bluuebunny/crossref_metadata_2025 huggingface dataset:
Involvement of nitric oxide in the modulation of dural arterial blood flow in the rat
Authors: Messlinger K , Suzuki A , Pawlak M , Zehnter A , Schmidt R F
Published: January 2005

Nitric oxide (NO) has been proposed to be a key molecule in the pathogenesis of migraine pain and other headaches that are linked to vascular disorders. Several lines of evidence indicate that the meningeal vascularization is crucially involved in the generation of these headaches. In an experimental model in the rat a dominating role of calcitonin gene‐related peptide (CGRP) in causing neurogenic vasodilatation and increased blood flow has been shown. The aim of the present study was to clarify the role of NO in this model with regard to the meningeal blood flow.

The blood flow in and around the medial meningeal artery (dural arterial flow) was recorded in the exposed parietal dura mater encephali of barbiturate anaesthetized rats using laser Doppler flowmetry. Local electrical stimulation of the dura mater (pulses of 0.5 ms delivered at 7.5–17.5 V and 5 or 10 Hz for 30 s) caused temporary increases in dural arterial flow for about 1 min that reached peaks of 1.6–2.6 times the basal flow. The effects of NO synthase (NOS) inhibitors on the basal flow and the electrically evoked increases in flow were examined.

Systemic (i.v.) administration of Nω‐nitro‐L‐arginine methyl ester (L‐NAME) at cumulative doses of 10 and 50 mg kg−1 lowered the basal flow to 87 and 72%, respectively, of the control and reduced the evoked increases in blood flow to 82 and 44% on an average. Both these effects could partly be reversed by 300 mg kg−1 L‐arginine. The systemic arterial pressure was increased by L‐NAME at both doses. Injection of the stereoisomer D‐NAME at same doses did not change basal flow and evoked increases in flow.

Topical application of L‐NAME (10−4–10−2 M) was effective only at the highest concentration, which caused lowering of the basal blood flow to 78% of the control; the evoked increases in flow were not changed. Topical application of 2‐amino‐5,6‐dihydro‐6‐methyl‐4H‐1,3‐thiazine (AMT), a specific inhibitor of the inducible NOS, at concentrations of 10−4–10−2 M lowered the basal flow to 89, 87.5 and 85%, respectively, but did not significantly change the evoked flow increases. Same concentrations of 7‐nitroindazole monosodium salt (7‐NINA), a specific inhibitor of the neuronal NOS, had no significant effects on basal flow and evoked increases in flow.

It is concluded that NO is involved in the maintenance of the basal level of dural arterial blood flow as well as in the electrically evoked flow increases, which have been shown to be mainly mediated by CGRP released from dural afferent fibres. The most important source of NO is probably the endothelium of dural arterial vessels. The synergistic effect of NO and CGRP on the stimulated blood flow may be in part due to a NO mediated facilitation of the CGRP release.

British Journal of Pharmacology (2000) 129, 1397–1404; doi:10.1038/sj.bjp.0703220
Contribution of B2 receptors for bradykinin in Arthus reaction‐induced plasma extravasation in wild‐type or B2 transgenic knockout mice
Authors: Samadfam R , Teixeira C , Bkaily G , Sirois P , De Brum‐Fernandes A , D'Orleans‐Juste P
Published: January 2005

The aim of the present study was to investigate the contribution of bradykinin (BK) B1 and B2 receptors in a model of type III hypersensitivity, the reverse passive Arthus reaction (RPA), in wild‐type mice and transgenic B2 knockout littermates.

BK (10 μg mouse−1) or bovine serum albumin (0.5 mg mouse−1) induced a sustained Evans blue extravasation for more than 80 min in naive or rabbit anti‐bovine serum albumin‐treated mice (RPA model), respectively. The response to the two stimuli was prevented by the B2 receptor antagonist, HOE‐140, but not by [Leu8]desArg9‐BK (B1 receptor antagonist).

In contrast to the wild‐type littermates, RPA and bradykinin were unable to trigger an increase in plasma extravasation in B2 knockout mice.

Furthermore, endothelin‐1 (5 μg mouse−1) and a selective NK‐1 receptor agonist [Sar9,Met (O2)11]‐SP (20 μg mouse−1), triggered a significant increase in peritoneal plasma extravasation in both wild‐type and B2 knockout animals.

A pretreatment with indomethacin (200 μg mouse−1) significantly reduced the RPA‐induced but not the BK‐induced increase in Evans blue extravasation. Furthermore, RPA, but not BK, triggered a significant indomethacin‐sensitive increase in peritoneal prostaglandin E2 content.

Our results suggest a pivotal role for B2 receptors in the mechanism of plasma extravasation which occurs during the reverse passive Arthus reaction in the mouse. Moreover, our results suggest an important contribution of prostanoids in the plasma leakage mechanisms triggered by RPA but not by bradykinin.

British Journal of Pharmacology (2000) 129, 1732–1738; doi:10.1038/sj.bjp.0703225
Diadenosine polyphosphates as antagonists of the endogenous P2Y1 receptor in rat brain capillary endothelial cells of the B7 and B10 clones
Authors: Vigne Paul , Breittmayer Jean Philippe , Frelin Christian
Published: January 2005

Diadenosine polyphosphates (ApnAs, n=2–7) are considered as stress mediators in the cardiovascular system. They act both via identified P2 purinoceptors and via yet to be characterized receptors. This study analyses the actions of ApnAs in clones of rat brain capillary endothelial cells that express P2Y1 receptors (B10 cells) or both P2Y1 and P2Y2 receptors (B7 cells).

B10 cells responded to Ap3A with rises in intracellular Ca2+ concentration ([Ca2+]i). This response was prevented by adenosine‐3′‐phosphate‐5′‐phosphate, an antagonist of P2Y1 receptors. It was largely suppressed by a treatment with apyrase VII or with creatine phosphokinase/creatine phosphate to degrade contaminating ADP.

ApnAs inhibited ADP induced increases in [Ca2+]i mediated by P2Y1 receptors by shifting ADP concentration‐response curves to larger concentrations. Apparent Ki values were estimated to be 6 μM for Ap4A, 10 μM for Ap5A and 47 μM for Ap6A. Ap2A and Ap3A were much less active.

ApnAs were neither agonists nor antagonists of the endogenous P2Y2 receptor in B7 cells.

ApnAs are neither agonists nor antagonists of the Gi‐coupled, ADP receptor in B10 cells.

The results suggest that most actions of ApnAs in B7 and B10 cells can be accounted for by endogenous P2Y1 receptors. Ap4A, Ap5A and Ap6A are specific antagonists of endogenous Ca2+‐coupled P2Y1 receptors.

British Journal of Pharmacology (2000) 129, 1506–1512; doi:10.1038/sj.bjp.0703228
Effects of cannabinoid receptor agonists on neuronally‐evoked contractions of urinary bladder tissues isolated from rat, mouse, pig, dog, monkey and human
Authors: Martin R S , Luong L A , Welsh N J , Eglen R M , Martin G R , MacLennan S J
Published: January 2005

This study investigated the cannabinoid receptor, known to inhibit neuronally‐evoked contractions of the mouse isolated urinary bladder, in bladder sections isolated from mouse, rat, dog, pig non‐human primate or human.

The CB1‐like pharmacology of the cannabinoid receptor in mouse isolated bladder observed previously was confirmed in this study by the rank order of agonist potencies: CP 55940WIN 55212‐2>HU 210>JWH 015>anandamide, the high affinity of the CB1 selective antagonist, SR 141716A (apparent pKB 8.7), and the low affinity of the CB2 antagonist, SR 144528 (apparent pKB<6.5). In these studies, SR 141716A (10–100 nM) significantly potentiated electrically‐evoked contractions in this tissue by an undetermined mechanism.

A similar rank order of agonist potencies was determined in rat isolated bladder sections (CP 55, 940WIN 55212‐2>JWH 015). In this tissue, the maximal inhibitory effect of all agonists was lower than in the mouse bladder. Indeed, the effects of both HU 210 and anandamide were too modest to quantify potency accurately.

In the rat isolated bladder, SR 141716A (30 nM) or SR 144528 (100 nM), reversed the inhibitory effect of WIN 55212‐2 (apparent pKB=8.4 and 8.0, respectively) or JWH 015 (apparent pKB=8.2 and 7.4, respectively). These findings may demonstrate pharmacological differences between the rat and mouse orthologues of the CB1 receptor. Alternatively, they may be attributed to a mixed population of CB1 and CB2 receptors that jointly influence neurogenic contraction of the rat bladder, but cannot be differentiated without more selective ligands.

WIN 55212‐2 had no effect on electrically‐evoked contractions of bladder sections isolated from dog, pig, cynomolgus monkey and human. These findings suggest that the effect of cannabinoid agonists to inhibit neurogenic contraction of the mouse and rat bladder is not conserved across all mammalian species.

British Journal of Pharmacology (2000) 129, 1707–1715; doi:10.1038/sj.bjp.0703229
Selective cyclo‐oxygenase‐2 inhibition with celecoxib elevates blood pressure and promotes leukocyte adherence
Authors: Muscará Marcelo N , Vergnolle Nathalie , Lovren Fina , Triggle Christopher R , Elliott Susan N , Asfaha Samuel , Wallace John L
Published: January 2005

Selective inhibitors of cyclo‐oxygenase‐2 have been shown to be effective anti‐inflammatory drugs with reduced gastrointestinal toxicity relative to conventional nonsteroidal anti‐inflammatory drugs (NSAIDs). In the present study, we examined the possibility that selective COX‐2 inhibition, by blocking prostacyclin synthesis, would increase blood pressure and cause leukocyte adherence and platelet aggregation.

Normal rats and rats with hypertension induced by chronic administration of Nω‐nitro‐L‐arginine methylester were given celecoxib (10 mg kg−1) daily for 3 weeks. Celecoxib significantly elevated of blood pressure in both the normal and hypertensive rats (mean increase of >33 mm Hg after 3 weeks).

In normal rats, celecoxib had no effect on serum 6‐keto prostaglandin (PG)F1α levels. Hypertensive rats exhibited a significant increase (82%) in serum 6‐keto PGF1α levels, and this was reduced to the levels of normal rats by treatment with celecoxib.

Rats treated with celecoxib exhibited significant increases in weight gain (20%), plasma arginine‐vasopressin levels (148%) and plasma urea (69%) relative to vehicle‐treated controls. Plasma creatinine levels were unaffected by treatment with celecoxib, while plasma renin levels were significantly decreased (30%) relative to controls.

Superfusion of mesenteric venules with celecoxib (3 μM) in vivo resulted in significant increases in leukocyte adherence to the endothelium in both normal and hypertensive rats.

These studies suggest that suppression of COX‐2 significantly influences vascular and/or renal function, leading to elevated blood pressure and leukocyte adherence.

British Journal of Pharmacology (2000) 129, 1423–1430; doi:10.1038/sj.bjp.0703232
Negative inotropic effects of isoprenaline on isolated left atrial assays from aged transgenic mice with cardiac over‐expression of human β2‐adrenoceptors
Authors: Prendergast C E , Shankley N P , Black J W
Published: January 2005

The action of isoprenaline has been evaluated in an isolated, left atrial assay, from aged transgenic mice with cardiac‐specific over‐expression of the β2‐adrenoceptor. In the assay, isoprenaline produced a negative inotropic concentration‐response curve that was not altered by incubation with CGP‐20712A (1 μM), a β1‐adrenoceptor antagonist. However, after incubation with ICI‐118,551 (300 nM), a selective β2‐adrenoceptor antagonist, isoprenaline produced a positive inotropic concentration‐effect curve that was located to the left of the negative inotropic curve. This suggests that the negative inotropic effect was mediated by a homogenous population of negatively‐coupled β2‐adrenoceptors. In the presence of CGP‐20712A (300 nM), the positive curve was shifted to the right, suggesting that the positive inotropic effect was mediated, at least in part, by β1‐adrenoceptors. These results differ substantially from those previously obtained in young transgenic mice. An outline of an explanatory model, based on a concept of over‐expressed receptors ‘stealing’ G‐proteins, is suggested.

British Journal of Pharmacology (2000) 129, 1285–1288; doi:10.1038/sj.bjp.0703238
Anti‐NO action of carvedilol in cell‐free system and in vascular endothelial cells
Authors: Yoshioka Toshimasa , Iwamoto Noriko , Tsukahara Fujiko , Irie Kaoru , Urakawa Ikuko , Muraki Takamura
Published: January 2005

Carvedilol, an adrenoceptor blocker with antioxidant activity, was studied for its ability to interact with NO in a cell‐free condition and in an endothelial cell line (ECV304).

In a cell‐free system, carvedilol attenuated NO‐dependent reduction of carboxy‐2‐phenyl‐4,4,5,5‐tetramethyl‐imidazoline‐1‐oxyl‐3‐oxide induced by a NO donor, 1‐hydroxy‐2‐oxo‐3‐(aminopropyl)‐3‐isopropyl‐1‐triazene (NOC5), which was determined by electron paramagnetic resonance (EPR) spectrometry. The EPR study also showed that nitrosylhaemoglobin formation in rat red blood cells by the addition of NO‐saturated solution was attenuated by prior incubation with 0.1–10 μM carvedilol.

NO‐induced fluorescence in 4,5‐diaminofluorescein‐2 diacethyl (DAF‐2DA)‐loaded ECV304 cells was attenuated by carvedilol but not by labetalol. The IC50 of carvedilol for NOC5 or sodium nitroprusside‐induced fluorescence of DAF‐2DA in ECV304 cells was 1.0×10−7 M, which was similar to the reported IC50 of carvedilol for the antioxidant effect.

Cell toxicity induced by a NO donor determined by the number of viable cells after 24 h treatment with 2‐2′(hydroxynitrosohydrazino)bis‐ethanamine was significantly attenuated by pretreatment with 1 μM carvedilol.

Both free and cell‐associated carvedilol quenched NO. Because NO mediates both physiological and pathophysiological processes, NO quenching by the drug may have diverse clinical implications depending upon specific functions of local NO in tissues where carvedilol is distributed.

British Journal of Pharmacology (2000) 129, 1530–1535; doi:10.1038/sj.bjp.0703241
Splice isoforms of α1a‐adrenoceptor in rabbit
Authors: Suzuki Fumiko , Taniguchi Takanobu , Takauji Rumiko , Murata Satoshi , Muramatsu Ikunobu
Published: January 2005

Two splice isoforms of rabbit α1a‐adrenergic receptor (AR), (named α1a‐OCU.2‐AR and α1a‐OCU.3‐AR) have been isolated from the liver cDNA library in addition to the previously reported isoform (α1a‐OCU.1‐AR). Although they have the identical splice position with human α1a‐AR isoforms, the C‐terminal sequences are distinct from those of human isoforms.

Among these rabbit α1a‐AR isoforms, there are no significant differences in pharmacological properties: high affinity for prazosin, WB4101, KMD‐3213 and YM617 and low affinity for BMY7378, using COS‐7 cells expressing each isoform by radioligand binding assay.

Competitive reverse transcription‐polymerase chain reaction (RT–PCR) analysis revealed that mRNA of α1a‐ARs was expressed in liver, thoracic aorta, brain stem and thalamus of rabbit. The splice isoforms exhibited a distinct distribution pattern in rabbit; α1a‐OCU.1‐AR was expressed most abundantly in those tissues.

CHO clones, stably expressing each isoforms with receptor density 740 fmol mg−1 protein in α1a‐OCU.1‐AR, 1200 fmol mg−1 in α1a‐OCU.2‐AR and 570 fmol mg−1 in α1a‐OCU.3‐AR, respectively, showed a noradrenaline‐induced increase in inositol trisphosphate which was suppressed by prazosin.

Noradrenaline elicited a concentration‐dependent increase in extracellular acidification rate (EAR) in the CHO clones with pEC50 values of 6.19 for α1a‐OCU.1‐AR, 6.49 for α1a‐OCU.2‐AR and 6.58 for α1a‐OCU.3‐AR, respectively.

Noradrenaline caused a concentration‐dependent increase in intracellular Ca2+ concentration ([Ca2+]i) in the CHO clones with pEC50 values of 6.14 for α1a‐OCU.1‐AR, 7.25 for α1a‐OCU.2‐AR and 7.70 for α1a‐OCU.3‐AR, respectively.

In conclusion, the present study shows the occurrence of three splice isoforms of rabbit α1a‐AR, which are unique in C‐terminal sequence and in tissue distribution. They show similar pharmacological profiles in binding studies but α1a‐OCU.3‐AR had the highest potency of noradrenaline in functional studies in spite of the lowest receptor density. These findings suggest that the structure of C‐terminus of α1a‐ARs may give the characteristic functional profile.

British Journal of Pharmacology (2000) 129, 1569–1576; doi:10.1038/sj.bjp.0703242
FP‐receptor mediated trophic effects of prostanoids in rat ventricular cardiomyocytes
Authors: Pönicke K , Giessler C , Grapow M , Heinroth‐Hoffmann I , Becker K , Osten B , Brodde O‐E
Published: January 2005

The aim of this study was to characterize the receptor subtype involved in cardiac effects of prostanoids. For this purpose we determined in neonatal and adult rat cardiomyocytes effects of prostanoids on inositol phosphate (InsP)‐formation (assessed as accumulation of total [3H]‐InsP's in myo‐[3H]‐inositol pre‐labelled cells) and on rate of protein synthesis (assessed as [3H]‐phenylalanine incorporation), and on contractile force in left ventricular strips of the rat heart. For comparison, effects of prostanoids on InsP‐formation and contractile force were determined in rat thoracic aorta, a classical TP‐receptor containing tissue.

Prostanoid increased InsP‐formation and rate of protein synthesis in neonatal as well as adult rat cardiomyocytes; the order of potency was in neonatal (PGF2α>PGD2PGE2U 46619>PGE1) and adult (PGF2α>PGD2PGE2>U 46619) rat cardiomyocytes well comparable. Moreover, in electrically driven left ventricular strips PGF2α caused positive inotropic effects (pD2 7.5) whereas U 46619 (up to 1 μM) was uneffective.

In contrast, in rat thoracic aorta U 46619 was about 100 times more potent than PGF2α in increasing InsP‐formation and contractile force.

The TP‐receptor antagonist SQ 29548 only weakly antagonized prostanoid‐induced increases in rate of protein synthesis (pKB about 6) in rat cardiomyocytes but was very potent (pKB about 8–9) in antagonizing prostanoid‐induced increases in InsP‐formation and contractile force in rat aorta.

We conclude that, in cardiomyocytes of neonatal and adult rats, the prostanoid‐receptor mediating increases in InsP‐formation and rate of protein synthesis is a FP‐receptor. Moreover, stimulation of these cardiac FP‐receptors can mediate increases in contractile force.

British Journal of Pharmacology (2000) 129, 1723–1731; doi:10.1038/sj.bjp.0703243
O‐1057, a potent water‐soluble cannabinoid receptor agonist with antinociceptive properties
Authors: Pertwee Roger G , Gibson T Michael , Stevenson Lesley A , Ross Ruth A , Banner W Kenneth , Saha Bijali , Razdan Raj K , Martin Billy R
Published: January 2005

Cannabinoids have low water solubility, necessitating the use of a solubilizing agent. In this paper we investigated whether a novel water‐soluble cannabinoid, 3‐(5′‐cyano‐1′,1′‐dimethylpentyl)‐1‐(4‐N‐morpholinobutyryloxy)‐Δ8‐tetrahydrocannabinol hydrochloride (O‐1057), would interact with cannabinoid receptors when water or saline were used as the only vehicle.

O‐1057 displaced [3H]‐CP55940 from specific binding sites on Chinese hamster ovary (CHO) cell membranes expressing CB1 or CB2 cannabinoid receptors, with pKi values of 8.36 and 7.95 respectively. It also displaced [3H]‐CP55940 from specific binding sites on rat brain membranes (pKi=7.86).

O‐1057 inhibited forskolin‐stimulated cyclic AMP production by both CB1‐ and CB2‐transfected CHO cells (pEC50=9.16 and 9.72 respectively), its potency matching that of CP55940 and exceeding that of Δ9‐tetrahydrocannabinol.

In the mouse isolated vas deferens, O‐1057 inhibited electrically‐evoked contractions with pEC50 and Emax values of 9.73 and 76.84% respectively. It was antagonized by 100 nM SR141716A, the pKB of SR141716A against O‐1057 (8.90) approximating to that against CP55940 (8.97).

O‐1057 also behaved as a CB1 receptor agonist in vivo, reducing mouse spontaneous activity and rectal temperature when injected intravenously and inducing antinociception in the mouse tail flick test when given intravenously (ED50=0.02 mg kg−1), intrathecally, intracerebroventricularly or by gavage. In all these assays, O‐1057 was more potent than Δ9‐tetrahydrocannabinol and, at 0.1 mg kg−1 i.v., was antagonized by SR141716A (3 mg kg−1 i.v.).

These data demonstrate the ability of the water‐soluble cannabinoid, O‐1057, to act as a potent agonist at CB1 and CB2 receptors and warrant investigation of the clinical potential of O‐1057 as an analgesic.

British Journal of Pharmacology (2000) 129, 1577–1584; doi:10.1038/sj.bjp.0703245
Histamine H3‐receptor antagonists inhibit gastroprotection by (R)‐α‐methylhistamine in the rat
Authors: Morini Giuseppina , Grandi Daniela , Stark Holger , Schunack Walter
Published: January 2005

(R)‐α‐methylhistamine, a selective agonist of histamine H3 receptors, is capable of protecting the gastric mucosa against differently acting damaging agents. The objective of the present study was to determine whether H3 receptors mediate its protective action in the rat.

Gastric mucosal lesions were induced intragastrically (i.g.) by 0.6 N HCl, 1 ml rat−1. (R)‐α‐methylhistamine, 100 mg kg−1 i.g., substantially reduced the severity of macroscopically and histologically assessed damage caused by concentrated acid. Prior treatment with highly selective H3‐receptor antagonists, ciproxifan (0.3, 1 and 3 mg kg−1 i.g.) and clobenpropit (3, 10 and 30 mg kg−1 i.g.), dose‐dependently inhibited the protection exerted by (R)‐α‐methylhistamine up to a complete reversal. When given alone at high doses, both antagonists tended to worsen the HCl‐induced histologic damage.

During basal conditions, (R)‐α‐methylhistamine, 100 mg kg−1 i.g., caused a significant increase in titratable acidity of the gastric juice. Prior treatment with ciproxifan (3 mg kg−1 i.g.) and clobenpropit (30 mg kg−1 i.g.) did not alter the secretory response to (R)‐α‐methylhistamine. Clobenpropit alone, but not ciproxifan, increased the volume of gastric juice, and both compounds alone had no effect on titratable acid.

Present findings support evidence that H3 receptors are actively involved in the maintenance of gastric mucosal integrity, with no apparent role in the regulation of basal gastric acid secretion.

British Journal of Pharmacology (2000) 129, 1597–1600; doi:10.1038/sj.bjp.0703249
Release of dopamine from human neocortex nerve terminals evoked by different stimuli involving extra‐ and intraterminal calcium
Authors: Bonanno Giambattista , Sala Roberta , Cancedda Laura , Cavazzani Paolo , Cossu Massimo , Raiteri Maurizio
Published: January 2005

The release of [3H]‐dopamine ([3H]‐DA) from human neocortex nerve terminals was studied in synaptosomes prepared from brain specimens removed in neurosurgery and exposed during superfusion to different releasing stimuli.

Treatment with 15 mM KCl, 100 μM 4‐aminopyridine, 1 μM ionomycin or 30 mM caffeine elicited almost identical overflows of tritium. Removal of external Ca2+ ions abolished the overflow evoked by K+ or ionomycin and largely prevented that caused by 4‐aminopyridine; the overflow evoked by caffeine was completely independent of external Ca2+.

Exposure of synaptosomes to 25 μM of the broad spectrum calcium channel blocker CdCl2 strongly inhibited the 4‐aminopyridine‐induced tritium overflow while that evoked by ionomycin remained unaffected.

The Ca2+ chelator, 1,2‐bis‐(2‐aminophenoxy)ethane‐N,N,N′,N′ tetraacetic acid (BAPTA), reduced significantly the K+‐ and the caffeine‐induced tritium overflow. The effect of caffeine was attenuated by exposure to the ryanodine receptor blocker dantrolene or when the membrane‐impermeant inositol trisphosphate receptor antagonist, heparin, was entrapped into synaptosomes; the combined treatment with dantrolene and heparin abolished the release elicited by caffeine.

Tetanus toxin, entrapped into human neocortex synaptosomes to avoid prolonged incubation, inhibited in a concentration‐dependent manner the K+‐ or the 4‐aminopyridine‐evoked tritium overflow; in contrast, the release stimulated by ionomycin and by caffeine were both totally insensitive to the same concentrations of tetanus toxin. Western blot analysis showed about 50% reduction of the content of the vesicular protein, synaptobrevin, in synaptosomes poisoned with tetanus toxin.

In conclusion, the release of dopamine from human neocortex nerve terminals can be triggered by Ca2+ ions originating from various sources. It seems that stimuli not leading to activation of voltage‐sensitive Ca2+ channels elicit Ca2+‐dependent, probably exocytotic, release that is insensitive to tetanus toxin.

British Journal of Pharmacology (2000) 129, 1780–1786; doi:10.1038/sj.bjp.0703251
Pharmacokinetic‐pharmacodynamic modelling of the convulsant interaction between norfloxacin and biphenyl acetic acid in rats
Authors: Marchand Sandrine , Pariat Claudine , Bouquet Serge , Courtois Philippe , Couet William
Published: January 2005

Fluoroquinolones (FQs) are associated with a low incidence of central nervous system (CNS) side effects, possibly leading to convulsions, especially when co‐administered with nonsteroidal anti‐inflammatory drugs (NSAIDS). Although the in vivo pro‐convulsant activity of NSAIDS is essentially unknown, the convulsant potential of FQs is traditionally evaluated by in vitro γ‐aminobutyric acid (GABA) binding experiments in the presence of 4‐biphenyl acetic acid (BPAA), the active metabolite of fenbufen.

The aim of this study was therefore to investigate the BPAA‐norfloxacin convulsant interaction in vivo.

Male Sprague‐Dawley rats (n=27) were given BPAA orally, at various doses 1 h before norfloxacin infusion, which was maintained until the onset of maximal seizures, when cerebrospinal fluid (CSF) and plasma samples were collected for analysis.

An inhibitory Emax effect model with a baseline effect parameter was fitted to the norfloxacin versus BPAA concentrations in the CSF, previously shown to be part of the biophase. This model includes three parameters: the concentrations of norfloxacin in the absence of BPAA (CCSF0, Nor), and when BPAA concentration tends toward infinity (CCSFbase, Nor), and the BPAA concentration for which half of the maximal effect is observed (CCSF50, BPAA). The maximal proconvulsant effect of BPAA is given by the CCSF0, Nor / CCSFbase, Nor ratio, estimated to approximately 6 in this study.

Derived models were developed in plasma to account for the non‐linear CSF diffusion of norfloxacin and protein binding of BPAA.

In conclusion this study has shown that the convulsant interaction between norfloxacin and BPAA in rats, can be adequately characterized by modelling of the CSF concentrations of the two drugs at the onset of activity, following their administration in various proportions.

British Journal of Pharmacology (2000) 129, 1609–1616; doi:10.1038/sj.bjp.0703260
Investigations into pharmacological antagonism of general anaesthesia
Authors: Little H J , Clark A , Watson W P
Published: January 2005

The effects of convulsant drugs, and of thyrotropin releasing hormone (TRH), were examined on the general anaesthetic actions of ketamine, ethanol, pentobarbitone and propofol in mice. The aim was to investigate the possibility of selective antagonism, which, if seen, would provide information about the mechanism of the anaesthesia.

The general anaesthetic effects of ketamine were unaffected by bicuculline; antagonism was seen with 4‐aminopyridine and significant potentiation with 300 mg kg−1 NMDLA (N‐methyl‐DL‐aspartate). The calcium agonist, Bay K 8644, potentiated the anaesthesia produced by ketamine and antagonism of such anaesthesia was seen with TRH.

A small, but significant, antagonism of the general anaesthesia produced by ethanol was seen with bicuculline, and a small, significant, potentiation with 4‐aminopyridine. There was an antagonist effect of TRH, but no effect of NMDLA.

Potentiation of the anaesthetic effects of pentobarbitone was seen with NMDLA and with 4‐aminopyridine and the lower dose of bicuculline (2.7 mg kg−1) also caused potentiation. There was no significant change in the ED50 value for pentobarbitone anaesthesia with TRH.

Bicuculline did not alter the anaesthetic actions of propofol, while potentiation was seen with NMDLA and 4‐aminopyridine. TRH had no significant effect on propofol anaesthetic, but Bay K 8644 at 1 mg kg−1 significantly potentiated the anaesthesia.

These results suggest that potentiation of GABAA transmission or inhibition of NMDA receptor‐mediated transmission do not appear to play a major role in the production of general anaesthesia by the agents used.

British Journal of Pharmacology (2000) 129, 1755–1763; doi:10.1038/sj.bjp.0703262
Antagonism of nicotinic receptors of rat chromaffin cells by N,N,N‐trimethyl‐1‐(4‐trans‐stilbenoxy)‐2‐propylammonium iodide: a patch clamp and ligand binding study
Authors: Di Angelantonio Silvia , Nistri Andrea , Moretti Milena , Clementi Francesco , Gotti Cecilia
Published: January 2005

The effect of the oxystilbene derivative F3 was tested on nAChRs of whole‐cell patch‐clamped rat chromaffin cells in vitro and of rat adrenal gland membranes using 125I‐epibatidine.

F3 (30 nM) rapidly and reversibly blocked inward currents generated by pulse applications of nicotine, shifting the dose‐response curve to the right in a parallel fashion without changing the maximum response. The action of F3 was voltage insensitive and not due to altered current reversal potential.

The R isomer of F3 was more potent (IC50=350±30 nM) than its S‐enantiomer (IC50=1.5±0.3 μM). Nicotine‐evoked currents were insensitive to 10 μM α‐bungarotoxin.

Equi‐amplitude currents evoked by nicotine or epibatidine were similarly antagonized by R‐F3 in a reversible fashion. Epibatidine‐evoked currents readily produced receptor desensitization.

Adrenal membranes specifically bound 125I‐epibatidine with a single population of binding sites endowed with high affinity (KD=159 pM) and Bmax of 6.5±1.3 fmol mg−1 of protein.

125I‐epibatidine binding was specifically displaced by cytisine (Ki=68 nM) or ACh (Ki=348 nM). F3 specifically displaced 125I‐epibatidine binding although with lower affinity (Ki=29.6 μM) than in electrophysiological experiments. 125I‐epibatidine binding to rat adrenal tissue was insensitive to α‐bungarotoxin which readily antagonized 125I‐epibatidine binding to bovine adrenal tissue.

The present results suggest that F3 is a relatively potent and apparently competitive antagonist of nAChRs on rat chromaffin cells. Since previous studies have indicated that F3 targets different subtypes on chick neuronal tissue, it appears that nAChRs display interspecies differences to be considered for drug development studies.

British Journal of Pharmacology (2000) 129, 1771–1779; doi:10.1038/sj.bjp.0703264
Impaired vascular sensitivity to nitric oxide in the coronary microvasculature after endotoxaemia
Authors: Bogle Richard G , McLean Peter G , Ahluwalia Amrita , Vallance Patrick
Published: January 2005

The effects of endotoxaemia on coronary vasodilator responses to bradykinin (BK), sodium nitroprusside (SNP) and nicardipine were investigated in the rat isolated heart perfused at constant flow ex vivo.

Dose‐dependent reductions in coronary perfusion pressure reaching a maximum of 56±3 and 57±5 mmHg were observed for BK and SNP respectively. The BK response was biphasic, consisting of a rapid dilator response that was insensitive to NGnitro‐L‐arginine methyl ester (L‐NAME, 0.1 mM) and a second slower component whose duration was attenuated by L‐NAME.

Hearts obtained from rats treated with endotoxin (2.5 mg kg−1, i.p.) for 2 or 6 h had increased basal coronary perfusion pressure and reduced vasodilator responses to BK or SNP. Dilator responses to nicardipine were not affected by endotoxin treatment. In vitro perfusion of hearts from endotoxin‐treated rats with L‐NAME (0.1 mM) restored SNP responses to control values.

Treatment with dexamethasone (1 mg kg−1), 1 h before endotoxin did not alter the endotoxin‐induced impairment of dilator responses to BK or SNP.

These results show that coronary microvascular responses are altered following endotoxin exposure. Endotoxin results in increased coronary microvascular tone despite induction of NO synthase and inhibits the dilator response to BK and SNP, vasodilators that act via the release of NO. Responses to SNP in endotoxin‐treated hearts were restored to control values in the presence of L‐NAME suggesting that enhanced endogenous NO synthesis might saturate guanylate cyclase resulting in reduced response to NO donors. The reduced response to vasodilators and increased coronary resistance might be important in determining the response of the coronary circulation to systemic inflammation and infection.

British Journal of Pharmacology (2000) 130, 118–124; doi:10.1038/sj.bjp.0703267
Proteinase‐activated receptor‐2 (PAR‐2): regulation of salivary and pancreatic exocrine secretion in vivo in rats and mice
Authors: Kawabata Atsufumi , Nishikawa Hiroyuki , Kuroda Ryotaro , Kawai Kenzo , Hollenberg Morley D
Published: January 2005

Proteinase‐activated receptor‐2 (PAR‐2) is expressed throughout the gastrointestinal tract including the pancreas, and may be involved in digestive functions. The aim of our study was to evaluate a potential role for PAR‐2 in regulating salivary and pancreatic exocrine secretion in vivo.

PAR‐2‐activating peptides (PAR‐2‐APs), but not selective PAR‐1‐APs, administered intravenously, increased salivary secretion in the mouse or rat; this effect of the PAR‐2‐APs was unaffected by atropine, phentolamine, propranolol or indomethacin.

Secretion (amylase) by rat parotid gland slices in vitro was also stimulated by PAR‐2‐APs and trypsin, but not by activation of other PARs.

PAR‐2‐APs, administered to rats in vivo, caused a prompt effect on pancreatic exocrine secretion.

PAR‐2 mRNA, known to be present in pancreatic tissue, was also detected in parotid tissue.

Our results indicate that in addition to a potential role in regulating cardiovascular and respiratory functions, PAR‐2 may also play a general role in vivo for the direct regulation of glandular exocrine secretion.

British Journal of Pharmacology (2000) 129, 1808–1814; doi:10.1038/sj.bjp.0703274
Evaluation of iNOS‐dependent and independent mechanisms of the microvascular permeability change induced by lipopolysaccharide
Authors: Fujii Emiko , Yoshioka Toshimasa , Ishida Hiroyasu , Irie Kaoru , Muraki Takamura
Published: January 2005

Subcutaneous injection of lipopolysaccharide (LPS) increases plasma leakage in mouse skin. Pretreatment with LPS conditions mice tolerant to the LPS‐induced plasma leakage. Nitric oxide (NO) has been suggested to be involved in these LPS effects. A specific role of inducible NO synthase (iNOS) was investigated in the LPS‐induced plasma leakage using iNOS deficient mice.

Plasma leakage in mouse skin was measured by the local accumulation of Pontamine sky blue at the site of subcutaneous injection of LPS (Sal. typhimurium). LPS (100–400 μg site−1) produced a dose‐related increase in dye leakage in both iNOS deficient and wild‐type mice with about 40% less dye leakage in iNOS deficient mice.

Indomethacin (5 mg kg−1), N‐[‐2‐cyclohexyloxy]‐4‐nitrophenyl methanesulphonamide (NS‐398) (1 mg kg−1), diphenhydramine (10 mg kg−1) and anti‐TNF‐α antibody (dilution 1 : 400, 10 ml kg−1) inhibited the LPS‐induced dye leakage in both iNOS deficient and wild‐type mice, whereas NG‐nitro‐L‐arginine methyl ester (L‐NAME) (10 mg kg−1) or aminoguanidine (10 mg kg−1) inhibited that in wild‐type but not in iNOS deficient mice.

Pretreatment with LPS (0.15 mg kg−1 i.p.) 4 h before decreased the LPS‐induced dye leakage in wild‐type but not in iNOS deficient mice. LPS pretreatment increased serum corticosterone levels in both mice, while it increased the serum nitrate/nitrite levels in wild‐type but not in iNOS deficient mice.

These studies indicate that an increase in vascular permeability induced by LPS is mediated by NO produced by iNOS, eicosanoids, histamine and TNF‐α. The tolerance against LPS‐induced vascular permeability change may be mediated by iNOS induction but not by an increased release of endogenous corticosteroids.

British Journal of Pharmacology (2000) 130, 90–94; doi:10.1038/sj.bjp.0703277
Evidence for the involvement of peroxynitrite in ischaemic preconditioning in rat isolated hearts
Authors: Altuǧ Sedat , Demiryürek A Tuncay , Kane Kathleen A , Kanzik İlker
Published: January 2005

The aim of this study was to investigate the involvement of peroxynitrite, reactive metabolite originating from nitric oxide and superoxide, in preconditioning of the ischaemic myocardium in rat isolated hearts.

Isolated hearts perfused with Krebs‐Henseleit solution were preconditioned either by 3 min of coronary artery occlusion (CAO) or by peroxynitrite administration at three different concentrations (0.1, 1, 10 μM) for 3 min, followed by 10 min reperfusion and 30 min of CAO. Peroxynitrite, at 1 μM concentration, decreased the incidence of VT from 100% (n=14) to 62% (n=13) and abolished the occurrence of VF (50% in the control group).

N‐2‐mercaptopropionylglycine (MPG, 1 μM–10 mM) produced a concentration‐dependent inhibition of peroxynitrite signals in luminol chemiluminescence and 67±1% inhibition was observed at 100 μM (n=7). MPG (at 300 μM, n=7) added to the perfusate 10 min prior to ischaemic preconditioning or peroxynitrite infusion and maintained until CAO, significantly reversed the beneficial effects of the ischaemic and peroxynitrite‐treated groups. MPG administration in the peroxynitrite‐treated group increased the incidence of VT from 62% (n=13) to 100% (n=10) and total VF from 0% (n=0) to 67% (n=10). Similarly, MPG elevated the incidence of VT from 50% (n=10) to 100% (n=8) in the ischaemic preconditioned group. On its own, MPG did not affect the severity of cardiac arrhythmias.

These results suggest that endogenously produced peroxynitrite plays a significant role in the antiarrhythmic effect of ischaemic preconditioning in the rat isolated hearts.

British Journal of Pharmacology (2000) 130, 125–131; doi:10.1038/sj.bjp.0703280
Enhanced expression of haem oxygenase‐1 by nitric oxide and antiinflammatory drugs in NIH 3T3 fibroblasts
Authors: Alcaraz Maria José , Habib Aïda , Lebret Marilyne , Créminon Christophe , Lévy‐Toledano Sylviane , Maclouf Jacques
Published: January 2005

Haem oxygenase‐1 (HO‐1) can exert protective effects against oxidative stress and inflammation. Fibroblasts participate in inflammatory responses where they produce high levels of prostaglandins (PGs) and nitric oxide (NO). However, little is known of the presence of HO‐1 in these cells and the possible interactions among these pathways. Incubation of cells with NO donors, spermine nonoate (SPNO) and S‐nitroso‐N‐acetylpenicillamine (SNAP), induced a dose‐ and time‐dependent expression of HO‐1 protein.

NO donors increased basal PGE2 release although they reduced PGE2 accumulated in the medium and cyclo‐oxygenase (COX) activity when cells were stimulated with lipopolysaccharide (LPS). COX‐2 protein was weakly induced by SPNO in basal conditions and in the presence of LPS a synergy for HO‐1 and COX‐2 protein expression was observed.

Our results indicate that reactive oxygen species participate in the inductive effect of NO donors or LPS on HO‐1 expression, whereas endogenous NO production may play a role in the mechanism of the synergy exhibited by SPNO and LPS on HO‐1 and COX‐2 expression. In this system, zinc protoporphyrin IX did not affect nitrite levels but reduced COX activity.

The selective COX‐2 inhibitors SC58125 and NS398 as well as the non‐selective COX inhibitor, indomethacin, strongly reduced PGE2 synthesis and showed a synergy with NO donors in HO‐1 and COX‐2 induction. Addition of PGE2 had no effect, suggesting a mechanism independent of PGs formation.

In inflammatory conditions a number of factors could cooperate to induce HO‐1 and COX‐2, with a positive regulation by COX inhibitors.

British Journal of Pharmacology (2000) 130, 57–64; doi:10.1038/sj.bjp.0703281
Suppression of arterial intimal hyperplasia by cilostamide, a cyclic nucleotide phosphodiesterase 3 inhibitor, in a rat balloon double‐injury model
Authors: Inoue Yoshihiro , Toga Kazuyuki , Sudo Toshiki , Tachibana Kazue , Tochizawa Shirou , Kimura Yukio , Yoshida Yoji , Hidaka Hiroyoshi
Published: January 2005

The effects of cilostamide, a cyclic nucleotide phosphodiesterase 3 (PDE3) selective inhibitor, on vascular intimal hyperplasia were evaluated using a single‐balloon injury model and a double‐injury model in which the rat common carotid artery was subjected to a second injury at a site injured 14 days previously.

In the double‐injury model, the second balloon injury caused more severe intimal hyperplasia (intima/media (IM) ratio, 1.88±0.10) than in the single‐injury model (1.09±0.08). Histopathological study revealed that vascular smooth muscle cells (VSMC) were the predominant cell‐type in the affected neointimal area.

Oral administration of cilostamide for 2 weeks after the second injury suppressed intimal hyperplasia in the double‐injury model (30 mg kg−1 bid, 83% inhibition in terms of the IM ratio, P<0.05; 100 mg kg−1 bid, 69% inhibition, P<0.05). Similar effects were also observed in the single‐injury model with oral administration of cilostamide for 2 weeks (100 mg kg−1 bid, 36% inhibition, P<0.01).

Cilostamide inhibited DNA synthesis of cultured VSMC stimulated by foetal calf serum or different kinds of growth factors, but did not affect their migration stimulated by platelet‐derived growth factor (PDGF)‐BB. Cilostamide significantly increased the cyclic AMP concentration of VSMC dose‐dependently.

These results indicate that cilostamide suppresses intimal hyperplasia both in the single‐ and double‐injury models of rat, presumably by inhibiting proliferation rather than migration of VSMC. It is suggested that PDE3 inhibitors might find application in preventing intimal hyperplasia following angioplasty such as percutaneous transluminal coronary angioplasty (PTCA) or stent.

British Journal of Pharmacology (2000) 130, 231–241; doi:10.1038/sj.bjp.0703287
Smooth muscle layer‐dependent distribution of 5‐hydroxytryptamine7 receptor in the porcine myometrium
Authors: Kitazawa Takio , Yamada Yuko , Iwano Hidetomo , Yokota Hiroshi , Yuasa Akira , Taneike Tetsuro
Published: January 2005

To analyse the mechanisms of muscle layer‐dependent inhibition of porcine myometrial contractility by 5‐hydroxytryptamine (5‐HT), the effects of 5‐HT, 5‐carboxamidotryptamine(5‐CT), 5‐methoxytryptamine (5‐MeOT), forskolin and cyclic adenosine 3′, 5′‐monophosphate (cyclic AMP) analogues on spontaneous and stimulant‐induced contractions were examined in longitudinal (LM) and circular muscles (CM). In addition, accumulation of cyclic AMP by 5‐HT and distribution of 5‐HT7 receptors in LM and CM layers were compared using biochemical and molecular approaches.

5‐HT receptor agonists inhibited the spontaneous contractions of LM and CM (5‐CT>5‐HT>5‐MeOT), but CM was more sensitive than was LM. The inhibition by the agonists was antagonized by methiothepin (100 nM).

Carbachol‐, high‐K+‐, histamine‐ and Ca2+‐induced contractions were inhibited by 5‐HT with different responsivenesses (CM>LM). Even in the presence of 3‐isobutyl‐1‐methylxanthine (IBMX), the inhibition by 5‐HT in the CM was still more conspicuous than that in the LM.

Compared with the CM, the inhibition of spontaneous contraction by forskolin, dibutyryl‐cyclic AMP and 8‐bromo‐cyclic AMP was marked in the LM.

5‐HT (1 nM–1 μM) increased the cyclic AMP in both muscle layers, but the increment in the CM was higher than that in the LM whether IBMX was present or not.

LM and CM layers contained a single class of [3H]‐5‐CT binding sites with a similar Kd value (0.21–0.24 nM). However, Bmax (5‐HT7 receptor concentration) in the CM (120.6 fmol mg−1 protein) was higher than that in the LM (30.4 fmol mg−1 protein).

The molecular study (reverse transcription polymerase chain reaction) demonstrated the expression of 5‐HT7 receptor mRNA in the CM was higher than that in the LM.

These results suggest that the muscle layer‐dependent difference in inhibition by 5‐HT is not restricted to spontaneous contraction but applies to various contractions in the porcine myometrium. Different inhibition of the contractility by 5‐HT is caused by muscle layer‐related accumulation of cyclic AMP (CM>LM), due to smooth muscle‐layer dependent distribution (CM>LM) of 5‐HT7 receptors.

British Journal of Pharmacology (2000) 130, 79–89; doi:10.1038/sj.bjp.0703290
Attenuation of pressure‐induced myogenic contraction and tyrosine phosphorylation by fasudil, a cerebral vasodilator, in rat cerebral artery
Authors: Masumoto Naohiro , Tanabe Yoshiyuki , Saito Maki , Nakayama Koichi
Published: January 2005

The mechanism by which fasudil inhibits pressure‐induced myogenic contraction was studied with regard to tyrosine phosphorylation in rat cerebral artery. Intracellular Ca2+ concentration ([Ca2+]i) and vessel diameter were simultaneously measured. Total tyrosine phosphorylation level and phosphorylation of tyrosine 419 on pp60src required for its full catalytic activity were immunocytochemically detected in situ.

Fasudil (1–100 μM) partially suppressed the increase in [Ca2+]i, and totally attenuated contraction elicited by pressurization from 10 to 60 mmHg. Furthermore, fasudil (100 μM) significantly attenuated tyrosine phosphorylation and the activity of pp60src augmented in situ by pressure.

Herbimycin A (1–100 nM) and genistein (3–30 μM), tyrosine kinase inhibitors, effectively attenuated the pressure‐induced increase in [Ca2+]i, contraction, tyrosine phosphorylation, and activation of pp60src. Both fasudil and herbimycin A directly inhibited the pp60src activity in a cell free system.

Orthovanadate (100 μM), a tyrosine phosphatase inhibitor, significantly potentiated the pressure‐induced increase in [Ca2+]i and contraction.

Nicardipine (100 nM), a Ca2+ antagonist, completely inhibited pressure‐induced increase in [Ca2+]i and contraction, but affected neither tyrosine phosphorylation nor activity of pp60src in the pressurized arteries.

Arginine‐glycine‐aspartic acid‐serine peptide (1–100 μM) concentration‐dependently reduced the pressure‐induced contraction.

In addition to the hitherto reported vasodilatory actions of fasudil, the present results suggest the inhibition by fasudil of pressure‐induced tyrosine phosphorylation and pp60src activation. The wide spectrum of inhibitory actions of fasudil may contribute to the effective attenuation of the pressure‐induced contraction in the cerebral artery.

British Journal of Pharmacology (2000) 130, 219–230; doi:10.1038/sj.bjp.0703292
Reversal of the vasoconstrictor step of hyperacute xenogeneic rejection of the liver by endothelin antagonists
Authors: Zhang Baimeng , Wen Lanling , Gomola Alexandra , Massault Pierre‐Philippe , Cherruau Brigitte , Houssin Didier , Weill Bernard , Calmus Yvon
Published: January 2005

The role of endothelin in the initial vasoconstrictor step of hyperacute xenogeneic rejection was investigated.

Isolated rat livers were perfused in recirculation. Perfusion with human sera provided an ex vivo model of hyperacute rejection in a discordant combination.

Perfusion of 10% xenogeneic serum induced a marked (70%) and sustained reduction of the liver flow and induced the release of endothelin into the perfusion medium. In contrast, perfusion of 10% allogeneic serum or of 10% decomplemented human serum induced a weak (25%) and transient reduction of the liver flow and induced the release of minimal amounts of endothelin. The simultaneous administration of BQ 123 and BQ 788, the respective antagonists of ETA and ETB endothelin receptors, or that of bosentan, a mixed ETA/ETB antagonist, antagonized the vasoconstrictor effect of 10% xenogeneic human serum, as well as that of 10−9 M endothelin‐1.

The vasoconstrictor effects of xenogeneic serum on liver circulation are, at least partly, mediated through the release of endothelin by the graft.

British Journal of Pharmacology (2000) 130, 402–408; doi:10.1038/sj.bjp.0703295