bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mode of action of bradycardic agent, S 16257, on ionic currents of rabbit sinoatrial node cells
Authors: Bois Patrick , Bescond Jocelyn , Renaudon Barbara , Lenfant Jacques 
Published: July 2012

The effect of the bradycardic agent S 16257 on the main ionic mechanisms of diastolic depolarization in sinoatrial node cells isolated from rabbit heart, was investigated by the patch‐clamp technique in whole‐cell and macro‐patch recordings.
In whole‐cell conditions, S 16257 induced a marked exponential use‐dependent blockade of the hyperpolarization‐activated If current, without shift of the voltage range of its activation curve. The rate of block increased with the drug concentration. The IC50 for the block of If was 2.8 × 10−6 m.
A similar use‐dependent decline of If was obtained with 3 μm S 16257, in cell‐attached and in inside‐out macro‐patch configurations, suggesting that the bradycardic agent interacts with If channels from the inside of the cell.
A high concentration of S 16257 (10 μm) had no detectable effect on T‐type calcium current and slightly decreased L‐type calcium current (−18.12±0.66%), without significant use‐dependent blockade.
S 16257 had no effect on the delayed outward potassium current IK at 3 μm and slightly decreased it only at high concentrations, −16.3±1.2% at 10 μm. In contrast, zatebradine, another bradycardic agent, reduced IK by 20.3±2.5% at 3 μm.
In conclusion, S 16257 may lower heart rate without significant negative inotropic action. In comparison with zatebradine, S 16257 had less effect on IK suggesting less prolongation of repolarization time.
A comparative study of the antithrombotic effect of aurintricarboxylic acid on arterial thrombosis in rats and guinea‐pigs
Authors: Takiguchi Yoshiharu , Shimazawa Masamitsu , Nakashima Mitsuyoshi 
Published: July 2012

. The antithrombotic effect of aurintricarboxylic acid (ATA) which inhibits binding of von Willebrand factor (vWF) to platelet glycoprotein lb (GPlb) receptor was evaluated in photochemically‐induced thrombosis models in the femoral artery of rats and guinea‐pigs.
. ATA at a dose of 10 mg kg−1 significantly prolonged the time required for thrombotic occlusion of the artery in rats. The antithrombotic efficacy was associated with a significant inhibition of platelet retention and ex vivo botrocetin‐induced platelet aggregation.
. On the other hand, in guinea‐pigs, ATA at the same dose inhibited the platelet retention and the platelet aggregation, but did not prevent thromboocclusion.
. ATA inhibited aggregation of washed platelets from rats or guinea‐pigs in response to botrocetin and thrombin in a dose‐dependent manner (1–30 μm), and to the same extent.
. ATA moderately increased activated partial thromboplastin time and bleeding time in both species.
. These results indicate that vWF may play a role in the development of occlusive arterial thrombosis in the rat, but not in the guinea‐pig.
. The antithrombotic activity of ATA may partly arise from its inhibitory effect on thrombin, in addition to that on the vWF‐GPlb pathway.
Direct positive chronotropic effects of angiotensin II and angiotensin III in pithed rats and in rat isolated atria
Authors: Li Q. , Zhang J. , Pfaffendorf M. , van Zwieten P.A. 
Published: July 2012

. The direct positive chronotropic effects of angiotensin II (AII) and its degradation products angiotensin III (AIII) and angiotensin IV (AIV) were established in pithed rats and in rat spontaneously beating right atria.
. In pithed rats, AII, AIII and AIV caused dose‐dependent tachycardia with similar maximal responses (110 beats min−1). The β‐adrenoceptor antagonist propranolol (3.37 × 10−6 mol kg−1) but not the α1‐adrenoceptor antagonist prazosin (2.38 × 10−7 mol kg−1) significantly reduced these effects (P < 0.05; n = 7–8), but 20–25% of the responses could not be blocked by propranolol.
. In isolated atria, AII, AIII and AIV caused concentration‐dependent increases in beating rate with similar maximal responses to AII and AIII (34.3 ± 0.4 and 34.7 ± 0.4 beats min−1; n = 9–10), and a lower maximal response to AIV (26.8 ± 0.6 beats min−1; P < 0.05; n = 8). AIII was about 9 times less potent than AII, whereas AIV proved approximately 3800 times less potent than AII. Neither propranolol (1 μm) nor prazosin (1 μm) could influence the effects of the angiotensin peptides.
. In isolated atria, the selective AT1‐receptor antagonist, losartan (10, 100 and 300 nM) caused parallel rightward shifts of the concentration‐response curves for AII and AIII, whereas the selective AT2‐receptor antagonist PD123177 (1 μm) did not influence the effects of AII and AIII. The aminopeptidase‐A and ‐M inhibitor amastatin (10 μm), significantly steepened the slope of the AIII curves and increased the potency of AIII about 6 fold. Amastatin did not influence the responses to AII.
. Our results indicate that both in vivo and in vitro, exogenous AII and AIII induced a direct dose‐dependent chronotropic effect, which is independent of the adrenergic system. This chronotropic effect is mediated by AT1‐subtype receptors.
The effect of the calcium‐antagonist nitrendipine on intracellular calcium concentration in endothelial cells
Authors: Salameh Aida , Schomecker Gunhild , Breitkopf Katja , Dhein Stefan , Klaus Wolfgang 
Published: July 2012

Nitrendipine induces NO‐release from coronary vascular endothelium presumably by activating endothelial NO‐synthase. We have investigated whether this effect may be mediated by an influence on the intracellular calcium in endothelial cells.Bovine aortic endothelial cells (BAEC) were incubated with Fura‐2/AM (1 μm) for 30 min and Fura‐2 fluorescence was measured at 510 nm in response to chopped excitation with both 340 and 380 nm. The ratio 340/380 nm (known to reflect changes in intracellular calcium) was calculated from these data.Nitrendipine (0.1 to 100 μm) led to a significant, concentration‐dependent, monophasic increase in [Ca2+]iin suspended BAEC by 11±2 nM (0.1 μm), 23±3 nM (1 μm), 34±4 nM (10 μm) and by 47±5 nM (100 μm) from a control level of 118±10 nM.This elevation of intracellular calcium was prevented by pretreatment of BAECs with gadolinium (100 μm) or by incubation with calcium free saline solution. In contrast, the application of 0.3 μmthapsigargin did not abolish the nitrendipine‐induced calcium signal. In additional experiments it was shown that the nitrendipine‐induced NO‐release (as measured with the oxy‐haemoglobin‐method could also be inhibited by gadolinium and was absent in calcium‐free solution.Thus, nitrendipine elevates intracellular calcium in suspended BAECs in a concentration‐dependent manner. This elevation is mainly due to a gadolinium‐sensitive calcium influx from the extracellular space rather than a calcium release from intracellular stores.
Identification of cyclic AMP phosphodiesterases 3, 4 and 7 in human CD4+ and CD8+ T‐lymphocytes: role in regulating proliferation and the biosynthesis of interleukin‐2
Authors: Giembycz Mark A. , Corrigan Christopher J. , Seybold Joachim , Newton Robert , Barnes Peter J. 
Published: July 2012

The cyclic AMP phosphodiesterases (PDE) expressed by CD4+ and CD8+ T‐lymphocytes purified from the peripheral blood of normal adult subjects were identified and characterized, and their role in modulating proliferation and the biosynthesis of interleukin (IL)‐2 and interferon (IFN)‐γ evaluated.
In lysates prepared from both subsets, SK&F 95654 (PDE3 inhibitor) and rolipram (PDE4 inhibitor) suppressed cyclic AMP hydrolysis indicating the presence of PDE3 and PDE4 isoenzymes in these cells. Differential centrifugation and subsequent inhibitor and kinetic studies revealed that the particulate fraction contained, predominantly, a PDE3 isoenzyme. In contrast, the soluble fraction contained a PDE4 (∼65% of total activity) and, in addition, a novel enzyme that had the kinetic characteristics of the recently identified PDE7.
Reverse transcription‐polymerase chain reaction (RT‐PCR) studies with primer pairs designed to recognise unique sequences in the human PDE4 and PDE7 genes amplified cDNA fragments that corresponded to the predicted sizes of HSPDE4A, HSPDE4B, HSPDE54D and HSPDE7. No message was detected for HSPDE4C after 35 cycles of amplification.
Functionally, rolipram inhibited phytohaemagglutinin‐ (PHA) and anti‐CD3‐induced proliferation of CD4+ and CD8+ T‐lymphocytes, and the elaboration of IL‐2, which was associated with a three to four fold increase in cyclic AMP mass. In all experiments, however, rolipram was approximately 60 fold more potent at suppressing IL‐2 synthesis than at inhibiting mitogenesis. In contrast, SK&F 95654 failed to suppress proliferation and cytokine generation, and did not elevate the cyclic AMP content in T‐cells. Although inactive alone, SK&F 95654 potentiated the ability of rolipram to suppress PHA‐ and anti‐CD3‐induced T‐cell proliferation, and PHA‐induced IL‐2 release.
When a combination of phorbol myristate acetate (PMA) and ionomycin were used as a co‐mitogen, rolipram did not affect proliferation but, paradoxically, suppressed IL‐2 release indicating that cyclic AMP can inhibit mitogenesis by acting at, or proximal to, the level of inositol phospholipid hydrolysis.
Collectively, these data suggest that PDE3 and PDE4 isoenzymes regulate the cyclic AMP content, IL‐2 biosynthesis and proliferation in human CD4+ and CD8+ T‐lymphocytes. However, the ability of rolipram to suppress markedly mitogen‐induced IL‐2 generation without affecting T‐cell proliferation suggests that growth and division of T‐lymphocytes may be governed by mediators in addition to IL‐2. Finally, T‐cells have the potential to express PDE7, although elucidating the functional role of this enzyme must await the development of selective inhibitors.
Neural 5‐HT4 receptors in the human isolated detrusor muscle: effects of indole, benzimidazolone and substituted benzamide agonists and antagonists
Authors: Candura S.M. , Messori Eliana , Franceschetti G.P. , D'Agostino TG. , Vicini D. , Tagliani Monica , Tonini M. 
Published: July 2012

In strips of human isolated detrusor muscle, the 5‐hydroxytryptamine (5‐HT) receptor (5‐HT4) that mediates facilitation of neuromuscular cholinergic transmission was further characterized by using 5‐HT and a series of ligands known for their 5‐HT4 agonist (5‐methoxytryptamine: 5‐MeOT, cisapride, (R,S)‐zacopride, BIMU 8) or antagonist (RS 23597, GR 125487, DAU 6285) properties.
In the presence of methysergide (1 μm) and ondansetron (3 μm) to isolate pharmacologically the 5‐HT4 receptors, 5‐HT (0.3 nM‐1 μm), 5‐MeOT (10 nM −30 μm), BIMU 8 (10 nM −3 μm), cisapride (0.1–10 μm) and (R,S)‐zacopride (0.1–30 μm) potentiated cholinergic contractions to electrical field stimulation in a concentration‐dependent manner. RS 23597 (10 nM‐10 μm), a competitive 5‐HT4 receptor antagonist in other systems, also showed agonist properties. The following rank order of potency as an agonist was obtained: 5‐HT (pEC50 = 8.0) > RS 23597 (7.0) = BIMU 8 (6.9) ≥ cisapride (6.6) > 5‐MeOT (6.0) ≥ (R,S)‐zacopride (5.7). Relative to 5‐HT (intrinsic activity = 1), 5‐MeOT acted as a full agonist (1.03), while BIMU 8 (0.76), (R,S)‐zacopride (0.61), RS 23597 (0.60) and cisapride (0.41) behaved as partial agonists.
The potentiation by 5‐HT was competitively antagonized by the selective 5‐HT4 receptor antagonist GR 125487 (0.3‐3 nM) with a pA2 estimate of 9.75 (Schild slope of 1.09), and by DAU 6285 (1 μm; pKB = 6.45). Additionally, GR 125487 (3 nM) antagonized the responses to 5‐MeOT (pKB = 9.72) and reversed the potentiation induced by RS 23597. As an antagonist, RS 23597 (10, 30 and 100 nM) inhibited the response to 5‐HT. In addition, 30 and 100 nM RS 23597 reduced the 5‐HT response maximum by 30 and 50%, respectively. The pKB value calculated at 10 nM was 8.0.
Thus, in the human isolated detrusor muscle, the 5‐HT4 receptors mediating facilitation of cholinergic neuromuscular transmission are activated by indoleamines (5‐HT, 5‐MeOT), substituted benzamide (cisapride, (R,S)‐zacopride), benzoate (RS 23597) and benzimidazolone (BIMU 8) derivatives. The activities (in terms of both potency and efficacy) of most agonists, as well as the affinity estimates of the antagonists GR 125487 and DAU 6285, are comparable to those found in other peripheral tissues. Exceptions are RS 23597, which acted either as a partial agonist or as an antagonist of the response to 5‐HT, and 5‐MeOT that showed an unusually low potency. The latter findings may be ascribed to differences in the efficiency of receptor coupling mechanisms and/or in the molecular structure (i.e. splice variants) of the 5‐HT4 receptor.
Enhancement by calcitonin gene‐related peptide of non‐contractile Ca2+‐induced nicotinic receptor desensitization at the mouse neuromuscular junction
Authors: Dezaki Katsuya , Kimura Ikuko , Tsuneki Hiroshi , Kimura Masayasu 
Published: July 2012

Nicotinic acetylcholine receptor (AChR)‐operated non‐contractile Ca2+ mobilization (unaccompanied by muscle contraction) depressed contractile Ca2+ mobilization (accompanied by muscle contraction) in mouse diaphragm muscles. In the process of nicotinic AChR desensitization, the enhancing role of calcitonin gene‐related peptide (CGRP) on the non‐contractile Ca2+‐induced depression of contractile Ca2+ mobilization was investigated by measurement of Ca2+‐aequorin luminescence in the presence of neostigmine (0.1 μm).
When the phrenic nerve was stimulated with paired pulses at intervals of 150, 300, 600, 1000 and 2000 ms, contractile Ca2+ transients were elicited during the generation of non‐contractile Ca2+ mobilization. The amplitude of the contractile Ca2+ transients elicited by the second pulse (S2) was depressed at the shorter pulse intervals, but not at the longer pulse intervals.
The extent of depression of S2 was enhanced when the duration of non‐contractile Ca2+ mobilization was prolonged by CGRP (10 nM). However, CGRP failed to enhance the depression of S2 when non‐contractile Ca2+ mobilization was not observed at the low external Ca2+ concentration (1.3 mM).
The enhancing effect by CGRP on the depression of S2 was counteracted by staurosporine (3 nM), a protein kinase‐C inhibitor, despite prolongation of the duration of non‐contractile Ca2+ mobilization.
When H‐89 (1 μm), a protein kinase‐A inhibitor, completely blocked non‐contractile Ca2+ mobilization, the depression of S2 was diminished. The prolongation of the duration of non‐contractile Ca2+ mobilization by AA373 (300 μm), a protein kinase‐A activator, enhanced the depression of S2. The enhancing effect was observed neither with CGRP nor with AA373, in the presence of H‐89 (0.1 μm).
These findings suggest that the CGRP mobilizes non‐contractile Ca2+ through activation of protein kinase‐A, which in turn may activate protein kinase‐C, then enhance the desensitization of postsynaptic nicotinic AChRs at the neuromuscular junction.
Development of cholinergic and inhibitory non‐adrenergic non‐cholinergic responses in the rat gastric fundus
Authors: Smits Geert J.M. , Lefebvre Romain A. 
Published: July 2012

Cholinergic contractions and inhibitory non‐adrenergic non‐cholinergic (NANC) relaxations were studied in longitudinal muscle strips of the gastric fundus of 2, 4 and 8 week old rats.
Contractions induced by electrical stimulation of the cholinergic neurones and by administration of acetylcholine decreased during development. The potentiating effect of physostigmine was similar in the 3 age groups.
Short train stimulation in NANC conditions induced fast relaxations, which were more pronounced in 4 and 8 week than in 2 week old rats. These relaxations were almost completely inhibited by NG‐nitro‐L‐arginine methyl ester (L‐NAME) in the 3 age groups. The nitric oxide‐induced relaxations did not change during development.
Sustained electrical stimulation in NANC conditions induced an initial relaxation, which was almost totally blocked by L‐NAME, followed by an almost complete recovery of tone at lower frequencies of stimulation. At higher frequencies of stimulation, the recovery of tone was incomplete or absent. This sustained relaxation was only partially reduced by L‐NAME and almost abolished by L‐NAME plus α‐chymotrypsin. The initial relaxations increased during development, while the sustained relaxations remained similar during this period. Vasoactive intestinal polypeptide‐induced relaxations were also similar in the 3 age groups.
These results show that the sensitivity of the gastric fundus to acetylcholine decreases from 2 weeks to 8 weeks postnatally, while the importance of the nitrergic innervation increases during this period.
Inhibition of exocytotic noradrenaline release by presynaptic cannabinoid CB1 receptors on peripheral sympathetic nerves
Authors: Ishac Edward J.N. , Jiang Liu , Lake Kristy D. , Varga Karoly , Abood Mary E. , Kunos George 
Published: July 2012

Activation of CB1 receptors by plant cannabinoids or the endogenous ligand, anandamide, causes hypotension via a sympathoinhibitory action in anaesthetized rats. In mouse isolated vas deferens, activation of CB1 receptors inhibits the electrically evoked twitch response. To determine if these effects are related to presynaptic inhibition of noradrenaline (NA) release, we examined the effects of Δ9‐tetrahydrocannabinol (‡9‐THC), anandamide and the CB1 antagonist, SR141716A, on exocytotic NA release in rat isolated atria and vasa deferentia.
In isolated atria and vasa deferentia preloaded with [3H]‐NA, electrical field stimulation caused [3H]‐NA release, which was abolished by tetrodotoxin 0.5 μm and concentration‐dependently inhibited by ‡9‐THC or anandamide, 0.3–10 μm. The inhibitory effect of ‡9‐THC and anandamide was competitively antagonized by SR141716A, 1–10 μm.
Tyramine, 1 μm, also induced [3H]‐NA release, which was unaffected by tetrodotoxin, ‡9‐THC or anandamide in either atria or vasa deferentia.
CB1 receptor mRNA is present in the superior cervical ganglion, as well as in whole brain, cerebellum, hypothalamus, spleen, and vas deferens and absent in medulla oblongata and atria, as demonstrated by reverse transcription‐polymerase chain reaction. There was no evidence of the presence of CB1A receptor mRNA in ganglia, brain, or cerebellum. These results suggest that activation of presynaptic CB1 receptors located on peripheral sympathetic nerve terminals mediate sympathoinhibitory effects in vitro and in vivo.
Pharmacological modulation of immunoreactive imidazoline receptor proteins in rat brain: relationship with non‐adrenoceptor [3H]‐idazoxan binding sites
Authors: Escribá Pablo V. , Alemany Regina , Sastre Magdalena , Olmos Gabriel , Ozaita Andrés , García‐Sevilla Jesús A. 
Published: July 2012

The densities of various imidazoline receptor proteins (with apparent molecular masses of ≅29/30 −45‐ and 66‐kDa) were quantitated by immunoblotting in the rat cerebral cortex after various drug treatments. The modulation of these imidazoline receptor proteins was then compared with the changes in the density of non‐adrenoceptor [3H]‐idazoxan binding sites (I2‐sites) induced by the same drug treatments.
Chronic treatment (7 days) with the I2‐selective imidazol(in)e drugs idazoxan (10 mg kg−1), cirazoline (1 mg kg−1) and LSL 60101 (10 mg kg−1) differentially increased the immunoreactivity of imidazoline receptor proteins. The levels of the 29/30‐kDa protein were increased by idazoxan and LSL 60101 (23%), the levels of the 45‐kDa protein only by cirazoline (44%) and those of the 66‐kDa protein only by idazoxan (50%). These drug treatments also increased the density of I2‐sites (32–42%).
Chronic treatment (7 days) with efaroxan (10 mg kg−1), RX821002 (10 mg kg−1) and yohimbine (10 mg kg−1), which possess very low affinity for I2‐imidazoline receptors, did not alter either the immunoreactivity of imidazoline receptor proteins or the density of I2‐sites.
Chronic treatment (7 days) with the monoamine oxidase (MAO) inhibitors clorgyline (10 mg kg−1) and phenelzine (10 mg kg−1) decreased the immunoreactivity of the 29/30‐kDa (17–24%), 45‐kDa (19%) and 66‐kDa (23–31%) imidazoline receptor proteins. The alkylating agent N‐ethoxycarbonyl‐2‐ethoxy‐1,2‐dihydroquinoline (1.6 mg kg−1, 6 h) also decreased the levels of the three imidazoline receptor proteins (20–47%). These drug treatments consistently decreased the density of I2‐sites (31–57%).
Significant correlations were found when the mean percentage changes in immunoreactivity of imidazoline receptor proteins were related to the mean percentage changes in the density of I2‐sites after the various drug treatments (r = 0.92 for the 29/30‐kDa protein, r = 0.69 for the 45‐kDa protein and r = 0.75 for the 66‐kDa protein).
In the rat cerebral cortex the I2‐imidazoline receptor labelled by [3H]‐idazoxan is heterogeneous in nature and the related imidazoline receptor proteins (29/30‐, 45‐ and 66‐kDa) detected by immunoblotting contribute differentially to the modulation of I2‐sites after drug treatment.
Evidence for the presence of cannabinoid CB1 receptors in mouse urinary bladder
Authors: Pertwee Roger G. , Fernando Susanthi R. 
Published: July 2012

CP 55,244, (−)−11‐hydroxy‐dimethylheptyl‐Δ8‐tetrahydrocannabinol, WIN 55,212‐2, Δ9‐tetrahydro‐cannabinol, nabilone and anandamide each inhibited electrically‐evoked contractions of the mouse isolated urinary bladder in a concentration‐related manner, their EC50 values being respectively 15.9, 18.27, 27.23, 1327.6, 1341.5 and 4950.3 nM. (+)‐11‐hydroxy‐dimethylheptyl‐Δ8‐tetrahydrocannabinol was inactive at the highest concentration used (10 μm).
SR141716A (31.62 or 100 nM) produced parallel rightward shifts in the log concentration‐response curves of CP 55,244, (−)−11‐hydroxy‐dimethylheptyl‐Δ8‐tetrahydrocannabinol, WIN 55,212‐2, Δ9‐tetrahydrocannabinol and anandamide for inhibition of electrically‐evoked bladder contractions. The effect of the antagonist on the log concentration‐response curve of CP 55,244 was shown to depend on the concentration of SR141716A used (31.62 to 1000 nM).
The amplitudes of contractions evoked by acetylcholine or β, γ‐methylene‐L‐ATP were not decreased by 316.2 nM CP 55,244 or 3162 nM Δ9‐tetrahydrocannabinol. Electrically‐evoked contractions were almost completely abolished by 200 nM tetrodotoxin.
The above results support the hypothesis that mouse urinary bladder contains prejunctional CB1 cannabinoid receptors which can mediate inhibition of electrically‐evoked contractions, probably by reducing contractile transmitter release.
AM 630 which behaves as a cannabinoid receptor antagonist in the mouse isolated vas deferens did not antagonize the ability of CP 55,244 or Δ9‐tetrahydrocannabinol to inhibit electrically‐evoked contractions of the mouse bladder.
SR141716A produced small but significant increases in the amplitude of electrically‐evoked contractions of the bladder suggesting that this tissue may release an endogenous cannabinoid receptor agonist or that some cannabinoid receptors in this tissue are precoupled to the effector system.