bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dissociation of the PAF‐receptor from NADPH oxidase and adenylate cyclase in human neutrophils results in accelerated influx and delayed clearance of cytosolic calcium
Authors: Steel H C. , Anderson R 
Published: January 2005

The magnitude and duration of the abruptly occurring increases in cytosolic Ca2+ in human neutrophils following activation with PAF (20 and 200 nM) and FMLP (1 μM), have been compared and related to alterations in NADPH oxidase activity, membrane potential and intracellular cyclic AMP.
Cytosolic Ca2+ and membrane potential were measured by spectrofluorimetry, transmembrane fluxes of Ca2+ by radiometric procedures, and NADPH oxidase activity and cyclic AMP by chemiluminescence and radioimmunoassay respectively.
Activation of neutrophils with both PAF (200 nM) and FMLP (1 μM) was accompanied by an abrupt increase in cytosolic Ca2+, which was of similar magnitude for each activator (393±9 and 378±17 nM respectively). Unlike FMLP‐activated cells in which Ca2+ was rapidly removed from the cytosol, peak levels of cytosolic Ca2+ were sustained for longer (0.14±0.02 vs 1.16±0.04 min, P0.0001) and declined at a slower rate in PAF‐treated neutrophils.
The prolonged elevation of cytosolic Ca2+ in PAF‐treated cells was due to accelerated store‐operated influx of extracellular cation and was attenuated by dibutyryl cyclic AMP (4 mM), the Ca2+‐chelator, EGTA (5 mM), and SKF 96365 (10 μM). In contrast to FMLP, basal levels of superoxide production and cyclic AMP were unaltered in PAF‐activated neutrophils, while only moderate membrane depolarization was detected.
These observations demonstrate that mechanisms which restore Ca2+ homeostasis to FMLP‐activated neutrophils, viz. activation of NADPH oxidase and adenylate cyclase, are not operative in PAF‐treated cells, presenting the potential hazard of Ca2+ overload and hyperactivity.

British Journal of Pharmacology (2002) 136, 81–89; doi:10.1038/sj.bjp.0704685
Release inhibitory receptors activation favours the A2A‐adenosine receptor‐mediated facilitation of noradrenaline release in isolated rat tail artery
Authors: Fresco Paula , Diniz Carmen , Queiroz Glória , Gonçalves Jorge 
Published: January 2005

Interactions between A2A‐adenosine receptors and α2‐, A1‐ and P2‐ release‐inhibitory receptors, on the modulation of noradrenaline release were studied in isolated rat tail artery. Preparations were labelled with [3H]‐noradrenaline, superfused with desipramine‐containing medium, and stimulated electrically (100 pulses at 5 Hz or 20 pulses at 50 Hz).
Blockade of α2‐autoreceptors with yohimbine (1 μM) increased tritium overflow elicited by 100 pulses at 5 Hz but not by 20 pulses at 50 Hz.
The selective A2A‐receptor agonist 2‐p‐(2‐carboxyethyl)phenethylamino‐5′‐N‐ethylcarboxamidoadenosine (CGS 21680; 1 – 100 nM) enhanced tritium overflow elicited by 100 pulses at 5 Hz. Yohimbine prevented the effect of CGS 21680, which was restored by the A1‐receptor agonist N6‐cyclopentyladenosine (CPA; 100 nM) or by the P2‐receptor agonist 2‐methylthioadenosine triphosphate (2‐MeSATP; 80 μM).
CGS 21680 (100 nM) failed to increase tritium overflow elicited by 20 pulses at 50 Hz. The α2‐adrenoceptor agonist 5‐bromo‐6‐(2‐imidazolin‐2‐ylamino)‐quinoxaline (UK 14304; 30 nM), the A1‐receptor agonist CPA (100 nM) or the P2‐receptor agonist 2‐MeSATP (80 μM) reduced tritium overflow. In the presence of these agonists CGS 21680 elicited a facilitation of tritium overflow.
Blockade of potassium channels with tetraethylammonium (TEA; 5 mM) increased tritium overflow elicited by 100 pulses at 5 Hz to values similar to those obtained in the presence of yohimbine but did not prevent the effect of CGS 21680 (100 nM) on tritium overflow.
It is concluded that, in isolated rat tail artery, the facilitation of noradrenaline release mediated by A2A‐adenosine receptors is favoured by activation of release inhibitory receptors.

British Journal of Pharmacology (2002) 136, 230–236; doi:10.1038/sj.bjp.0704686
Airway hyperresponsiveness to adenosine induced by lipopolysaccharide in Brown Norway rats
Authors: Tigani B , Hannon J. P. , Rondeau C. , Mazzoni L. , Fozard J. R. 
Published: January 2005

We have explored the effects of bacterial endotoxin (lipopolysaccharide; LPS) on the response of the airways of Brown Norway (BN) rats to adenosine. Comparisons have been drawn with the effects on responses to methacholine and 5‐hydroxytryptamine.
In vehicle‐challenged animals, adenosine, given i.v. was only a weak bronchoconstrictor. In contrast, 1 h following intratracheal administration of LPS, 0.3 mg kg−1, bronchoconstrictor responses to adenosine were markedly and selectively enhanced. At this time point, there were no significant changes in leukocyte numbers, eosinophil peroxidase and myeloperoxidase activities or protein concentrations in bronchoalveolar lavage (BAL) fluid. Twenty‐four hours after challenge, the sensitivity of the airways to both adenosine and methacholine was reduced relative to the earlier time point and there were substantial increases in each marker of inflammation in BAL fluid.
The bronchoconstrictor response to adenosine was blocked selectively by methysergide, disodium cromoglycate and the broad‐spectrum adenosine receptor antagonist, 8‐SPT, but not by DPCPX or ZM 243185, selective antagonists for the A1 and A2A receptors, respectively.
Thus, the response to adenosine augmented following LPS is mast cell mediated and involves a receptor which can be blocked by 8‐SPT but not by selective A1 or A2A receptor antagonists. It thus bears similarity to the augmented response to adenosine induced by allergen challenge in actively sensitized BN rats. Exposure to LPS could be a factor along with allergen in determining the increased sensitivity of the airways of asthmatics to adenosine.

British Journal of Pharmacology (2002) 136, 111–119; doi:10.1038/sj.bjp.0704688
Effect of sodium nitroprusside and 8‐bromo cyclic GMP on nerve‐mediated and acetylcholine‐evoked secretory responses in the rat pancreas
Authors: Yago Maria D. , Tapia Jose A. , Salido Gines M. , Adeghate Ernest , Juma Lubna M. O. , Martinez‐Victoria Emilio , Mañas Mariano , Singh Jaipaul 
Published: January 2005

The effects of sodium nitroprusside (SNP) and 8‐bromo‐guanosine 3′5′ cyclic monophosphate (8‐Br‐cyclic GMP) on nerve‐mediated and acetylcholine (ACh)‐evoked amylase secretion, tritiated choline ([3H]‐choline) release and on intracellular free calcium concentration ([Ca2+]i) in the isolated rat pancreas were investigated.
Electrical field stimulation (EFS; 10 Hz) and ACh (1×10−5 M) caused large increases in amylase output from pancreatic segments. The response to ACh was blocked by atropine (1×10−5 M) whereas the EFS‐evoked response was markedly reduced but not abolished. In contrast, pretreatment with tetrodotoxin (1×10−6 M) abolished the secretory effect of EFS.
Either SNP (1×10−3 M) or 8‐Br‐cyclic GMP (1×10−4 M) inhibited amylase secretion compared to basal. Combining either SNP or 8‐Br‐cyclic GMP with EFS resulted in a marked decrease in amylase output compared to EFS alone. In contrast, either SNP or 8‐Br‐cyclic GMP had no significant effect on the amylase response to ACh. When extracellular Ca2+ concentration ([Ca2+]o) was elevated from 2.56 mM to 5.12 mM, SNP failed to inhibit the response to EFS.
EFS stimulated the release of 3H from pancreatic segments preloaded with [3H]‐choline. Either SNP or 8‐Br‐cyclic GMP had no effect on basal 3H release but significantly reduced the EFS‐evoked response.
In fura‐2 loaded acinar cells, SNP elicited a small decrease in [Ca2+]i compared to basal and had no effect on the ACh‐induced [Ca2+]i peak response.
Nitric oxide may modulate the release of endogenous neural ACh in response to EFS in the rat pancreas.

British Journal of Pharmacology (2002) 136, 49–56; doi:10.1038/sj.bjp.0704693
Modulation of 5‐HT4 receptor function in the rat isolated ileum by fluoxetine: the involvement of endogenous 5‐hydroxytryptamine
Authors: Tuladhar B R. , Costall B , Naylor R J. 
Published: January 2005

The effect of the selective serotonin reuptake inhibitor fluoxetine was examined on the 5‐HT4 receptor‐mediated relaxation in the rat isolated ileum.
Fluoxetine unsurmountably antagonized the relaxation to exogenous 5‐HT with abolition of the response at 10 μM. Fluoxetine (10 μM) also caused a gradual loss of the resting tension. These effects of fluoxetine were prevented by a prior addition of the 5‐HT4 receptor selective antagonist GR113808 (100 nM), which itself caused a contraction of the tissues when administered alone.
Fluoxetine (10 μM) also failed to prevent the relaxation due to exogenous 5‐HT and the 5‐HT4 receptor agonist 5‐methoxytryptamine in tissues taken from the rats treated with para‐chlorophenylalanine (300 mg kg−1) for 3 and 6 days, which reduced the 5‐HT level in the mucosa by 88 and 97.5% respectively.
The contraction of the tissues with GR113808 indicates the presence of an endogenous 5‐HT tone at the 5‐HT4 receptor in the rat ileum. It is hypothesized that in the presence of fluoxetine, the concentration of endogenous 5‐HT at the receptor was increased sufficiently to reduce or abolish the relaxation to 5‐HT added exogenously. The inability of fluoxetine to prevent the relaxation to 5‐HT in the presence of GR113808 or after the p‐CPA treatment supports this hypothesis.

British Journal of Pharmacology (2002) 136 150–156; doi:10.1038/sj.bjp.0704694
Effect of low frequency electromagnetic fields on A2A adenosine receptors in human neutrophils
Authors: Varani Katia , Gessi Stefania , Merighi Stefania , Iannotta Valeria , Cattabriga Elena , Spisani Susanna , Cadossi Ruggero , Borea Pier Andrea 
Published: January 2005

The present study describes the effect of low frequency, low energy, pulsing electromagnetic fields (PEMFs) on A2A adenosine receptors in human neutrophils.
Saturation experiments performed using a high affinity adenosine antagonist [3H]‐ZM 241385 revealed a single class of binding sites in control and in PEMF‐treated human neutrophils with similar affinity (KD=1.05±0.10 and 1.08±0.12 nM, respectively). Furthermore, after 1 h of exposure to PEMFs the receptor density was statistically increased (P<0.01) (Bmax =126±10 and 215±15 fmol mg−1 protein, respectively).
The effect of PEMFs was specific to the A2A adenosine receptors. This effect was also intensity, time and temperature dependent.
In the adenylyl cyclase assays the A2A receptor agonists, HE‐NECA and NECA, increased cyclic AMP accumulation in untreated human neutrophils with an EC50 value of 43 (40 – 47) and 255 (228 – 284) nM, respectively. The capability of HE‐NECA and NECA to stimulate cyclic AMP levels in human neutrophils was increased (P<0.01) after exposure to PEMFs with an EC50 value of 10(8 – 13) and 61(52 – 71) nM, respectively.
In the superoxide anion (O2−) production assays HE‐NECA and NECA inhibited the generation of O2− in untreated human neutrophils, with an EC50 value of 3.6(3.1 – 4.2) and of 23(20 – 27) nM, respectively. Moreover, in PEMF‐treated human neutrophils, the same compounds show an EC50 value of 1.6(1.2 – 2.1) and of 6.0(4.7 – 7.5) nM respectively.
These results indicate the presence of significant alterations in the expression and in the functionality of adenosine A2A receptors in human neutrophils treated with PEMFs.

British Journal of Pharmacology (2002) 136, 57–66; doi:10.1038/sj.bjp.0704695
Effects of benzothiazepines on human neuronal nicotinic receptors expressed in Xenopus oocytes
Authors: Sala Francisco , Mulet José , Valor Luis Miguel , Criado Manuel , Sala Salvador 
Published: January 2005

We have investigated the effect of diltiazem and its newly synthesized derivative (+,−)‐trans‐3‐acetoxy‐8‐chloro‐2,3‐dihydro‐5[2‐diisopropylamine)ethyl]‐2‐(4‐methoxyphenyl)‐1,5‐benzothiazepin‐4‐(5H)‐ona hydrochloride (JAC‐65) on several recombinant human neuronal nicotinic acetylcholine receptors (nAChRs) expressed in Xenopus oocytes.
At 3 μM, both drugs have little effect on the maximal currents evoked by brief pulses of acetylcholine (ACh) in five subtypes of nAChRs (α7, α3β2, α4β2, α3β4, and α4β4), showing little selectivity among subtypes.
However, both drugs accelerate the decay of the ionic currents evoked upon continuous stimulation of ACh, being this effect larger with JAC‐65, and in β4*‐nAChRs. Such an effect was dependent on the concentrations of both the drug and of the agonist used, and showed the characteristics of a non‐competitive antagonism.
We have further investigated the effect of both drugs when combined with submicromolar concentrations of nicotine, such as those present in plasma of cigarette smokers, and found that JAC‐65, but not diltiazem, is able to greatly enhance the desensitizing effect of these low concentrations of nicotine, specially in β4*‐nAChRs.
Experiments in α4β4‐nAChRs failed to show voltage dependence of the action of JAC‐65. Moreover, recovery from desensitization followed the same time course regardless of the presence of the drug, suggesting that the main mechanism of action of JAC‐65 does not involve open channel block.
In summary, both drugs, diltiazem and JAC‐65, seem to act through a non‐competitive mechanism, accelerating the decay of the ionic currents, being JAC‐65 more effective than diltiazem at the concentrations used in β4*‐nAChRs. Thus, the differences between both benzothiazepines when measuring various parameters suggest that their mechanisms of action could be slightly different. This would require further investigation.

British Journal of Pharmacology (2002) 136, 183–192; doi:10.1038/sj.bjp.0704699
Reduced coronary vasodilator responses to amlodipine in pacing‐induced heart failure in conscious dogs: role of nitric oxide
Authors: Champagne Stéphane , Hittinger Luc , Héloire François , Suto Yukio , Sambin Lucien , Crozatier Bertrand , Su Jin Bo 
Published: January 2005

This study examined whether NO is involved in the in‐vivo coronary vasodilator effects of amlodipine (a calcium channel blocker) and whether heart failure (HF) alters the coronary responses to amlodipine.
Nine conscious dogs were chronically instrumented to measure circumflex coronary blood flow (CBF) and coronary diameter (CD). Drugs were administered directly into the circumflex artery through an indwelling catheter to avoid systemic changes. HF was induced by right ventricular pacing (240 b.p.m., 3 weeks).
Compared with control (C), in HF, coronary responses to acetylcholine (1–10 ng kg−1) were reduced while responses to nitroglycerin (0.1–0.5 μg kg−1) were unchanged. In C, amlodipine (30–150 μg kg−1), increased dose‐dependently CBF and CD. After LNA (a NO synthase inhibitor, 2 mg kg−1), amlodipine produced less increases in CBF and CD (+121±26 ml min−1 and +76±35 μm versus +196±40 ml min−1 and +153±39 μm respectively for 150 μg kg−1 amlodipine alone, both P<0.05). In HF, the coronary responses to amlodipine were reduced (150 μg kg−1 of amlodipine increased CBF and CD +121±23 ml min−1 and +77±21 μm respectively, both P<0.05). After LNA, the CBF responses to amlodipine tended to be reduced (+94±19 ml min−1 at 150 μg kg−1) but CD responses were significantly reduced (+41±16 μm, P<0.05). The supplementation with L‐arginine did not enhance the coronary responses to amlodipine.
These results indicate that, in conscious dogs, NO participates in the coronary responses to amlodipine and in HF, the coronary responses to amlodipine are reduced, which is related to a reduced NO production.

British Journal of Pharmacology (2002) 136, 264–270; doi:10.1038/sj.bjp.0704701
Presynaptic adenosine A2A receptors enhance GABAergic synaptic transmission via a cyclic AMP dependent mechanism in the rat globus pallidus
Authors: Shindou Tomomi , Nonaka Hiromi , Richardson Peter J , Mori Akihisa , Kase Hiroshi , Ichimura Michio 
Published: January 2005

We previously reported a presynaptic facilitatory action of A2A receptors on GABAergic synaptic transmission in the rat globus pallidus (GP). In the present study we identify the intracellular signalling mechanisms responsible for this facilitatory action of A2A receptors, using biochemical and patch‐clamp methods in rat GP slices.
The adenosine A2A receptor selective agonist CGS21680 (1, 10 μM) and the adenylyl cyclase activator forskolin (1, 10 μM) both significantly increased cyclic AMP accumulation in GP slices. The CGS21680 (1 μM)‐mediated increase in cyclic AMP was inhibited by the A2A receptor selective antagonist KF17837 (10 μM).
In an analysis of miniature inhibitory postsynaptic currents (mIPSCs), forskolin (10 μM) increased the mIPSC frequency without affecting their amplitude distribution, a result similar to that previously reported with CGS21680.
The adenylyl cyclase inhibitor 9‐(tetrahydro‐2‐furanyl)‐9H‐purin‐6‐amine (SQ22,536, 300 μM) abolished the CGS21680‐induced enhancement in the frequency of mIPSCs.
H‐89 (10 μM), a selective inhibitor for cyclic AMP‐dependent protein kinase (PKA), blocked the CGS21680‐induced enhancement of the mIPSC frequency.
The calcium channel blocker CdCl2 (100 μM) did not prevent CGS21680 from increasing the frequency of mIPSCs.
These results indicate that A2A receptor‐mediated potentiation of mIPSCs in the GP involves the sequential activation of the A2A receptor, adenylyl cyclase, and then PKA, and that this facilitatory modulation could occur independently of presynaptic Ca2+ influx.

British Journal of Pharmacology (2002) 136, 296–302; doi:10.1038/sj.bjp.0704702
Inhibitory effects of tramadol on nicotinic acetylcholine receptors in adrenal chromaffin cells and inXenopusoocytes expressing α7 receptors
Authors: Shiraishi Munehiro , Minami Kouichiro , Uezono Yasuhito , Yanagihara Nobuyuki , Shigematsu Akio , Shibuya Izumi 
Published: January 2005

Tramadol has been used clinically as an analgesic; however, the mechanism of its analgesic effects is still unknown.We used bovine adrenal chromaffin cells to investigate effects of tramadol on catecholamine secretion, nicotine‐induced cytosolic Ca2+concentration ([Ca2+]i) increases and membrane current changes. We also investigated effects of tramadol on α7 nicotinic acetylcholine receptors (AChRs) expressed inXenopusoocytes.Tramadol concentration‐dependently suppressed carbachol‐induced catecholamine secretion to 60% and 27% of the control at the concentration of 10 and 100 μM, respectively, whereas it had little effect on veratridine‐ or high K+‐induced catecholamine secretion.Tramadol also suppressed nicotine‐induced ([Ca2+]i) increases in a concentration‐dependent manner. Tramadol inhibited nicotine‐induced inward currents, and the inhibition was unaffected by the opioid receptor antagonist naloxone.Tramadol inhibited nicotinic currents carried by α7 receptors expressed inXenopusoocytes.Tramadol inhibited both α‐bungarotoxin‐sensitive and ‐insensitive nicotinic currents in bovine adrenal chromaffin cells.In conclusion, tramadol inhibits catecholamine secretion partly by inhibiting nicotinic AChR functions in a naloxone‐insensitive manner and α7 receptors are one of those inhibited by tramadol.British Journal of Pharmacology(2002)136, 207–216; doi:10.1038/sj.bjp.0704703
IL‐1β signalling in glial cells in wildtype and IL‐1RI deficient mice
Authors: Parker Lisa C , Luheshi Giamal N , Rothwell Nancy J , Pinteaux Emmanuel 
Published: January 2005

Interleukin‐1 (IL‐1) has been implicated in neurodegeneration and in central nervous system (CNS)‐mediated host defence responses to inflammation. All actions of IL‐1 identified to date appear to be mediated through its only known functional type I receptor (IL‐1RI). However, our recent evidence suggests that some actions of IL‐1 in the brain may be IL‐1RI independent, suggesting the involvement of a new, hitherto unknown functional receptor for IL‐1.
The objective of the present study was to determine if primary mixed glial cells express additional functional IL‐1 receptors by studying the signalling mechanisms responsible for the pro‐inflammatory actions of IL‐1β in cultures derived from IL‐1RI−/− and wildtype mice, and to characterize the functional importance of IL‐1 signalling pathways in glia.
IL‐1β induced marked release of IL‐6 and prostaglandin‐E2 (PGE2) in the culture medium, and activated nuclear factor‐kappa B (NFκB) and the mitogen‐activated protein kinases (MAPK) p38, c‐Jun N‐terminal kinase (JNK) and the extracellular signal‐regulated protein kinase (ERK1/2) in cells from wildtype mice. These responses were dependent on IL‐1RI, since cells isolated from IL‐1R1−/− mice did not demonstrate any of these responses.
In wildtype mice, inhibition of p38 or ERK1/2 MAPKs significantly reduced IL‐1β induced IL‐6 release, whilst the NFκB inhibitor caffeic acid phenethyl ester (CAPE) modulated IL‐1 induced IL‐6 release by action on NFκB and MAPKs pathways.
These data demonstrate that IL‐1RI is essential for IL‐1β signalling in cultured mixed glial cells. Thus IL‐1 actions observed in IL‐1RI−/− mice in vivo may occur via an alternative pathway and/or via different CNS cells.

British Journal of Pharmacology (2002) 136, 312–320; doi:10.1038/sj.bjp.0704715
Pharmacological characterization of the 5‐HT receptors mediating contraction and relaxation of canine isolated proximal stomach smooth muscle
Authors: Janssen P , Prins N H , Meulemans A L , Lefebvre R A 
Published: January 2005

We aimed to characterize 5‐HT receptors mediating contraction and relaxation to 5‐HT in dog proximal stomach longitudinal muscle (LM) strips.
Of the tryptamine analogues tested, 5‐HT was the most potent contractile agent at basal length, while 5‐CT was the most potent relaxant of PGF2α‐induced contraction. Neither the contractions to 5‐HT, nor the relaxations to 5‐CT were influenced by tetrodotoxin, illustrating that action potential propagation is not involved.
The 5‐HT‐induced contraction was antagonized by mesulergine (0.03 to 0.3 μM) and ketanserin (2–20 nM), but the antagonism was not of a simple competitive nature, indicating multiple receptor involvement. Ketanserin (3 to 30 nM) and mesulergine (30 nM) competitively antagonized the α‐Me‐5‐HT‐induced contraction (pKB: 8.83±0.09 and pA2: 8.25±0.06 respectively). These affinity values are in line with literature affinities of ketanserin and mesulergine at 5‐HT2A receptors in various bioassays.
The 5‐CT‐induced inhibition of PGF2α‐induced contraction was competitively antagonized by mesulergine (pKB estimate: 8.52±0.12) and by the selective 5‐HT7 receptor antagonist SB‐269970 (pKB estimate: 9.36±0.14). Both pKB estimates are in line with literature affinities of these compounds for 5‐HT7 receptors. Mesulergine (30 nM) and SB‐269970 (10 nM) shifted the relaxant curve to 5‐HT parallel to the right in the presence of ketanserin (0.3 μM) (pA2 estimates of 8.08±0.10 and 8.75±0.14 respectively), indicative of 5‐HT7 receptor involvement.
It is concluded that 5‐HT induces dog proximal stomach (LM) contraction via smooth muscle 5‐HT2A receptors and relaxation via smooth muscle 5‐HT7 receptors.

British Journal of Pharmacology (2002) 136, 321–329; doi:10.1038/sj.bjp.0704716