bluuebunny/crossref_metadata_2025_split huggingface dataset:
The in vitro pharmacology of ZM 241385, a potent, non‐xanthine, A2a selective adenosine receptor antagonist
Authors: Poucher S.M. , Keddie J.R. , Singh P. , Stoggall S.M. , Caulkett P.W.R. , Jones G. , Collis M.G. 
Published: July 2012

This paper describes the in vitro pharmacology of ZM 241385 (4‐(2‐[7‐amino‐2‐(2‐furyl) [1,2,4]‐triazolo[2,3‐a][1,3,5]triazin‐5‐yl amino]ethyl) phenol), a novel non‐xanthine adenosine receptor antagonist with selectivity for the A2a receptor subtype.
ZM 241385 had high affinity for A2a receptors. In rat phaeochromocytoma cell membranes, ZM 241385 displaced binding of tritiated 5′‐N‐ethylcarboxamidoadenosine (NECA) with a pIC50 of 9.52, (95% confidence limits, c.l., 9.02–10.02). In guinea‐pig isolated Langendorff hearts, ZM 241385 antagonized vasodilatation of the coronary bed produced by 2‐chloroadenosine (2‐CADO) and 2‐[p‐(2‐carboxyethyl) phenethylamino]‐5′‐N‐ethylcarboxamidoadenosine (CGS21680) with pA2 values of 8.57 (c.l., 8.45‐8.68) and 9.02 (c.l., 8.79‐9.24) respectively 3 ZM 241385 had low potency at A2b receptors and antagonized the relaxant effects of adenosine in the guinea‐pig aorta with a pA2 of 7.06, (c.l., 6.92‐7.19).
ZM 241385 had a low affinity at A1 receptors. In rat cerebral cortex membranes it displaced tritiated R‐phenylisopropyladenosine (R‐PIA) with a pIC50 of 5.69 (c.l., 5.57‐5.81). ZM 241385 antagonized the bradycardie action of 2‐CADO in guinea‐pig atria with a pA2 of 5.95 (c.l., 5.72‐6.18).
ZM 241385 had low affinity for A3 receptors. At cloned rat A3 receptors expressed in Chinese hamster ovary cells, it displaced iodinated aminobenzyl‐5′‐N‐methylcarboxamido adenosine (AB‐MECA) with a pIC50 of 3.82 (c.l., 3.67‐4.06).
ZM 241385 had no significant additional pharmacological effects on the isolated tissues used in these studies at concentrations three orders of magnitude greater than those which block A2a receptors. At 10 μm it displayed only minor inhibition of the bradycardic effects in guinea‐pig atria to some concentrations of carbachol. At 10 μm, ZM 241385 had a small inhibitory effect on relaxant effects of isoprenaline in guinea‐pig aortae but no effect on sodium nitrite‐induced relaxation. ZM 241385 (100 μm) was without effect on phenylephrine‐induced tone in guinea‐pig aortae.
ZM 241385 (10 μm) had no inhibitory effect on rat hepatocyte phosphodiesterase types I, II, III and IV but caused a small inhibition of the calcium calmodulin‐activated type I enzyme.
ZM 241385 is the most selective adenosine A2a receptor antagonist yet described and is therefore a useful tool for characterization of responses mediated by A2 adenosine receptors.
Coupling of an endogenous 5‐HT1B‐like receptor to increases in intracellular calcium through a pertussis toxin‐sensitive mechanism in CHO‐K1 cells
Authors: Dickenson John M. , Hill Stephen J. 
Published: July 2012

Chinese hamster ovary cells (CHO‐K1) express an endogenous 5‐hydroxytryptamine (5‐HT)1B‐like receptor that is negatively coupled to adenylyl cyclase through a pertussis toxin (PTX)‐sensitive mechanism. Furthermore, the human adenosine A1 receptor when expressed in CHO‐K1 cells (CHO‐A1) has been shown to mobilize intracellular Ca2+ through a PTX‐sensitive mechanism. Therefore the aim of this investigation was to determine whether the endogenous 5‐HT1B‐like receptor was able to stimulate increases in intracellular free [Ca2+] ([Ca2+]i) in CHO‐A1 cells.
In agreement with previous studies using CHO cells, 5‐hydroxytryptamine (5‐HT) elicited a concentration‐dependent inhibition of forskolin‐stimulated [3H]‐cyclic AMP production in CHO‐A1 cells (p[EC50] = 7.73±0.13). 5‐HT (1 μm) inhibited 47±5% of the [3H]‐cyclic AMP accumulation induced by 3 μm forskolin. Forskolin stimulated [3H]‐cyclic AMP accumulation was also inhibited by the 5‐HT1 receptor agonists (p[EC50] values) 5‐carboxyamidotryptamine (5‐CT; 8.07±0.08), RU 24969 (8.12 ±0.33) and sumatriptan (5.80 ±0.31).
5‐HT elicited a concentration‐dependent increase in [Ca2+]i in CHO‐A1 cells (p[EC50] = 8.07 ±0.05). In the presence of 2mM extracellular Ca2+, 5‐HT (1 μm) increased [Ca2+]i from 174±17nM to 376 ±22 nM. The 5‐HT1 receptor agonists (p[EC50] values), 5‐carboxyamidotryptamine (5‐CT; 7.9 ±0.02), RU 24969 (8.1 ±0.07) and sumatriptan (5.9 ±0.11) all elicited concentration‐dependent increases in [Ca2+]i. Similar maximal increases in [Ca2+]i were obtained with each agonist. The selective 5‐HT1A receptor agonist, 8‐OH‐DPAT (10 μm) did not stimulate increases in [Ca2+]i. 5‐HT (100 μm) and 5‐CT (10 μm) did not stimulate a measurable increase in [3H]‐inositol phosphate accumulation in CHO‐A1 cells.
5‐HT (1 μm)‐mediated increases in [Ca2+]i were insensitive to the 5‐HT receptor antagonist, ritanserin (5‐HT2; 100 nM), ketanserin (5‐HT2; 100 nM), LY‐278,584 (5‐HT3; 1 μm) and WAY 100635 (5‐HT1A; 1 μm). The response to 5‐HT (100 nM) was antagonized by the non‐selective 5‐HT1 antagonist, methiothepin (pKb = 8.90±0.09) and the 5‐HT1D antagonist GR 127935 (pKb= 10.44±0.06).
Pretreatment with PTX (200 ng ml−1 for 4 h) completely attenuated the Ca2+ response to 100 μm 5‐HT.
In untransfected CHO‐K1 cells, 5‐HT (1 μm), RU 24969 (1 μm), and 5‐CT (1 μm) elicited increases in [Ca2+]i similar to those observed in CHO‐A1 cells.
These data demonstrate that in CHO‐K1 cells the endogenously expressed 5‐HT1B‐like receptor couples to the phospholipase C/Ca2+ signalling pathway through a PTX‐sensitive pathway, suggesting the involvement of Gi/Go protein(s).
The effects of temperature on the interactions between volatile general anaesthetics and a neuronal nicotinic acetylcholine receptor
Authors: Dickinson R. , Lieb W.R. , Franks N.P. 
Published: July 2012

Completely isolated identified neurones from the right parietal ganglion of the pond snail Lymnaea stagnalis were investigated under two‐electrode voltage clamp. Neuronal nicotinic acetylcholine receptor (AChR) currents were studied at low acetylcholine concentrations (≤200 nM).
Inhibition of the ACh‐induced currents by three volatile general anaesthetics (halothane, isoflurane and methoxyflurane) and the specific inhibitor (+)‐tubocurarine was studied as a function of temperature (over the range 4–25°C).
The inhibition by the volatile anaesthetics increased (inhibition constants decreased) with decreasing temperature while the inhibition by (+)‐tubocurarine did not change significantly near room temperature, but decreased at lower temperatures. The (+)‐tubocurarine inhibition appeared to be competitive in nature and showed no significant voltage‐dependence.
The van't Hoff plots, (logarithms of the dissociation constants against reciprocal absolute temperature) were linear for the anaesthetics, but markedly non‐linear for (+)‐tubocurarine. From these plots, values for the changes in the standard Gibbs free energy ΔG°water→AChR, enthalpy ΔH°water→.AChR, entropy ΔS°water→AChR and heat capacity ΔC°p water→AChR were determined. Tubocurarine was found to bind very much tighter to the receptor than the volatile anaesthetics due, entirely, to a favourable increase in entropy on binding.
A comparison between the temperature‐dependence of the anaesthetic inhibition of the ACh receptor and that of general anaesthetic potencies in animals indicates that the temperature‐dependence of animal potencies might be simply accounted for in terms of changes in anaesthetic/receptor binding.
Comparative effects of angiotensin II and its degradation products angiotensin III and angiotensin IV in rat aorta
Authors: Li Q. , Zhang J. , Pfaffendorf M. , van Zwieten P.A. 
Published: July 2012

In the present study, the contractile effects of angiotensin III (AIII) and angiotensin IV (AIV) compared with those of angiotensin II (All) were determined in rat aortic ring preparations.
All three peptides caused concentration‐dependent contractions with similar maximal responses. AIII proved approximately 4 times less potent than All, whereas AIV was about 1000 times less active than AII
The selective AT1‐receptor antagonist, losartan (10–300 nM) caused parallel rightward shifts of the concentration‐response curves (CRC) for all three peptides. The Schild plot slopes for the effect of losartan on AIII curves were significantly lower than unity (P<0.05). The selective AT2‐receptor antagonist, PD123177 did not influence the CRCs for All and AIV. However, the AIII curves were moderately shifted leftward in the presence of PD123177 (0.1 and 1 μm).
Destruction of the endothelium or incubation with the NO‐synthesis inhibitor NG‐monomethyl‐l‐arginine acetate (l‐NMMA) (0.1 mm) significantly enhanced the contractile responses to all three peptides.
Tachyphylaxis was investigated by constructing a second CRC for all three peptides, after an interval of 1 h. The presence of endothelium significantly enhanced the development of tachyphylaxis to all three peptides. However, in endothelium‐denuded preparations, the Emax value of the second curve elicted by All was about 50%, compared with the first one, whereas for AIII and AIV Emax values were as high as 90% and 100%, respectively.
Our results indicate that both AIII and AIV are less potent but similarly efficacious vasoconstrictor agents compared with AII Their contractile effects are also mediated by AT1receptors and probably modulated by endothelium. Tachyphylaxis induced by AIII and AIV proved weaker than that for AII Tachyphylaxis appears to be enhanced by the presence of an intact endothelium.
Dose‐response comparisons of five lung surfactant factor (LSF) preparations in an animal model of adult respiratory distress syndrome (ARDS)
Authors: Häfner Dietrich , Beume Rolf , Kilian Ulrich , Krasznai Georg , Lachmann Burkhard 
Published: July 2012

We have examined the effects of five different lung surfactant factor (LSF) preparations in the rat lung lavage model. In this model repetitive lung lavage leads to lung injury with some similarities to adult respiratory distress syndrome with poor gas exchange and protein leakage into the alveolar spaces. These pathological sequelae can be reversed by LSF instillation soon after lavage.
The tested LSF preparations were: two bovine: Survanta and Alveofact: two synthetic: Exosurf and a protein‐free phospholipid based LSF (PL‐LSF) and one Recombinant LSF at doses of 25, 50 and 100 mg kg−1 body weight and an untreated control group.
Tracheotomized rats (10–12 per dose) were pressure‐controlled ventilated (Siemens Servo Ventilator 900C) with 100% oxygen at a respiratory rate of 30 breaths min−1, inspiration expiration ratio of 1: 2, peak inspiratory pressure (PIP) of 28 cmH2O at positive end‐expiratory pressure (PEEP) of 8 cmH2O. Two hours after LSF administration, PEEP and in parallel PIP was reduced from 8 to 6 (1st reduction), from 6 to 3 (2nd reduction) and from 3 to 0 cmH2O (3rd reduction).
Partial arterial oxygen pressure (Pao2, mmHg) at 5 min and 120 min after LSF administration and during the 2nd PEEP reduction (Pao2(PEEP23/3)) were used for statistical comparison. All LSF preparations caused a dose‐dependent increase for the Pao2(120′), whereas during the 2nd PEEP reduction only bovine and recombinant LSF exhibited dose‐dependency. Exosurf did not increase Pao2 after administration of the highest dose. At the highest dose Exosurf exerted no further improvement but rather a tendency to relapse. The bovine and the Recombinant LSF are superior to both synthetic LSF preparations.
In this animal model and under the described specific ventilatory settings, even between bovine LSF preparations there are detectable differences that are pronounced when compared to synthetic LSF without any surfactant proteins. We conclude that the difference between bovine and synthetic LSF preparations can be overcome by addition of the surfactant protein C.
Renal effects of infusion of rilmenidine and guanabenz in conscious dogs: contribution of peripheral and central nervous system α2–adrenoceptors
Authors: Evans Roger G. , Anderson Warwick P. 
Published: July 2012

We tested the renal effects of the α2‐adrenoceptor agonists, rilmenidine and guanabenz and the antagonists, 2‐methoxyidazoxan and idazoxan, in conscious dogs. Our aim was to test the hypothesis that putative imidazoline (I) receptors influence renal function. We reasoned that since rilmenidine and guanabenz are selective for I1‐ and I2‐binding sites respectively, an influence of one of these receptive sites on renal function would be reflected in qualitative differences between the effects of these agents. Moreover, effects mediated by putative I‐receptors should be relatively resistant to antagonism by the selective α2‐adrenoceptor antagonist, 2‐methoxyidazoxan. Since the effects of these drugs on renal function could be mediated in the central nervous system or periphery, the dogs were studied under both normal and ganglion‐blocked conditions.
In dogs with intact autonomic reflexes, 2‐methoxyidazoxan (15 μg kg−1 plus 0.6 μg kg−1 min−1) produced effects consistent with a generalized increase in sympathetic drive, including increases in mean arterial pressure and plasma renin activity, and a reduction in sodium excretion. In ganglion‐blocked dogs, 2‐methoxyidazoxan reduced sodium excretion but had no discernible effect on systemic or renal haemodynamics. We conclude that an α2‐adrenoceptor‐mediated mechanism in the central nervous system tonically inhibits sympathetic drive in the conscious dog.
In ganglion‐blocked dogs idazoxan (3‐300 μg kg−1) dose‐dependently increased arterial pressure. This was not abolished by concomitant administration of 2‐methoxyidazoxan (0.3‐30 μg kg−1). The pressor effect of idazoxan is therefore probably mediated by an agonist action at α‐adrenoceptors.
The effects of infusions of rilmenidine (0.1‐1.0 mg kg−1) and guanabenz (10‐100 μg kg−1) were indistinguishable. They comprised dose‐dependent increases in mean arterial pressure, urine excretion, and glomerular filtration rate (the latter in ganglion blocked dogs only), and dose‐dependent reductions in heart rate, renal blood flow and sodium excretion (only in dogs with intact autonomic reflexes). All of these effects were antagonized by 2‐methoxyidazoxan.
We conclude that the renal effects of rilmenidine and guanabenz infusions in conscious dogs are predominantly, if not completely, attributable to activation of α2‐adrenoceptors. Our results do not support the hypothesis that putative I‐receptors contribute towards the renal effects of these agents.
Calcium channel subtypes for the sympathetic and parasympathetic nerves of guinea‐pig atria
Authors: Hong S.J. , Chang C.C. 
Published: July 2012

The Ca2+ channel subtypes of the autonomic nerves of guinea‐pig atria were elucidated by monitoring the effects of specific Ca2+ channel blockers on the negative and positive inotropic responses associated respectively, with stimulation of the parasympathetic and sympathetic nerves.
In left atria paced at 2–4 Hz, the negative inotropic effect induced by field stimulation of parasympathetic nerves (in the presence of propranolol) was abolished by ω‐conotoxin MVIIC, a blocker of N‐type and OPQ subfamily Ca2+ channels. ω‐Conotoxin GVIA (an N‐type blocker), ω‐agatoxin IVA (a P‐type blocker), nifedipine (an L‐type blocker) and Ni2+ (a T‐ and R‐type blocker) were much less effective.
The positive inotropic response resulting from field stimulation of the sympathetic nerves (in the presence of atropine) was abolished by both ω‐conotoxins, while ω‐agatoxin IVA, nifedipine and Ni2+ were ineffective.
In the spontaneously beating right atria, the early negative inotropic effect produced by 1,1‐dimethyl‐4‐phenylpiperazinium was abolished by ω‐conotoxin MVIIC; whereas the late positive inotropic effect was partially reduced, but not abolished, by a high concentration of ω‐conotoxin GVIA.
None of the peptide toxins affected the chronotropic and the inotropic responses evoked by carbachol and isoprenaline.
These results suggested that, under physiological conditions, the release of acetylcholine from paraysmpathetic nerves is dominated by an OPQ subfamily Ca2+ channel while that of noradrenaline from sympathetic nerves is controlled by an N‐type Ca2+ channel. Ligand‐induced noradrenaline release appeared to recruit additional type(s) of Ca2+ channel.
Sequential induction of nitric oxide synthase by Corynebacterium parvum in different organs of the mouse
Authors: Rees D.D. , Cunha F.Q. , Assreuy J. , Herman A.G. , Moncada S. 
Published: July 2012

The ability of Corynebacterium parvum (C. parvum) to induce nitric oxide (NO) synthase in the macrophage, spleen, liver, aorta, heart and brain, and to elevate plasma NO2−/NO3− in the mouse was investigated. In addition, the relationship between NO synthase activity and blood pressure was studied.
C. parvum (100 mg kg−1, i.p.) induced a time‐dependent expression of a Ca2+‐independent NO synthase in the macrophage, spleen, liver, aorta and heart. The time course of induction of the NO synthase varied such that the maximum enzyme activity was at day 8 in the macrophage and liver, day 12 in the spleen and heart and day 16 in the aorta.
There was no significant induction of a Ca2+‐independent NO synthase in the brain, nor was there any change in the Ca2+‐dependent enzyme in this organ, during the study period.
C. parvum produced a gradual decrease in blood pressure, with a maximum fall at day 16 (from 108 ± 1 mmHg to 79 ± 3 mmHg), which recovered gradually by day 28.
Plasma NO2−/NO3− was significantly elevated between days 8 and 24, with a maximum increase at day 12.
These results show that C. parvum induces a Ca2+‐independent NO synthase in a number of tissues and that this induction occurs initially in macrophages and the liver. This suggests that induction of the NO synthase in the other tissues is secondary and probably the result of activation of macrophages and some cells of the liver.
Furthermore, the decrease in blood pressure induced by C. parvum is associated with the induction of NO synthase in the vasculature, whereas the increased concentration of plasma NO2−/NO3− seems to result from the generation of NO by a number of tissues.
Adenosine A2 receptor‐induced inhibition of leukotriene B4 synthesis in whole blood ex vivo
Authors: Krump E. , Lemay G. , Borgeat P. 
Published: July 2012

Engagement of adenosine A2 receptors suppresses several leukocyte functions. In the present study, we examined the effect of adenosine on the inhibition of leukotriene B4 (LTB4) synthesis in heparinized human whole blood, pretreated with lipopolysaccharide (LPS) and tumour necrosis factor α (TNF‐α) and stimulated with the chemotactic peptide, N‐formyl‐Met‐Leu‐Phe (FMLP).
The FMLP‐induced synthesis of LTB4 in whole blood pretreated with LPS and TNF‐α was dose‐dependently inhibited by adenosine analogues in the following order of potency; 5′(N‐ethyl)carbox‐ amidoadenosine (NECA) ≅ CGS 21680 > 2‐Cl‐adenosine > N6‐cyclopentyladenosine (CPA), indicating the involvement of the adenosine A2 receptor subtype. The IC50 values for NECA, CGS 21680, 2‐Cl‐ adenosine, and CPA were 6nM, 9nM, 180nM, and 990 nM, respectively.
Dipyridamole, an agent that blocks the cellular uptake of adenosine by red cells and causes its accumulation in plasma, also inhibited the synthesis of LTB4 in LPS and TNF‐α‐treated whole blood stimulated by FMLP; moreover, this inhibition was reversed upon addition of adenosine deaminase.
A highly selective antagonist of the adenosine A2 receptor, 8‐(3‐chlorostyryl)caffeine (CSC), reversed the inhibition of LTB4 synthesis by 2‐Cl‐adenosine and dipyridamole in LPS and TNF‐α‐treated whole blood, stimulated by FMLP.
LTB4 synthesis in whole blood originates predominantly from neutrophils and to a lesser extent from monocytes. 2‐Cl‐adenosine also inhibited the synthesis of LTB4 induced by FMLP in these isolated LPS and TNF‐α‐treated cells; however, 2‐Cl‐adenosine was a more potent inhibitor of LTB4 synthesis in neutrophils than monocytes.
The present data demonstrate that adenosine, acting through A2 receptors, exerts a potent inhibitory effect on the synthesis of LTB4 and thus contribute to the understanding of its anti‐inflammatory properties.
Some effects of nipradilol, a β‐antagonist possessing a nitroxy group, on smooth muscle of the pig coronary artery
Authors: Abe Shimako , Nakamura Motoomi , Kanaide Hideo 
Published: July 2012

The effects of nipradilol, a β‐adrenoceptor antagonist which possesses a nitroxy group, on cytosolic Ca2+ concentration ([Ca2+]i) and on tension development were simultaneously measured by front‐surface fluorometry and fura‐2‐loaded strips in the proximal portion of pig coronary arteries.
Nipradilol reduced in a concentration‐dependent manner both the [Ca2+]i and tension, irrespective of whether the strips were unstimulated or exposed to either high K+ or histamine containing solutions. However, both in the case of contractions induced by high K+‐depolarization and histamine stimulation, for a given [Ca2+]i elevation the tension which developed in the presence of nipradilol was smaller than that generated in its absence, so that the [Ca2+]i‐tension curves during the contraction were shifted to the right.
In the absence of extracellular Ca2+, the [Ca2+]i elevation due to the release of Ca2+ from histamine‐sensitive store was inhibited by nipradilol. Nipradilol had no effect on the [Ca2+]i elevation due to the release of Ca2+ from caffeine‐sensitive stores; however, it did inhibit the caffeine‐induced increase in tension. A derivative of nipradilol, which lacked a nitroxy molecule (Nip(‐N)), had no effect on the [Ca2+]i and tension elevated by histamine or caffeine in the absence of extracellular Ca2+.
The β‐adrenoceptor agonist, isoprenaline, reduced [Ca2+]i and tension when applied to steady state contractions induced by high K+, or at the peak level of tension to histamine. The reduction of [Ca2+]i and tension induced by isoprenaline was inhibited by Nip(‐N) in a concentration‐dependent manner and nipradilol inhibited the isoprenaline‐induced relaxation with bell‐shaped concentration‐response curves. At lower concentrations, nipradilol acted as a β‐blocker, the IC50 value being smaller than that of Nip(‐N), and at higher concentrations, it acted as a nitrovasodilator.
Thus, it is suggested that, at lower concentrations, nipradilol, an antianginal drug, acts as a β‐adrenoceptor antagonist. At higher concentrations, it relaxes the proximal portion of the coronary artery by directly reducing [Ca2+]i and the Ca2+‐sensitivity of the myofilaments, apparently due to the presence of the nitroxy molecule.