bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pharmacological characterization of [3H]‐prostaglandin E2 binding to the cloned human EP4 prostanoid receptor
Authors: Davis T L , Sharif N A 
Published: January 2005

Prostaglandin (PG) E2 (PGE2) is a potent prostanoid derived from arachidonic which can interact with EP1, EP2, EP3 and EP4 prostanoid receptor subtypes.
Recombinant human EP4 receptors expressed in human embryonic kidney (HEK‐293) cells were evaluated for their binding characteristics using [3H]‐PGE2 and a broad panel of natural and synthetic prostanoids in order to define their pharmacological properties.
[3H]‐PGE2 binding was optimal in 2‐[N‐Morpholino]ethanesulphonic acid (MES) buffer (pH 6.0) yielding 98±0.7% specific binding. The receptor displayed high affinity (Kd=0.72±0.12 nM; n=3) for [3H]‐PGE2 and interacted with a saturable number of binding sites (Bmax=6.21±0.84 pmol mg−1 protein).
In competition studies, PGE2 (Ki=0.75±0.03 nM; n=12) and PGE1 (Ki=1.45±0.24 nM; n=3) displayed high affinities, as did two derivatives of PGE1, namely 11‐deoxy‐PGE1 (Ki=1.36±0.34 nM) and 13,14‐dihydro‐PGE1 (Ki=3.07±0.29 nM).
Interestingly, synthetic DP receptor‐specific agonists such as BW245C (Ki=64.7±1.0 nM; n=3) and ZK118182 (Ki=425±42 nM; n=4), and the purported EP3 receptor‐specific ligand enprostil (Ki=43.1±4.4 nM), also displayed high affinity for the EP4 receptor.
Two known EP4 receptor antagonists were weak inhibitors of [3H]‐PGE2 binding akin to their known functional potencies, thus: AH23848 (Ki=2690±232 nM); AH22921 (Ki=31,800±4090 nM).
These studies have provided a detailed pharmacological characterization of the recombinant human EP4 receptor expressed in HEK‐293 cells.

British Journal of Pharmacology (2000) 130, 1919–1926; doi:10.1038/sj.bjp.0703525
The 5HT1B receptor agonist, CP‐93129, inhibits [3H]‐GABA release from rat globus pallidus slices and reverses akinesia following intrapallidal injection in the reserpine‐treated rat
Authors: Chadha Anita , Sur Cyrille , Atack John , Duty Susan 
Published: January 2005

This study examined whether activation of 5HT1B receptors in the rodent globus pallidus (GP) could reduce GABA release in vitro and reverse reserpine‐induced akinesia in vivo.
Microdissected slices of GP from male Sprague Dawley rats (300–350 g) were preloaded with [3H]‐GABA. During subsequent superfusion, 4 min fractions were collected for analysis of release. The effects of the 5HT1B receptor agonist, 3‐(1,2,5,6‐tetrahydropyrid‐4‐yl)pyrrolo[3,2‐b]pyrid‐5‐one (CP‐93129), on 25 mM KCl‐evoked release were examined using a standard dual stimulation paradigm.
Male Sprague Dawley rats (270–290 g), stereotaxically cannulated above the GP, were rendered akinetic by injection of reserpine (5 mg kg−1 s.c.). Eighteen hours later, the rotational behaviour induced by unilateral injection of CP‐93129 was examined.
CP‐93129 (0.6–16.2 μM) produced a concentration‐dependent inhibition of 25 mM KCl‐evoked [3H]‐GABA release reaching a maximum inhibition of 52.5±4.5%. The effect of a submaximal concentration of CP‐93129 (5.4 μM) was fully inhibited by the 5HT1B receptor antagonist, isamoltane (10 μM).
Following intrapallidal injection, CP‐93129 (30–330 nmol in 0.5 μl) produced a dose‐dependent increase in net contraversive rotations reaching a maximum of 197±32 rotations in 240 min at 330 nmol. Pre‐treatment with isamoltane (10 nmol in 1 μl) inhibited the effects of a submaximal dose of CP‐93129 (220 nmol) by 84±6%.
These data suggest that at least some 5HT1B receptor function as heteroreceptors in the GP, reducing the release of GABA. Moreover, CP‐93129‐mediated activation of these receptors in the GP provides relief of akinesia in the reserpine‐treated rat model of PD.

British Journal of Pharmacology (2000) 130, 1927–1932; doi:10.1038/sj.bjp.0703526
Inhibition of neuronal M2 muscarinic receptor function in the lungs by extracellular nitric oxide
Authors: Golkar Laleh , Yarkony Kathryn A , Fryer Allison D 
Published: January 2005

These experiments were carried out to test whether neuronal M2 muscarinic receptor function in the lungs is affected by nitric oxide (NO) and whether the source of the NO is epithelial or neuronal.
In pathogen free, anaesthetized guinea‐pigs, the muscarinic agonist pilocarpine inhibited vagally induced bronchoconstriction demonstrating functional neuronal M2 muscarinic receptors. In the presence of the NO donor, 3‐morpholino‐sydnonimine (SIN‐1), pilocarpine no longer inhibited vagally induced bronchoconstriction. In contrast, inhibiting endogenous NO with NG‐monomethyl‐L‐arginine methyl ester (L‐NMMA) did not affect the ability of pilocarpine to decrease vagally induced bronchoconstriction.
In isolated tracheas, pilocarpine inhibited contractions induced by electrical field stimulation demonstrating that neuronal M2 muscarinic receptors function in vitro. As in the anaesthetized guinea‐pigs, SIN‐1 shifted the pilocarpine dose response curve to the right, demonstrating decreased neuronal M2 receptor function. However, in vitro, L‐NMMA shifted the pilocarpine dose response curve to the left, demonstrating that endogenous NO was inhibiting the ability of the M2 receptors to decrease acetylcholine (ACh) release.
Both haemoglobin (Hb), which scavenges NO, and epithelial removal also shifted the pilocarpine dose response curve to the left, demonstrating that the NO inhibiting neuronal M2 receptor function was extracellular and probably of epithelial origin.
In conclusion, extracellular NO appears to inhibit the ability of the M2 receptors to decrease ACh release from the parasympathetic nerves in the lungs in vivo and in vitro in pathogen free guinea‐pigs. However, while the neuronal M2 receptors will respond to NO (from SIN‐1) in vivo, there does not appear to be an endogenous source of NO since L‐NMMA had no effect in vivo.

British Journal of Pharmacology (2000) 131, 312–318; doi:10.1038/sj.bjp.0703542
Influence of gender and the oestrous cycle on in vitro contractile responses of the rat urinary bladder to cholinergic stimulation
Authors: Longhurst Penelope A , Levendusky Mark 
Published: January 2005

Experiments were done to determine the influence of gender and the oestrous cycle on rat urinary bladder contractility in response to cholinergic stimulation.
Bladder strips from female rats responded to high frequency stimulation with smaller contractile responses than did strips from males, and to low concentrations of carbachol with greater responses. The decreased responsiveness of bladder strips from female rats to electrical field stimulation can be primarily attributed to the rats in the oestrous stage of the oestrous cycle.
Bladder strips from female rats in all stages of the oestrous cycle were more sensitive to carbachol than those from males, but there were no differences in sensitivity to electrical field stimulation.
The contractile responses of strips from both male and female rats to carbachol were antagonized by muscarinic antagonists with the following rank order of affinity (pA2) estimates: 4‐DAMP>>pirenzepine>methoctramine, suggesting that the receptor mediating contraction was the M3 subtype. There were no differences in pA2 values between bladder strips from male and female rats.
The data indicate that responsiveness of bladder strips to electrical field stimulation and carbachol is altered in female rats in the oestrous stage of the oestrous cycle. Furthermore, gender influences the sensitivity of rat bladder to muscarinic stimulation.

British Journal of Pharmacology (2000) 131, 177–184; doi:10.1038/sj.bjp.0703551
Participation of thromboxane A2 in the cough response in guinea‐pigs: antitussive effect of ozagrel
Authors: Shinagawa Kazuhiko , Kojima Masami , Ichikawa Kiyoshi , Hiratochi Masahiro , Aoyagi Shigemi , Akahane Masuo 
Published: January 2005

The purpose of this study was to investigate the involvement of thromboxane A2 (TXA2) in the cough response in a guinea‐pig cough model. Here, we describe results obtained using a selective TXA2 synthetase inhibitor, ozagrel, and a selective TXA2 agonist, U‐46619.
Guinea‐pigs were anaesthetized and exposed to an aerosol of capsaicin (100 μM) to elicit coughing. The number of coughs was 20.0±5.8 during capsaicin provocation (5 min), but only 2.8±0.4 during a 5‐min inhalation of phosphate‐buffered saline (PBS) (P<0.05).
TXB2 levels in BAL were 101.4±8.0 and 58.4±8.7 pg ml−1 following capsaicin and PBS inhalation, respectively (P<0.01), but there was no intergroup difference in the cell populations in BAL.
Inhalation of U‐46619 did not induce a cough response by itself at concentrations of 100 ng ml−1 to 10 μg ml−1. However, it caused a 2 fold increase in the number of capsaicin‐induced coughs.
To explore the source of the TXA2, BAL cells were stimulated with capsaicin and the supernatants collected for analysis. The TXB2 concentration in BAL was increased dose‐dependently, indicating that TXA2 is released from BAL cells in response to capsaicin.
Ozagrel was administered orally 1 h before a 5 min capsaicin provocation and the number of coughs was counted during the capsaicin inhalation. Ozagrel decreased the number of coughs dose‐dependently (ED50 value, 26.3 mg kg−1).
These results show that TXA2 modulates the capsaicin‐induced cough response by increasing capsaicin‐sensitivity.

British Journal of Pharmacology (2000) 131, 266–270; doi:10.1038/sj.bjp.0703553
A novel positive allosteric modulator of the GABAA receptor: the action of (+)‐ROD188
Authors: Thomet Urs , Baur Roland , Razet Rodolphe , Dodd Robert H , Furtmüller Roman , Sieghart Werner , Sigel Erwin 
Published: January 2005

(+)‐ROD188 was synthesized in the search for novel ligands of the GABA binding site. It shares some structural similarity with bicuculline. (+)‐ROD188 failed to displace [3H]‐muscimol in binding studies and failed to induce channel opening in recombinant rat α1β2γ2 GABAA receptors functionally expressed in Xenopus oocytes.
(+)‐ROD188 allosterically stimulated GABA induced currents. Displacement of [3H]‐Ro15‐1788 indicated a low affinity action at the benzodiazepine binding site. In functional studies, stimulation by (+)‐ROD188 was little sensitive to the presence of 1 μM of the benzodiazepine antagonist Ro 15‐1788, and (+)‐ROD188 also stimulated currents mediated by α1β2, indicating a major mechanism of action different from that of benzodiazepines.
Allosteric stimulation by (+)‐ROD188 was similar in α1β2N265S as in unmutated α1β2, while that by loreclezole was strongly reduced.
(+)‐ROD188 also strongly stimulated currents elicited by either pentobarbital or 5α‐pregnan‐3α‐ol‐20‐one (3α‐OH‐DHP), in line with a mode of action different from that of barbiturates or neurosteroids as channel agonists.
Stimulation by (+)‐ROD188 was largest in α6β2γ2 (α6β2γ2>>α1β2γ2=α5β2γ2>α2β2γ2= α3β2γ2), indicating a unique subunit isoform specificity.
Miniature inhibitory postsynaptic currents (mIPSC) in cultures of rat hippocampal neurons, caused by spontaneous release of GABA showed a prolonged decay time in the presence of 30 μM (+)‐ROD188, indicating an enhanced synaptic inhibitory transmission.

British Journal of Pharmacology (2000) 131, 843–850; doi:10.1038/sj.bjp.0703558
Induction by inhibitors of nitric oxide synthase of hyperresponsiveness in the human nasal airway
Authors: Turner P J , Maggs J R L , Foreman J C 
Published: January 2005

The effects of inhibitors of nitric oxide synthase (NOS) on the responsiveness of the human nasal airway were investigated, by measuring the nasal response to histamine and bradykinin.
Repeated intranasal administration of NG‐nitro‐L‐arginine methyl ester (L‐NAME) or NG‐monomethyl‐L‐arginine (L‐NMMA), 1 μmol per nostril every 30 min for 6 h, increased the nasal obstruction induced by histamine, 50–500 μg, and bradykinin, 200 μg per nostril. A single administration of L‐NAME, 1 μmol per nostril did not induce hyperresponsiveness to histamine.
Pretreatment with L‐arginine, 30 μmol, abolished the hyperresponsiveness to histamine caused by L‐NAME, 1 μmol. Pretreatment with NG‐nitro‐D‐arginine methyl ester (D‐NAME), 1 μmol, did not induce hyperresponsiveness to histamine.
Repeated administration of L‐NAME, 1 μmol, caused a significant reduction in the amount of nitric oxide measured in the nasal cavity.
Neither L‐NMMA, 1 μmol, nor L‐arginine, 30 μmol, altered the nasal hyperresponsiveness induced by platelet activating factor (PAF), 60 μg. PAF did not alter the levels of nitric oxide in the nasal cavity.
The results suggest that inhibition of nitric oxide synthase induces a hyperresponsiveness in the human nasal airway, and that this occurs by a mechanism different from that involved in PAF‐induced hyperresponsiveness.

British Journal of Pharmacology (2000) 131, 363–369; doi:10.1038/sj.bjp.0703561
Differential role of angiotensin II receptor subtypes on endothelial superoxide formation
Authors: Sohn Hae Young , Raff Ulrike , Hoffmann Anke , Gloe Torsten , Heermeier Kathrin , Galle Jan , Pohl Ulrich 
Published: January 2005

The physiological role of the angiotensin II AT2 receptor subtype is not fully characterized. We studied whether AT2 receptor could antagonize AT1 mediated superoxide formation in endothelial cells.
In quiescent human umbilical vein endothelial cells (HUVEC) superoxide formation was measured after long‐term incubation (6 h) with angiotensin II in the presence or absence of its receptor blocker candesartan (AT1) or PD123319 (AT2) using the cytochrome c assay. In separate experiments, the effects of AT2 mediated effects on activities of cellular phosphates including the src homology 2 domain containing phosphatases (SHP‐1) was studied.
The basal superoxide formation (0.19±0.03 nmol superoxide mg protein−1 min−1) in HUVEC was increased by 37.1% after exposure to angiotensin II (100 nM,) which was due to an activation of a NAD(P)H oxidase. This was abolished by candesartan (1 μM) as well as the tyrosine kinase inhibitor genistein. In contrast, blockade of AT2 receptors by PD123319 enhanced the superoxide formation by 73.7% in intact cells. Stimulation of AT2 went along with an increased activity of tyrosine phosphatases in total cell lysates (29.8%) and, in particular, a marked stimulation of src homology 2 domain containing phosphatases (SHP‐1, by 293.4%). The tyrosine phosphatase inhibitor vanadate, in turn, prevented the AT2 mediated effects on superoxide formation. The expression of both angiotensin II receptor subtypes AT1 and AT2 was confirmed by RT–PCR analysis.
It is concluded that AT2 functionally antagonizes the AT1 induced endothelial superoxide formation by a pathway involving tyrosine phosphatases.

British Journal of Pharmacology (2000) 131, 667–672; doi:10.1038/sj.bjp.0703566
Methyl p‐hydroxybenzoate (E‐218) a preservative for drugs and food is an activator of the ryanodine receptor Ca2+ release channel
Authors: Cavagna Dario , Zorzato Francesco , Babini Elena , Prestipino Gianfranco , Treves Susan 
Published: January 2005

Haloperidol is a drug used in the management of several psychotic disorders and its use has been linked to Neuroleptic Malignant Syndrome. In the present study we have investigated the effect of a commercial preparation of haloperidol, Serenase, on skeletal muscle sarcoplasmic reticulum.
Addition of Serenase to isolated terminal cisternae caused a rapid release of calcium. We tested whether the active Ca2+‐releasing substance was haloperidol or another compound present in the preparation.
Our results show that methyl p‐hydroxybenzoate, one of the preservatives and a commonly used anti‐microbial agent (E‐218) is an activator of Ca2+ release (E.C.50=2.0 mM), mediated by a ruthenium red‐sensitive Ca2+ release channel present in skeletal muscle terminal cisternae.

British Journal of Pharmacology (2000) 131, 335–341; doi:10.1038/sj.bjp.0703571
A novel, competitive mGlu5 receptor antagonist (LY344545) blocks DHPG‐induced potentiation of NMDA responses but not the induction of LTP in rat hippocampal slices
Authors: Doherty A J , Palmer M J , Bortolotto Z A , Hargreaves A , Kingston A E , Ornstein P L , Schoepp D D , Lodge D , Collingridge G L 
Published: January 2005

We have investigated the pharmacological properties of LY344545, a structurally related epimer of the broad spectrum competitive metabotropic glutamate receptor antagonist, LY341495. We have found that LY344545 also antagonizes competitively nearly all mGlu receptor subtypes, but with a wide spectrum of activity. The order of potency for the human receptor isoforms was mGlu5a (IC50 of 5.5±0.6 μM)>mGlu2=mGlu3>mGlu1α=mGlu7>mGlu6=mGlu8. No significant mGlu4 receptor antagonist activity was detected at the highest concentration used (100 μM). 100 μM LY344545 displaced 50±5% of [3H]‐CGP39653 binding, but less than 30% of [3H]‐kainate or [3H]‐AMPA in radioligand binding assays.
LY344545 antagonized L‐glutamate stimulated Ca2+ release in CHO cells transfected with mGlu receptors in a concentration dependent manner with a 10 fold higher affinity for the rat mGlu5a receptor (Ki=2.1±0.6 μM) compared to the rat mGlu1α receptor (Ki=20.5±2.1 μM). 50 μM (1S, 3R)‐ACPD‐induced Ca2+ rises in hippocampal CA1 neurones were also antagonized (IC50=6.8±0.7 μM).
LY344545 antagonized 10 μM (S)‐3,5‐DHPG‐induced potentiation of NMDA depolarizations in CA1 neurones (EC50=10.6±1.0 μM). At higher concentrations (100 μM), LY344545 was an NMDA receptor antagonist.
LY344545 also blocked the induction, but not the expression, of LTP at CA3 to CA1 synapses with an IC50>300 μM. This effect is consistent with its weak activity at NMDA receptors.
These results demonstrate that the binding of ligands to mGlu receptor subtypes is critically dependent on the spatial orientation of the same molecular substituents within a given chemical pharmacophore. The identification of LY344545 as the first competitive antagonist to show selectivity towards mGlu5 receptors supports the potential to design more selective and potent competitive antagonists of this receptor.
These results further indicate that mGlu receptor‐mediated potentiation of NMDA responses is not essential for the induction of LTP.

British Journal of Pharmacology (2000) 131, 239–244; doi:10.1038/sj.bjp.0703574
Arachidonic acid‐mediated cooxidation of all‐trans‐retinoic acid in microsomal fractions from human liver
Authors: Nadin Louise , Murray Michael 
Published: January 2005

The quantitative importance of prostaglandin H synthase (PGHS)‐mediated cooxidation of all‐trans‐retinoic acid (ATRA) was evaluated in human liver microsomes (n=17) in relation to CYP‐dependent ATRA 4‐hydroxylation.
Observed rates of ATRA cooxidation (4.6–20 pmol mg protein−1 min−1) and 4‐hydroxylation (8.7–45 pmol mg protein−1 min−1) were quantitatively similar and exhibited similar individual variation (4 and 5 fold, respectively).
From kinetic studies cooxidation was an efficient process in human hepatic microsomes (VmaxKm−1=0.25) compared with NADPH‐ and NADH‐mediated 4‐hydroxylation by CYP (VmaxKm−1=0.14 and 0.02, respectively).
The capacity of lipid hydroperoxide metabolites of arachidonic acid to mediate ATRA oxidation was established directly, but downstream products (D, E, F and I‐series prostaglandins) were inactive.
cDNA‐expressed CYPs supported ATRA oxidation by lipid hydroperoxides. Whereas CYPs 2C8, 2C9 and 3A4, but not CYPs 1A2 or 2E1, were effective catalysts of the NADPH‐mediated reaction, cooxidation supported by 15(S)‐hydroperoxyeicosatetraenoic acid was mediated by all five CYPs. The cooxidation reaction in human hepatic microsomes was inhibited by the CYP inhibitor miconazole.
These findings indicate that ATRA oxidation is quantitatively significant in human liver. Lipid hydroperoxides generated by intracellular enzymes such as prostaglandin synthase and lipoxygenases are sources of activated oxygen for CYP‐mediated deactivation of ATRA to polar products.

British Journal of Pharmacology (2000) 131, 851–857; doi:10.1038/sj.bjp.0703579
Effects of tetrandrine on calcium transport, protein fluorescences and membrane fluidity of sarcoplasmic reticulum
Authors: Chen Lan‐Ying , Chen Xi , Tian Xiao‐Li , Yu Xiao‐Hong 
Published: January 2005

To understand whether the molecular mechanism of Tetrandrine (Tet)'s pharmacological effects is concerned with sarcoplasmic reticulum calcium transport so as to be involved in myocardial contractility, we observed the effects of Tet on calcium transport and membrane structure of rabbit skeletal muscle sarcoplasmic reticulum vesicles (SR) and rat cardiac sarcoplasmic reticulum vesicles (CSR).
Calcium uptake was monitored with a dual‐wavelength spectrophotometer. Protein conformation and fluorescence polarization were measured by fluospectrophotometric method and membrane lipids labelled with fluorescence probes for SR, respectively.
128 μmol l−1 Tet reduced the initial rate of calcium uptake to 59% of control 6 min after reaction. Tet un‐competitively inhibited SR Ca2+,Mg2+‐ATPase activity, causing the stoichiometric ratio of SR Ca2+/ATP to decrease to 1.43 from 2.0 of control.
Inhibitory rates on SR Ca2+,Mg2+‐ATPase by Tet were reduced from 60% in the absence of phosphate to 50% in the presence of phosphate and reduced from 92% in 1 mmol l−1 ATP to 60% in 5 mmol l−1 ATP.
Tet markedly reduced SR intrinsic protein fluorescence, while it slightly decreased the thiol(SH)‐modified protein fluorescence of SR labelled with N‐(3‐pyrene)‐maleimide.
Tet slightly increased fluorescence polarization in the middle and deep layers of SR membrane lipids labelled with 7‐ or 12‐(9‐anthroyloxy) stearic acid (AS) probes, whereas it did not change that of SR labelled with 1,6‐diphenyl‐1,3,5‐hexatrine (DPH).
These results revealed that prevention of SR calcium uptake by Tet was due to inhibition of the SR calcium pump Ca2+,Mg2+‐ATPase, changes in spatial conformation of the pumps protein molecules and a decrease in the extent of motion of membrane lipid molecules, thus altering the regulation of [Ca2+]i and myocardial contractility.

British Journal of Pharmacology (2000) 131, 530–536; doi:10.1038/sj.bjp.0703582
Cefaclor, a cephalosporin antibiotic, delays gastric emptying rate by a CCK‐A receptor‐mediated mechanism in the rat
Authors: Bozkurt Ayhan , Deniz Mustafa , Yegen Berrak Ç 
Published: January 2005

Studies in vitro suggest that cephalosporin antibiotics release the gut hormone cholecystokinin. Cholecystokinin is known to inhibit gastric emptying. Here we examine the effects of cefaclor on gastric emptying and intestinal motility.
Male Sprague‐Dawley rats were fitted with gastric cannulas. Following a 3‐week recovery, the rate of gastric emptying of saline, peptone (4.5%) or cefaclor was determined after instillation into the gastric cannula, while intestinal transit was measured by using the propagation of arabic gum + charcoal mixture given intraduodenally.
Gastric emptying of saline was significantly delayed by the addition of cefaclor (3, 10, 30 or 100 mM). The CCK‐A antagonist SR‐27897B (1 mg kg−1, i.p.) reversed the delay induced by 10 mM cefaclor, whereas the CCK‐B antagonist CI‐988 (1 mg kg−1, i.p.) had no significant effect. In capsaicin‐treated rats, 10 mM cefaclor emptied more rapidly than in vehicle‐treated animals.
Thirty‐minute intestinal transit was increased at 30 and 100 mM of cefaclor, while the gastric acid secretion following cefaclor instillation was no different than the group which received saline.
The cephalosporin antibiotic cefaclor appears to be a potent stimulant of CCK release from gut endocrine cells, resembling the effects of peptone. Cefaclor delays gastric emptying via capsaicin‐sensitive afferent pathways, which involve CCK‐A receptor interaction.

British Journal of Pharmacology (2000) 131, 399–404; doi:10.1038/sj.bjp.0703585