bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modulation of antagonist binding to histamine H1‐receptors by sodium ions and by 2‐amino‐2‐hydroxymethyl‐propan‐1,3‐diol HCl
Authors: Gibson W.J. , Roques T.W. , Young J.M. 
Published: July 2012

NaCl (100 mm) reduced the potency of (+)‐N‐methyl‐4‐methyldiphenhydramine ((+)‐QMDP) as an inhibitor of the binding of [3H]‐mepyramine to histamine H1‐receptors on guinea‐pig cerebellar membranes to a greater extent than that of mepyramine, consistent with the greater inhibitory effect of Na+on the binding of [3H]‐QMDP than on the binding of [3H]‐mepyramine.
The concentration of 2‐amino‐2‐hydroxymethyl‐propan‐1,3‐diol HCl (Tris, HCl) buffer, pH 7.5, present had little effect on the temelastine‐insensitive binding of [3H]‐mepyramine, but caused a concentration‐dependent inhibition of the binding of [3H]‐mepyramine sensitive to 1 μm temelastine (H1‐receptor binding), with an approximate IC50 of 75 mm, assuming that complete inhibition would have been achieved.
Inhibition of [3H]‐mepyramine binding by Na+was more marked in 10 mm than in 50 mm Tris HCl and was not evident in 200 mm Tris HCl.
The Kd for the temelastine‐sensitive binding of [3H]‐mepyramine measured in 10 mm Tris HCl, 0.24 ± 0.01 nm, was increased by 2.2 ± 0.2 fold by 100 mm NaCl, without any significant change in the maximum binding (Bmax). The Bmax for [3H]‐mepyramine was similarly unchanged in 50 mm Tris HCl, but the Kd was increased 2.5 ± 0.2 fold.
The Kd for the temelastine‐sensitive binding of [3H]‐mepyramine was also increased in 50 mm, compared with 10 mm, N‐[2‐hydroxyethyl]piperazine‐N′‐[2‐ethanesulphonic acid] KOH (HEPES.KOH) buffer (Kd 0.25 ± 0.02 nm in 10 mm HEPES), but the evidence for an interaction between HEPES and Na+was less clear.
The effect of 100 mm NaCl on the inhibition of [3H]‐mepyramine binding in 10 mm Tris HCl was examined for a range of antagonists. The decrease in potency caused by Na+was greatest for triprolidine, (+)‐chlorpheniramine and benzilylcholine (9.6–10.3 fold increase in Kd values) but the binding of mepyramine and promethazine was much less affected (1.8 and 1.9 fold increase in Kd respectively). The Kd for temelastine was not significantly changed. In contrast to the general decrease in antagonist affinity in the presence of Na+, the Kd for MDL 16,455A (4‐[1‐hydroxy‐4‐[4‐(hydroxydiphenylmethyl)‐1‐piperidinyl]butyl]‐α,α‐dimethylbenzene acetic acid) was increased, but only by 1.5 fold.
It is concluded that Na+can act as an allosteric effector of the binding of antagonists at the histamine H1‐receptor. Tris HCl also appears to have an allosteric action at the H1‐receptor.
Loss of contractile activity of endothelin‐1 induced by electrical field stimulation‐generated free radicals
Authors: Yasuda Nobuyuki , Kasuya Yoshitoshi , Yamada Goro , Hama Hiroshi , Masaki Tomoh , Goto Katsutoshi 
Published: July 2012

Electrical field stimulation (EFS; 10 V, 10 Hz, 2 ms) of porcine coronary artery strips precontracted with 10 nm endothelin‐1 (ET‐1) for 5 min caused a biphasic response, consisting of a slight contraction during EFS and a marked and irreversible relaxation just after EFS. This irreversible relaxation after EFS has never been investigated. In the present study, we have investigated the mechanism of the relaxation after EFS.
The EFS‐induced response was not affected by the presence or absence of endothelium and was insensitive to 10 μm tetrodotoxin (TTX).
In the presence of free radical scavengers (40 u ml−1 superoxide dismutase (SOD), 1200 u ml−1 catalase or 80 mm d‐mannitol), the relaxation after EFS was significantly inhibited. Moreover, relaxation after EFS was not observed in porcine coronary artery strips precontracted with 20 mm KCl.
In a cascade experiment, EFS of Krebs‐Ringer solution containing 10 nm ET‐1 induced marked suppression of the contractile activity of ET‐1 in porcine coronary artery strips, which was in accord with the observed decrease in release of immunoreactive ET‐1 (ir‐ET‐1). This effect of EFS was significantly inhibited by each of the free radical scavengers, 3 mm vitamin C, 40 u ml−1 SOD, 1200 u ml−1 catalase and 80 mm d‐mannitol.
The exchange of 95% O2/5% CO2 gas for 95% N2/5% CO2 gas significantly inhibited the EFS‐induced decrease in release of ir‐ET‐1.
Neither superoxide anions generated by xanthine (10 μm) plus xanthine oxidase (0.1 u ml−1) nor hydrogen peroxide (10 μm) exogenously added to Krebs‐Ringer solution containing 10 nm ET‐1 affected the level of ir‐ET‐1.
Generation of hydroxyl radicals was detected in the EFS‐applied Krebs‐Ringer solution. The EFS‐induced generation of hydroxyl radicals was dependent on the period of stimulation and O2‐bubbling, and significant generation of hydroxyl radicals was detectable with stimulation of over 5 min. Moreover, hydroxyl radicals generated in 50 mm NaCl solution containing 10 nm ET‐1 by H2O2 plus Fe2+, i.e. the Fenton reaction, significantly decreased the level of ir‐ET‐1.
These findings suggest that oxygen‐derived hydroxyl radicals generated by EFS of porcine coronary artery strips inactivate ET‐1, probably by structural modification. Thus, porcine coronary artery strips precontracted with ET‐1 are potently relaxed by EFS.
The involvement of bradykinin B1 and B2 receptor mechanisms in cytokine‐induced mechanical hyperalgesia in the rat
Authors: Davis A.J. , Perkins M.N. 
Published: July 2012

Interleukin‐1β (IL‐1β), IL‐2 and IL‐8 induced a mechanical hyperalgesia following intra‐articular (i.artic.) injection into rat knee joints, whereas IL‐6 and tumour necrosis factor α (TNF‐α) were without effect.
Co‐administration of IL‐1 receptor antagonist (0.1 μg) with IL‐1β (1 u), IL‐2 (10 u) or IL‐8 (0.1 u) prevented the subsequent development of the hyperalgesia.
Co‐administration of desArg9Leu8BK (0.5–5 nmol) with IL‐1β (1 u), IL‐2 (10 u) or IL‐8 (0.1 u) reduced the level of hyperalgesia at 1, 4 and 6h post administration, whereas Hoe 140 (5 pmol) antagonized the hyperalgesia only at the 1 h time point.
Intravenous administration of desArg9Leu8BK (10 nmol kg−1) or Hoe 140 (100 pmol kg−1) following IL‐1β (1 u), IL‐2 (10 u), or IL‐8 (0.1 u) reversed the subsequent hyperalgesia.
Administration of desArg9BK into joints 24 h after pre‐treatment with IL‐1β (1 u) produced analgesia at low doses (50 pmol) and hyperalgesia at a higher dose (0.5 nmol). Both these effects were blocked by desArg9Leu8BK (0.5 nmol).
Administration of desArg9BK (0.5 nmol i.artic.) to animals 24 h after pre‐treatment with IL‐2 (1–100 u) or IL‐8 (0.1–10 u) had no effect on the load tolerated by the treated joint.
Administration of indomethacin (1 mg kg−1, s.c.) prior to IL‐1β (1 u i.artic.) prevented the development of hyperalgesia. Administration of desArg9BK (5 pmol‐0.5 nmol, i.artic.) to animals 24 h after indomethacin and IL‐1β pretreatment had no effect on the load tolerated by the treated joint.
These data suggest that both bradykinin B1 and B2 receptors are involved in the induction and maintenance of cytokine‐induced hyperalgesia. They also show that the induction of B1 receptor‐mediated hyperalgesia requires both cyclo‐oxygenase products and IL‐1 in vivo.
Effect of in vivo desensitization to leukotriene B4 on eosinophil infiltration in response to C5a in guinea‐pig skin
Authors: Pettipher E.R. , Salter E.D. , Showell H.J. 
Published: July 2012

The effect of in vivo desensitization to leukotriene B4 (LTB4) on eosinophil infiltration in response to recombinant C5a was examined in guinea‐pig skin.
LTB4 (10–300 ng) and C5a (1–10 μg) caused a dose‐dependent increase in the levels of eosinophil peroxidase activity (a measure of eosinophil infiltration) 4h after injection into guinea‐pig skin. Leukotriene B4 and C5a were approximately equipotent on a molar basis. Platelet activating factor (0.01–10 μg) also caused eosinophil accumulation but was much less active than LTB4 or C5a.
20‐Hydroxy‐LTB4 caused a dose‐dependent desensitization of eosinophil responses to LTB4 (ED50 = 1.6 μg kg−1, s.c.) and partially reduced responses to C5a. At a dose of 20‐hydroxy‐LTB4 (10 μg) which inhibited responses to LTB4 completely, responses to C5a were reduced by 56.5 ± 1.8% (n = 5). The structurally related metabolite of 20‐hydroxy‐LTB4, 20‐carboxy‐LTB4, which does not cause desensitization to the effects of LTB4, did not inhibit eosinophil infiltration in response to C5a.
The LTB4 receptor antagonist, SC‐41,930 (10 mg kg−1, p.o.), also inhibited eosinophil accumulation in response to C5a by 63.0 ± 3.9% (n = 5) at a dose which inhibited responses to LTB4 by 86.5 ± 1.9% (n = 5).
These data indicate that eosinophil infiltration in response to C5a may, in part, be mediated by the generation of secondary chemotactic factors such as LTB4.
Effects of chronic infusions of α‐trinositol on regional and cardiac haemodynamics in conscious rats
Authors: Gardiner S.M. , Kemp P.A. , Fallgren B. , Bennett T. 
Published: July 2012

Male, Long Evans rats (350–450 g) were chronically instrumented for the measurement of renal, mesenteric and hindquarters haemodynamics, and were given three consecutive, 24 h infusions of vehicle (sterile saline at 0.3 ml h−1; n = 8) or α‐trinositol (d‐mjyo‐inositol‐1,2,6‐triphosphate) at 5, 20 and 80 mg kg−1 h−1 (0.3 ml h−1; n = 9). During infusion of α‐trinositol at 5 or 20 mg kg−1 h−1, cardiovascular changes were little different from those seen during saline infusion. However, during infusion of α‐trinositol at 80 mg kg−1 h−1 there were increases in hindquarters vascular conductance, renal flow and vascular conductance, that were all significantly different from the changes seen in the saline group. Infusion of α‐trinositol at the high dose in naive rats (n = 8) had even more marked vasodilator effects.
Two groups of rats (n = 8 in each), chronically instrumented for the measurement of cardiac haemodynamics, were given 48 h infusions of saline (0.3 ml h−1) or α‐trinositol (2 mg kg−1 bolus, 80 mg kg−1 h−1 infusion at 0.3 ml h−1). During the infusion of saline, there were slight reductions in heart rate, cardiac index, peak aortic flow, dF/dtmax and central venous pressure. In the animals receiving α‐trinositol, with the exception of central venous pressure, all the above variables, together with total peripheral conductance, increased.
These results, collectively, indicate that incremental infusions of α‐trinositol do not reveal its full vasodilator potential, possibly due to concurrent activation of counter‐regulatory vasoconstrictor mechanisms. However, infusion of α‐trinositol at a high dose causes substantial increases in renal, mesenteric and hindquarters flows and vascular conductances, supported by significant increases in indices of cardiac inotropism. Such effects, in the absence of significant hypotension, tachycardia or signs of desensitization, give α‐trinositol a unique cardiovascular profile.
Factors underlying the increased sensitivity to field stimulation of urinary bladder strips from streptozotocin‐induced diabetic rats
Authors: Tammela Teuvo L.J. , Briscoe Janice A.K. , Levin Robert M. , Longhurst Penelope A. 
Published: July 2012

The responses of bladder strips from control, streptozotocin‐diabetic, and sucrose‐drinking rats to electrical field stimulation were investigated. Sucrose‐drinking rats were included as additional controls because they have enlarged bladders as a result of non‐diabetic diuresis.
Bladder strips from diabetic rats developed more spontaneous activity than those from the two control groups. Indomethacin reduced the amplitude and frequency of spontaneous contractions suggesting that they resulted from endogenous prostaglandin formation. Tetrodotoxin (TTX) had little effect, while α,β‐methylene ATP caused increases in spontaneous activity.
Bladder strips from diabetic rats responded to field stimulation with greater contractions than controls in the absence of antagonists as well as in the presence of atropine and α,β‐methylene ATP. Increasing TTX concentrations caused a step‐wise depression of the contractile response to electrical stimulation which was not affected by preincubation with either atropine or α,β‐methylene ATP.
Atropine and indomethacin had no effect on stength‐duration curves constructed to measure threshold contractile responses to five pulses stimulation. The curves were shifted to the right by both TTX and α,β‐methylene ATP, indicating that the responses were neurogenic in nature and at least partially, the result of stimulation of P2‐purinoceptors. In the absence of drugs, bladder strips from diabetics responded at lower voltages and pulse widths than those of control and sucrose‐drinking rats, suggesting that they were more excitable.
The response curve of bladder strips from diabetics to field stimulation at increasing voltage was shifted upwards and to the left compared to strips from control or sucrose‐drinking rats.
Bladder strips from diabetics responded to stimulation at increasing pulse width with greater responses than those from control or sucrose‐drinking rats. At 1.0 ms pulse width, the TTX‐resistant response of strips from diabetic rats was still greater than that of the other groups, indicating that a myogenic component was also involved.
The data suggest that bladder strips from diabetic rats are more excitable than those of control or sucrose‐drinking rats. This may result from diabetes‐induced decreases in bladder lipid or other membrane changes, and/or be a result of partial depolarization, perhaps related to diabetic neuropathy.
Benzodiazepine‐induced intestinal motor disturbances in rats: mediation by ω2 (BZ2) sites on capsaicin‐sensitive afferent neurones
Authors: Bonnafous Cécile , Scatton Bernard , Buéno Lionel 
Published: July 2012

The central and peripheral effects of the ω (benzodiazepine) site ligands, clonazepam, alpidem, zolpidem, triazolam, flumazenil, ethyl β carboline‐3‐carboxylate (β‐CCE) and N‐methyl β carboline‐3‐carboxylate (β‐CCM) on intestinal myoelectrical activity were evaluated in conscious rats, chronically fitted with Nichrome electrodes implanted on the duodenum and jejunum. The localization of the ω (benzodiazepine) receptors involved in these effects was evaluated by use of systemic and perivagal capsaicin treatments.
When administered intraperitoneally (i.p.) the ω site inverse agonists β‐CCE and β‐CCM, and the ω site antagonist flumazenil, did not affect the duodeno‐jejunal motility. Alpidem and zolpidem, two selective ω1 site agonists induced an inhibition of migrating myoelectric complexes (MMCs) only at a high dose (5 mg kg−1). In contrast, clonazepam (a mixed ω1/ω2 agonist) and triazolam (a preferential ω2 site agonist) disrupted the MMC‐pattern at doses as low as 0.05 mg kg−1, the effect of triazolam being of much longer duration than that of clonazepam. None of these drugs altered MMC‐pattern when administered centrally (i.c.v.).
Administered i.p. or i.c.v. prior to triazolam, alpidem blocked the effect of triazolam on duodeno‐jejunal spike activity. Administered i.p. prior to triazolam, flumazenil suppressed the triazolam‐induced MMC‐disruption. Previous systemic but not perivagal capsaicin treatment suppressed the effects of clonazepam on MMCs.
It is concluded that ω‐site agonists but not antagonist or inverse agonists, administered systemically induce intestinal motor disturbances which may be linked to activation of ω2 (BZ2) sites located on nonvagal capsaicin‐sensitive afferent neurones.
Suppression of VEGF‐induced angiogenesis by the protein tyrosine kinase inhibitor, lavendustin A
Authors: Hu D.E. , Fan T.‐P.D. 
Published: July 2012

Vascular endothelial growth factor (VEGF) is a heparin‐binding angiogenic factor which specifically acts on endothelial cells via distinct membrane‐spanning tyrosine kinase receptors. Here we used the rat sponge implant model to test the hypothesis that the angiogenic activity of VEGF can be suppressed by protein tyrosine kinase (PTK) inhibitors.
Neovascular responses in subcutaneous sponge implants were determined by measurements of relative sponge blood flow by use of a 133Xe clearance technique, and confirmed by histological studies and morphometric analysis.
Daily local administration of 250 ng VEGF165 accelerated the rate of 133Xe clearance from the sponges and induced an intense neovascularisation. This VEGF165‐induced angiogenesis was inhibited by daily co‐administration of the selective PTK inhibitor, lavendustin A (10 μg), but not its negative control, lavendustin B (10 μg). Blood flow measurements and morphometric analysis of 8‐day‐old sponges showed that lavendustin A reduced the 133Xe clearance of VEGF 165‐treated sponges from 32.9 ± 1.5% to 20.9 ± 1.6% and the total fibrovascular growth area from 62.4 ± 6.1% to 21.6 ± 6.8% (n = 12, P <0.05).
Co‐injection of suramin (3 mg), an inhibitor of heparin‐binding growth factors, also suppressed the VEGF165‐elicited neovascular response. In contrast, neither lavendustin A nor suramin produced any effect on the basal sponge‐induced angiogenesis.
When given alone, low doses of VEGF165 (25 ng) or basic fibroblast growth factor (bFGF; 10 ng) did not modify the basal sponge‐induced neovascularisation. However, co‐administration of these two peptides to a single sponge together caused a significant increase in the rate of 133Xe clearance and angiogenesis similar to that seen with the high dose of VEGF 165 (250 ng) acting alone. This VEGF/bFGF neovascular response was also blocked by daily co‐administration of lavendustin A (10 μg), suramin (3 mg) or a monoclonal anti‐bFGF antibody (DG2, 1 μg), but not lavendustin B (10 μg).
These results suggest that selective inhibition of PTK could have therapeutic potential in angiogenic diseases where VEGF plays a dominant role. Furthermore, blockade of the angiogenic activity of VEGF and VEGF bFGF by suramin reveals an alternative strategy in angiosuppression.
Failure of nitric oxide donors to alter arrhythmias induced by acute myocardial ischaemia or reperfusion in anaesthetized rats
Authors: Barnes Christopher S. , Coker Susan J. 
Published: July 2012

The aim of the present studies was to examine the effects of nitric oxide donors on arrhythmias induced by coronary artery occlusion and reperfusion, and on cardiac cyclic nucleotides. Experiments were performed in pentobarbitone‐anaesthetized rats prepared for occlusion of the left coronary artery.
Sodium nitroprusside (0.1, 0.3 and 1 μg kg−1 min−1) had no significant effects on the incidence of ventricular tachycardia, total ventricular fibrillation or the mortality resulting from 25 min of acute myocardial ischaemia when compared with values in controls. In addition, there was no alteration in the number of ventricular premature beats that occurred in survivors.
3‐Morpholinosydnonimine‐N‐ethylcarbamide (SIN‐1, 10, 20 and 40 μg kg−1 min−1) caused marked hypotension but did not alter the incidence or severity of ischaemia‐induced arrhythmias. In rats subject to abrupt reperfusion after 5 min of myocardial ischaemia, lower doses of SIN‐1 (1, 3 and 10 μg kg−1 min−1) still caused significant reductions in systolic and diastolic blood pressure but were devoid of antiarrhythmic activity.
In separate experiments in sham‐operated rats, sodium nitroprusside (1 μg kg−1 min−1), isosorbide dinitrate (30 and 60 μg kg−1 min−1) and SIN‐1 (20 and 40 μg kg−1 min−1) had no significant effects on cardiac cyclic GMP content.
These results indicate that nitric oxide donors do not alter arrhythmias induced by acute coronary artery occlusion or reperfusion in anaesthetized rats. Although increases in total cardiac cyclic GMP could not be detected, the results suggest that, at least in the rat, cyclic GMP does not influence these arrhythmias.
Inhibitory action of SR33557 on L‐type calcium current in single ventricular myocytes of rat
Authors: Yasui Kenji , Palade Philip 
Published: July 2012

The effect of SR33557 on L‐type Ca2+ currents in rat ventricular myocytes was investigated by use of the whole‐cell patch‐clamp technique.
SR33557 inhibited Ca2+ current (ICa) in a concentration‐dependent manner without change in the current‐voltage relationship.
The inhibitory effect of SR33557 on ICa was dependent on the holding potential (Vh). The IC50 values were estimated to be 2.2 times 10−8 m at Vh = −50 mV and 9.0 times 10−6 m at Vh = −80 mV. SR33557 (10−7 m) shifted the steady state inactivation curve of ICa toward more negative potentials. Thus, the affinity of the drug for inactivated channels was considerably higher than for resting channels.
Blockade of ICa by SR33557 was both tonic and use‐dependent.
The time constant of onset of block was 36.4 s at − 50 mV and 41.9 ± 11.1 s at − 40 mV.
The time course of unblock was voltage‐dependent. The time constant declined from 400.7 ± 68.1 s at − 50 mV to 5.2 ± 1.2 s at − 80 mV.
The rate of block of ICa was related to the number of openings per unit time and to the amount of time spent depolarized. The affinity of drug for open channels was considered to be similar to that for inactivated channels.
These results suggest that SR33557 inhibits L‐type Ca2+ current through binding to both open and inactivated channels in rat ventricular myocytes.
Interacting roles of nitric oxide and ATP in the pulmonary circulation of the rat
Authors: Hasséssian Haroutioun , Burnstock Geoffrey 
Published: July 2012

The potentiating effect of NG‐nitro‐l‐arginine methyl ester, (l‐NAME) a nitric oxide synthesis inhibitor, on responses of the rat pulmonary vascular pressure (PVP) to purinoceptor agonists was examined.
At a constant flow of 23 ml min−1 the PVP was 22.4 ± 2.5 mmHg (n = 15), and treatment with 100 μm l‐NAME for 15 min was without effect on the PVP. After the tone was raised with 28 nmol 9,11‐dideoxy‐11α, 9α‐epoxymethano‐prostaglandin F2α (U‐46619), the PVP was 29.4 ± 3.3 mmHg and treatment with 100 μm l‐NAME was still without effect on the PVP. It appears that there is a graded release of nitric oxide in response to different levels of steady shear stress and in our experimental model the threshold for detection was not reached under basal conditions.
In contrast, when the circulation was challenged with 30 s step, additive increases in flow between 11 and 50 ml min−1 (n = 8), treatment with 100 μm l‐NAME produced a significant (P <0.05) increase in PVP suggesting that changes in flow‐derived forces evoke the release of nitric oxide. This was evident for flow rates above 30 ml min−1.
In preparations in which tone was raised with U‐46619, a dose of 1 times 10−8 mol ATP or 2‐meSATP evoked a drop in PVP while α,β‐meATP produced an increase in PVP under constant flow of 23 ml min−1. After treatment with 100 μm l‐NAME, all three purinoceptor agonists evoked an increase in PVP. The increase in PVP evoked by α,β‐meATP was not affected by l‐NAME. These results suggest that P2Y‐purinoceptor stimulation evokes the release of nitric oxide to produce vasodilatation.
Under conditions of constant flow and basal pressure, 100 μm l‐NAME significantly (P <0.05) potentiated the increase in PVP evoked by 1 times 10−6 mol ATP, although the increase evoked by 1 times 10−8 mol α,β‐meATP, which was of similar magnitude, was not affected. These results indicate that a blockade of evoked nitric oxide release is responsible for the potentiation of the increase in PVP evoked by ATP.
This study shows that, while nitric oxide does not appear to be released in the pulmonary circulation of the rat under constant flow conditions, nitric oxide release evoked by purinoceptor agonists attenuates increases in pulmonary vascular pressure.