bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of the effects of P2 purinoceptor ligands on the micturition reflex in female urethane‐anaesthetized rats
Authors: King Brian F , Knowles Ian D , Burnstock Geoffrey , Ramage Andrew G 
Published: June 2004

The effects of purinoceptor ligands for P2X1 and/or P2X3 receptors (α,β‐meATP, IP5I, TNP‐ATP, MRS 2179, PPADS, Phenol red and RO116‐6446/008; i.v., n=4–5) and for P2Y1 receptors (PPADS, MRS 2179 and MRS 2269; i.v., n=3–5) were investigated on the distension‐evoked ‘micturition reflex’ in the urethane‐anaesthetized female rat.
α,β‐meATP (180 nmol kg−1 min−1), IP5I (10, 30 and 100 nmol kg−1), TNP‐ATP (1 μmol kg−1), MRS 2179 (1 μmol kg−1) and PPADS (17 μmol kg−1) each caused maintained bladder contractions to occur during the infusion of saline into the bladder. PPADS (17 μmol kg−1 min−1) had a similar effect when infused intravesicularly. Regular bladder contractions were not observed until the infusion of saline was halted. For IP5I, TNP‐ATP, MRS 2179 and PPADS, the magnitude of postinfusion isovolumetric contractions was significantly reduced and, for IP5I, this action was also associated with a significant reduction in urethral relaxation. Additionally, TNP‐ATP caused a significant increase in the pressure and volume thresholds required to initiate a reflex.
Phenol red (a P2X1/P2X3 antagonist; 0.1 and 1 μmol kg−1) caused a significant increase in the pressure and volume thresholds required to initiate a reflex and, at the higher dose, also caused a reduction in postinfusion isovolumetric contractions.
RO116‐6446/008 (a P2X1‐selective antagonist; 1 and 10 μmol kg−1) only caused a reduction in postinfusion isovolumetric contractions.
It is concluded that P2X1 and P2X3 receptors play a fundamental role in the micturition reflex in urethane‐anesthetized female rats. P2X3 receptor blockade raised the pressure and volume thresholds for the reflex, whereas P2X1 receptor blockade diminished motor activity associated with voiding. P2Y1 receptors may be involved in inhibition of rat detrusor tone.

British Journal of Pharmacology (2004) 142, 519–530. doi:10.1038/sj.bjp.0705790
NO and KATP channels underlie endotoxin‐induced smooth muscle hyperpolarization in rat mesenteric resistance arteries
Authors: Wu C C , Chen S J , Garland C J 
Published: June 2004

Smooth muscle membrane potential and tension measurements were made in isolated mesenteric resistance arteries from rats exposed to bacterial endotoxin (lipopolysaccharide, LPS; 10 mg kg−1, i.p.) for 3 h to mimic septic shock syndrome.
Over this period, rats developed an endotoxaemic response, assessed in vivo as a 41±4 mmHg drop in mean blood pressure, vascular hyporeactivity to noradrenaline (1 μg kg−1, i.v.) and a significant increase in core body temperature.
In mesenteric small resistance arteries from these rats (o.d. 180 – 240 μm), phenylephrine (0.01–3 μM)‐evoked contraction was not altered when compared with arteries from sham‐operated animals, but the concentration–relaxation curve to acetylcholine (ACh; 0.01 – 3 μM) displayed a small, but significant, shift to the right.
The smooth muscle resting membrane potential (−70.3±1.6 mV) in arteries from LPS‐treated rats was significantly greater than in control arteries (−55.4±1.2 mV), but in both cases the smooth muscle was depolarized to a similar potential by the application of Nω‐nitro‐L‐arginine methyl ester (L‐NAME; 0.3 mM; −54.1±2.3 vs −52.4±2.5 mV) or glibenclamide (10 μM; −55.0±2.1 vs −50.4±2.0 mV).
ACh (1 μM) elicited a maximal hyperpolarization, which ranged from −14.7±3.2 mV (in arteries from LPS‐treated rats) to –20.6±2.4 mV (in arteries from sham‐operated rats), and was not altered by the presence of L‐NAME. Levcromakalim (1 μM) increased the smooth muscle membrane potential by around −24 mV in arteries from both sets of experimental animals.
These results indicate that at the level of the resistance vasculature, endotoxaemia is associated with pronounced smooth muscle hyperpolarization reflecting the action of NO on KATP channels. These changes were not associated with vascular hyporeactivity or depressed endothelial cell function in vitro, suggesting that mesenteric resistance arteries may not contribute to equivalent changes in vivo.

British Journal of Pharmacology (2004) 142, 479–484. doi:10.1038/sj.bjp.0705794
Inhibition of cardiac HERG currents by the DNA topoisomerase II inhibitor amsacrine: mode of action
Authors: Thomas Dierk , Hammerling Bettina C , Wu Kezhong , Wimmer Anna‐Britt , Ficker Eckhard K , Kirsch Glenn E , Kochan Mary C , Wible Barbara A , Scholz Eberhard P , Zitron Edgar , Kathöfer Sven , Kreye Volker A W , Katus Hugo A , Schoels Wolfgang , Karle Christoph A , Kiehn Johann 
Published: June 2004

The topoisomerase II inhibitor amsacrine is used in the treatment of acute myelogenous leukemia. Although most anticancer drugs are believed not to cause acquired long QT syndrome (LQTS), concerns have been raised by reports of QT interval prolongation, ventricular fibrillation and death associated with amsacrine treatment. Since blockade of cardiac human ether‐a‐go‐go‐related gene (HERG) potassium currents is an important cause of acquired LQTS, we investigated the acute effects of amsacrine on cloned HERG channels to determine the electrophysiological basis for its proarrhythmic potential.
HERG channels were heterologously expressed in human HEK 293 cells and Xenopus laevis oocytes, and the respective potassium currents were recorded using patch‐clamp and two‐microelectrode voltage‐clamp electrophysiology.
Amsacrine blocked HERG currents in HEK 293 cells and Xenopus oocytes in a concentration‐dependent manner, with IC50 values of 209.4 nM and 2.0 μM, respectively.
HERG channels were primarily blocked in the open and inactivated states, and no additional voltage dependence was observed. Amsacrine caused a negative shift in the voltage dependence of both activation (−7.6 mV) and inactivation (−7.6 mV). HERG current block by amsacrine was not frequency dependent.
The S6 domain mutations Y652A and F656A attenuated (Y652A) or abolished (F656A, Y652A/F656A) HERG current blockade, indicating that amsacrine binding requires a common drug receptor within the pore‐S6 region.
In conclusion, these data demonstrate that the anticancer drug amsacrine is an antagonist of cloned HERG potassium channels, providing a molecular mechanism for the previously reported QTc interval prolongation during clinical administration of amsacrine.

British Journal of Pharmacology (2004) 142, 485–494. doi:10.1038/sj.bjp.0705795
Differential modulation of Nav1.7 and Nav1.8 peripheral nerve sodium channels by the local anesthetic lidocaine
Authors: Chevrier P , Vijayaragavan K , Chahine M 
Published: June 2004

Voltage‐gated Na+ channels are transmembrane proteins that are essential for the propagation of action potentials in excitable cells. Nav1.7 and Nav1.8 dorsal root ganglion Na+ channels exhibit different kinetics and sensitivities to tetrodotoxin (TTX). We investigated the properties of both channels in the presence of lidocaine, a local anesthetic (LA) and class I anti‐arrhythmic drug.
Nav1.7 and Nav1.8 Na+ channels were coexpressed with the β1‐subunit in Xenopus oocytes. Na+ currents were recorded using the two‐microelectrode voltage‐clamp technique.
Dose–response curves for both channels had different EC50 (dose producing 50% maximum current inhibition) (450 μM for Nav1.7 and 104 μM for Nav1.8). Lidocaine enhanced current decrease in a frequency‐dependent manner. Steady‐state inactivation of both channels was also affected by lidocaine, Nav1.7 being the most sensitive. Only the steady‐state activation of Nav1.8 was affected while the entry of both channels into slow inactivation was affected by lidocaine, Nav1.8 being affected to a larger degree.
Although the channels share homology at DIV S6, the LA binding site, they differ in their sensitivity to lidocaine. Recent studies suggest that other residues on DI and DII known to influence lidocaine binding may explain the differences in affinities between Nav1.7 and Nav1.8 Na+ channels.
Understanding the properties of these channels and their pharmacology is of critical importance to developing drugs and finding effective therapies to treat chronic pain.

British Journal of Pharmacology (2004) 142, 576–584. doi:10.1038/sj.bjp.0705796
Ginseng saponins induce store‐operated calcium entry inXenopusoocytes
Authors: Jeong Sang Min , Lee Jun‐Ho , Kim Sunoh , Rhim Hyewhon , Lee Byung‐Hwan , Kim Jong‐Hoon , Oh Jae‐Wook , Lee Sang‐Mok , Nah Seung‐Yeol 
Published: June 2004

We investigated the effect of the active ingredients ofPanaxginseng, ginsenosides, on store‐operated Ca2+entry (SOCE) using a two‐electrode voltage clamp technique inXenopusoocytes in which SOCE is monitored through Ca2+‐activated Cl−currents.Under hyperpolarizing voltage clamp conditions, treatment with ginsenosides produced a biphasic Ca2+‐activated Cl−current consisting of a rapid transient inward current and a slowly developing secondary sustained inward current. The transient inward current was inactivated rapidly, whereas the sustained inward current persisted for nearly 10 min. The effect of ginsenosides on the biphasic current was dose‐dependent and reversible. The EC50was 42.8±11.6 and 46.6±7.1μg ml−1for the transient and sustained inward current, respectively.In the absence of extracellular Ca2+ginsenosides induced only a transient inward current but in the presence of extracellular Ca2+ginsenosides induced the biphasic current. Magnitudes of the sustained currents were dependent on extracellular Ca2+concentration. Sustained inward current induced by ginsenosides, but not transient inward current, and ginsenoside‐induced store‐operated Ca2+(SOC) currents (ISOC) were blocked by La3+, a Ca2+channel blocker, suggesting that the sustained inward current andISOCwas derived from an influx of extracellular Ca2+.Treatment with 2‐APB and heparin, which are IP3receptor antagonists, inhibited the ginsenoside‐induced biphasic current. Treatment with the PLC inhibitor, U73122, also inhibited the ginsenoside‐induced biphasic current. Intraoocyte injection of ATP‐γS, but not adenylyl AMP‐PCP, induced a persistent activation of ginsenoside‐induced sustained current but did not affect the transient current.In rat hippocampal neurons, ginsenosides inhibited both carbachol‐stimulated intracellular Ca2+release and intracellular Ca2+depletion‐activated SOCE.These results indicate that ginsenoside might act as a differential regulator of intracellular Ca2+levels in neurons andXenopusoocytes.British Journal of Pharmacology(2004)142, 585–593. doi:10.1038/sj.bjp.0705797
Effects of chronic treatment with escitalopram or citalopram on extracellular 5‐HT in the prefrontal cortex of rats: role of 5‐HT1A receptors
Authors: Ceglia I , Acconcia S , Fracasso C , Colovic M , Caccia S , Invernizzi R W 
Published: June 2004

Microdialysis was used to study the acute and chronic effects of escitalopram (S‐citalopram; ESCIT) and chronic citalopram (CIT), together with the 5‐HT1A receptor antagonist WAY100,635 (N‐[2‐[methoxyphenyl)‐1‐piperazinyl]ethyl]‐N‐(2‐pyridinyl) cyclohexane carboxamide trihydrochloride) and the 5‐HT1A receptor agonist 8‐hydroxy‐2‐(di‐n‐propylamino)tetralin (8‐OH‐DPAT), on extracellular 5‐hydroxytryptamine (5‐HT) levels in the rat prefrontal cortex.
Extracellular 5‐HT rose to 234 and 298% of basal values after subcutaneous (s.c.) acute doses of 0.15 and 0.63 mg kg−1 ESCIT. No further increase was observed at 2.5 mg kg−1 ESCIT (290%).
The effect of 13‐day s.c. infusion of 10 mg kg−1day−1 ESCIT on extracellular 5‐HT (422% of baseline) was greater than after 2 days (257% of baseline), whereas exposure to ESCIT was similar. In contrast, the increase in extracellular 5‐HT induced by the infusion of CIT for 2 (306%) and 13 days (302%) was similar. However, brain and plasma levels of S‐citalopram in rats infused with CIT for 13 days were lower than after 2 days.
Acute treatment with 2.5 mg kg−1 ESCIT or 5 mg kg−1 CIT raised extracellular 5‐HT by 243 and 276%, respectively, in rats given chronic vehicle but had no effect in rats given ESCIT (10 mg kg−1 day−1) or CIT (20 mg kg−1 day−1) for 2 or 13 days, suggesting that the infused doses had maximally increased extracellular 5‐HT. WAY100,635 (0.1 mg kg−1 s.c.) increased extracellular 5‐HT levels by 168, 174 and 169% of prechallenge values in rats infused with vehicle or ESCIT for 2 or 13 days, respectively. WAY100,635 enhanced extracellular 5‐HT levels to 226, 153 and 164% of prechallenge values in rats infused with vehicle or CIT for 2 and 13 days, respectively.
8‐OH‐DPAT (0.025 mg kg−1) reduced extracellular 5‐HT by 54% in control rats, but had no effect in those given ESCIT and CIT for 13 days.
This series of experiments led to the conclusion that chronic treatment with ESCIT desensitizes the 5‐HT1A receptors, regulating the release of 5‐HT in the prefrontal cortex and enhances the effect of the drug on extracellular 5‐HT. They also indicate that chronic treatment with ESCIT and CIT did not prevent WAY100,635 from raising extracellular 5‐HT.

British Journal of Pharmacology (2004) 142, 469–478. doi:10.1038/sj.bjp.0705800
Heterogeneity in the mechanisms of vasorelaxation to anandamide in resistance and conduit rat mesenteric arteries
Authors: O'Sullivan Saoirse E , Kendall David A , Randall Michael D 
Published: June 2004

In order to address mechanistic differences between arterial vessel types, we have compared the vasorelaxant actions of anandamide in resistance (G3) and conduit (G0) mesenteric arteries.
Anandamide produced concentration‐dependent relaxations of pre‐constricted G3 arteries with a maximal response that was significantly greater than seen in G0.
The CB1 receptor selective antagonists SR141716A (100 nM) and AM251 (100 nM) caused reductions in the vasorelaxant responses to anandamide in both arteries. Maximal vasorelaxant responses to anandamide were reduced in both arteries after treatment with capsaicin to deplete sensory neurotransmitters (10 μM for 1 h).
Vasorelaxation to anandamide was not affected by the nitric oxide synthase inhibitor NG‐nitro‐L‐arginine methyl ester (L‐NAME, 300 μM) in either artery. Only responses in G3 arteries were sensitive to removal of the endothelium. In G3 vessels only, vasorelaxation to anandamide was reduced by inhibition of EDHF activity with a combination of charybdotoxin (100 nM) and apamin (500 nM) in the presence of L‐NAME (300 μM) and indomethacin (10 μM).
Antagonism of the novel endothelial cannabinoid receptor (O‐1918, 1 μM) caused a reduction in the sensitivity to anandamide in G3 but not G0.
G3, but not G0, vessels showed a small reduction in vasorelaxant responses to anandamide after inhibition of gap junctional communication with 18α‐GA (100 μM).
These results demonstrate that there are differences in the mechanisms of vasorelaxation to anandamide between conduit and resistance mesenteric arteries. In small resistance vessels, vasorelaxation occurs through stimulation of vanilloid receptors, CB1 receptors, and an endothelial receptor coupled to EDHF release. By contrast, in the larger mesenteric artery, vasorelaxation is almost entirely due to stimulation of vanilloid receptors and CB1 receptors, and is endothelium‐independent.

British Journal of Pharmacology (2004) 142, 435–442. doi:10.1038/sj.bjp.0705810
A novel inhibitor of vacuolar ATPase, FR167356, which can discriminate between osteoclast vacuolar ATPase and lysosomal vacuolar ATPase
Authors: Niikura Kazuaki , Takano Mikiko , Sawada Masae 
Published: June 2004

Vacuolar ATPase (V‐ATPase) has been proposed as a drug target in lytic bone diseases. Studies of bafilomycin derivatives suggest that the key issue regarding the therapeutic usefulness of V‐ATPase inhibitors is selective inhibition of osteoclast V‐ATPase. Previous efforts to develop therapeutic inhibitors of osteoclast V‐ATPase have been frustrated by a lack of synthetically tractable and biologically selective leads. Therefore, we tried to find novel potent and specific V‐ATPase inhibitors, which have new structural features and inhibition selectivity, from random screening using osteoclast microsomes. Finally, a novel V‐ATPase inhibitor, FR167356, was obtained through chemical modification of a parental hit compound.
FR167356 inhibited not only H+ transport activity of osteoclast V‐ATPase but also H+ extrusion from cytoplasm of osteoclasts, which depends on the V‐ATPase activity. As expected, FR167356 remarkably inhibited bone resorption in vitro.
FR167356 also showed inhibitory effects on other V‐ATPases, renal brush border V‐ATPase, macrophage microsome V‐ATPase and lysosomal V‐ATPase. However, FR167356 was approximately seven‐fold less potent in inhibiting lysosomal V‐ATPase compared to osteoclast V‐ATPase. Moreover, LDL metabolism in cells, which depends on acidification of lysosome, was blocked merely at higher concentration than bone resorption, suggesting that FR167356 inhibits V‐ATPase of osteoclast ruffled border membrane still more selectively than lysosome at the cellular level.
These results from the experiments seem to indicate that osteoclast V‐ATPase may be different from lysosomal V‐ATPase in respect of their structure.
FR167356 had a novel chemical structural feature as well as inhibitory characteristics distinctly different from any previously known V‐ATPase inhibitor family. Therefore, FR167356 is thought to be a useful tool for estimating the essential characteristics of V‐ATPase inhibitors for drug development.

British Journal of Pharmacology (2004) 142, 558–566. doi:10.1038/sj.bjp.0705812
Chronic NGF treatment of rat nociceptive DRG neurons in culture facilitates desensitization and deactivation of GABAA receptor‐mediated currents
Authors: Fabbro Alessandra , Nistri Andrea 
Published: June 2004

The present study tested the hypothesis that nerve growth factor (NGF) could affect presynaptic inhibition mediated by GABAA (GABA‐sensitive ionotropic receptors) receptors on the afferents of nociceptive dorsal root ganglia (DRG) neurons, thus reducing the filtering of central nociceptive signals.
To investigate this issue, small‐diameter, nociceptive DRG neurons were cultured for 48–72 h either in the normal medium or in the presence of NGF (50 ng ml−1). After 15 min washout, cells were patch clamped with Cs+ containing electrodes to block GABAB (GABA‐sensitive metabotropic receptors) receptor‐activated currents.
Chronically treated DRG neurons showed no difference in the peak amplitude of GABA‐induced currents. However, NGF‐treated cells exhibited increased fading of the response to continuous GABA application, with faster desensitization onset, decreased residual current at the end of agonist application and slower recovery from desensitization. Moreover, the deactivation phase after brief agonist pulses was also accelerated.
Unlike responses to GABA, chronic NGF treatment had no effect on the desensitization process to the excitatory transmitter ATP, as no difference in peak amplitude, fast and slow time constants of current decay was found.
Experimental tests indicated that the observed effects on GABA currents were not a reactive process triggered by washing out NGF after its long application. Acutely applied NGF did not change GABAA receptor‐mediated responses.
NGF‐treated neurons showed decreased sensitivity to the antagonist picrotoxin. The action of pentobarbitone, midazolam, bicuculline or gabazine was, however, unchanged.
These observations suggest that the modulation of GABAA receptor function of DRG nociceptors by NGF may contribute to the algogenic action of this neurotrophin.

British Journal of Pharmacology (2004) 142, 425–434. doi:10.1038/sj.bjp.0705813
Nitric oxide‐dependent modulation of the delayed rectifier K+ current and the L‐type Ca2+ current by ginsenoside Re, an ingredient of Panax ginseng, in guinea‐pig cardiomyocytes
Authors: Bai Chang‐Xi , Takahashi Kentaro , Masumiya Haruko , Sawanobori Tohru , Furukawa Tetsushi 
Published: June 2004

Ginsenoside Re, a major ingredient of Panax ginseng, protects the heart against ischemia–reperfusion injury by shortening action potential duration (APD) and thereby prohibiting influx of excessive Ca2+. Ginsenoside Re enhances the slowly activating component of the delayed rectifier K+ current (IKs) and suppresses the L‐type Ca2+ current (ICa,L), which may account for APD shortening.
We used perforated configuration of patch‐clamp technique to define the mechanism of enhancement of IKs and suppression of ICa,L by ginsenoside Re in guinea‐pig ventricular myocytes.
S‐Methylisothiourea (SMT, 1 μM), an inhibitor of nitric oxide (NO) synthase (NOS), and N‐acetyl‐L‐cystein (LNAC, 1 mM), an NO scavenger, inhibited IKs enhancement. Application of an NO donor, sodium nitroprusside (SNP, 1 mM), enhanced IKs with a magnitude similar to that by a maximum dose (20 μM) of ginseonside Re, and subsequent application of ginsenoside Re failed to enhance IKs. Conversely, after IKs had been enhanced by ginsenoside Re (20 μM), subsequently applied SNP failed to further enhance IKs.
An inhibitor of guanylate cyclase, 1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ, 10 μM), barely suppressed IKs enhancement, while a thiol‐alkylating reagent, N‐ethylmaleimide (NEM, 0.5 mM), clearly suppressed it. A reducing reagent, di‐thiothreitol (DTT, 5 mM), reversed both ginsenoside Re‐ and SNP‐induced IKs enhancement.
ICa,L suppression by ginsenoside Re (3 μM) was abolished by SMT (1 μM) or LNAC (1 mM). NEM (0.5 mM) did not suppress ICa,L inhibition and DTT (5 mM) did not reverse ICa,L inhibition, whereas in the presence of ODQ (10 μM), ginsenoside Re (3 μM) failed to suppress ICa,L.
These results indicate that ginsenoside Re‐induced IKs enhancement and ICa,L suppression involve NO actions. Direct S‐nitrosylation of channel protein appears to be the main mechanism for IKs enhancement, while a cGMP‐dependent pathway is responsible for ICa,L inhibition.

British Journal of Pharmacology (2004) 142, 567–575. doi:10.1038/sj.bjp.0705814
Drosophila melanogaster GRD and LCCH3 subunits form heteromultimeric GABA‐gated cation channels
Authors: Gisselmann Günter , Plonka Justina , Pusch Hermann , Hatt Hanns 
Published: June 2004

In addition to its action as a fast inhibitory neurotransmitter, γ‐aminobutyric acid (GABA) is thought to mediate excitatory action by activating cation currents in some cell types in invertebrates. However, to date no GABA receptor capable of mediating such action has been identified at the molecular level in insects. Using a systematic expression screening approach, we found that the Drosophila ligand‐gated ion channel subunits GRD and LCCH3 combine to form cation‐selective GABA‐gated ion channels when coexpressed in Xenopus laevis oocytes. The heteromultimeric receptor is activated by GABA (EC50=4.5 μM), muscimol (EC50=4.8 μM) and trans‐4‐aminocrotonic acid (EC50=104.5 μM), and partially by cis‐4‐aminocrotonic acid (EC50=106.3 μM). Picrotoxin effectively blocked the GABA‐gated channel (IC50=0.25 μM), but bicuculline, TPMTA, dieldrin and lindane did not. The benzodiazepines flunitrazepam and diazepam did not potentiate the GABA‐evoked current. Our data suggest that heteromultimeric channels composed of GRD and LCCH3 subunits form GABA‐gated cation channels in insects.British Journal of Pharmacology (2004) 142, 409–413. doi:10.1038/sj.bjp.0705818