bluuebunny/crossref_metadata_2025 huggingface dataset:
Active intestinal elimination of ciprofloxacin in rats: modulation by different substrates
Authors: Dautrey S , Felice K , Petiet A , Lacour B , Carbon C , Farinotti R
Published: January 2005

Two in vivo models, in the rat, were used to investigate, in the presence of different substrates, the overall and net intestinal elimination of ciprofloxacin: an open‐intestinal perfusion model and an intestinal loop model respectively.

In the presence of quinidine, verapamil and cyclosporin (substrates of the P‐glycoprotein (P‐gp)), plasma AUCs of ciprofloxacin were 1.5–2 fold increased, while biliary clearance (1.5–2 fold), intestinal overall and net clearances (2–4 fold and 1.5–8 fold respectively) decreased. The weak effect obtained with cyclosporin as compared to verapamil and especially quinidine, suggests, for ciprofloxacin, the existence of transport systems distinct from the P‐gp, as the OCT1 transporter which could be inhibited by quinidine.

With cephalexin and azlocillin, two β‐lactam antibiotics, plasma AUCs of ciprofloxacin increased and biliary and intestinal overall clearances decreased in a similar fashion (1.3–2 fold), suggesting the involvement of organic anion and/or cation transporters.

In the presence of structural analogues, the effect was dependent on the compound administered: Sparfloxacin had no effect on intestinal clearance of ciprofloxacin. In contrast, with pefloxacin, overall intestinal clearance of ciprofloxacin was decreased and net intestinal clearance increased.

The specificity of ciprofloxacin intestinal transport appears to be different from P‐gp as outlined by the lack of competition with sparfloxacin, a P‐gp substrate. Ciprofloxacin intestinal elimination seems to be mediated by organic anion and/or cation transporters and a mechanism sensitive to quinidine and verapamil.

British Journal of Pharmacology (1999) 127, 1728–1734; doi:10.1038/sj.bjp.0702703
An inhibitor of poly (ADP‐ribose) synthetase activity reduces contractile dysfunction and preserves high energy phosphate levels during reperfusion of the ischaemic rat heart
Authors: Docherty John C , Kuzio Bozena , Silvester Jocelyn A , Bowes Joanne , Thiemermann Christoph
Published: January 2005

The cardioprotective properties of inhibition of poly (ADP‐ribose) synthetase (PARS) were investigated in the isolated perfused heart of the rat. Hearts were perfused in the Langendorff mode and subjected to 23 min total global ischaemia and reperfused for 60 min.

Left ventricular function was assessed by means of an intra‐ventricular balloon. High energy phosphates were measured by 31P‐NMR spectroscopy. Intracellular levels of NAD were measured by capillary electrophoresis of perchloric acid extracts of hearts at the end of reperfusion.

Reperfusion in the presence of the PARS inhibitor 1,5 didroxyisoquinoline (ISO, 100 μM) attenuated the mechanical dysfunction observed following 1 h of reperfusion; 27±13 and 65±8% recovery of preischaemic rate pressure product for control and 100 μM ISO, respectively.

This cardioprotection was accompanied by a preservation of intracellular high‐energy phosphates during reperfusion; 38±2 vs 58±4% (P<0.05) of preischaemic levels of phosphocreatine (PCr) for control and 100 μM ISO respectively and 23±1 vs 31±3% (P<0.05) of preischaemic levels of ATP for control and 100 μM ISO respectively.

Cellular levels of NAD were higher in ISO treated hearts at the end of reperfusion; 2.56±0.45 vs 4.76±1.12 μmoles g−1 dry weight (P<0.05) for control and ISO treated.

These results demonstrate that the cardioprotection afforded by inhibition of PARS activity with ISO is accompanied by a preservation of high‐energy phosphates and cellular NAD levels and suggest that the mechanism responsible for this cardioprotection may involve prevention of intracellular ATP depletion.

British Journal of Pharmacology (1999) 127, 1518–1524; doi:10.1038/sj.bjp.0702705
Maitotoxin‐induced nerve growth factor production accompanied by the activation of a voltage‐insensitive Ca2+ channel in C6‐BU‐1 glioma cells
Authors: Obara Yutaro , Takahashi Masami , Nakahata Norimichi , Ohizumi Yasushi
Published: January 2005

The aim of the present study was to determine the effects of maitotoxin on nerve growth factor production and the Ca2+ influx in clonal rat glioma cells (C6‐BU‐1).

Maitotoxin (1–10 ng ml−1) induced a profound increase in 45Ca2+ influx in an extracellular Ca2+‐dependent manner. However, high KCl had no effect at all. These effects were supported by the results from the analysis of intracellular Ca2+ concentration using fura 2.

The maitotoxin‐induced 45Ca2+ influx was inhibited by inorganic Ca2+ antagonists, such as Mg2+, Mn2+ and Co2+. The inhibitory effect of Co2+ was antagonized by increasing the extracellular Ca2+ concentrations.

Maitotoxin (3 ng ml−1) as well as A‐23187 (1 μM) and dibutyryl cyclic AMP (0.5 mM) caused an acceleration of nerve growth factor (NGF) production in C6‐BU‐1 cells, as determined by NGF enzyme immunoassay.

Reverse transcription polymerase chain reaction (RT–PCR) analysis showed that maitotoxin (10 ng ml−1) enhanced the expression of NGF mRNA, which was abolished by the removal of extracellular Ca2+. A‐23187 also accelerated its expression.

These results suggest that maitotoxin activates a voltage‐insensitive Ca2+ channel and accelerates NGF production mediated through a Ca2+ signalling pathway in C6‐BU‐1 glioma cells.

British Journal of Pharmacology (1999) 127, 1577–1582; doi:10.1038/sj.bjp.0702706
Repeated challenge with dinitrobenzene sulphonic acid in dinitrofluorobenzene‐sensitized mice results in vascular hyperpermeability in the trachea: a role for tachykinins
Authors: Van Houwelingen A H , Van Der Avoort L A , Van Heuven‐Nolsen D , Kraneveld A D , Nijkamp F P
Published: January 2005

This study investigates the role of tachykinins in a repeated challenge with dinitrobenzene sulphonic acid (DNS) on the tracheal vascular permeability in dinitrofluorobenzene (DNFB)‐sensitized mice.

DNFB‐contact sensitization was followed by an intranasal (i.n.) challenge with DNS. A second challenge with DNS was administered 24 h after the first challenge. To assess changes in tracheal vascular permeability, Evans blue dye accumulation in tracheal tissue was measured.

A repeated challenge with DNS in DNFB‐sensitized mice led to a 2.8 fold increase in tracheal vascular permeability when compared to DNFB‐sensitized and vehicle‐challenged mice or a 2.5 fold increase when compared to DNFB‐sensitized single DNS‐challenged mice (P<0.001, ANOVA).

RP67580 (10−9 mol mouse−1 i.v.) reduced the increased tracheal vascular permeability induced by a second exposure to DNS in DNFB‐sensitized mice completely when injected 15 min before the second challenge (P<0.001, ANOVA).

The increased tracheal vascular permeability response induced by the second exposure to DNS could be mimicked with i.n. application of capsaicin (10−10 mol mouse−1) or substance P (SP) (10−12 mol mouse−1) to DNFB‐sensitized and single DNS‐challenged mice.

These results suggest that both tachykinin NK1 receptors and sensory nerves are involved in the development of vascular hyperpermeability changes found in the trachea of DNFB‐sensitized mice after a repeated DNS‐challenge.

British Journal of Pharmacology (1999) 127, 1583–1588; doi:10.1038/sj.bjp.0702707
A771726, the active metabolite of leflunomide, directly inhibits the activity of cyclo‐oxygenase‐2 in vitro and in vivo in a substrate‐sensitive manner
Authors: Hamilton Lorna C , Vojnovic Ivana , Warner Timothy D
Published: January 2005

The immunosuppressive and anti‐inflammatory drug leflunomide has several sites of action, although its precise mode of action is unknown.

Here we show in vitro and in vivo that leflunomide and/or its active metabolite A771726, inhibit the activity of cyclo‐oxygenase (COX) at doses below those that affect protein expression.

In J774.2 macrophages treated with endotoxin for 24 h to induce COX‐2 and iNOS, leflunomide and A771726 inhibited more potently the accumulation of PGE2 (A771726, IC50 3.5 μg ml−1) than of NO2 (A771726, IC50 380 μg ml−1). At high concentrations (>300 μg ml−1) A771726 also exhibited the expression of COX‐2 and iNOS proteins.

In A549 cells treated for 24 h with interleukin‐1β, to induce COX‐2, A771726 potently inhibited PGE2 synthesis (IC50 0.13 μg ml−1). In the same cells, A771726 was notably less active (IC50, 52 μg ml−1) at inhibiting the formation of PGE2 stimulated by exposure to 30 μM arachidonic acid.

In a human whole blood assay, measuring the accumulation of TxB2 in response to calcium ionophore as a measure of COX‐1 activity and in response to incubation with bacterial endotoxin as a measure of COX‐2 activity, leflunomide inhibited COX‐1 and COX‐2 with IC50 values of 31 and 185 μg ml−1; for A771726 the corresponding values were 40 and 69 μg ml−1.

Pre‐treatment of rats with leflunomide or A771726 (10 mg kg−1, i.p.) inhibited the plasma accumulation of 6‐keto‐PGF1α but not NO2/NO3 following infusion of endotoxin. Injection of a bolus of arachidonic acid following 6 h infusion of endotoxin caused a marked acute rise in plasma 6‐keto‐PGF1α which was inhibited only by higher doses of A771726 (50 mg kg−1, i.p.).

In conclusion, leflunomide via A771726 can directly inhibit the activity of COX, an effect that appears blunted both by increases in substrate supply and possibly by plasma binding. Only at much higher drug levels does leflunomide and/or A771726 inhibit the induction of COX‐2 or iNOS proteins.

British Journal of Pharmacology (1999) 127, 1589–1596; doi:10.1038/sj.bjp.0702708
Evidence that the ATP‐induced increase in vasomotion of guinea‐pig mesenteric lymphatics involves an endothelium‐dependent release of thromboxane A2
Authors: Gao Jinnan , Zhao Jun , Rayner Sharyn E , Van Helden Dirk F
Published: January 2005

Experiments were made to investigate mechanisms by which adenosine 5′‐trisphosphate (ATP) enhanced vasomotion in mesenteric lymphatic vessels isolated from young guinea‐pigs.

ATP (10−8–10−3 M) caused a concentration‐dependent increase of perfusion‐induced vasomotion with the endothelium mediating a fundamental role at low ATP concentrations (10−8–10−6 M).

The response to 10−6 M ATP showed tachyphylaxis when applied at intervals of 10 min but not at intervals of 20 or 30 min.

Suramin (10−4 M) or reactive blue 2 (3×10−5 M) but not PPADS (3×10−5 M) abolished the excitatory response to 10−6 M ATP confirming an involvement of P2 purinoceptors.

The excitatory response to 10−6 M ATP was abolished by treatment with either pertussis toxin (100 ng ml−1), antiflammin‐1 (10−9 M), indomethacin (3×10−6 M) or SQ29548 (3×10−7 M), inhibitors of specific G proteins, phospholipase A2, cyclo‐oxygenase and thromboxane A2 receptors respectively.

ATP simultaneously induced a suramin‐sensitive inhibitory response, which was normally masked by the excitatory response. ATP‐induced inhibition was mediated by endothelium‐derived nitric oxide (EDNO) as the response was abolished by NG‐nitro‐L‐arginine (L‐NOARG; 10−4 M), an inhibitor of nitric oxide synthase.

We conclude that ATP modulates lymphatic vasomotion by endothelium‐dependent and endothelium‐independent mechanisms. One of these is a dominant excitation caused through endothelial P2 purinoceptors which because of an involvement of a pertussis toxin sensitive G‐protein may be of the P2Y receptor subtype. Their stimulation increases synthesis of phospholipase A2 and production of thromboxane A2, an arachidonic acid metabolite which acts as an endothelium‐derived excitatory factor.

British Journal of Pharmacology (1999) 127, 1597–1602; doi:10.1038/sj.bjp.0702710
Microtubule cytoskeleton involvement in muscarinic suppression of voltage‐gated calcium channel current in guinea‐pig ileal smooth muscle
Authors: Unno T , Komori S , Ohashi H
Published: January 2005

Effects of agents, which affect microtubule polymerization‐depolymerization cycle, on Ba2+ current (IBa) flowing through voltage‐gated Ca2+ channels and carbachol (CCh)‐induced sustained suppression of IBa were examined in whole‐cell voltage‐clamped smooth muscle cells of guinea‐pig ileum.

Colchicine (100 μM) and vinblastine (100 μM), microtubule depolymerizers, increased the ampitude of IBa. Lumicolchicine (100 μM), an inactive analogue of colchicine, had no effect on IBa.

Taxol (1–100 μM), a microtubule polymerizer, decreased IBa in a concentration‐dependent manner and accelerated the rate of inactivation of IBa. Baccatin III (100 μM), an inactive analogue of taxol, had no effect on IBa.

Colchicine (100 μM) and vinblastine (100 μM), but not lumicolchicine (100 μM), decreased or abolished the sustained component of CCh (10 μM)‐induced IBa suppression.

Pretreatment with taxol (10–100 μM) resulted in a concentration‐dependent decrease in IBa and the action of CCh on IBa. The inhibitory effects of taxol and CCh on IBa were not additive.

Colchicine (100 μM) or taxol (100 μM) had no effect on voltage‐gated K+ channel current or CCh‐induced non‐selective cationic channel current.

These results suggest that polymerization of microtubules leads to suppression of Ca2+ channel activity, and that muscarinic sustained suppression of Ca2+ channel current is mediated by a signal transduction element which involves microtubule cytoskeleton.

British Journal of Pharmacology (1999) 127, 1703–1711; doi:10.1038/sj.bjp.0702711
Block and modified gating of cardiac calcium channel currents by terodiline
Authors: Ogura Toshitsugu , Jones Stephen , Shuba Lesya M , McCullough John R , McDonald Terence F
Published: January 2005

Terodiline, an anticholinergic/antispasmodic drug effective in the treatment of urinary incontinence, is presently restricted due to adverse side effects on cardiac function. To characterize its effects on cardiac L‐type Ca2+‐channel current carried by Ca2+ (ICa,L) and Ba2+ (IBa,L), concentrations ranging from 0.1 to 100 μM were applied to whole‐cell‐configured guinea‐pig ventricular myocytes.

Although sub‐micromolar concentrations of terodiline had no effect on ICa,L at 0 mV, 100 μM drug reduced its amplitude to ca. 10% of pre‐drug control. The estimated IC50 (15.2 μM in K+‐dialysed cells, 12.2 μM in Cs+‐dialysed cells; 0.1 Hz pulsing rate) is eight times higher than reported for ICa,L in bladder smooth muscle myocytes.

Terodiline affected ICa,L in a use‐dependent manner; block increased when the pulsing rate was increased from 0.1 to 2–3 Hz, and when holding potential was lowered from −43 mV. The drug accelerated the decay of ICa,L at 0 mV in a concentration‐dependent manner, and slowed the recovery of channels from inactivation.

Terodiline reduced peak IBa,L more effectively than peak ICa,L, and markedly accelerated the rate of inactivation of the current.

The results are discussed in terms of mechanisms of Ca2+ channel block and relation to the therapeutic and cardiotoxic effects of the drug.

British Journal of Pharmacology (1999) 127, 1837–1845; doi:10.1038/sj.bjp.0702713
Synthesis of nitric oxide in the dorsal motor nucleus of the vagus mediates the inhibition of gastric acid secretion by central bombesin
Authors: Beltrán Belén , Barrachina Ma Dolores , Méndez Asunción , Quintero Enrique , Esplugues Juan V
Published: January 2005

Central administration of bombesin inhibits gastric acid production independently of the centrally or peripherally‐acting stimuli employed. This study evaluates the role and location of the cerebral nitric oxide (NO) implicated in the inhibitory effect of central bombesin on in vivo rat gastric acid secretion, as induced by distension with 15 cm H2O, insulin (0.75 u.i. kg−1 i.p.) TRH (1.2 μg kg−1, i.c.) or pentagastrin (100 μg kg−1, i.p.).

The acid‐inhibitory effect of i.c. bombesin (40 ng kg−1) was prevented by prior administration of L‐NAME (80 μg kg−1) in the dorsal motor nucleus of the vagus (DMN). This dose of L‐NAME when administered into the nucleus of the tractus solitarious (NTS) did not influence the effects of bombesin. Administration of L‐arginine (400 μg kg−1) into the DMN restored the acid‐inhibitory effect of i.c. bombesin in animals treated with L‐NAME.

Microinjection of bombesin (12 ng kg−1) into the paraventricular nucleus of the hypothalamus (PvN) inhibits acid secretion stimulated by pentagastrin. This inhibitory effect was prevented by a previous injection of L‐NAME (80 μg kg−1) into the DMN.

The release of NO in the DMN following i.c. administration of bombesin was confirmed by in vivo electrochemical detection.

Administration by microdialysis in the DMN of the NO‐donor SNAP (25 mM in 1.5 μl min−1) into the DMN inhibits pentagastrin‐stimulated gastric acid secretion.

The present study suggests that nNOS‐containing neurons in the DMN have an inhibitory role in the control of gastric acid responses.

British Journal of Pharmacology (1999) 127, 1603–1610; doi:10.1038/sj.bjp.0702717
Characterization of the 5‐hydroxytryptamine receptors mediating contraction in the intestine of Suncus murinus
Authors: Javid Farideh A , Naylor Robert J
Published: January 2005

The effects of 5‐HT and 5‐HT agonists to induce contraction and the 5‐HT receptors mediating these effects were investigated in the proximal, central and terminal intestinal segments of Suncus murinus.

The contraction curves to 5‐HT (3 nM–30 μM) were shifted to the right by methysergide (1 μM) and ritanserin (0.1 μM), without affecting the maximum response.

In the central and terminal segments (but not the proximal segments) ondansetron (1 μM) and atropine (1 μM) significantly attenuated the contractions to higher concentrations of 5‐HT. The selective 5‐HT4 receptor antagonist SB204070 (1 nM), failed to modify 5‐HT induced contractions in any segment examined.

5‐carboxamidotryptamine, α‐methyl‐5‐HT and 5‐methoxytryptamine (0.003–3.0 μM) induced contractions but unlike 5‐HT, higher concentrations of these three agents failed to increase the response or were associated with a decrease in response. 2‐methyl‐5‐HT (0.03–1.0 μM) was ten times less potent than 5‐HT to induce contraction but achieved the same maximum response.

The contractions induced by the lower concentrations of 2‐methyl‐5‐HT (0.03–1.0 μM) in all segments were markedly reduced or abolished by methysergide (1.0 μM); the response to the higher concentrations of 2‐methyl‐5‐HT (3–30.0 μM) were markedly reduced by atropine (1.0 μM) and ondansetron (1.0 μM).

In all segments examined, tetrodotoxin (1 μM) significantly reduced the 5‐HT‐induced contraction.

It is concluded that the 5‐HT‐induced contraction was mediated via 5‐HT2 (ritanserin sensitive) receptors in all regions of the intestine, with 5‐HT3 (ondansetron sensitive) receptors mediating an additional major component in the central and terminal regions.

British Journal of Pharmacology (1999) 127, 1867–1875; doi:10.1038/sj.bjp.0702729
Alterations of insulin secretion from mouse islets treated with sulphonylureas: perturbations of Ca2+ regulation prevail over changes in insulin content
Authors: Anello Marcello , Gilon Patrick , Henquin Jean‐Claude
Published: January 2005

To determine how pretreatment with sulphonylureas alters the β cell function, mouse islets were cultured (18–20 h) without (controls) or with (test) 0.01 μM glibenclamide. Acute responses to glucose were then determined in the absence of glibenclamide.

Test islets were insensitive to drugs (sulphonylureas and diazoxide) acting on K+‐ATP channels, and their [Ca2+]i was already elevated in the absence of stimulation.

Insulin secretion was increased in the absence of glucose, and mainly stimulated between 0–10 instead of 7–20 mM glucose in controls. The maximum response was halved, but this difference disappeared after correction for the 45% decrease in the islet insulin content.

The first phase of glucose‐induced insulin secretion was abrogated because of a paradoxical decrease of the high basal [Ca2+]i in β cells. The second phase was preserved but occurred with little rise of [Ca2+]i. These abnormalities did not result from alterations of glucose metabolism (NADPH fluorescence).

In islets cultured with 50 μM tolbutamide, glucose induced biphasic increases in [Ca2+]i and insulin secretion. The decrease in the secretory response was matched by the decrease in insulin content (45%) except at maximal glucose concentrations. Islets pretreated with tolbutamide, however, behaved like those cultured with glibenclamide if tolbutamide was also present during the acute functional tests.

In conclusion, treatment with a low glibenclamide concentration causes long‐lasting blockade of K+‐ATP channels and rise of [Ca2+]i in β cells. Glucose‐induced insulin secretion occurs at lower concentrations, is delayed and is largely mediated by a modulation of Ca2+ action on exocytosis. It is suggested that glucose regulation of insulin secretion mainly depends on a K+‐ATP channel‐independent pathway during in vivo sulphonylurea treatment.

British Journal of Pharmacology (1999) 127, 1883–1891; doi:10.1038/sj.bjp.0702731
Pharmacological characterization of ATP‐ and LPS‐induced IL‐1β release in human monocytes
Authors: Grahames C B A , Michel A D , Chessell I P , Humphrey P P A
Published: January 2005

We have utilized the human monocytic cell line, THP‐1, and freshly isolated adherent human monocytes with the compounds pyridoxalphosphate‐6‐azophenyl‐2′,4′‐disuphonic acid (PPADS), oxidized ATP, and 1‐(N,O‐bis{5‐isoquinolinesufonyll}‐N‐methyl‐L‐tyrosyl)‐4‐phenylpiperazine (KN‐62) to pharmacologically characterize the P2 receptor involved in ATP‐induced release of interleukin 1β (IL‐1β). We have also investigated the involvement of P2 receptors in lipopolysaccharide (LPS)‐induced IL‐1β release from both cell types.

ATP caused release of IL‐1β from LPS primed THP‐1 cells in both a time‐ and concentration‐dependent manner, with a minimal effective ATP concentration of 1 mM. Stimulation of cells with 5 mM ATP resulted in detectable concentrations of IL‐1β in cell supernatants within 30 min.

The ATP analogue benzoylbenzoyl ATP (DBATP), a P2X7 receptor agonist, was approximately 10 fold more potent than ATP at eliciting IL‐1β release.

KN‐62 (1 μM), PPADS (100 μM) or oxidized ATP (100 uM) significantly inhibited 5 mM ATP‐induced IL‐1β release by 81, 90 and 66% respectively, but failed to significantly inhibit LPS‐induced IL‐1β release in both THP‐1 cells and in freshly isolated human monocytes.

In both THP‐1 cells and freshly isolated human monocytes, addition of the ATP degrading enzyme apyrase (0.4 U ml−1) to cell supernatants prior to LPS activation failed to significantly inhibit the LPS‐induced IL‐1β release. In addition there was no correlation between extracellular ATP concentrations and IL‐1β release in THP‐1 cells when studied over a 6 h time period.

In conclusion our data confirm the involvement of P2X7 receptors in ATP‐induced IL‐1β release in human monocytes. However no evidence was obtained which would support the involvement of either endogenous ATP release or P2X7 receptor activation as the mechanism by which LPS‐induces IL‐1β release in either the THP‐1 cell line or in freshly isolated human monocytes.

British Journal of Pharmacology (1999) 127, 1915–1921; doi:10.1038/sj.bjp.0702732
In vitro functional evidence of different neurotensin‐receptors modulating the motor response of human colonic muscle strips
Authors: Croci Tiziano , Aureggi Giulio , Guagnini Fabio , Manara Luciano , Gully Danielle , Le Fur Gérard , Maffrand Jean‐Pierre , Mukenge Sylvain , Ferla Gianfranco , Ferrara Pascual , Chalon Pascale , Vita Natalio
Published: January 2005

The newly developed non‐peptide neurotensin (NT)‐receptor antagonists SR 48692 and SR 142948 were used to challenge NT responses of human colonic circular smooth muscle strips in vitro. The presence of NT1 and NT2 receptor transcripts in this tissue was tested by reverse transcriptase polymerase chain reaction (RT–PCR) analysis.

NT potently and dose‐dependently contracted muscle strips, with significant regional differences in potency and efficacy between the transverse and distal colon: EC50, 3.6 and 7.5 nM; the maximal effect was 70 and 55% of 0.1 mM carbachol. Colonic responses to NT in both segments were virtually the same in the presence of atropine (1 μM), levocabastine (10 μM) or tetrodotoxin (1 μM).

SR 142948 (10 nM–1 μM) competitively antagonized NT responses in the transverse and distal colon with similar affinities: pA2 values 8.71 and 8.45, slopes 0.98 and 0.99. SR 48692 (10 nM–10 μM) antagonized the NT response competitively in the distal colon (pA2 6.55, slope 0.79) and non‐competitively in the transverse colon (pA2 8.0, slope 0.51). Neither compound had any agonist effect.

The fact that the specific antagonists prevented NT‐evoked atropine‐ and tetrodotoxin‐insensitive mechanical responses of colonic muscle strips is highly consistent with the presence in these tissues of non‐neuronal NT receptors, whose heterogeneity in the transverse segment is supported by the non‐competitive antagonism of SR 48692. The finding of NT1 receptor transcript in both transverse and distal colon suggests its identity with the lower affinity site disclosed functionally by SR 48692 in these segments.

British Journal of Pharmacology (1999) 127, 1922–1928; doi:10.1038/sj.bjp.0702734
Differentiated effects on splanchnic homeostasis by selective and non‐selective endothelin receptor antagonism in porcine endotoxaemia
Authors: Oldner Anders , Wanecek Michael , Weitzberg Eddie , Sundin Pierre , Sollevi Alf , Rubio Carlos , Hellström Per M , Alving Kjell , Rudehill Anders
Published: January 2005

The non‐selective endothelin (ET) receptor antagonist bosentan has been shown to restore systemic and gut oxygen delivery and reverse intestinal mucosal acidosis in porcine endotoxin shock.

To further elucidate the specific role of the ETA as opposed to the ETB receptor and their effects in the splanchnic region a non‐selective (ETMIXra) A‐182086 and selective ETA (ETAra) PD155080 and ETB (ETBra) A‐192621 receptor antagonists were administered, separately or simultaneously (ETA+Bra) 2 h after onset of endotoxin shock. These four groups were compared to a control group receiving only endotoxin and vehicle.

Thirty‐nine pigs were anaesthetized and catheterized for measurement of central and regional haemodynamics. A tonometer in the distal ileum was used for measurement of mucosal PCO2. Blood gases and plasma ET‐1‐LI levels as well as histological samples from the gut were assessed. Intervention was started 2 h after onset of endotoxemia and the experiments were terminated after 5 h.

Endotoxin‐induced changes in systemic, gut oxygen delivery and portal hepatic vascular resistance and systemic acidosis were effectively counteracted by both ETA+Bra and ETMIXra. ETAra administration was not effective while ETBra proved to be fatal as all animals in this group died prior to full time of the experiment. While both ETA+Bra and ETMIXra improved gut oxygen delivery only the latter attenuated the profound endotoxin‐induced ileal mucosal acidosis.

The lethal effect seen from selective ETB receptor antagonism in the current study may be due to increased ETA receptor activity as plasma levels of ET‐1 is increased several fold by blocking the ETB receptor and thereby the plasma‐ET‐1‐clearing function. Furthermore, a loss of endothelial ETB receptor vasodilating properties may also have contributed to the lethal course in the ETBra group

The findings in this study suggest that ET is involved in the profound endotoxin‐induced disturbances in splanchnic homeostasis in porcine endotoxaemia. Furthermore, antagonism of both ETA and ETB receptors is necessary to effectively counteract these changes.

British Journal of Pharmacology (1999) 127, 1793–1804; doi:10.1038/sj.bjp.0702736
The ethanol metabolite acetaldehyde inhibits the induction of long‐term potentiation in the rat dentate gyrus in vivo
Authors: Abe Kazuho , Yamaguchi Shinichi , Sugiura Minoru , Saito Hiroshi
Published: January 2005

Ethanol has been reported to inhibit the induction of long‐term potentiation (LTP) in the hippocampus. However, the correlation between the effects of ethanol in vivo and in vitro remained unclear. In addition, previous works have little considered the possibility that the effect of ethanol is mediated by its metabolites. To solve these problems, we investigated the effects of ethanol and acetaldehyde, the first metabolite in the metabolism of ethanol, on the induction of LTP at medial perforant path‐granule cell synapses in the dentate gyrus of anaesthetized rats in vivo.

Oral administration of 1 g kg−1 ethanol significantly inhibited the induction of LTP, confirming the effectiveness of ethanol in vivo.

A lower dose of ethanol (0.5 g kg−1) failed to inhibit the induction of LTP in intact rats, but significantly inhibited LTP in rats treated with disulfiram, an inhibitor of aldehyde dehydrogenase, demonstrating that LTP is inhibited by acetaldehyde accumulation following ethanol administration.

Intravenous injection of acetaldehyde (0.06 g kg−1) significantly inhibited the induction of LTP.

The inhibitory effect of acetaldehyde on LTP induction was also observed when it was injected into the cerebroventricules, suggesting that acetaldehyde has a direct effect on the brain. The intracerebroventricular dose of acetaldehyde effective in inhibiting LTP induction (0.1–0.15 mg brain−1) was approximately 10 fold lower than that of ethanol (1.0–1.5 mg brain−1).

It is possible that acetaldehyde is partly responsible for memory impairments induced by ethanol intoxication.

British Journal of Pharmacology (1999) 127, 1805–1810; doi:10.1038/sj.bjp.0702738
Role of shear stress in nitric oxide‐dependent modulation of renal angiotensin II vasoconstriction
Authors: Endlich Karlhans , Muller Catherine , Barthelmebs Mariette , Helwig Jean‐Jacques
Published: January 2005

Renal vasoconstriction in response to angiotensin II (ANGII) is known to be modulated by nitric oxide (NO). Since shear stress stimulates the release of a variety of vasoactive compounds from endothelial cells, we studied the impact of shear stress on the haemodynamic effect of ANGII in isolated perfused kidneys of rats under control conditions and during NO synthase inhibition with L‐NAME (100 μM).

Kidneys were perfused in the presence of cyclo‐oxygenase inhibitor (10 μM indomethacin) with Tyrode's solution of relative viscosity ζ=1 (low viscosity perfusate, LVP) or, in order to augment shear stress, with Tyrode's solution containing 7% Ficoll 70 of relative viscosity ζ=2 (high viscosity perfusate, HVP).

Vascular conductance was 3.5±0.4 fold larger in HVP as compared with LVP kidneys, associated with an augmentation of overall wall shear stress by 37±5%. During NO inhibition, vascular conductance was only 2.5±0.2 fold elevated in HVP vs LVP kidneys, demonstrating shear stress‐induced vasodilatation by NO and non‐NO/non‐prostanoid compound(s).

ANGII (10–100 pM) constricted the vasculature in LVP kidneys, but was without effect in HVP kidneys. During NO inhibition, in contrast, ANGII vasoconstriction was potentiated in HVP as compared with LVP kidneys.

The potentiation of ANGII vasoconstriction during NO inhibition has been shown to be mediated by endothelium‐derived P450 metabolites and to be sensitive to AT2 receptor blockade in our earlier studies. Accordingly, in HVP kidneys, increasing concentrations of the AT2 receptor antagonist PD123319 (5 and 500 nM) gradually abolished the potentiation of ANGII vasoconstriction during NO inhibition, but did not affect vasoconstriction in response to ANGII in LVP kidneys.

Our results demonstrate, that augmentation of shear stress by increasing perfusate viscosity induces vasodilatation in the rat kidney, which is partially mediated by NO. Elevated levels of shear stress attenuate renal ANGII vasoconstriction through enhanced NO production and are required for AT2 sensitive potentiation during NO inhibition.

British Journal of Pharmacology (1999) 127, 1929–1935; doi:10.1038/sj.bjp.0702739
Electroencephalographic effects of thiopentone and its enantiomers in the rat: correlation with drug tissue distribution
Authors: Mather Laurence E , Edwards Stephen R , Duke Colin C
Published: January 2005

To better understand the pharmacology of the thiopentone enantiomers, we studied their quantitative electroencephalographic effects and their distribution into vital tissues.

Adult Wistar rats were infused with rac‐, R‐ or S‐thiopentone at 4 mg kg−1min−1 until death ensued. The EEG signal was acquired continuously; serial arterial plasma and terminal tissue thiopentone concentrations were measured enantiospecifically. Relevant drug tissue : plasma distribution coefficients and plasma concentration‐EEG effect relationships were determined.

Doses (mg kg−1) (mean±s.e.mean) for anaesthesia (toe pinch) and lethality (respiratory failure), respectively, decreased in the order R‐thiopentone (55.8±2.4 and 176.2±11.2)> rac‐thiopentone (39.3±2.1 and 97.5±3.9)> S‐thiopentone (35.6±1.9 and 74.2±5.2); plasma drug concentrations (μg ml−1) decreased in the order R‐thiopentone (66.3±4.5 and 89.8±5.2)> rac‐thiopentone (56.7±2.0 and 77.8±2.8)> S‐thiopentone (55.0±1.9 and 64.1±2.8).

Initial EEG activation was similar for all thiopentone forms. Plasma drug concentrations for the same extent of EEG deactivation reflected the potency order.

After infusion of rac‐thiopentone, tissue : plasma distribution coefficients were higher for R‐ than for S‐thiopentone in brain and visceral regions, but not in fat or muscle. After infusion of the separate enantiomers, the relative heart : brain distribution ratio was for S‐thiopentone was double that for R‐thiopentone.

The therapeutic index of R‐thiopentone (3.16±0.14) was more advantageous than either rac‐thiopentone (2.52±0.13) or S‐thiopentone (2.10±0.14), possibly due to the relatively greater distribution into CNS tissues than heart. The data suggest that R‐thiopentone could make a satisfactory single enantiomer substitute for rac‐thiopentone.

British Journal of Pharmacology (1999) 128, 83–91; doi:10.1038/sj.bjp.0702745
[Phe1ψ(CH2‐NH)Gly2]nociceptin‐(1–13)‐NH2 activation of an inward rectifier as a partial agonist of ORL1 receptors in rat periaqueductal gray
Authors: Chiou Lih‐Chu
Published: January 2005

[Phe1ψ(CH2‐NH)Gly2]nociceptin‐(1–13)‐NH2 (Pheψ), a tridecapeptide analogue of orphanin FQ/nociceptin (OFQ/N), was introduced as a competitive antagonist of opioid receptor‐like orphan receptor (ORL1) in guinea‐pig ileum and mouse vas deferens preparations in vitro but was recently found to act as an agonist in vivo.

In the periaqueductal gray, a site enriched with both OFQ/N and ORL1 and involved in OFQ/N‐induced hyperalgesia and anti‐analgesia, the effects of Pheψ and OFQ/N on the membrane current were studied using whole cell patch clamp recording technique in rat brain slices.

OFQ/N (0.01–1 μM) activated an inwardly rectifying type of K+ channels in ventrolateral neurons of PAG. Pheψ (0.03–1 μM), like OFQ/N, also activated this inward rectifier but had only 30% efficacy of OFQ/N.

At maximal effective concentration (1 μM), Pheψ reversed the increment of K+ conductance induced by OFQ/N (300 nM) by 46%. On the other hand, Pheψ also prevented the effect of OFQ/N if pretreated before OFQ/N.

It is suggested that Pheψ acts as a partial agonist of ORL1 that mediates the activation of inwardly rectifying K+ channels in ventrolateral neurons of rat periaqueductal gray.

British Journal of Pharmacology (1999) 128, 103–107; doi:10.1038/sj.bjp.0702746
Modulation by fluoxetine of striatal dopamine release following Δ9‐tetrahydrocannabinol: a microdialysis study in conscious rats
Authors: Malone Daniel T , Taylor David A
Published: January 2005

The present study was undertaken to investigate the effect of Δ9‐tetrahydrocannabinol (Δ9‐THC) and possible serotoninergic involvement on the extracellular level of dopamine (DA) in the striatum using microdialysis in conscious, freely‐moving rats.

A dose‐dependent increase in striatal DA release occurred after i.v. administration of 0.5–5 mg kg−1 Δ9‐THC when compared with vehicle (n=5–8, P<0.05). Maximum increases, ranging from 42.1±5.4% to 97.4±5.9% (means±s.e.mean) of basal levels occurred 20 min after Δ9‐THC. This effect was abolished by pretreatment with the cannabinoid CB1 receptor antagonist, SR 141716 (2.5 mg kg−1 i.p.).

Pretreatment with fluoxetine (10 mg kg−1 i.p.) abolished the Δ9‐THC‐induced DA release. Fluoxetine 10 mg kg−1 i.p. administered 40 min after Δ9‐THC had no significant effect on Δ9‐THC‐induced DA release. However, fluoxetine perfused locally into the striatum by adding it to the microdialysis perfusion fluid (10 μM) 40 min after Δ9‐THC significantly potentiated the Δ9‐THC‐induced DA release (n=6–8, P<0.05).

These results suggest that DA release induced by Δ9‐THC is modulated by serotoninergic changes induced by fluoxetine, the effect of which depends on the time of its administration relative to that of Δ9‐THC. Fluoxetine induces an acute increase in extracellular 5‐HT through reuptake inhibition, which can activate autoreceptors which may decrease serotoninergic neuronal activity. This may be the reason fluoxetine pretreatment abolished the Δ9‐THC‐induced DA release. The potentiation of Δ9‐THC‐induced DA release by fluoxetine perfusion added 40 min after Δ9‐THC may be due to an acute increase in 5‐HT produced by reuptake inhibition.

British Journal of Pharmacology (1999) 128, 21–26; doi:10.1038/sj.bjp.0702753
Inhibition of quantal release from motor nerve by wortmannin
Authors: Hong S J , Chang C C
Published: January 2005

The effects of wortmannin, an inhibitor of phosphatidylinositol (PI) kinases and myosin light chain kinase, on the quantal release of neurotransmitter from mouse phrenic nerve were investigated.

Wortmannin (10–100 μM) initially enhanced, thereafter progressively depressed spontaneous quantal discharge (miniature endplate potential, mepp). The mean amplitude and the amplitude distribution of mepp were not altered.

The compound inhibited and prevented the intensive quantal release evoked by high KC1 solution as well as the mepp burst induced by α‐latrotoxin, a polypeptide toxin that possesses Ca2+‐independent synaptic action to trigger quantal release. The inhibitory actions of wortmannin were partially reversible.

Wortmannin depressed the amplitude of endplate potentials (epps) and increased the coefficient of variance of epps. The profile of epps in response to high frequency nerve stimulation exhibited fluctuations between run‐down and run‐up. The phenomenon is thus different from the consistency of run‐up characteristic as the motor nerve Ca2+ channel is blocked by ω‐agatoxin IVA.

LY294002, another inhibitor of PI 3‐kinase, raised mepp frequency without causing late phase suppressions. The compound did not inhibit KC1‐, α‐latrotoxin‐ or nerve stimulation‐evoked quantal release.

The results suggest that wortmannin could depress quantal release beyond the step of Ca2+ channel blockade, probably by interfering with the exocytotic cascade.

British Journal of Pharmacology (1999) 128, 142–148; doi:10.1038/sj.bjp.0702754
Electrochemical and electrophysiological characterization of neurotransmitter release from sympathetic nerves supplying rat mesenteric arteries
Authors: Dunn William R , Brock James A , Hardy Todd A
Published: January 2005

Characteristic features of noradrenaline (NA) and adenosine 5′‐triphosphate (ATP) release from postganglionic sympathetic nerves in rat small mesenteric arteries in vitro have been investigated on an impulse‐by‐impulse basis. NA release was measured using continuous amperometry and ATP release was monitored by intracellular recording of excitatory junction potentials (e.j.ps).

Electrical stimuli evoked transient increases in oxidation current. During trains of ten stimuli at 0.5–4 Hz there was a depression in the amplitude of oxidation currents evoked following the first stimulus in the train.

The neuronal NA uptake inhibitor, desmethylimipramine (1 μM), increased the amplitude of the summed oxidation current evoked by ten stimuli at 1 Hz and slowed the decay of oxidation currents evoked by trains of ten stimuli at 1 and 10 Hz.

The α2‐adrenoceptor antagonist, idazoxan (1 μM), increased the amplitudes of the oxidation currents evoked during trains of ten stimuli at 0.5–10 Hz but had no effect on the oxidation currents evoked by the first stimulus in the train.

Idazoxan (1 μM) increased the amplitude of all e.j.ps evoked during trains of stimuli at 0.5 and 1 Hz. In addition, the facilitatory effect of idazoxan on e.j.ps was significantly greater than that on oxidation currents.

The findings indicate that NA release from sympathetic nerves supplying small mesenteric arteries is regulated by activation of presynaptic α2‐adrenoceptors and that clearance of released NA in this tissue depends, in part, upon neuronal uptake. The different effects of idazoxan on the oxidation currents and e.j.ps may indicate that the release of NA and ATP is differentially modulated.

British Journal of Pharmacology (1999) 128, 174–180; doi:10.1038/sj.bjp.0702760
Evidence for 5‐HT7 receptors mediating relaxation of human colonic circular smooth muscle
Authors: Prins Nicolaas H , Briejer Michel R , Van Bergen Patrick J E , Akkermans Louis M A , Schuurkes Jan A J
Published: January 2005

5‐HT4 receptors mediate relaxation of human colon circular muscle. However, after 5‐HT4 receptor blockade (SB 204070 10 nM), 5‐HT still induced a relaxation (pEC50 6.3). 5‐HT4 receptors were sufficiently blocked, as the curves to 5‐HT obtained in the presence of 10 and 100 nM SB 204070 were indistinguishable. This 5‐HT‐induced relaxation was tetrodotoxin‐insensitive, indicative of a smooth muscle relaxant 5‐HT receptor. This, and the rank order of potency (5‐CT=5‐MeOT=5‐HT) suggested involvement of 5‐HT1 or 5‐HT7 receptors. Mesulergine, a 5‐HT7 receptor antagonist at nanomolar concentrations, and a 5‐HT1 receptor antagonist at micromolar concentrations, competitively antagonized the 5‐HT‐induced relaxation (pKB 8.3) and antagonized the relaxation to 5‐CT. Methysergide antagonized the 5‐HT‐induced relaxation (pA2 7.6). It is concluded that the profile of the smooth muscle inhibitory 5‐HT receptor resembles that of the 5‐HT7 receptor. These data provide the first evidence for functional human 5‐HT7 receptors.

British Journal of Pharmacology (1999) 128, 849–852; doi:10.1038/sj.bjp.0702762
Effects of C‐type natriuretic peptide on rat cardiac contractility
Authors: Brusq Jean‐Marie , Mayoux Eric , Guigui Laurent , Kirilovsky Jorge
Published: January 2005

Natriuretic peptide receptors have been found in different heart preparations. However, the role of natriuretic peptides in the regulation of cardiac contractility remains largely elusive and was, therefore, studied here.

The rate of relaxation of electrically stimulated, isolated rat papillary muscles was enhanced (114.4±1.4%, P<0.01) after addition of C‐type natriuretic peptide (CNP; 1 μM). Time to peak tension decreased in parallel (88±3 and 75±2 msec before and 5 min after addition of CNP, respectively, P<0.01). On the other hand, the rate of contraction slowly decreased when CNP was added to the papillary muscles. These results show that CNP displays a positive lusitropic effect associated with a negative inotropic effect. The effects of CNP were mimicked by 8‐bromo‐guanosine 3′,5′ cyclic monophosphate.

Addition of CNP to isolated adult rat cardiomyocytes, induced a 25 fold increase in guanosine 3′,5′ cyclic monophosphate (cGMP) levels and stimulated the phosphorylation of phospholamban and troponin I, two proteins involved in the regulation of cardiac contractility. The levels of adenosine 3′,5′ cyclic monophosphate (cAMP) were not affected by the addition of CNP to the myocytes. The CNP‐dependent phospholamban phosphorylation was accompanied by the activation of the sarcoplasmic reticulum Ca2+‐ATPase.

In summary, CNP exerts a positive lusitropic effect, in rat papillary muscles. The putative mechanism involved in the lusitropism induced by this peptide, a cGMP‐dependent enhancement of the rate of relaxation with a slowly developing negative inotropic effect, seems different to that described for catecholamines.

British Journal of Pharmacology (1999) 128, 206–212; doi:10.1038/sj.bjp.0702766
Block of gating currents related to K+ channels as a mechanism of action of clofilium and d‐sotalol in isolated guinea‐pig ventricular heart cells
Authors: Malécot Claire O , Argibay Jorge A
Published: January 2005

The possibility that the class III antiarrhythmic drugs clofilium and d‐sotalol might affect delayed rectifier potassium channels at the level of their gating currents was assessed with the whole‐cell patch‐clamp technique in guinea‐pig isolated ventricular heart cells.

Clofilium (up to 20 μM) and d‐sotalol (1 μM) did not decrease the Na current, the L‐type Ca current or the background K current iKl, but significantly depressed the time‐dependent delayed outward K current iK.

Clofilium partially decreased in a dose‐dependent manner (1–20 μM) QON of intramembrane charge movements (ICM) elicited by a depolarizing pulse applied from a holding potential of −110 mV or following a 100 ms inactivating prepulse to −50 mV. D‐sotalol (1 μM) also decreased QON. Channel density estimated from the clofilium‐sensitive ICM closely matched that of the delayed rectifier channels.

Clofilium and d‐sotalol decreased QOFF seen on repolarization in a dose‐ and voltage‐dependent manner. The kinetics of the decay of the OFF gating currents were not affected, and only the fast phase was depressed.

In control conditions, QON availability with voltage was most of the time well described by two inactivating components. In the presence of clofilium and d‐sotalol, a complex behaviour of QON availability was observed, unmasking additional components. The reactivation kinetics of QON after a 500 ms inactivating pulse to 0 mV was not affected.

We conclude that delayed rectifier K channels significantly contribute to QON and QOFF of ICM in guinea‐pig ventricular heart cells, besides Na and Ca channels, and that clofilium and d‐sotalol directly interact with these K channels proteins by affecting their gating properties.

British Journal of Pharmacology (1999) 128, 301–312; doi:10.1038/sj.bjp.0702768
Differential sensitivity of normal and cystic fibrosis airway epithelial cells to epinephrine
Authors: Goncz Kaarin K , Feeney Luz , Gruenert Dieter C
Published: January 2005

Exposure to epinephrine has been shown to have a range of effects on cells and tissues. A recent study suggested that the proliferative ability of CF epithelial cells, exposed to high concentrations of epinephrine (200–300 μM), was reduced when compared to that of normal cells. This approach could potentially provide a means to effectively separate cells with functional cyclic AMP‐dependent Cl‐ion transport from those defective in this pathway.

The sensitivity to killing by epinephrine is reported here for four different CF cell lines, three normal cell lines, and two CF epithelial cell lines complemented with wild‐type (wt) CF transmembrane conductance regulator (CFTR) cDNA.

While each cell line exhibited varying sensitivity to 200 μM epinephrine, no predictable pattern was observed between the expression of wt‐CFTR and cell survival following epinephrine exposure. Overall, normal cell lines did exhibit a greater resistance to epinephrine‐induced cell death although, the most resistant cell line was derived from CF tracheal epithelium (ΣCFTE29o‐).

The expression of exogenous wt‐CFTR increased the survival of one cell line (CFDEo‐) when compared to the parent line, but in another complemented line, survival was reduced.

These findings suggest that while epinephrine induces cell killing, it is not consistently effective for preferential selection of normal over CF cells. Although CFTR may play a role in the mechanism(s) of epinephrine killing, other factors such as cell density, proliferative ability, cell type origin and phenotype are involved.

British Journal of Pharmacology (1999) 128, 227–233; doi:10.1038/sj.bjp.0702772