bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitric oxide and sodium nitroprusside‐induced relaxation of the human umbilical artery
Authors: Lovren Fina , Triggle Chris 
Published: January 2005

In the human umbilical artery (HUA) pre‐contracted with the thromboxane mimetic U46619 or with 5‐hydroxytryptamine (5‐HT), (and pretreated with indomethacin (3 μM) to suppress the synthesis of prostanoids), authentic nitric oxide (NO) evoked concentration‐dependent relaxation (pEC50 7.05 and 5.99, respectively). In contrast, sodium nitroprusside (SNP) induced relaxation only in U46619 pre‐contracted HUA (pEC50 6.52).
At high (>300 mmHg) vs low (<55 mmHg) oxygen tension the dose‐response curves to NO‐ and SNP‐induced relaxations were biphasic and shifted leftward.
Preincubation of the arterial rings with the soluble guanylyl cyclase (sGC) inhibitor 1H[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ; 10 μM) shifted the concentration‐response curve to NO, reduced the maximal relaxation response to NO (Emax 71%) and to SNP (Emax 10%).
Pre‐exposure of HUA rings to high extracellular K+ (50 mM) reduced Emax relaxation responses to NO (36%) and SNP (1%).
Pretreatment of the HUA with the K+ channel inhibitors, tetraethylammonium (TEA, 1 mM), 4‐aminopyridine (4‐AP, 0.5 mM), charybdotoxin (0.1 μM) or iberiotoxin (0.1 μM) increased the pEC30 for NO and SNP and changed the shape of the dose‐response curves from biphasic to monophasic.
Pre‐incubation of HUA rings with TEA (1 mM), 4‐AP (0.5 mM) and ODQ (10 μM) significantly reduced the NO‐induced maximal relaxation (Emax 26%) but not the pEC50 (5.60).
These data indicate that SNP‐induced relaxation in the HUA is primarily mediated via sGC‐cyclic GMP whereas NO‐induced relaxation also involves the activation of KV and KCa channels and a cyclic GMP/K+ channel‐independent mechanism(s).

British Journal of Pharmacology (2000) 131, 521–529; doi:10.1038/sj.bjp.0703588
The effect of Gi‐protein inactivation on basal, and β1‐ and β2AR‐stimulated contraction of myocytes from transgenic mice overexpressing the β2‐adrenoceptor
Authors: Gong Haibin , Adamson Dawn L , Ranu Hardeep K , Koch Walter J , Heubach Jürgen F , Ravens Ursula , Zolk Oliver , Harding Sian E 
Published: January 2005

The atria and ventricles of transgenic mice (TGβ2) with cardiac overexpression of the human β2‐adrenoceptor (β2AR) were initially reported to show maximum contractility in the absence of β‐AR stimulation. However, we have previously observed a different phenotype in these mice, with myocytes showing normal contractility but reduced βAR responses. We have investigated the roles of cyclic AMP and Gi in basal and βAR function in these myocytes.
ICI 118,551 at inverse agonist concentrations decreased contraction by 32%. However, the cyclic AMP antagonist Rp‐cAMPS had no effect on contraction in TGβ2 myocytes, indicating that there was no tonic influence of raised cyclic AMP. These findings cannot be explained by the proposed model for inverse agonism, where the activated receptor (R*) raises cyclic AMP levels and so increases contraction in the absence of agonist.
After pertussis toxin (PTX) pretreatment to produce inactivation of Gi, the basal contraction in 1 mM Ca2+ was increased in TGβ2 mice (7.82±0.47%, n=23) compared to LM mice (3.60±0.59%, n=11) (P<0.001). The contraction amplitude of myocytes to the maximal concentration of isoprenaline was also increased significantly by PTX in TGβ2 mice (9.40±1.22%, n=8) and was no longer reduced compared to LM mice (8.93±1.50%, n=11). Both β1‐ and β2AR subtypes were affected both by the original desensitization and by the resensitization with PTX.
PTX treatment has therefore restored the original phenotype, with high basal contractility and little further effect of isoprenaline. We suggest that both β‐AR desensitization and lack of increased basal contraction in ventricular myocytes from our colony of TGβ2 mice were due to increased activity of PTX‐sensitive G‐proteins.

British Journal of Pharmacology (2000) 131, 594–600; doi:10.1038/sj.bjp.0703591
The involvement of cytokines in the second window of ischaemic preconditioning
Authors: Yamashita Nobushige , Hoshida Shiro , Otsu Kinya , Taniguchi Naoyuki , Kuzuya Tsunehiko , Hori Masatsugu 
Published: January 2005

We utilized a rat model of myocardial infarction to investigate whether manganese superoxide dismutase (Mn‐SOD), an intrinsic radical scavenger, and tumour necrosis factor‐ α (TNF‐α) and/or interleukin‐1β (IL‐1β) are involved in the late phase of ischaemic preconditioning (IP).
IP was induced in anaesthetized rats by four 3‐min left coronary artery (LCA) occlusions, each separated by 10 min of reperfusion. Twenty‐four hours after the repetitive brief ischaemia, the LCA was occluded for 20 min followed by reperfusion for 48 h. IP reduced the infarct size by approximately 46% as determined after 48 h of reperfusion.
Antisense oligodeoxynucleotides to Mn‐SOD inhibited the increases in Mn‐SOD content and activity, and abolished the expected decrease in myocardial infarct size. Sense or scrambled oligodeoxynucleotides did not abolish either Mn‐SOD induction or tolerance to ischaemia/reperfusion.
The simultaneous administration of the antibodies to TNF‐α (0.5 ml) and IL‐1β (0.5 mg) prior to IP abolished the cardioprotection and the increase in Mn‐SOD activity induced by IP.
We conclude that the induction and activation of Mn‐SOD, mediated by TNF‐α and IL‐1β after IP, plays an important role in the acquisition of late‐phase cardioprotection against ischaemia/reperfusion injury in rats.

British Journal of Pharmacology (2000) 131, 415–422; doi:10.1038/sj.bjp.0703594
Gene expression of receptors and enzymes involved in GABAergic and glutamatergic neurotransmission in the CNS of rats behaviourally dependent on ethanol
Authors: Eravci Murat , Schulz Olaf , Grospietsch Thorsten , Pinna Graziano , Brödel Oliver , Meinhold Harald , Baumgartner Andreas 
Published: January 2005

The steady state levels of the messenger RNA (mRNA) of eight GABAA receptor subunits, five glutamate receptor subunits and seven enzymes involved in the synthesis of glutamate and GABA were measured in eight regions of rat brain in a recently developed animal model of ‘behavioural dependence’ on ethanol.
‘Behavioural dependence’ including loss of control was induced by offering the rats the choice between ethanol and water over a 9‐month period (Group A). This group was compared with a group given the choice between ethanol and water for only 2 months (not yet ‘behaviourally dependent’, Group B), a group forced to consume ethanol as sole fluid over a 9‐month period (also not ‘behaviourally dependent’, Group C) and ethanol‐naive control rats (Group D). All groups were sacrificed 1 month after the ethanol was withdrawn.
The mRNA concentrations of all eight GABA receptor subunits, four out of the five subunits of different glutamate receptors and those of seven enzymes involved in GABA and glutamate production were reduced almost exclusively in the parieto‐occipital cortex in Groups A and B, but not Group C.
These data suggest that the synthesis of glutamate and GABA and the activities of their respective neurons are selectively impaired in the parieto‐occipital cortex in the groups having consumed ethanol in a free‐choice design, in which its rewarding properties can better take effect than after forced administration.
As the parieto‐occipital cortex is believed to contain emotional memory structures, it may be hypothesized that the glutamatergic and GABAergic neuronal systems in this area are involved in the development of memory for reward from ethanol. However, they are not specifically associated with ‘behavioural dependence’.

British Journal of Pharmacology (2000) 131, 423–432; doi:10.1038/sj.bjp.0703596
Cannabinoid receptor‐mediated inhibition of acetylcholine release from hippocampal and cortical synaptosomes
Authors: Gifford Andrew N , Bruneus Magalie , Gatley S John , Volkow Nora D 
Published: January 2005

In previous studies cannabinoid agonists have been found to inhibit and cannabinoid antagonists to enhance electrically‐evoked [3H]‐acetycholine (ACh) release in hippocampal slices. The present study was undertaken to determine if similar cannabinoid effects could be observed in synaptosomes.
[3H]‐ACh release was evoked by two methods, both sensitive to presynaptic receptor effects. The first involved the addition of 1.3 mM calcium following perfusion with calcium‐free Krebs and the second the addition of 11 mM potassium following perfusion with normal Krebs.
In hippocampal synaptosomes the 1.3 mM calcium‐evoked release and the high potassium‐evoked [3H]‐ACh release were inhibited by the cannabinoid agonist, WIN 55212‐2, by 59 and 39%, respectively, and with an EC50 of approximately 1 nM. WIN 55212‐2 produced a similar, although less potent, inhibition of [3H]‐ACh release in cortical synaptosomes. No inhibitory effect of WIN 55212‐2 on [3H]‐ACh release in striatal synaptosomes was observed, supporting previous data collected in this area with brain slices.
The cannabinoid antagonist, SR 141716A, produced a robust enhancement of 1.3 mM calcium‐evoked [3H]‐ACh release in hippocampal synaptosomes (EC50<0.3 nM) but had no effect on potassium‐evoked release or on [3H]‐ACh release in the cortex or striatum.
In conclusion our data demonstrates the inhibitory effects of WIN 55212‐2 observed on ACh release in brain slices can be observed in hippocampal and cortex synaptosomes, suggesting a direct action of these compounds on the synaptic terminals. The SR 141716A‐induced enhancement of ACh release can similarly be observed in hippocampal synaptosomes and is probably due to an inverse agonist action at constitutively active receptors.

British Journal of Pharmacology (2000) 131, 645–650; doi:10.1038/sj.bjp.0703599
Further evidence for the role of the α2δ subunit of voltage dependent calcium channels in models of neuropathic pain
Authors: Field Mark J , Hughes John , Singh Lakhbir 
Published: January 2005

Current analgesic therapy is dominated by NSAIDs and opiates, however these agents have limited efficacy in the treatment of neuropathic pain. The novel anticonvulsant agent gabapentin (Neurontin) has been shown to be an effective treatment for neuropathic pain in the clinic. Recent studies have demonstrated that gabapentin selectively interacts with the α2δ subunit of voltage dependent calcium channels (VDCCs) which may be important in its mechanism of action.
Previous studies have identified a gabapentin analogue, 3‐methyl gabapentin, that stereoselectively interacts with the α2δ subunit of VDCCs. Thus, whilst (1S,3R) 3‐methyl gabapentin binds to the α2δ protein with high affinity (IC50=42 nM), the corresponding (1R,3R) isomer is 300 times weaker (Bryans et al., 1998: J. Med. Chem., 41, 1838–1845). The present study examines the activity of diastereoisomers of 3‐methyl gabapentin in two rat models of neuropathic pain to assess the importance of an interaction with the α2δ subunit of VDCCs.
(1S,3R) 3‐methyl‐gabapentin dose‐dependently (10–100 mg kg−1, p.o.) blocked the maintenance of static allodynia in the rat streptozocin and Chung models of neuropathic pain with MEDs of 30 mg kg−1. This isomer also dose‐dependently blocked the maintenance of dynamic allodynia in both models with respective MEDs of 30 and 100 mg kg−1. In contrast, (1R,3R) 3‐methyl gabapentin (100 mg kg−1, p.o.) failed to block either static or dynamic allodynia in the streptozocin model.
It is concluded that these data further support the hypothesis that the α2δ subunit of VDCCs plays an important role in the maintenance of mechanical hypersensitivity in models of neuropathic pain.

British Journal of Pharmacology (2000) 131, 282–286; doi:10.1038/sj.bjp.0703604
Inhibition of small G proteins of the Rho family by statins or Clostridium difficile toxin B enhances cytokine‐mediated induction of NO synthase II
Authors: Hausding Michael , Witteck Andrea , Rodriguez‐Pascual Fernando , Von Eichel‐Streiber Christian , Förstermann Ulrich , Kleinert Hartmut 
Published: January 2005

In order to investigate the involvement of Ras and/or Rho proteins in the induction of the inducible isoform of nitric oxide synthase (NOS II) we used HMG‐CoA reductase inhibitors (statins) and Clostridium difficile toxin B (TcdB) as pharmacological tools. Statins indirectly inhibit small G proteins by preventing their essential farnesylation (Ras) and/or geranylgeranylation (Rho). In contrast, TcdB is a glucosyltransferase and inactivates Rho‐proteins directly.
Human A549/8‐ and DLD‐1 cells as well as murine 3T3 fibroblasts were preincubated for 18 h with statins (1–100 μM) or TcdB (0.01–10 ng ml−1). Then NOS II expression was induced by cytokines. NOS II mRNA was measured after 4–8 h by RNase protection assay, and NO production were measured by the Griess assay after 24 h.
Statins and TcdB markedly increased cytokine‐induced NOS II mRNA expression and NO production. Statin‐mediated enhancement of NOS II mRNA expression was reversed almost completely by cotreatment with mevalonate or geranylgeranylpyrophosphate. It was only slightly reduced by farnesylpyrophosphate. Therefore, small G proteins of the Rho family are likely to be involved in NOS II induction.
In A549/8 cells stably transfected with a luciferase reporter gene under the control of a 16 kb fragment of the human NOS II promoter (pNOS2(16)Luc), statins produced only a small increase in cytokine‐induced NOS II promoter activity. In contrast, statins had a considerable superinducing effect in DLD‐1 cells stably transfected with pNOS2(16)Luc.
In conclusion, our studies provide evidence that statins and TcdB potentiate cytokine‐induced NOS II expression via inhibition of small G proteins of the Rho family. This in turn results in an enhanced NOS II promoter activity and/or a prolonged NOS II mRNA stability.

British Journal of Pharmacology (2000) 131, 553–561; doi:10.1038/sj.bjp.0703607
Developmental regulation of hippocampal excitatory synaptic transmission by metabotropic glutamate receptors
Authors: Ross F M , Cassidy J , Wilson M , Davies S N 
Published: January 2005

The aims of this study were, to use agonists selective for the 3 mGlu receptor groups to identify developmental changes in their effects, and to assess the usefulness of proposed selective antagonists as pharmacological tools.
Hippocampal slices (400 μm) were prepared from neonate (9–14 days) and young adult (5–7 weeks) Sprague‐Dawley rats. Field excitatory postsynaptic potentials (fEPSP) were recorded from CA1.
DHPG (100 μM), a group I agonist, produced a slowly developing enhancement of fEPSP slope in slices from adults. In slices from neonates, DHPG (75 μM) depressed fEPSP slope.
DCG‐IV (500 nM), a group II agonist, did not affect the fEPSP recorded from slices from adults whereas perfusion in neonate slices produced a sustained depression.
The group III agonist L‐AP4 (50 μM) was ineffective in adult slices but depressed fEPSP slope in slices prepared from neonates.
DHPG‐induced depression of fEPSP slope was inhibited by 4‐CPG (400 μM), a group I antagonist, but was unaffected by MCCG (500 μM) and MAP4 (500 μM), group II and III receptor antagonists respectively. MCCG but not MAP4 antagonized the effects of DCG‐IV with 4‐CPG producing variable effects. The effect of L‐AP4 was unaffected by MCCG, blocked by MAP4, and enhanced by 4‐CPG.
The results show that the effects of the agonists for all groups of mGlu receptors are developmentally regulated. Furthermore, MCCG and MAP4 behave as effective and selective antagonists for group II and group III mGlu receptors respectively, whereas the usefulness of 4‐CPG as a group I antagonist may be limited.

British Journal of Pharmacology (2000) 131, 453–464; doi:10.1038/sj.bjp.0703610
Characterization of the binding of [125I]‐human prolactin releasing peptide (PrRP) to GPR10, a novel G protein coupled receptor
Authors: Langmead Christopher J , Szekeres Philip G , Chambers Jonathan K , Ratcliffe Steven J , Jones Declan N C , Hirst Warren D , Price Gary W , Herdon Hugh J 
Published: January 2005

GPR10 is a novel G‐protein coupled receptor that is the human orthologue of rat Unknown Hypothalamic Receptor‐1 (UHR‐1). Human prolactin‐releasing peptide (PrRP) has been identified as an endogenous ligand for GPR10, and occurs as 31 and 20 amino acid forms. The present study characterizes the binding of [125I]‐PrRP‐20 to HEK293 cells stably expressing GPR10 receptors.
Specific binding of [125I]‐PrRP‐20 was saturable, and analysis suggested evidence of both high and low affinity sites, with KD values of 0.026±0.006 and 0.57±0.14 nM respectively, and Bmax values of 3010±400 and 8570±2240 fmol mg protein−1 respectively. Kinetic studies were unable to distinguish two sites, but single site analysis of association and dissociation data produced a KD of 0.012 nM.
Competition studies revealed that human and rat PrRP‐20 and PrRP‐31 all display high affinity for GPR10. A range of other drugs which are known ligands at receptors which share limited homology with GPR10 were also tested. None of the drugs tested, including the RF‐amide neuropeptide FF, demonstrated any affinity for GPR10.
Human PrRP‐20 failed to alter basal or forskolin‐stimulated levels of intracellular cyclic AMP in HEK293‐GPR10 cells, suggesting that GPR10 does not couple via either Gs or Gi.
Functional studies using measurements of intracellular calcium confirmed that human and rat PrRP‐20 and PrRP‐31 are all potent, full agonists at the GPR10 receptor. The response was blocked both by thapsigargin, indicating mobilization of intracellular Ca2+ stores.
These studies indicate that [125I]‐PrRP‐20 is a specific, high affinity radioligand for GPR10. The availability of this radioligand binding assay will be a valuable tool for the investigation of the key features involved in PrRP binding and studies on the localization and function of GPR10.

British Journal of Pharmacology (2000) 131, 683–688; doi:10.1038/sj.bjp.0703617
Delayed myocardial protection induced by endotoxin does not involve kinin B1‐receptors
Authors: Mazenot C , Gobeil F , Ribuot C , Regoli D , Godin‐Ribuot D 
Published: January 2005

Endotoxin is known to confer a delayed protection against myocardial infarction. Lipopolysaccharide (LPS) treatment also induces the de novo synthesis of kinin B1‐receptors that are not present in normal conditions. The aim of this study was to evaluate whether LPS‐induced B1‐receptors are implicated in the reduction of infarct size brought about by LPS.
Rabbits were submitted to a 30‐min coronary artery occlusion and 3‐h reperfusion sequence. Six groups were studied: pretreated or not (control animals) with LPS (5 μg kg−1 i.v.) 24 h earlier and treated 15 min before and throughout ischaemia–reperfusion with either the B1‐antagonist R‐715 (1 mg kg−1 h−1), the B1‐agonist Sar‐[D‐Phe8]‐des‐Arg9‐bradykinin (15 μg kg−1 h−1) or vehicle (saline). Infarct size and area at risk were assessed by differential staining and planimetric analysis.
The presence of B1‐receptors in LPS‐pretreated animals was confirmed by a decrease in mean arterial pressure in response to B1 stimulation. LPS‐pretreatment significantly reduced infarct size (6.4±1.7%, of area at risk vs 24.1±2.5% in control animals, P<0.05). This protection was not modified by B1‐receptor antagonism (7.4±2.2%, NS) or stimulation (5.2±1.2%, NS). Neither antagonist nor agonist modified infarct size in control animals.
In conclusion, these data suggest that LPS‐induced myocardial protection in the rabbit is not related to concomitant de novo B1‐receptor induction.

British Journal of Pharmacology (2000) 131, 740–744; doi:10.1038/sj.bjp.0703619
Bicuculline, pentobarbital and diazepam modulate spontaneous GABAA channels in rat hippocampal neurons
Authors: Birnir Bryndis , Eghbali Mansoureh , Everitt Andrea B , Gage Peter W 
Published: January 2005

Spontaneously opening, chloride‐selective channels that showed outward rectification were recorded in ripped‐off patches from rat cultured hippocampal neurons and in cell‐attached patches from rat hippocampal CA1 pyramidal neurons in slices.
In both preparations, channels had multiple conductance states and the most common single‐channel conductance varied. In the outside‐out patches it ranged from 12 to 70 pS (Vp=40 mV) whereas in the cell‐attached patches it ranged from 56 to 85 pS (−Vp=80 mV).
Application of GABA to a patch showing spontaneous channel activity evoked a rapid, synchronous activation of channels. During prolonged exposure to either 5 or 100 μM GABA, the open probability of channels decreased. Application of GABA appeared to have no immediate effect on single‐channel conductance.
Exposure of the patches to 100 μM bicuculline caused a gradual decrease on the single‐channel conductance of the spontaneous channels. The time for complete inhibition to take place was slower in the outside‐out than in the cell‐attached patches.
Application of 100 μM pentobarbital or 1 μM diazepam caused 2–4 fold increase in the maximum channel conductance of low conductance (<40 pS) spontaneously active channels.
The observation of spontaneously opening GABAA channels in cell‐attached patches on neurons in slices suggests that they may have a role in neurons in vivo and could be an important site of action for some drugs such as benzodiazepines, barbiturates and general anaesthetics.

British Journal of Pharmacology (2000) 131, 695–704; doi:10.1038/sj.bjp.0703621
Negative feedback regulation of reactive oxygen species on AT1 receptor gene expression
Authors: Nickenig Georg , Strehlow Kerstin , Bäumer Anselm T , Baudler Stefanie , Waßmann Sven , Sauer Heinrich , Böhm Michael 
Published: January 2005

Free radicals as well as the AT1 receptor are involved in the pathogenesis of cardiovascular disease. Both the intracellular mechanisms of AT1 receptor regulation and the effect of free radicals on AT1 receptor expression are currently unknown. This study investigates the role of free radicals in the modulation of AT1 receptor expression and in the angiotensin II‐induced AT1 receptor regulation.
AT1 receptor mRNA was assessed by Northern blotting and AT1 receptor density by radioligand binding assays, respectively, in vascular smooth muscle cells (VSMC). Free radical release was measured by confocal laser scanning microscopy. AT1 receptor mRNA transcription rate was determined by nuclear run‐on assays and AT1 receptor mRNA half‐life was measured under transcriptional blockade.
Angiotensin II caused a time‐dependent decrease of AT1 receptor mRNA expression in rat VSMC in culture (30±6% at 4 h with 100 nM angiotensin II). This was followed by a consistent decrease in AT1 receptor density. Angiotensin II caused release of reactive oxygen species in VSMC which was abolished by preincubation with 100 μM diphenylene iodonium (DPI). DPI inhibited partially the down‐regulating effect of angiotensin II on the AT1 receptor. Incubation of VSMC with either hydrogen peroxide or xanthine/xanthine oxidase caused a dose‐dependent decrease in AT1 receptor mRNA expression which was not mediated by a decreased rate of transcription but rather through destabilization of AT1 receptor mRNA. Experiments which included preincubation of VSMC with various intracellular inhibitors suggested that free radicals caused AT1 receptor downregulation through activation of p38‐MAP kinase and intracellular release of calcium. However, angiotensin II‐induced AT1 receptor expression was not inhibited by blockade of p38‐MAP kinase activation or intracellular calcium release.
Free radicals may at least in part mediate angiotensin II‐induced AT1 receptor regulation through direct post‐transcriptional effects on AT1 receptor mRNA expression which involves intracellular release of calcium and activation of p38‐MAP kinase. These findings may help to clarify the intracellular mechanisms involved in AT1 receptor regulation and reveal a novel biological feature for reactive oxygen species.

British Journal of Pharmacology (2000) 131, 795–803; doi:10.1038/sj.bjp.0703623