bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inhibition by chloride channel blockers of anion secretion in cultured epididymal epithelium and intact epididymis of rats
Authors: Wong P.Y.D. 
Published: July 2012

Anion secretion by primary monolayer cultures of rat epididymal cells was studied by the short circuit current technique.
Monolayers had a transepithelial potential difference of 1.34 mV, apical side negative and a short circuit current of 2.45 μA cm−2. The transepithelial resistance was 504 Ω cm2.
Addition of anthracene‐9‐carboxylate (9‐AC) to the apical side caused a biphasic response, a decrease followed by an increase in the short circuit current (SCC) which then returned to the basal level. Addition of 9‐AC to the basolateral side also caused a biphasic response but the increase in current was sustained.
Addition of diphenylamine‐2‐carboxylate (DPC) and 5‐nitro‐2‐(3‐phenylpropylamino)‐benzoate (NPPB) caused an inhibition of the SCC when added to the apical or basolateral side.
When the epithelium was stimulated with adrenaline (0.23 μm, basolaterally), the SCC rose to a peak value of 10.36 μA cm−2 and then stabilized at 3.82 μA cm−2 after 15 min. Addition of 9‐AC to the apical side caused a triphasic response: a decrease, reversal to the original level followed by a slow inhibition which was sustained. The inhibition achieved at the steady state was concentration‐dependent with an apparent IC50 value of 2.51 mm. Addition of 9‐AC to the basolateral side produced a similar response but a time lag of 20 s was observed.
DPC and NPPB also caused the SCC to decrease when added to the apical side of the monolayers stimulated with adrenaline. The IC50 values were 0.148 mm and 0.049 mm for DPC and NPPB, respectively. Basolateral application also caused an inhibition but higher concentrations were required to inhibit 50% of the adrenaline stimulated SCC.
Serosal to mucosal flux of chloride was studied in intact epididymis luminally perfused in vivo. 9‐AC added to the luminal perfusion solution inhibited the C1 flux in a dose‐dependent manner with an IC50 value similar to that observed in cultured epithelium in vitro.
It is concluded that anion secretion by the epididymal cells may conform to models proposed for other Cl secreting epithelia and may involve anion diffusion across the apical channels which are blocked by Cl channel blockers.
Effect of a Paf antagonist, WEB 2086, on airway microvascular leakage in the guinea‐pig and platelet aggregation in man
Authors: Evans Timothy W. , Dent Gordon , Rogers Duncan F. , Aursudkij Boonrut , Chung K. Fan , Barnes Peter J. 
Published: July 2012

The triazolodiazepine WEB 2086 has been evaluated as an antagonist of platelet‐activating factor (Paf) by studying its effects on Paf‐induced human platelet aggregation and microvascular leakage in guinea‐pigs.
WEB 2086 inhibited Paf‐induced platelet aggregation in platelet‐rich plasma in vitro (IC50 = 117 ± 35 nm, mean ± s.d.) but had no effect on adenosine 3′,5′‐diphosphate‐induced aggregation.
Paf‐induced microvascular leakage, measured by the extravasation of intravenously‐injected Evans blue dye, was inhibited in a dose‐related fashion in the airways and other tissues by WEB 2086, achieving a maximal inhibitory effect at 10 μg kg−1, i.v.
However, WEB 2086 (10 μg kg−1, i.v.) did not inhibit a comparable increase in vascular permeability induced by ovalbumin in sensitized guinea‐pigs.
We conclude that WEB 2086 is a potent antagonist of Paf and that Paf does not appear to be responsible for antigen‐induced microvascular leakage.
Opiates distinguish spinal excitation from inhibition evoked by noxious heat stimuli in the rat: relevance to theories of analgesia
Authors: Harris N.C. , Ryall R.W. 
Published: July 2012

Experiments were performed to test the hypothesis that a significant part of the action of opiates in reducing responses to noxious stimuli is a reduction in the release of neurotransmitter from primary afferent fibres.
The effects of locally and systemically administered opiates were examined on the excitatory and γ‐aminobutyric acid (GABA)‐mediated inhibitory responses of spinal dorsal horn neurones to noxious heat stimulation in the anaesthetized rat: the inhibitions are thought to involve the same C‐fibre afferents as the excitation.
Microionophoretically administered morphine reduced the excitatory response in a small proportion of the cells, reduced the background firing in a larger proportion but was ineffective on the inhibition.
Intravenously injected morphine (0.5–6 mg kg−1) or etorphine (0.1–2 μg kg−1) invariably attenuated the excitation of dorsal horn neurones by noxious stimuli but had no effect on the inhibition.
It was concluded that the data do not support the hypothesis that the production of analgesia is due mainly to a reduction in the release of transmitter from primary afferent fibres.
Effects of the muscarinic antagonists pirenzepine and gallamine on spontaneous and evoked responses of rat cerebral cortical neurones
Authors: Swanson Thomas H. , Phillis John W. 
Published: July 2012

The muscarinic receptor antagonists gallamine and pirenzepine were iontophoretically applied to rat cerebral cortical cholinoceptive neurones, including corticospinal neurones, to assess their effects on spontaneous firing, and firing induced by: stimulation of the nucleus basalis magnocellularis (NBM); contralateral hindpaw stimulation; application of acetylcholine (ACh); and application of glutamate.
Both compounds potently inhibited firing induced by ACh iontophoresis, whilst neither compound consistently altered firing induced by application of glutamate.
Gallamine was very effective and pirenzepine less effective, at inhibiting both spontaneous firing and the delayed firing induced by NBM stimulation. The short‐latency excitations elicited by NBM stimulation were enhanced by these muscarinic antagonists.
Gallamine and pirenzepine enhanced cortical cholinoceptive cell firing induced by contralateral hindpaw stimulation.
It is concluded that gallamine depresses spontaneous activity more than pirenzepine, and that both compounds can affect the cortical cell firing evoked by stimulation of the NBM and of thalamo‐cortical afferent fibres.
Prejunctional muscarinic (M1)‐receptor interactions on guinea‐pig ileum: lack of effect of cisapride
Authors: Schuurkes J.A.J. , Van Bergen P.J.E. , Van Nueten J.M. 
Published: July 2012

Cisapride stimulates gastrointestinal motility, probably by enhancing the release of acetylcholine from myenteric nerve endings. Such an effect could be mediated via presynaptic muscarinic (M1)‐receptors. Our aim was to determine whether cisapride could antagonize the inhibitory effects of a M1‐agonist, McN‐A‐343 or mimic the effects of a M1‐antagonist, pirenzepine.
Longitudinal segments were suspended in Krebs solution (95% O2, 5% CO2, 37.5°C) for isometric tension recording (preload 1 g) during electrical transmural stimulation (0.1 Hz, 1 ms, sub‐ or supramaximal current).
McN‐A‐343 (2.0 times 10−6 m) reduced the contractile response to supramaximal stimulation (EC50 = 1.6 × 10−6 m), but had no effect on the contractions induced by exogenous acetylcholine.
The inhibitory effect of McN‐A‐343 on the contractile response to electrical stimulation could be reversed by pirenzepine (EC50 = 1.6 × 10−8m) but not by atropine. At these concentrations pirenzepine itself did not modify the contractile response to electrical stimulation. However, at 50 times higher concentrations pirenzepine inhibited the response to electrical stimulation as well as the response to exogenous acetylcholine (EC50 = 8.5 × 10−7m).
Cisapride enhanced the contractile response to submaximal electrical stimulation by 49 ± 10%. This stimulating effect of cisapride was not affected by the presence of pirenzepine but was reduced in the presence of McN‐A‐343 (22 ± 7%).
In conclusion: the effects of McN‐A‐343 and pirenzepine on the electrically stimulated guinea‐pig ileum are compatible with an interaction on presynaptic muscarinic‐(M1)‐receptors. Cisapride enhances the twitch amplitude via mechanisms independent of such M1‐receptor interactions.
Different effects of bombesin on glucose‐ and tolbutamide‐induced insulin release in man
Authors: Scarpignato Carmelo , Gioffré Mara , Gulino Filippo Mario , Micali Biagio 
Published: July 2012

The effect of bombesin, a neurograstrointestinal peptide, on basal and stimulated insulin release was studied in man.
Two different stimuli were used, hyperglycaemic (20 g glucose) and hypoglycaemic (1 g tolbutamide). They were injected intravenously to two groups of male healthy volunteers during saline or bombesin (5 ng kg−1 min−1 for 60 min) infusion.
The peptide had no significant effect on basal levels of glucose and insulin. However, the insulin response to intravenous glucose was strongly potentiated by bombesin, the integrated insulin response being 2.23 ± 0.59 mu ml−1 · 90 min and 0.98 ± 0.19 mu ml−1 · 90 min during infusion of bombesin and saline, respectively (P < 0.05). The behaviour of plasma glucose was not significantly modified by the peptide. Indeed, the glucose disappearance rate (K of Conard, mg min 10−2) changed from 2.5 ± 0.3 during saline to 2.4 ± 0.4 during bombesin infusion.
When the hypoglycaemic stimulus (i.e. tolbutamide) was used, no effect of the peptide on insulin release could be detected. Here again, the drop in plasma glucose (expressed as Marigo's coefficient) was not affected by the peptide, with a value of 92.8 ± 12.6 and 84.0 ± 10.9 during bombesin and saline administration.
These data therefore show that, at normal or low blood glucose levels, the dose of bombesin used is unable to modify insulin release and suggest that this peptide might be regarded as a glucose‐dependent insulinotropic peptide.
Effect of acute lung injury on metabolism of adenine nucleotides in rat perfused lung
Authors: Grantham C.J. , Bakhle Y.S. 
Published: July 2012

The hydrolysis of adenosine di‐ and monophosphate (ADP, AMP) was studied in perfused lungs isolated from rats treated with α‐naphthylthiourea (ANTU) to induce acute lung injury. This injury is associated with damage to the endothelium, the locus of the ADP and AMP hydrolysing enzymes.
Treatment with ANTU did not change the proportion of [3H]‐ADP surviving a single passage through the pulmonary circulation, at any time up to 50 h after ANTU. Less than 8% and 2% respectively of 1 or 0.1 μmol ADP, given as a bolus, appeared in lung effluent.
The metabolites of ADP, AMP and adenosine in lung effluent were increased from 2 h after ANTU.
Metabolism of [3H]‐AMP as substrate was always low but, following ANTU treatment, the adenosine content of lung effluent increased four fold.
It appears that, in spite of considerable endothelial cell damage, as demonstrated by pulmonary oedema, the ectoenzymes catalysing ADP and AMP hydrolysis were relatively little affected by ANTU.
Effect of calcium and calmodulin antagonists on contractile responses of the human uterine artery
Authors: Kostrzewska A. , Laudanski T. , Batra S. 
Published: July 2012

The dependence on extracellular calcium of contractile responses of intramyometrial arteries (0.5–2 mm diameter), as well as the effects of various types of calcium antagonists on these responses, were studied. Contractions were induced by K‐depolarization (K) and noradrenaline (NA).
Whereas the K response was completely abolished in a calcium‐free medium containing 2 mM LaCl3, the NA response was substantially maintained.
Nimodipine strongly inhibited the K response but had a relatively weak effect on the NA response; the IC50 values for the K and NA responses being 2 nM and 6 μm, respectively. Corresponding values for verapamil were about 0.7 and 10 μm.
Calmodulin antagonists, particularly trifluoperazine and flunarizine, caused a greater inhibition of the NA than of the K response.
These results indicate that besides the extracellular calcium which appears to be the major source of activator calcium, there is an intracellular pool of calcium which can be utilized to activate, albeit to a limited extent, drug‐induced contractile responses.
The competitive antagonistic effect of compounds from Mandevilla velutina on kinin‐induced contractions of rat uterus and guinea‐pig ileum in vitro
Authors: Calixto João B. , Pizzolatti Moacir G. , Yunes Rosendo A. 
Published: July 2012

Pure non‐peptide compounds obtained in crystal form from the crude extract of the plant Mandevilla velutina (Apocynaceae) were analysed for their antagonistic effects on rat uterine and guinea‐pig smooth muscle contractions induced by bradykinin (Bk), lisyl‐bradykinin (L‐Bk), acetylcholine (ACh), oxytocin and histamine, in vitro.
Pre‐incubation of rat uterine muscle with compounds MV 8608, MV 8609, MV 8610, MV 8611 and MV 8612 (5 to 40 μg ml−1) caused parallel and concentration‐dependent rightward displacements of the Bk concentration‐response curves (1 to 1000 nm). Schild plots of these data were linear (correlation close to 1) and yielded nominal pA2 values (gml−1) of 5.7, 5.6, 5.4, 5.7 and 5.3, respectively. Compounds MV 8608, MV 8611 and MV 8612 (5 to 20 μg ml−1) also caused concentration‐dependent and parallel displacements to the right of the concentration‐response curve to L‐Bk (1 to 10,000 nm). The Schild plots were linear and furnished nominal pA2 values (g ml−1) of 5.4, 5.8 and 5.1, respectively. With the exception of the antagonist effect of compound MV 8606 against Bk‐induced contraction, all compounds behaved as simple competitive kinin antagonists since the calculated slopes were not different from unity.
In the guinea‐pig ileum, both MV 8608 and MV 8612 (5 to 20 μg ml−1), produced concentration‐dependent rightward displacements of the concentration‐response curve to Bk (0.1 to 1000 nm) when the experiments were performed in the presence but not in the absence of atropine (2.5 μm). However, in contrast to the result obtained in the rat uterus, compound MV 8608 also caused a significant reduction of the maximal response to Bk. The Schild plot for compound MV 8612 was linear (correlation close to unity) and furnished a nominal pA2 value (g ml−1) of 5.3 and a slope not different from unity.
In rat uterine muscle, compounds MV 8608 and MV 8612 at concentrations producing marked rightward displacements of the kinin concentration‐response curves (10 and 20 μg ml−1), did not influence the uterine contractile response to oxytocin or ACh, indicating some selectivity towards kinin receptors. Similarly, compound MV 8612 (10 and 20 μg ml−1) did not interfere with the sensitivities or the maximal responses to ACh and histamine in the guinea‐pig ileum, whereas compound MV 8608 (10 and 20 μg ml−1) caused a slight reduction of ACh‐ and histamine‐induced maximal contractions, allied to decrease of the sensitivity to histamine at concentrations of 20 μg ml−1 or more.
These results extend our previous data, indicating the existence of several non‐peptide compounds in the crude extract of Mandevilla velutina that act as simple, competitive, selective and reversible kinin receptor antagonists in the rat isolated uterus and guinea‐pig ileum smooth muscle.
Protection of rat atrial myocardium against electrical, mechanical and structural aspects of injury caused by exposure in vitro to conditions of simulated ischaemia
Authors: Northover Ann M. , Northover B.J. 
Published: July 2012

Rat isolated and superfused atria were exposed for varying periods to a solution simulating the composition of extracellular fluid during myocardial ischaemia (SI).
Atria subjected to SI showed a loss of systolic contractile tension, a rise in diastolic tension, a shortening of electrical refractory periods, a slowing of action potential conduction velocity and disruption of the mitochondrial ultrastructure. All these features were reversible when the muscle was returned to normal superfusate.
Atria pretreated with a superfusate containing a calcium channel antagonist, a calmodulin inhibitor or an intracellular calcium antagonist showed fewer features of the response to SI than did controls.
Atria pretreated with a superfusate containing various non‐steroidal anti‐inflammatory agents did not show identical responses to SI. Sulphinpyrazone protected against all features of the response to SI but ibuprofen, flurbiprofen and GP25671 (a metabolite of sulphinpyrazone) had little effect. Flufenamate, phenylbutazone and salicylate enhanced the responses to SI.
The interaction of substituted benzamides with brain benzodiazepine binding sites in vitro
Authors: Horton Roger W. , Lowther Sandra , Chivers Jane , Jenner Peter , Marsden C. David , Testa Bernard 
Published: July 2012

The interaction of substituted benzamides with brain benzodiazepine (BDZ) binding sites was examined by their ability to displace [3H]‐flunitrazepam ([3H]‐FNm) from specific binding sites in bovine cortical membranes in vitro.
Clebopride, Delagrange 2674, Delagrange 2335 and BRL 20627 displayed concentration‐dependent displacement of [3H]‐FNM with IC50 values of 73 nM, 132 nM, 7.7 μm and 5.9 μm, respectively. Other substituted benzamides including metoclopramide, sulpiride, tiapride, sultopride and cisapride were inactive at 10−5 m.
Inhibition by clebopride and Delagrange 2674 of [3H]‐FNM binding was apparently competitive and readily reversible.
In the presence of γ‐aminobutyric acid (GABA), the ability of diazepam and Delagrange 2674 to displace [3H]‐Ro 15–1788 binding was increased 3.6 and 1.6 fold respectively, compared to the absence of GABA, while ethyl β‐carboline‐3‐carboxylate (βCCE) and clebopride were less potent in the presence of GABA.
Diazepam was 30 fold less potent at displacing [3H]‐Ro 15–1788 in membranes that had been photoaffinity labelled with FNM than in control membranes, whereas the potency of βCCE did not differ. Clebopride and Delagrange 2674 showed a less than two fold loss of potency in photoaffinity labelled membranes.
The pattern of binding of clebopride and Delagrange 2674 in these in vitro tests is similar to that found previously with partial agonists or antagonists at BDZ binding sites.
Clebopride and Delagrange 2674 inhibited [3H]‐FNM binding with similar potency in rat cerebellar and hippocampal membranes, suggesting they have no selectivity for BDZ1 and BDZ2 binding sites.
Clebopride and Delagrange 2674 are structurally dissimilar to other BDZ ligands and represent another chemical structure to probe brain BDZ binding sites.
The mechanism of action of calcium antagonists on arrhythmias in early myocardial ischaemia: studies with nifedipine and DHM9
Authors: Curtis M.J. , Walker M.J.A. 
Published: July 2012

Nifedipine and DHM9 (carboxymethyl methyl 1,4‐dihydro‐2,6‐dimethyl‐4‐(3‐nitrophenyl)−3,5‐pyridinedicarboxylate) were studied for their effects on arrhythmias resulting from regional myocardial ischaemia in conscious rats, and for their effects on left ventricular developed pressure in vitro.
Nifedipine possessed antiarrhythmic activity at a high dose of 10 mg kg−1 i.v., but not at 0.5 or 2 mg kg−1. Ventricular fibrillation (VF), tachycardia (VT), and ventricular premature beats (VPB) were all attenuated to a similar degree; nifedipine did not have a selectivity of action for high frequency arrhythmias.
Before coronary occlusion, the three doses of nifedipine reduced arterial blood pressure by a similar magnitude, indicating a similar (maximal) degree of systemic vasodilatation. The reductions in blood pressure were accompanied by reflex tachycardia. Heart rate and blood pressure did not correlate with the incidence or severity of arrhythmias.
DHM9 had no influence on arrhythmias, haemodynamic variables or the ECG, even at 20 mg kg−1 i.v.
Nifedipine concentration‐dependently reduced contractility in perfused paced (5 Hz) rat ventricles in vitro. Raising the concentration of K+ in the perfusion fluid from 3 to 10 mequiv.1−1 increased the potency (‐log10 EC50) of nifedipine up to four fold, and caused a significant depression in excitability.
DHM9 at up to 3 × 10‐5 m had no significant influence on ventricular contractility in vitro.
The results provided indirect evidence in support of the hypothesis that calcium antagonists inhibit ischaemia‐induced arrhythmias by virtue of inhibition of the slow inward current (Isi) in the ischaemic ventricular myocardium.
Prostaglandin E2 inhibits and indomethacin and aspirin enhance, A23187‐stimulated leukotriene B4 synthesis by rat peritoneal macrophages
Authors: Elliott Graham R. , Lauwen Adrianus P.M. , Bonta Ivan L. 
Published: July 2012

The calcium ionophore, A23187, stimulated leukotriene B4 (LTB4), thromboxane B2 (TxB2) and prostaglandin E2 (PGE2) synthesis by 4 day carrageenin‐elicited rat peritoneal macrophages.
At concentrations of 2 × 10−7‐2 × 10−5 m indomethacin and aspirin enhanced A23187‐stimulated LTB4 synthesis and inhibited PGE2 and TXB2 formation.
PGE2 inhibited A23187‐stimulated LTB4 and TXB2 formation as well as the augmentation of LTB4 release caused by aspirin and indomethacin. However, PGE2 was ineffective when the cells were challenged with arachidonic acid (AA).
Dibutyryl adenosine 3′: 5′‐cyclic monophosphate (db‐cyclic AMP) partially inhibited A23187‐stimulated LTB4 production.
Our results suggest that PGE2 inhibits macrophage LTB4 synthesis by limiting the availability of AA. Indomethacin and aspirin, possibly by removing the regulatory effect of PGE2, promote the synthesis of the pro‐inflammatory LTB4.
The human astrocytoma cell line 1321 N1 contains M2‐glandular type muscarinic receptors linked to phosphoinositide turnover
Authors: Kunysz Elizabeth A. , Michel Anton D. , Whiting Roger L. , Woods Kris 
Published: July 2012

Muscarinic receptors present in the human astrocytoma cell line 1321 N1 were characterized in radioligand binding studies and in functional studies of carbachol‐stimulated phosphatidylinositol (PI) turnover.
In radioligand binding studies the muscarinic receptor in intact cells could be labelled using [3H]‐N‐methylscopolamine ([3H]‐NMS) but not by [3H]‐pirenzepine. In the intact cells these receptors displayed low pirenzepine affinity (pKi = 6.83) indicating that they were not of the M1 subtype. Furthermore, the 1321 N1 muscarinic receptors displayed low affinity for the two M2‐cardiac selective ligands methoctramine (pKi = 5.82) and AF‐DX 116 (pKi = 6.29). This pharmacology was consistent with the 1321 N1 cells containing a single population of muscarinic receptors that displayed a similar pharmacology to the M2‐receptor present in exocrine gland tissue.
The M2‐gland nature of the receptors was further indicated in the functional studies where antagonist affinities were determined from their ability to antagonize carbachol‐stimulated PI turnover in 1321 N1 cells. pA2 values for pirenzepine (7.31), methoctramine (6.10) and AF‐DX 116 (6.52) were similar to those determined in the binding studies.
From these studies we conclude that 1321 N1 astrocytoma cells contain an M2‐gland muscarinic receptor which mediates muscarinic receptor‐mediated stimulation of PI turnover in these cells.