. Furthermore, mutating cysteines 744 and 798 of NR1, which constitute the principal redox modulatory site of the NR1/NR2B receptor configuration, did not affect the inhibition produced by NO.

The NR2A subunit may contribute its own redox‐sensitive site. However, the effects of NO on NR1/NR2A receptors were very similar to those seen for all other receptor configurations evaluated. Hence, we conclude that NO does not exert its inhibition of NMDA‐induced responses via a modification of any of the previously described redox‐sensitive sites on the receptor.

British Journal of Pharmacology (1999) 126, 296–300; doi:10.1038/sj.bjp.0702295
Selective effects of a 4‐oxystilbene derivative on wild and mutant neuronal chick α7 nicotinic receptor
Authors: Maggi L , Palma E , Eusebi F , Moretti M , Balestra B , Clementi F , Gotti C
Published: January 2005

We assessed the pharmacological activity of triethyl‐(β‐4‐stilbenoxy‐ethyl) ammonium (MG624), a drug that is active on neuronal nicotinic receptors (nicotinic AChR). Experiments on the major nicotinic AChR subtypes present in chick brain, showed that it inhibits the binding of [125I]‐αBungarotoxin (αBgtx) to the α7 subtype, and that of [3H]‐epibatidine (Epi) to the α4β2 subtype, with Ki values of respectively 106 nM and 84 μM.

MG624 also inhibited ACh elicited currents (IACh) in the oocyte‐expressed α7 and α4β2 chick subtypes with half‐inhibitory concentrations (IC50) of respectively 109 nM and 3.2 μM.

When tested on muscle‐type AChR, it inhibited [125I]‐αBgtx binding with a Ki of 32 μM and ACh elicited currents (IACh) in the oocyte‐expressed α1β1γδ chick subtype with an IC50 of 2.9 μM.

The interaction of MG624 with the α7 subtype was investigated using an α7 homomeric mutant receptor with a threonine‐for‐leucine 247 substitution (L247T α7). MG624 did not induce any current in oocytes expressing the wild type α7 receptor, but did induce large currents in the oocyte‐expressed L247T α7 receptor. The MG624 elicited current (IMG624) has an EC50 of 0.2 nM and a Hill coefficient nH of 1.9, and is blocked by the nicotinic receptor antagonist methyllycaconitine (MLA).

These binding and electrophysiological studies show that MG624 is a potent antagonist of neuronal chick α7 nicotinic AChR, and becomes a competitive agonist following the mutation of the highly conserved leucine residue 247 located in the M2 channel domain.

British Journal of Pharmacology (1999) 126, 285–295; doi:10.1038/sj.bjp.0702299
Growth‐inhibitory effect of cyclic GMP‐ and cyclic AMP‐dependent vasodilators on rat vascular smooth muscle cells: effect on cell cycle and cyclin expression
Authors: Kronemann Nicola , Nockher Wolfgang A , Busse Rudi , Schini‐Kerth Valérie B
Published: January 2005

The possibility that the antiproliferative effect of cyclic GMP‐ and cyclic AMP‐dependent vasodilators involves an impaired progression of vascular smooth muscle cells (VSMC) through the cell cycle and expression of cyclins, which in association with the cyclin‐dependent kinases control the transition between the distinct phases of the cell cycle, was examined.

FCS (10%) stimulated the transition of quiescent VSMC from the G0/G1 to the S phase (maximum within 18–24 h and then to the G2/M phase (maximum within 22–28 h). Sodium nitroprusside and 8‐Br‐cyclic GMP, as well as forskolin and 8‐Br‐cyclic AMP markedly reduced the percentage of cells in the S phase after FCS stimulation.

FCS stimulated the low basal protein expression of cyclin D1 (maximum within 8–24 h) and E (maximum within 8–38 h) and of cyclin A (maximum within 14–30 h). The stimulatory effect of FCS on cyclin D1 and A expression was inhibited, but that of cyclin E was only minimally affected by the vasodilators.

FCS increased the low basal level of cyclin D1 mRNA after a lag phase of 2 h and that of cyclin A after 12 h. The vasodilators significantly reduced the FCS‐stimulated expression of cyclin D1 and A mRNA.

These findings indicate that cyclic GMP‐ and cyclic AMP‐dependent vasodilators inhibit the proliferation of VSMC by preventing the progression of the cell cycle from the G0/G1 into the S phase, an effect which can be attributed to the impaired expression of cyclin D1 and A.

British Journal of Pharmacology (1999) 126, 349–357; doi:10.1038/sj.bjp.0702305
Effects of heptanol on the neurogenic and myogenic contractions of the guinea‐pig vas deferens
Authors: Venkateswarlu K , Dange Sumedha Y , Manchanda Rohit
Published: January 2005

The effects of the putative gap junction uncoupler, 1‐heptanol, on the neurogenic and myogenic contractile responses of guinea‐pig vas deferens were studied in vitro.

Superfusion of 2.0 mM heptanol for 20–30 min produced the following reversible changes in the biphasic neurogenic contractile response (8 trials): (i) suppression of both phases; (ii) delayed development of both the first as well as the second phase, accompanied by complete temporal separation of the two phases; (iii) prominent oscillations of force during the second (noradrenergic) phase only.

To eliminate prejunctional effects of heptanol, myogenic contractions were evoked by field stimulation of the vas in the presence of suramin (200 μM) and prazosin (1 μM). Heptanol (2.0 mM) abolished these contractions reversibly.

These results show that (i) heptanol inhibits both excitatory junction potential (EJP)‐dependent and non EJP‐dependent contractions of the vas; (ii) a postjunctional site of action of heptanol, probably intercellular uncoupling of smooth muscle cells, contributes to the inhibition of contraction.

British Journal of Pharmacology (1999) 126, 227–234; doi:10.1038/sj.bjp.0702307
Secretory pathways in endothelin synthesis
Authors: Russell Fraser D , Davenport Anthony P
Published: January 2005

British Journal of Pharmacology (1999) 126, 391–398; doi:10.1038/sj.bjp.0702315
Acute troglitazone action in isolated perfused rat liver
Authors: Preininger Kurt , Stingl Harald , Englisch Rainer , Fürnsinn Clemens , Graf Jürg , Waldhäusl Werner , Roden Michael
Published: January 2005

The thiazolidinedione compound, troglitazone, enhances insulin action and reduces plasma glucose concentrations when administered chronically to type 2 diabetic patients.

To analyse to what extent thiazolidinediones interfere with liver function, we examined the acute actions of troglitazone (0.61 and 3.15 μM) on hepatic glucose and lactate fluxes, bile secretion, and portal pressure under basal, insulin‐ and/or glucagon‐stimulated conditions in isolated perfused rat livers.

During BSA‐free perfusion, high dose troglitazone increased basal (P<0.01), but inhibited glucagon‐stimulated incremental glucose production by ∼75% (10.0±2.5 vs control: 40.0±7.2 μmol g liver−1, P<0.01). In parallel, incremental lactate release rose ∼6 fold (13.1±5.9 vs control: 2.2±0.8 mmol g liver−1, P<0.05), while bile secretion declined by ∼67% [0.23±0.02 vs control: 0.70±0.05 mg g liver−1 min−1), P<0.001]. Low dose troglitazone infusion did not enhance the inhibitory effect of insulin on glucagon‐stimulated glucose production, but rapidly increased lactate release (P<0.0005) and portal venous pressure (+0.17±0.07 vs +0.54±0.07 cm buffer height, P<0.0001).

These results indicate that troglitazone exerts both insulin‐like and non‐insulin‐like hepatic effects, which are blunted by addition of albumin, possibly due to troglitazone binding.

British Journal of Pharmacology (1999) 126, 372–378; doi:10.1038/sj.bjp.0702318
Mibefradil (Ro 40‐5967) inhibits several Ca2+ and K+ currents in human fusion‐competent myoblasts
Authors: Liu Jian‐Hui , Bijlenga Philippe , Occhiodoro Teresa , Fischer‐Lougheed Jacqueline , Bader Charles R , Bernheim Laurent
Published: January 2005

The effect of mibefradil (Ro 40–5967), an inhibitor of T‐type Ca2+ current (ICa(T)), on myoblast fusion and on several voltage‐gated currents expressed by fusion‐competent myoblasts was examined.

At a concentration of 5 μM, mibefradil decreases myoblast fusion by 57%. At this concentration, the peak amplitudes of ICa(T) and L‐type Ca2+ current (ICa(L)) measured in fusion‐competent myoblasts are reduced by 95 and 80%, respectively. The IC50 of mibefradil for ICa(T) and ICa(L) are 0.7 and 2 μM, respectively.

At low concentrations, mibefradil increased the amplitude of ICa(L) with respect to control.

Mibefradil blocked three voltage‐gated K+ currents expressed by human fusion‐competent myoblasts: a delayed rectifier K+ current, an ether‐à‐go‐go K+ current, and an inward rectifier K+ current, with a respective IC50 of 0.3, 0.7 and 5.6 μM.

It is concluded that mibefradil can interfere with myoblast fusion, a mechanism fundamental to muscle growth and repair, and that the interpretation of the effect of mibefradil in a given system should take into account the action of this drug on ionic currents other than Ca2+ currents.

British Journal of Pharmacology (1999) 126, 245–250; doi:10.1038/sj.bjp.0702321
Modulation of ATP‐responses at recombinant rP2X4 receptors by extracellular pH and zinc
Authors: Wildman S S , King B F , Burnstock G
Published: January 2005

The modulatory effects of extracellular H+ and Zn2+ were tested against ATP‐responses at rat P2X4 (rP2X4) receptors expressed in Xenopus oocytes under voltage‐clamp conditions.

ATP (0.1–100 μM, at pH 7.5), evoked inward currents via rP2X4 receptors (EC50 value, 4.1±0.98 μM; nH, 1.2±0.1). ATP potency was reduced 2 fold, at pH 6.5, without altering maximal activity. ATP potency was reduced by a further 4 fold, at pH 5.5, and the maximal activity of ATP was also reduced. Alkaline conditions (pH 8.0) had no effect on ATP‐responses.

Zn2+ (100 nM–10 μM) potentiated ATP‐responses at the rP2X4 receptor by 2 fold, whereas higher concentrations (30 μM–1 mM) inhibited ATP‐responses. Zn2+ potentiation was due to an increase in ATP potency, whereas its inhibitory action was due to a reduction in ATP efficacy.

Zn2+ modulation of ATP‐responses was pH‐dependent. At pH 6.5, the bell‐shaped curve for Zn2+ was shifted to the right by 1 log unit. At pH 5.5, Zn2+ potentiation was abolished and its inhibitory effect reduced considerably.

Suramin (50 μM) also potentiated ATP‐responses at rP2X4 receptors. Neither H+ (pH 6.5 and 5.5), Zn2+ (10–100 μM) or a combination of both failed to reveal an inhibitory action of suramin at rP2X4 receptors.

In conclusion, H+ and Zn2+ exerted opposite effects on the rP2X4 receptor by lowering and raising agonist potency, respectively. H+ (3 μM) and Zn2+ (30 μM) also reduces agonist efficacy by lowering the number of rP2X4 receptors available for activation. The striking differences between the modulatory actions of H+ and Zn2+ at rP2X4 and rP2X2 receptors are discussed.

British Journal of Pharmacology (1999) 126, 762–768; doi:10.1038/sj.bjp.0702325
Endothelin receptor expression and pharmacology in human saphenous vein graft
Authors: Maguire Janet J , Davenport Anthony P
Published: January 2005

We have investigated the expression and pharmacology of endothelin (ET) receptors in human aortocoronary saphenous vein grafts.

Subtype‐selective ligands were used to autoradiographically identify ETA ([125I]‐PD151242) and ETB ([125I]‐BQ3020) receptors. In graft saphenous vein ETA receptors predominated in the media, with few ETB receptors identified. Neither subtype was detected in the thickened neointima.

The ratio of medial ETA:ETB receptors was 75% : 25% in both graft and control saphenous vein.

ET‐1 contracted control (EC50 2.9 nM) and graft (EC50 4.5 nM) saphenous vein more potently than diseased coronary artery (EC50 25.5 nM).

In all three blood vessels ET‐1 was 100 times more potent than ET‐3 and three times more potent than sarafotoxin 6b (S6b). Little or no response was obtained in any vessel with the ETB agonist sarafotoxin 6c (S6c).

The ETA antagonist PD156707 (100 nM) blocked ET‐1 responses in all three vessels with pKb values of approximately 8.0.

For individual graft veins the EC50 value for ET‐1 and ‘age’ of graft in years showed a significant negative correlation.

In conclusion there is no alteration in ET receptor expression in the media of saphenous veins grafted into the coronary circulation compared to control veins. ETA receptors predominantly mediate the vasoconstrictor response to ET‐1 in graft vein, with no apparent up‐regulation of ETB receptors. The sensitivity of the graft vein to ET‐1 increased with graft ‘age’, suggesting that these vessels may be particularly vulnerable to the increased plasma ET levels that are detected in patients with cardiovascular disease.

British Journal of Pharmacology (1999) 126, 443–450; doi:10.1038/sj.bjp.0702326
Leukocyte‐endothelial cell adhesion: avenues for therapeutic intervention
Authors: Panés Julián , Perry Michael , Granger D Neil
Published: January 2005

British Journal of Pharmacology (1999) 126, 537–550; doi:10.1038/sj.bjp.0702328
Signalling by CXC‐chemokine receptors 1 and 2 expressed in CHO cells: a comparison of calcium mobilization, inhibition of adenylyl cyclase and stimulation of GTPγS binding induced by IL‐8 and GROα
Authors: Hall David A , Beresford Isabel J M , Browning Christopher , Giles Heather
Published: January 2005

The effect of interleukin‐8 (IL‐8) and growth‐related oncogene α (GROα) on [35S]‐guanosine 5′‐O‐(3‐thiotriphosphate) ([35S]GTPγS) binding, forskolin‐stimulated cyclic AMP accumulation and cytosolic calcium concentration were determined in recombinant CHO cells expressing HA‐tagged CXC‐chemokine receptors 1 and 2 (CXCR1 and CXCR2).

Radioligand binding assays confirmed that the binding profiles of the recombinant receptors were similar to those of the native proteins. IL‐8 displaced [125I]‐IL‐8 binding to CXCR1 and CXCR2 with pKi values of 8.89±0.05 and 9.27±0.03, respectively. GROα, a selective CXCR2 ligand, had a pKi value of 9.66±0.39 at CXCR2 but a pKi>8 at CXCR1. Calcium mobilization experiments were also consistent with previous reports on native receptors.

Activation of both receptors resulted in stimulation of [35S]GTPγS binding and inhibition of adenylyl cyclase.

A comparison of the functional data at CXCR1 showed that a similar potency order (IL‐8>>GROα) was obtained in all three assays. However, at CXCR2 whilst the potency orders for calcium mobilization and inhibition of adenylyl cyclase were similar (IL‐8GROα), the order was reversed for stimulation of [35S]GTPγS binding (GROα>IL‐8).

All of the functional responses at both receptors were inhibited by pertussis toxin (PTX), suggesting coupling to a Gi/Go protein. However, the calcium mobilization induced by IL‐8 at CXCR1 was not fully inhibited by PTX, suggesting an interaction with a G‐protein of the Gq family. Our results with pertussis toxin also suggested that, in the [35S]GTPγS binding assay, CXCR1 displays some constitutive activity.

Thus, we have characterized the binding and several functional responses at HA‐tagged CXCRs 1 and 2 and have shown that their pharmacology agrees well with that of the native receptors. We also have preliminary evidence that CXCR1 displays constitutive activity in our cell line and that CXCR2 may traffic between different PTX sensitive G‐proteins.

British Journal of Pharmacology (1999) 126, 810–818; doi:10.1038/sj.bjp.0702329
Absence of G‐protein activation by μ‐opioid receptor agonists in the spinal cord of μ‐opioid receptor knockout mice
Authors: Narita Minoru , Mizoguchi Hirokazu , Narita Michiko , Sora Ichiro , Uhl George R , Tseng Leon F
Published: January 2005

The ability of μ‐opioid receptor agonists to activate G‐proteins in the spinal cord of μ‐opioid receptor knockout mice was examined by monitoring the binding to membranes of the non‐hydrolyzable analogue of GTP, guanosine‐5′‐O‐(3‐[35S]thio)triphosphate ([35S]GTPγS).

In the receptor binding study, Scatchard analysis of [3H][D‐Ala2,NHPhe4,Gly‐ol]enkephalin ([3H]DAMGO; μ‐opioid receptor ligand) binding revealed that the heterozygous μ‐knockout mice displayed approximately 40% reduction in the number of μ‐receptors as compared to the wild‐type mice. The homozygous μ‐knockout mice showed no detectable μ‐binding sites.

The newly isolated μ‐opioid peptides endomorphin‐1 and ‐2, the synthetic selective μ‐opioid receptor agonist DAMGO and the prototype of μ‐opioid receptor agonist morphine each produced concentration‐dependent increases in [35S]GTPγS binding in wild‐type mice. This stimulation was reduced by 55–70% of the wild‐type level in heterozygous, and virtually eliminated in homozygous knockout mice.

No differences in the [35S]GTPγS binding stimulated by specific δ1‐ ([D‐Pen2,5]enkephalin), δ2‐ ([D‐Ala2]deltorphin II) or κ1‐ (U50,488H) opioid receptor agonists were noted in mice of any of the three genotypes.

The data clearly indicate that μ‐opioid receptor gene products play a key role in G‐protein activation by endomorphins, DAMGO and morphine in the mouse spinal cord. They support the idea that μ‐opioid receptor densities could be rate‐limiting steps in the G‐protein activation by μ‐opioid receptor agonists in the spinal cord. These thus indicate a limited physiological μ‐receptor reserve. Furthermore, little change in δ1‐, δ2‐ or κ1‐opioid receptor‐G‐protein complex appears to accompany μ‐opioid receptor gene deletions in this region.

British Journal of Pharmacology (1999) 126, 451–456; doi:10.1038/sj.bjp.0702330
Effects of vitamin C and of a cell permeable superoxide dismutase mimetic on acute lipoprotein induced endothelial dysfunction in rabbit aortic rings
Authors: Fontana L , McNeill K L , Ritter J M , Chowienczyk P J
Published: January 2005

Low density lipoprotein (LDL) inhibits endothelium‐dependent relaxation. The mechanism is uncertain, but increased production of superoxide anion O2− with inactivation of endothelium‐derived NO and formation of toxic free radical species have been implicated. We investigated effects of the cell permeable superoxide dismutase mimetic manganese (III) tetrakis (1‐methyl‐4‐pyridyl) porphyrin (MnTMPyP), the free radical scavenger vitamin C and arginine (which may reduce O2− formation) on acute LDL‐induced endothelial dysfunction in rabbit aortic rings, using LDL prepared by ultracentrifugation of plasma from healthy men and aortic rings from New Zealand white rabbits.

LDL (150 μg protein ml−1 for 20 min) markedly inhibited relaxation of aortic rings (in Krebs' solution at 37°C and pre‐constricted to 80% maximum tension with noradrenaline) to acetylcholine 82±10% (mean percentage difference between sum of relaxations after each concentration of acetylcholine in the presence and absence of LDL, ±s.e.mean, n=26, P<0.001) but not to the endothelium‐independent agonist nitroprusside.

MnTMPyP (10 μM) reduced inhibitory effects of LDL from 124±27 to 56±17% (n=6, P<0.05).

Vitamin C (1  mM) reduced inhibitory effects of LDL from 59±8 to 22±5% (n=6, P<0.05).

Inhibitory effects of LDL were similar in the absence or presence of arginine (84±12 vs 79±16%, n=14, P=0.55). Effects of L‐arginine (10 mM) did not differ significantly from those of D‐arginine (10 mM).

Acute (20 min) exposure of aortic rings to LDL impairs endothelium‐dependent relaxation which can be partially restored by MnTMPyP and vitamin C. This is consistent with LDL causing increased O2− generation.

British Journal of Pharmacology (1999) 126, 730–734; doi:10.1038/sj.bjp.0702331
Inhibition of poly(ADP‐ribose) synthetase (PARS) and protection against peroxynitrite‐induced cytotoxicity by zinc chelation
Authors: Virág László , Szabó Csaba
Published: January 2005

Peroxynitrite, a potent oxidant formed by the reaction of nitric oxide and superoxide causes thymocyte necrosis, in part, via activation of the nuclear enzyme poly(ADP‐ribose) synthetase (PARS). The cytotoxic PARS pathway initiated by DNA strand breaks and excessive PARS activation has been shown to deplete cellular energy pools, leading to cell necrosis. Here we have investigated the effect of tetrakis‐(2‐pyridylmethyl)‐ethylenediamine (TPEN) a heavy metal chelator on peroxynitrite‐induced cytotoxicity.

TPEN (10 μM) abolished cell death induced by authentic peroxynitrite (25 μM) and the peroxynitrite generating agent 3‐morpholinosidnonimine (SIN‐1, 250 μM). Preincubation of TPEN with equimolar Zn2+ but not Ca2+ or Mg2+ blocked the cytoprotective effect of the chelator.

TPEN (10 μM) markedly reduced the peroxynitrite‐induced decrease of mitochondrial transmembrane potential, secondary superoxide production and mitochondrial membrane damage, indicating that it acts proximal to mitochondrial alterations.

Although TPEN (1–300 μM) did not scavenge peroxynitrite, it inhibited PARS activation in a dose‐dependent manner.

The cytoprotective effect of TPEN is only partly mediated via PARS inhibition, as the chelator also protected PARS‐deficient thymocytes from peroxynitrite‐induced death.

While being cytoprotective against peroxynitrite‐induced necrotic death, TPEN (10 μM), similar to other agents that inhibit PARS, enhanced apoptosis (at 5–6 h after exposure), as characterized by phosphatydilserine exposure, caspase activation and DNA fragmentation.

In conclusion, the current data demonstrate that TPEN, most likely by zinc chelation, exerts protective effects against peroxynitrite‐induced necrosis. Its effects are, in part, mediated by inhibition of PARS.

British Journal of Pharmacology (1999) 126, 769–777; doi:10.1038/sj.bjp.0702332
Non‐specific action of methoxamine on Ito, and the cloned channels hKv 1.5 and Kv 4.2
Authors: Parker Chris , Li Qi , Fedida David
Published: January 2005

The α1‐adrenoceptor agonist methoxamine acted independently of receptor activation to reduce Ito and the sustained outward current in rat ventricular myocytes, and hKv 1.5 and Kv 4.2 cloned K+ channel currents. Two hundred μM methoxamine reduced Ito by 36% in the presence of 2 μM prazosin, and by 37 and 38% after preincubation of myocytes with either N‐ethylmaleimide or phenoxybenzamine (n=6). The EC50 values at +60 mV for direct reduction of Ito, hKv 1.5, and Kv 4.2 by methoxamine were 239, 276, and 363 μM, respectively, with Hill coefficients of 0.87–1.5.

Methoxamine accelerated Ito and Kv 4.2 current inactivation in a concentration‐ and voltage‐dependent manner. Apparent rate constants for methoxamine binding and unbinding gave Kd values in agreement with EC50 values measured from dose‐response relations. The voltage‐dependence of block supported charged methoxamine binding to a putative intracellular site that sensed ∼20% of the transmembrane electrical field.

In the presence of methoxamine, deactivating Kv 4.2 tail currents displayed a distinct rising phase, and were slowed relative to control, such that tail current crossover was observed. These observations support a dominant mechanism of open channel block, although closed channel block could not be ruled out.

Single‐channel data from hKv 1.5 patches revealed increased closed times with blank sweeps and decreased burst duration in the presence of drug, and a reduction of mean channel open time from 1.8 ms in control to 0.4 ms in 500 μM methoxamine. For this channel, therefore, both open and closed channel block appeared to be important mechanisms for the action of methoxamine.

British Journal of Pharmacology (1999) 126, 595–606; doi:10.1038/sj.bjp.0702335
Pharmacological diversity between native human 5‐HT1B and 5‐HT1D receptors sited on different neurons and involved in different functions
Authors: Marcoli Manuela , Maura Guido , Munari Claudio , Ruelle Antonio , Raiteri Maurizio
Published: January 2005

The releases of [3H]5‐hydroxytryptamine ([3H]5‐HT) and of endogenous glutamic acid and their modulation through presynaptic h5‐HT1B autoreceptors and h5‐HT1D heteroreceptors have been investigated in synaptosomal preparations from fresh neocortical samples obtained from patients undergoing neurosurgery.

The inhibition by 5‐HT of the K+ (15 mM)‐evoked overflow of [3H]5‐HT was antagonized by the 5‐HT1B/5‐HT1D receptor ligand GR 127935, which was ineffective on its own; this drug was previously found to behave as a full agonist at the h5‐HT1D heteroreceptor regulating glutamate release.

The recently proposed selective h5‐HT1B receptor ligand SB‐224289 also prevented the effect of 5‐HT at the autoreceptor, being inactive on its own; in contrast, SB‐224289, at 1 μM, was unable to interact with the h5‐HT1D heteroreceptor.

The inhibitory effect of 5‐HT on the K+‐evoked overflow of glutamate was antagonized by the h5‐HT1D receptor ligand BRL‐15572; added in the absence of 5‐HT the compound was without effect. BRL‐15572 (1 μM) was unable to modify the effect of 5‐HT at the autoreceptor regulating [3H]5‐HT release.

The selective 5‐HT1A receptor antagonist (+)‐WAY 100135, previously found to be an agonist at the h5‐HT1D heteroreceptor regulating glutamate release, could not interact with the h5‐HT1B autoreceptor when added at 1 μM.

It is concluded that native h5‐HT1B and h5‐HT1D receptors exhibit a hitherto unexpected pharmacological diversity.

British Journal of Pharmacology (1999) 126, 607–612; doi:10.1038/sj.bjp.0702336
Effects of a new C5a receptor antagonist on C5a‐ and endotoxin‐ induced neutropenia in the rat
Authors: Short Anna , Wong Allan K , Finch Angela M , Haaima Gerald , Shiels Ian A , Fairlie David P , Taylor Stephen M
Published: January 2005

A new C5a receptor antagonist, the cyclic peptide Phe‐[Orn‐Pro‐D‐cyclohexylalanine‐Trp‐Arg], (F‐[OPdChaWR]), was tested for its ability to antagonize the neutropenic effects of both C5a and endotoxin in rats. Human recombinant C5a (2 μg kg−1 i.v.) caused rapid neutropenia, characterized by an 83% decrease in circulating polymorphonuclear leukocytes (PMNs) at 5 min. Administration of F‐[OPdChaWR] (0.3–3 mg kg−1 i.v.), did not affect the levels of circulating PMNs but, when given 10 min prior to C5a, it inhibited the C5a‐induced neutropenia by up to 70%. Administration of E. Coli lipopolysaccharide (LPS, 1 mg kg−1 i.v.) also caused neutropenia with an 88% decrease in circulating PMNs after 30 min. When rats were pretreated with F‐[OPdChaWR] (0.3–10 mg kg−1 i.v.) 10 min prior to LPS, there was a dose‐dependent antagonism of the neutropenia caused by LPS, with up to 69% reversal of neutropenia observed 30 min after LPS administration. These findings suggest that C5a receptor antagonists may have therapeutic potential in the many diseases known to involve either endotoxin or C5a.

British Journal of Pharmacology (1999) 126, 551–554; doi:10.1038/sj.bjp.0702338
Inhibition of inducible nitric oxide synthase by β‐lapachone in rat alveolar macrophages and aorta
Authors: Liu Shing‐Hwa , Tzeng Huei‐Ping , Kuo Min‐Liang , Lin‐Shiau Shoei‐Yn
Published: January 2005

β‐Lapachone, a plant product, has been shown to be a novel inhibitor of DNA topoisomerase. In this study, we performed experiments to examine the effects of β‐lapachone on lipopolysaccharide (LPS)‐induced inducible nitric oxide (NO) synthase (iNOS) in rat alveolar macrophages and aortic rings.

In alveolar macrophages, incubation with LPS (10 μg ml−1) for various time intervals resulted in a significant increase in nitrite production and iNOS protein synthesis, that was inhibited by co‐incubation with β‐lapachone (1–4.5 μM) without any cytotoxic effects. However, addition of β‐lapachone after induction of NO synthase by LPS failed to affect the nitrite production.

Treatment with LPS (10 μg ml−1) for 6 h resulted in significant expression of mRNA for iNOS which was significantly inhibited in the presence of β‐lapachone (3 μM) in alveolar macrophages.

In endothelium‐intact rings of thoracic aorta, β‐lapachone (1 and 3 μM) markedly inhibited the hypocontractility to phenylephrine in aortic rings treated with LPS (10 μg ml−1) for 4 h. When β‐lapachone was added 3 h after LPS into the medium, the contractions evoked by phenylephrine were not significantly different in the presence or absence of β‐lapachone.

Treatment with LPS (10 μg ml−1) for 4 h resulted in a significant increase in iNOS protein synthesis which was inhibited in the presence of β‐lapachone (3 μM), but did not affect the constitutive (endothelial and neuronal) NOS forms in aortic rings.

These results indicate that β‐lapachone is capable of inhibiting expression and function of iNOS in rat alveolar macrophages and aortic rings. It is considered that β‐lapachone can be developed as a potential anti‐inflammatory agent in the future.

British Journal of Pharmacology (1999) 126, 746–750; doi:10.1038/sj.bjp.0702341
Assessment of the effects of endothelin‐1 and magnesium sulphate on regional blood flows in conscious rats, by the coloured microsphere reference technique
Authors: Kemp P A , Gardiner S M , March J E , Rubin P C , Bennett T
Published: January 2005

There is evidence to suggest that magnesium (Mg2+) is beneficial in the treatment of a number of conditions, including pre‐eclampsia and acute myocardial infarction. The mode of action of Mg2+ in these conditions is not clear, although the vasodilator properties of Mg2+ are well documented both in vitro and in vivo.

Previously, we demonstrated that i.v. infusion of magnesium sulphate (MgSO4) alone, or in the presence of vasoconstrictors, caused increases in flow and conductance in the common carotid, internal carotid and hindquarters vascular beds, in conscious rats. Therefore, the objective of the present study was to investigate the regional and subregional changes in haemodynamics in response to the vasoconstrictor peptide endothelin‐1 (ET‐1) and MgSO4 in more detail, using the coloured microsphere reference technique.

Infusion of ET‐1 and MgSO4 had similar effects on heart rate and mean arterial pressure as in our previous study. Infusion of ET‐1 caused a rise in mean arterial pressure and a fall in heart rate, and infusion of MgSO4 returned mean arterial pressure to control levels with no effect on heart rate.

The responses to MgSO4 in the presence of ET‐1 showed considerable regional heterogeneity with blood flow increasing (e.g. skeletal muscle), decreasing (e.g. stomach) or not changing (e.g. kidney). Of particular interest was the finding that MgSO4 caused increases in flow in the cerebral and coronary vascular beds.

This, and our previous studies, have shown that MgSO4 can reverse vasoconstriction in a number of vascular beds, and indicate that this compound may have therapeutic benefit in conditions associated with vasospasm.

British Journal of Pharmacology (1999) 126, 621–626; doi:10.1038/sj.bjp.0702342
Attenuation of haloperidol‐induced catalepsy by a 5‐HT2C receptor antagonist
Authors: Reavill C , Kettle A , Holland V , Riley G , Blackburn T P
Published: January 2005

Atypical neuroleptics produce fewer extrapyramidal side‐effects (EPS) than typical neuroleptics. The pharmacological profile of atypical neuroleptics is that they have equivalent or higher antagonist affinity for 5‐HT2 than for dopamine D2 receptors. Our aim was to identify which 5‐HT2 receptor contributed to the atypical profile. Catalepsy was defined as rats remaining immobile over a horizontal metal bar for at least 30 s, 90 min after dosing. Radioligand binding assays were carried out with homogenates of human recombinant 5‐HT2A, 5‐HT2B and 5‐HT2C receptors expressed in Human Embryo Kidney (HEK293) cells. Haloperidol (1.13 mg kg−1 i.p.) induced catalepsy in all experiments. The selective 5‐HT2C/2B receptor antagonist, SB‐228357 (0.32–10 mg kg−1 p.o.) significantly reversed haloperidol‐induced catalepsy whereas the 5‐HT2A and 5‐HT2B receptor antagonists, MDL‐100907 (0.003–0.1 mg kg−1 p.o.) and SB‐215505 (0.1–3.2 mg kg−1 p.o.) respectively did not reverse haloperidol‐induced catalepsy. The data suggest a role for 5‐HT2C receptors in the anticataleptic action of SB‐228357.

British Journal of Pharmacology (1999) 126, 572–574; doi:10.1038/sj.bjp.0702350
Roles of oxygen radicals and elastase in citric acid‐induced airway constriction of guinea‐pigs
Authors: Lai Y ‐L , Chiou W ‐Y , Lu F J , Chiang L Y
Published: January 2005

Antioxidants attenuate noncholinergic airway constriction. To further investigate the relationship between tachykinin‐mediated airway constriction and oxygen radicals, we explored citric acid‐induced bronchial constriction in 48 young Hartley strain guinea‐pigs, divided into six groups: control; citric acid; hexa(sulphobutyl)fullerenes+citric acid; hexa(sulphobutyl)fullerenes+phosphoramidon+citric acid; dimethylthiourea (DMTU)+citric acid; and DMTU+phosphoramidon+citric acid. Hexa(sulphobutyl)fullerenes and DMTU are scavengers of oxygen radicals while phosphoramidon is an inhibitor of the major degradation enzyme for tachykinins.

Animals were anaesthetized, paralyzed, and artificially ventilated. Each animal was given 50 breaths of 4 ml saline or citric acid aerosol. We measured dynamic respiratory compliance (Crs), forced expiratory volume in 0.1 (FEV0.1), and maximal expiratory flow at 30% total lung capacity (V[dot above]max30) to evaluate the degree of airway constriction.

Citric acid, but not saline, aerosol inhalation caused marked decreases in Crs, FEV0.1 and V[dot above]max30, indicating marked airway constriction. This constriction was significantly attenuated by either hexa(sulphobutyl)fullerenes or by DMTU. In addition, phosphoramidon significantly reversed the attenuating action of hexa(sulphobutyl)fullerenes, but not that of DMTU.

Citric acid aerosol inhalation caused increases in both lucigenin‐ and t‐butyl hydroperoxide‐initiated chemiluminescence counts, indicating citric acid‐induced increase in oxygen radicals and decrease in antioxidants in bronchoalveolar lavage fluid. These alterations were significantly suppressed by either hexa(sulphobutyl)fullerenes or DMTU.

An elastase inhibitor eglin‐c also significantly attenuated citric acid‐induced airway constriction, indicating the contributing role of elastase in this type of constriction.

We conclude that both oxygen radicals and elastase play an important role in tachykinin‐mediated, citric acid‐induced airway constriction.

British Journal of Pharmacology (1999) 126, 778–784; doi:10.1038/sj.bjp.0702352
Dual coupling of heterologously‐expressed rat P2Y6 nucleotide receptors to N‐type Ca2+ and M‐type K+ currents in rat sympathetic neurones
Authors: Filippov Alexander K , Webb Tania E , Barnard Eric A , Brown David A
Published: January 2005

The P2Y6 receptor is a uridine nucleotide‐specific G protein‐linked receptor previously reported to stimulate the phosphoinositide (PI) pathway. We have investigated its effect in neurones, by micro‐injecting its cRNA into dissociated rat sympathetic neurones and recording responses of N‐type Ca2+ (ICa(N)) and M‐type K+ (IK(M)) currents.

In P2Y6 cRNA‐injected neurones, UDP or UTP produced a voltage‐dependent inhibition of ICa(N) by ∼53% in whole‐cell (disrupted‐patch) mode and by ∼73% in perforated‐patch mode; no inhibition occurred in control cells. Mean IC50 values (whole‐cell) were: UDP, 5.9±0.3 nM; UTP, 20±1 nM. ATP and ADP (1 μM) had no significant effect. Pertussis toxin (PTX) substantially (∼60%) reduced UTP‐mediated inhibition in disrupted patch mode but not in perforated‐patch mode.

Uridine nucleotides also inhibited IK(M) in P2Y6 cRNA‐injected cells (by up to 71% at 10 μM UTP; perforated‐patch). Mean IC50 values were: UDP, 30±3 nM; UTP, 115±12 nM. ATP (10 μM) again had no effect. No significant inhibition occurred in control cells. Inhibition was PTX‐resistant.

Thus, the P2Y6 receptor, like the P2Y2 subtype studied in this system, couples to both of these two neuronal ion channels through at least two different G proteins. However, the P2Y6 receptor displays a much higher sensitivity to its agonists than the P2Y2 receptor in this expression system and higher than previously reported using other expression methods. The very high sensitivity to both UDP and UTP suggests that it might be preferentially activated by any locally released uridine nucleotides.

British Journal of Pharmacology (1999) 126, 1009–1017; doi:10.1038/sj.bjp.0702356
An in vitro electrophysiological study on the effects of phenytoin, lamotrigine and gabapentin on striatal neurons
Authors: Calabresi P , Centonze D , Marfia G A , Pisani A , Bernardi G
Published: January 2005

We performed intracellular recordings from a rat corticostriatal slice preparation in order to compare the electrophysiological effects of the classical antiepileptic drug (AED) phenytoin (PHT) and the new AEDs lamotrigine (LTG) and gabapentin (GBP) on striatal neurons.

PHT, LTG and GBP affected neither the resting membrane potential nor the input resistance/membrane conductance of the recorded cells. In contrast, these agents depressed in a dose‐dependent and reversible manner the current‐evoked repetitive firing discharge.

These AEDs also reduced the amplitude of glutamatergic excitatory postsynaptic potentials (EPSPs) evoked by cortical stimulation. However, substantial pharmacological differences between these drugs were found. PHT was the most effective and potent agent in reducing sustained repetitive firing of action potentials, whereas LTG and GBP preferentially inhibited corticostriatal excitatory transmission. Concentrations of LTG and GBP effective in reducing EPSPs, in fact, produced only a slight inhibition of the firing activity of these cells.

LTG, but not PHT and GBP, depressed cortically‐evoked EPSPs increasing paired‐pulse facilitation (PPF) of synaptic transmission, suggesting that a presynaptic site of action was implicated in the effect of this drug. Accordingly, PHT and GBP, but not LTG reduced the membrane depolarizations induced by exogenously‐applied glutamate, suggesting that these drugs preferentially reduce postsynaptic sensitivity to glutamate released from corticostriatal terminals.

These data indicate that in the striatum PHT, LTG and GBP decrease neuronal excitability by modulating multiple sites of action. The preferential modulation of excitatory synaptic transmission may represent the cellular substrate for the therapeutic effects of new AEDs whose use may be potentially extended to the therapy of neurodegenerative diseases involving the basal ganglia.

British Journal of Pharmacology (1999) 126, 689–696; doi:10.1038/sj.bjp.0702361
Aryl propanolamines: comparison of activity at human β3 receptors, rat β3 receptors and rat atrial receptors mediating tachycardia
Authors: Cohen Marlene L , Bloomquist William , Kriauciunas Aidas , Shuker Anthony , Calligaro David
Published: January 2005

The in vitro activity of four aryl propanolamines was compared to two prototypic β3 receptor agonists, CGP 12177 and CL316243 at the human β3 receptor, the rat β3 receptor in the stomach fundus and receptors mediating atrial tachycardia.

L‐739,574 was the most potent (EC50=9 nM) and selective agonist at the human β3 receptor with high maximal response (74% of the maximal response to isoproterenol).

A phenol‐biaryl ether analogue possessed modest affinity for the human β3 receptor (EC50=246 nM), but was highly efficacious with a maximal response 82% of the maximal response to isoproterenol. The other derivatives were intermediate in potency with low maximal responses.

These agonists at the human β3 receptor did not activate the rat β3 receptor in the rat stomach fundus. In fact, the aryl propanolamines (10−6 M) inhibited CL316243‐induced activation of the rat β3 receptor. Thus, agonist activity at the human β3 receptor translated into antagonist activity at the rat β3 receptor.

L739,574 and the phenol biaryl ether increased heart rate via β1 receptors.

Although CGP12177 produced atrial tachycardia, neither the indole sulphonamide nor biphenyl biaryl ether did, although both had high affinity for the human β3 receptor. Thus, the atrial tachycardic receptor was not identical to the human β3 receptor.

These studies (a) characterized four aryl propanolamines with high affinity at the human β3 receptor, (b) found that they were antagonists at the rat β3 receptor, an observation with profound implications for in vivo rat data, and (c) established that the rodent atrial non‐β1, β2 or β3 tachycardic receptor was also unrelated to the human β3 receptor.

British Journal of Pharmacology (1999) 126, 1018–1024; doi:10.1038/sj.bjp.0702364
Studies on the role of dopamine in the degeneration of 5‐HT nerve endings in the brain of Dark Agouti rats following 3,4‐methylenedioxymethamphetamine (MDMA or ‘ecstasy’) administration
Authors: Colado M I , O'Shea E , Granados R , Esteban B , Martín A B , Green A R
Published: January 2005

We investigated whether dopamine plays a role in the neurodegeneration of 5‐hydroxytryptamine (5‐HT) nerve endings occurring in Dark Agouti rat brain after 3,4‐methylenedioxymethamphetamine (MDMA or ‘ecstasy’) administration.

Haloperidol (2 mg kg−1 i.p.) injected 5 min prior and 55 min post MDMA (15 mg kg−1 i.p.) abolished the acute MDMA‐induced hyperthermia and attenuated the neurotoxic loss of 5‐HT 7 days later. When the rectal temperature of MDMA+haloperidol treated rats was kept elevated, this protective effect was marginal.

MDMA (15 mg kg−1) increased the dopamine concentration in the dialysate from a striatal microdialysis probe by 800%. L‐DOPA (25 mg kg−1 i.p., plus benserazide, 6.25 mg kg−1 i.p.) injected 2 h after MDMA (15 mg kg−1) enhanced the increase in dopamine in the dialysate, but subsequent neurodegeneration was unaltered. L‐DOPA (25 mg kg−1) injected before a sub‐toxic dose of MDMA (5 mg kg−1) failed to induce neurodegeneration.

The MDMA‐induced increase in free radical formation in the hippocampus (indicated by increased 2,3‐ and 2,5‐dihydroxybenzoic acid in a microdialysis probe perfused with salicylic acid) was unaltered by L‐DOPA.

The neuroprotective drug clomethiazole (50 mg kg−1 i.p.) did not influence the MDMA‐induced increase in extracellular dopamine.

These data suggest that previous observations on the protective effect of haloperidol and potentiating effect of L‐DOPA on MDMA‐induced neurodegeneration may have resulted from effects on MDMA‐induced hyperthermia.

The increased extracellular dopamine concentration following MDMA may result from effects of MDMA on dopamine re‐uptake, monoamine oxidase and 5‐HT release rather than an ‘amphetamine‐like’ action on dopamine release, thus explaining why the drug does not induce degeneration of dopamine nerve endings.

British Journal of Pharmacology (1999) 126, 911–924; doi:10.1038/sj.bjp.0702373
Investigation of the inhibitory effects of homocysteine and copper on nitric oxide‐mediated relaxation of rat isolated aorta
Authors: Emsley Alison M , Jeremy Jamie Y , Gomes Guiomar N , Angelini Gianni D , Plane Frances
Published: January 2005

Elevated plasma levels of homocysteine (HC) and copper have both been associated with the development of inflammatory vascular diseases, such as atherosclerosis. In this study, the effects of a combination of HC and copper on nitric oxide (NO)‐mediated relaxation of isolated rat aortic rings were investigated.

Exposure to HC (10–100 μM; 30 min) had no effect on relaxation to acetylcholine (ACh; 0.01–10 μM, n=4). Pre‐incubation of aortic rings with a higher concentration of HC for an extended period (1 mM; 180 min) significantly inhibited endothelium‐dependent relaxation (n=4), but this inhibition was prevented by the presence of the copper chelator bathocuprione (10 μM, 180 min, n=6).

Exposure to HC (100 μM) and copper (10–100 μM; 30 min) caused a copper concentration‐dependent inhibition of endothelium‐dependent relaxation (n=4). This inhibitory effect was reduced in the presence of either superoxide dismutase (SOD; 100 u ml−1; n=4) or catalase (100 u ml−1; n=4), and further reduced by the presence of both enzymes (n=5).

HC and copper (100 μM; 30 min) significantly inhibited endothelium‐independent relaxation to glyceryl trinitrate (0.01–10 μM; n=8). In contrast, HC (1 mM), alone or in combination with copper (100 μM), did not inhibit relaxation to the endothelium‐independent relaxant sodium nitroprusside (0.01–10 μM; n=4).

These data indicate that the presence of copper greatly enhances the inhibitory actions of HC on NO‐mediated relaxation of isolated aortic rings. The reduction of inhibition by catalase and SOD indicates a possible role for copper‐catalyzed generation of superoxide and hydrogen peroxide leading to an increased inactivation or decreased production of endothelium‐derived NO.

British Journal of Pharmacology (1999) 126, 1034–1040; doi:10.1038/sj.bjp.0702374