bluuebunny/crossref_metadata_2025_split huggingface dataset:
The vasoconstrictor effects of L‐NAME, a nitric oxide synthase inhibitor, in pregnant rabbits
Authors: Losonczy Gy. , Mucha I. , Müller V. , Kriston T. , Ungvári Z. , Tornóci L. , Rosivall L. , Venuto R. 
Published: July 2012

We have used anaesthetized, acutely instrumented non‐pregnant (NP) and late pregnant (P) New Zealand white rabbits to examine the possible role of nitric oxide (NO) in the pregnancy‐induced fall of vascular tone and arterial pressure. Systemic, renal and pulmonary vascular resistance, as well as plasma concentrations of cyclic GMP (PcGMP) were compared before and after the inhibition of NO synthesis by NG‐nitro‐L‐arginine methyl ester (L‐NAME).
P rabbits had lower baseline total peripheral resistance (TPR), mean arterial pressure (MAP) and higher PcGMP than NP controls (all P<0.05 or less). L‐NAME (1, 10, 50 mg kg−1, i.v.) resulted in dose‐dependent elevation of TPR in both groups. However, the absolute, as well as percentage increases in TPR were greater (P<0.05) in NP than in P rabbits.
Cardiac output (CO) was reduced more (P<0.01) by NO inhibition in NP than P rabbits. Therefore, despite the smaller increase in TPR, the elevation of MAP was greater (P<0.001) in P than NP rabbits. After L‐NAME, NP rabbits developed more severe bradycardia and a greater increase of pulmonary vascular resistance which might have contributed to the more pronounced reduction of CO.
PcGMP increased in both groups following L‐NAME, but more (P<0.01) in NP than P rabbits.
Infusion of acetylcholine (ACh, 0.02 μmol l−1 kg−1) reduced MAP and TPR more (both P<0.05) in NP than P rabbits and L‐NAME reduced the ACh‐induced depressor response only in NP rabbits.
These results suggest that the low vascular tone and arterial pressure in pregnant rabbits is not mediated by NO.
Further investigation into the signal transduction mechanism of the 5‐HT4‐like receptor in the circular smooth muscle of human colon
Authors: McLean Peter G. , Coupar Ian M. 
Published: July 2012

The nature of the receptor coupling mechanism of the 5‐hydroxytryptamine4 (5‐HT4) receptor in the circular smooth muscle of the human colon has been further investigated.
5‐HT stimulated cyclic AMP generation and caused a relaxation in a concentration‐dependent fashion, with EC50 values of 175.5 and 274.9 nM respectively. DAU 6236 increased cyclic AMP formation and caused a relaxant effect but was a partial agonist relative to 5‐HT.
The 5‐HT4 receptor antagonist, GR 113808, inhibited cyclic AMP formation and relaxation induced by 5‐HT with ‐log Ki values of 9.1 (cyclic AMP) and 8.9 (relaxation) and apparent pA2 values of 9.2 (cyclic AMP) and 9.5 (relaxation).
Ondansetron and methysergide failed to inhibit cyclic AMP formation or the relaxation induced by 5‐HT.
The phosphodiesterase inhibitor, IBMX, produced a concentration‐dependent relaxation (EC50 = 30 μm) and at 1 μm it enhanced the 5‐HT‐induced relaxation producing a leftward shift of the 5‐HT concentration‐effect curve with a concentration‐ratio of 4.1. Rolipram caused a concentration‐dependent relaxation (EC50 = 564.8 nM) and at 200 nM caused a leftward shift of the concentration‐effect curve to 5‐HT with a concentration‐ratio of 5.5.
Application of the adenylyl cyclase inhibitor, SQ 22536 (0.1 mM), and the protein kinase inhibitors, H7 (100 nM) and H89 (200 nM), inhibited the relaxant effect of 5‐HT inducing a rightward shift of the concentration‐effect curve with concentration‐ratios of 10.1, 2.7 and 4.2 respectively.
Forskolin stimulated cyclic AMP production and caused a relaxation. The maximum relaxant effect of forskolin (6 μm, 13.8±1.9 cm.s) was not significantly different from the maximum relaxant effect of 5‐HT (10 μm, 12.7±4.9 cm.s). However, the cyclic AMP levels stimulated by forskolin (6 μm, 49.3±6.6 pmol mg−1) were markedly greater than those stimulated by 5‐HT (10 μm, 7.6±2.0 pmol mg−1).
In conclusion, these results indicate that the 5‐HT4 receptors of the circular smooth muscle of human colon mediate relaxation and inhibition of spontaneous contractions via activation of adenylyl cyclase, formation of cyclic AMP and activation of protein kinase A.
Neuroprotective properties of a protein kinase inhibitor against ischaemia‐induced neuronal damage in rats and gerbils
Authors: Satoh S. , Ikegaki I. , Suzuki Y. , Asano T. , Shibuya M. , Hidaka H. 
Published: July 2012

. The neuroprotective properties of fasudil (HA1077), a novel protein kinase inhibitor, were evaluated in two animal models of cerebral ischaemia: transient bilateral carotid artery occlusion in Mongolian gerbils and cerebral microembolization in rats.
. The cytoprotective effect of fasudil on delayed neuronal death in gerbils was compared with the effects of nimodipine, a calcium channel antagonist and ozagrel, a thromboxane A2 synthetase inhibitor. The average of the neuronal cell density in the ischaemic control group was 17.8 ± 2.1 cells mm−1, whereas fasudil (30 mg kg−1) significantly diminished the loss of CA1 neurones with the average of the neuronal cell density of 101.0 ± 22.0 cells mm−1; nimodipine (10 mg kg−1) and ozagrel (30 mg kg−1) did not significantly protect against the ischaemia‐induced neuronal loss.
. In the rat model, the effects of fasudil on the histological and neurological consequences of cerebral microembolization produced via the injection of microspheres were examined. Twenty‐four hours after the injection of microspheres into the internal carotid artery, all animals in the control group showed typical symptoms of stroke. Neurological function was significantly improved in the fasudil‐treated animals. In the controls, the infarcted area in a cortical slice selected to include the hippocampal area was 0.25 ± 0.01 cm2 (mean ± s.e.mean) (43.9 ± 2.4% of cortical section of the half hemisphere); the difference was significant compared to the mean area of 32.7 ± 2.8 and 21.5 ± 4.8% observed in rats treated with fasudil (3, 10 mg kg−1), respectively. Fasudil (10 mg kg−1) significantly suppressed the increased water content in ischaemic brain tissues (saline‐treated rats, 82.4 ± 0.2% vs fasudil‐treated rats, 81.0 ± 0.4%).
. These results suggest that: (i) various protein kinases are involved in the pathogenesis of ischaemic injury; and (ii) the inhibition of protein kinases may be efficacious in preventing neuronal death, thus improving neurological function in the brain damage associated with ischaemic stroke.
Characterization of the PGE2 receptor subtype in bovine chondrocytes in culture
Authors: de Brum‐Fernandes Artur J. , Morisset Sophie , Bkaily Ghassan , Patry Caroline 
Published: July 2012

. Prostaglandin E2 (PGE2) is an autacoid that decreases proteoglycan synthesis, increases metalloprotease production by cultured chondrocytes, and can modulate some of the actions of interleukin‐1 on cartilage. The objective of the present study was to characterize the subtype of prostaglandin E2 receptor present in bovine chondrocytes in culture.
. Primary cultures of articular chondrocytes were prepared from slices of bovine carpal cartilage by sequential digestion with type III hyaluronidase, trypsin, type II collagenase, followed by overnight incubation in Dulbecco's Modified Eagle's Medium (DMEM) with type II collagenase, washing, and seeding at a density of 2 × 105 cells cm−2 in DMEM with 10% foetal bovine serum.
. PGE2 and carbaprostacyclin induced dose‐dependent increases in intracellular cyclic AMP in bovine chondrocytes in culture. The potencies of these compounds were different, and maximal doses of PGE2 and carbaprostacyclin had an additive effect. PGD2 induced a small increase in intracellular cyclic AMP only at a high concentration (10−5 m).
. PGE2 was more potent that the EP2 agonist 11‐deoxy‐PGE1 at inducing increases in intracellular cyclic AMP. The EP2 agonist butaprost, however, induced only a small increase at a concentration of 10−5 m. 17‐Phenyl‐PGE2 (EP1 agonist), sulprostone and MB 28767 (15S‐hydroxy‐9‐oxo‐16‐phenoxy‐γ‐tetranorprost‐13E‐enoic acid) (EP3 agonists) did not induce an increase in intracellular cyclic AMP at concentrations up to 10−5 m.
. The EP4 antagonist AH 23848B ([1α(Z),2β,5α]‐(±)‐7‐[5‐[[(1,1′‐biphenyl)‐4‐yl]methoxy]‐2‐(4‐morpholinyl)‐3‐oxocyclopentyl]‐5‐heptenoic acid) antagonized PGE2 but not carbaprostacyclin effects on intracellular cyclic AMP. The Schild plot slope was different from 1 but this could be due to an interaction of PGE2 with IP receptors in high doses. The exact nature of the antagonism by compound AH 23848B could not be definitely established in these experimental conditions.
. Neither PGE2 nor any of its analogues inhibited the increase in intracellular cyclic AMP induced by forskolin, and pertussis toxin did not alter the response to PGE2, suggesting that no Gi‐coupled PGE2 receptors are present in these cells. Stimulation with PGE2 did not induce significant increases in intracellular inositol‐trisphosphate levels nor increases in intracellular free calcium as determined by confocal microscopy, suggesting the absence of phospholipase‐C‐coupled or of calcium channel‐coupled PGE2 receptors in bovine chondrocytes in these experimental conditions.
. These results show for the first time that bovine chondrocytes in culture present a functional PGE2 receptor that has some pharmacological characteristics of an EP4 subtype, as well as an IP receptor.
Mediation by 5‐HT3 receptors of an excitatory effect of 5‐HT on dorsal vagal preganglionic neurones in anaesthetized rats: an ionophoretic study
Authors: Wang Yun , Ramage Andrew G. , Jordan David 
Published: July 2012

. Extracellular recordings were made from 141 vagal preganglionic neurones in the dorsal vagal nucleus (DVN). The effects of ionophoretic administration of 5‐hydroxytryptamine (5‐HT), the 5‐HT3 receptor agonist, phenylbiguanide (PBG) and the antagonists, granisetron and tropisetron (ICS 205–930) on these vagal preganglionic neurones were studied in pentobarbitone sodium anaesthetized rats.
. Ionophoretic application of 5‐HT at low currents (< 10 nA) increased the activity in 46 (73%) of 63 neurones tested. Application of granisetron (5–20 nA) or tropisetron (5–20 nA) abolished or attenuated the 5‐HT excitatory responses in 8 out of 11 and 5 out of 5 neurones respectively. At the currents used, neither antagonist had any effect on baseline firing rate.
. Ionophoresis of the selective 5‐HT3 receptor agonist, phenylbiguanide (0–40 nA) excited 54 (82%) of the 66 vagal neurones tested, whilst the remaining 12 neurones were unaffected.
. Granisetron applied either ionophoretically (8/11) or intravenously (3/3), abolished or attenuated the excitations evoked by PBG. Similarly, tropisetron administered either ionophoretically (2/3) or intravenously (2/2), attenuated the PBG excitation. In contrast, the PBG excitations were unaffected by the 5‐HT2 receptor antagonist, cinanserin (2/2), and the selective 5‐HT1A receptor antagonist, WAY‐100802 (6/6).
. In conclusion, excitation of vagal preganglionic neurones evoked by ionophoretic application of 5‐HT is mediated in part by 5‐HT3 receptors and activation of 5‐HT3 receptors on and/or in the vicinity of vagal motoneurones causes excitation of these neurones.
Interleukin‐1β stimulation of 45 Ca2+ release from rat striatal slices
Authors: Palmi Mitri , Frosini Maria , Sgaragli Gianpietro 
Published: July 2012

. Previous observations that centrally injected interleukin‐1β (IL‐1β) into rabbits induces a sustained rise in cerebrospinal fluid (CSF) Ca2+ concentration ([Ca2+]) as well as fever, prompted us to undertake an in vitro study to corroborate the in vivo results and gain insight as to the source and mechanism of IL‐1β‐induced Ca2+ mobilization.
. IL‐1β treatment of rat striatal slices preloaded with 45Ca2+ elicited a rise in spontaneous 45Ca2+ release which was dose‐dependent, delayed in onset and of extended duration. At concentrations of 1, 5 and 10 ng ml−1, the 45Ca2+ efflux increased by 6.3 ± 1.3 (s.e.mean), 33.4 ± 5.0 and 159 ± 10.5% respectively.
. At 1 μg ml−1, the specific IL‐1 receptor antagonist, IRAP, antagonized the effect induced by, 10 ng ml−1 IL‐1.
. Caffeine 10 mM, which failed to release calcium on its own, potentiated IL‐1‐elicited 45Ca2+ release.
. Perfusion with a Ca2+‐free medium obtained by use of excess EGTA (3 mM) or in the presence of the Ca2+ channel blocker, nifedipine (3 × 10−8 m) abolished the potentiating effect of caffeine without affecting the IL‐1‐induced 45Ca2+ release.
. Preincubation of slices for 4 h with Bordetella pertussis toxin (PTX, 1.3 μg ml−1) did not change the pattern of Ca2+ efflux in response to IL‐1.
. In conclusion, these data indicate that IL‐1 stimulates calcium release from brain tissue by a specific, receptor‐mediated mechanism which partly depends on extracellular calcium but does not involve a PTX‐sensitive G protein as part of the transducing signal.
Analysis of variation in L‐365,260 competition curves in radioligand binding assays
Authors: Harper E.A. , Roberts S.P. , Shankley N.P. , Black J.W. 
Published: July 2012

. For several years, we have used the cholecystokinin (CCK)B/gastrin receptor selective antagonist, L‐365,260, as a reference compound in a variety of studies in CCKB/gastrin receptor radioligand binding assays. Here, we have analysed the competition curve data sets obtained between L‐365,260 and [125I]‐BH‐CCK8S in guinea‐pig gastric gland and mouse and rat cerebral cortex preparations.
. Competition curves obtained for L‐365,260 in the mouse cortex assay were not different from rectangular hyperbolae (slope = 1.01 ± 0.02) implying the presence of a single population of binding sites (pKI = 8.41 ± 0.01; data from 47 experiments, slope constrained to unity). However, in the rat cortex and guinea‐pig gastric gland assays, the mean slope of the competition curves was significantly less than one and the mean apparent pKI significantly lower than that obtained in the mouse cortex (slope = 0.85 ± 0.03, 0.90 ± 0.03; apparent pKI = 7.98 ± 0.05, 8.07 ± 0.05; 48 and 45 experiments, in rat and guinea‐pig, respectively). The distribution of the individual pK1 and slope estimates of the competition curves in these two assays was consistent with expectations for the variable expression (in terms of absolute number and proportion) of two binding sites. The two sites were characterized by pK1 values for L‐365,260 of 8.50 ± 0.04 and 8.48 ± 0.04 for the high affinity site and 7.32 ± 0.04 and 7.22 ± 0.06 for the low affinity site in guinea‐pig and rat, respectively.
. The affinity estimates for L‐365,260, although obtained on different tissues, are consistent with data obtained from the analysis of L‐365,260 antagonism of pentagastrin‐stimulated responses in mouse and rat stomach (acid secretion) and guinea‐pig gastric muscle (isotonic contraction) assays. To this extent, these data suggest the existence of two CCKB/gastrin receptor subtypes.
Induction of calcium release from sarcoplasmic reticulum of skeletal muscle by xanthone and norathyriol
Authors: Kang J.J. , Cheng Y.W. , Ko F.N. , Kuo M.L. , Lin C.N. , Teng C.M. 
Published: July 2012

. Effects of xanthone and its derivative, 1,3,6,7‐tetrahydroxyxanthone (norathyriol), on Ca2+ release and ryanodine binding were studied in isolated sarcoplasmic reticulum (SR) vesicles from rabbit skeletal muscle.
. Both xanthone and norathyriol dose‐dependently induced Ca2+ release from the actively loaded SR vesicles which was blocked by ruthenium red, a specific Ca2+ release inhibitor, and Mg2+.
. Xanthone and norathyriol also dose‐dependently increased apparent [3H]‐ryanodine binding. Norathyriol, but not xanthone, produced a synergistic effect on binding activation when added concurrently with caffeine.
. In the presence of Mg2+, which inhibits ryanodine binding, both caffeine and norathyriol, but not xanthone, could restore the binding to the level observed in the absence of Mg2+.
. Xanthone activated the Ca2+‐ATPase activity of isolated SR vesicles dose‐dependently reaching 70% activation at 300 μm.
. When tested in mouse diaphragm, norathyriol potentiated the muscle contraction followed by twitch depression and contracture in either a Ca2+‐free bathing solution or one containing 2.5 mM Ca2+. These norathyriol‐induced effects on muscle were inhibited by pretreatment with ruthenium red or ryanodine.
. These data suggest that xanthone and norathyriol can induce Ca2+ release from the SR of skeletal muscle through a direct interaction with the Ca2+ release channel, also known as the ryanodine receptor.
Analysis of the variation in the action of L‐365,260 at CCKB/gastrin receptors in rat, guinea‐pig and mouse isolated gastric tissue assays
Authors: Roberts S.P. , Harper E.A. , Watt G.F. , Gerskowitch V.P. , Hull R.A.D. , Shankley N.P. , Black J.W. 
Published: July 2012

. Since L‐365,260 was first described as a selective antagonist at cholecystokinin (CCK)B/gastrin receptors, we have used it periodically as a reference compound in isolated tissue assays of guinea‐pig gastric muscle and lumen‐perfused stomachs from mouse and immature rat. L‐365,260 behaved as a surmountable antagonist and produced parallel rightward shifts of pentagastrin con***ćentration‐effect curves in each of the replicate experiments. The experiments were performed by several different experimenters in the same laboratories over a five year period.
. In the isolated, lumen‐perfused, immature rat stomach assay, L‐365,260 behaved as a simple competitive antagonist (Schild plot slope = 1.00 ± 0.10, pKB = 7.54 ± 0.03 from a global analysis of the data) acting at a homogeneous population of receptors in five separate, highly‐reproducible, experiments. In contrast, the replicate data sets obtained from the interaction in the isolated, lumen‐perfused mouse stomach and guinea‐pig gastric muscle assays, over the same period, were not consistent with the presence of a single receptor population. The guinea‐pig gastric muscle data were relatively reproducible between experiments but some individual Schild plot slopes and the slope estimated from a global analysis of all the data were significantly less than unity (slope = 0.80 ± 0.07, pA2 = 8.56 ± 0.05 from the global analysis). The data obtained in the mouse stomach were significantly more variable than that obtained in the same assay, during the same period, from the interaction between histamine and the H2‐receptor antagonist, famotidine. The individual Schild plot slopes ranged from being very flat (0.20) to being not significantly different from unity (1.23) and the pA2 values ranged from 7.68 to 8.70.
. Overall, the data could be accounted for by assuming the variable expression of two receptor subtypes across the assays. The rat stomach appeared to express a single receptor characterized by a low affinity constant for L‐365,260 (pKB ∼ 7.5). The guinea‐pig gastric muscle and mouse stomach data could be explained by the presence of this receptor and a second one characterized by a high affinity constant for L‐365,260 (pKB ∼ 8.6). The activity of the two proposed receptor subtypes was consistent between experiments in the guinea‐pig and the high affinity receptor appeared to be predominant. In contrast, the mouse stomach data could only be simulated by assuming that the proportion and absolute number of each subtype varied significantly between the replicate experiments.
. The L‐365,260 affinity estimates at the inferred receptor subtypes were indistinguishable from those obtained in a corresponding analysis of the behaviour of L‐365,260 in CCKB/gastrin receptor radioligand binding experiments in guinea‐pig gastric gland and mouse and rat cerebral cortex preparations.
Potent block of volume‐activated chloride currents in endothelial cells by the uncharged form of quinine and quinidine
Authors: Voets Thomas , Droogmans Guy , Nilius Bernd 
Published: July 2012

. The effects of quinine and quinidine on the volume‐activated chloride current (ICl(vol)) in cultured endothelial cells from bovine pulmonary artery were studied by use of the whole‐cell patch‐clamp technique.
. At pH 7.4 both quinine and quinidine induced a fast and reversible block of ICl(vol) with Ki values of 20 ± 4 μm and 30 ± 10 μm, respectively.
. The blocking efficiency of both drugs increased dramatically with increasing extracellular pH, indicating that the blockade is mediated by the uncharged form of quinine and quinidine.
. These results suggest a hydrophobic interaction with high affinity between volume‐activated chloride channels and uncharged quinine and quinidine within the membrane bilayer of endothelial cells.
Effect of opiates on transmitter release from visualized hypogastric boutons innervating the rat pelvic ganglia
Authors: Warren Darren A. , Lavidis Nickolas A. 
Published: July 2012

The effect of opiates on neurotransmission between visualized hypogastric nerve boutons and postganglionic cell bodies has been examined using extracellular recording of nerve bouton impulses (NBIs) and excitatory postsynaptic currents (e.p.s.cs).
Morphine (10 to 40 μm) did not affect neurotransmission in the ganglia. Dynorphin‐A (4 μm) and U50488H (1 μm) decreased quantal transmitter release and naloxone (10 μm) reversed these effects.
Morphine (10 μm), dynorphin‐A (4 μm) and U50488H (1 μm) did not affect either the time course or consistency with which the NBI was recorded.
Dynorphin‐A (1 to 4 μm) and U50488H (1 μm) decreased the average amplitude of e.p.s.cs by increasing the number of failures to release quanta from single or small groups of 2 to 4 boutons during continuous nerve stimulation at 0.1 Hz.
The decrease in quantal release induced by dynorphin‐A and U50488H in 0.2 to 0.5 mM [Ca2+]o was readily reversed by increasing the extracellular calcium ion concentration to 1 mM.
It was concluded that k‐opioid receptors are located on the boutons of the hypogastric nerve and when activated by k‐opioid receptor agonists reduce quantal release without affecting the NBI.
Identification of potent P2Y‐purinoceptor agonists that are derivatives of adenosine 5′‐monophosphate
Authors: Boyer José L. , Siddiqi Suhaib , Fischer Bilha , Romero‐Avila Teresa , Jacobson Kenneth A. , Harden T. Kendall 
Published: July 2012

A series of chain‐extended 2‐thioether derivatives of adenosine monophosphate were synthesized and tested as agonists for activation of the phospholipase C‐linked P2Y‐purinoceptor of turkey erythrocyte membranes, the adenylyl cyclase‐linked P2Y‐purinoceptor of C6 rat glioma cells, and the cloned human P2U‐receptor stably expressed in 1321N1 human astrocytoma cells.
Although adenosine monophosphate itself was not an agonist in the two P2Y‐purinoceptor test systems, eleven different 2‐thioether‐substituted adenosine monophosphate analogues were full agonists. The most potent of these agonists, 2‐hexylthio AMP, exhibited an EC50 value of 0.2 nM for activation of the C6 cell receptor. This potency was 16,000 fold greater than that of ATP and was only 10 fold less than the potency of 2‐hexylthio ATP in the same system. 2‐hexylthio adenosine was inactive.
Monophosphate analogues that were the most potent activators of the C6 cell P2Y‐purinoceptor were also the most potent activators of the turkey erythrocyte P2Y‐purinoceptor. However, agonists were in general more potent at the C6 cell receptor, and potency differences varied between 10 fold and 300 fold between the two receptors.
Although 2‐thioether derivatives of adenosine monophosphate were potent P2Y‐purinoceptor agonists no effect of these analogues on the human P2U‐purinoceptor were observed.
These results support the view that a single monophosphate is sufficient and necessary for full agonist activity at P2Y‐purinoceptors, and provide insight for strategies for development of novel P2Y‐purinoceptor agonists of high potency and selectivity.