bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nedocromil sodium inhibits antigen‐induced contraction of human lung parenchymal and bronchial strips, and the release of sulphidopeptide‐leukotrienes and histamine from human lung fragments
Authors: Napier Fiona E. , Shearer Melanie A. , Temple Diana M. 
Published: July 2012

The effects of nedocromil sodium on antigen‐induced release of sulphidopeptide‐leukotrienes and histamine from passively sensitized fragments of human lung, and on antigen‐induced contraction of sensitized strips of human lung parenchyma and bronchus, have been studied.
Nedocromil sodium 0.1 and 1 μm inhibited leukotriene release from fragments of human lung by 30% and 38% respectively, and histamine release by 43% for both concentrations, but 10 μm was ineffective. The lung fragments, which were passively sensitized to house dust mite, Dermataphagoides pteronyssinus, in control experiments released leukotrienes (6.58 ± 0.12 nmol equiv. leukotriene C4 per g, n = 6) and histamine (10.3% ± 1.8 of total tissue histamine, n = 5) when challenged with house dust mite extract.
Isolated strips of human lung parenchyma, passively sensitized to D. pteronyssinus, contracted when treated with house dust mite extract to a mean value of 40% of the maximal histamine response for each strip. Nedocromil sodium 0.1 and 1 μm inhibited these contractions by 50% and 70% of the control response, but 10 μm had no inhibitory effect.
Isolated rings from human bronchus, also passively sensitized to D. pteronyssinus, contracted when treated with house dust mite extract to a mean value of 86% of the maximal histamine response. Nedocromil sodium 1 μm, but not 0.1 or 10 μm, inhibited contractions by 48% of the control response.
The therapeutic effects of nedocromil sodium in allergic asthma may depend, partly, on its inhibition of antigen‐induced release of leukotrienes and histamine in human lung and its consequent inhibition of antigen‐induced contractions of parenchymal and bronchial tissue.
GABAA receptor‐mediated increase in membrane chloride conductance in rat paratracheal neurones
Authors: Allen T.G.J. , Burnstock G. 
Published: July 2012

The actions of γ‐aminobutyric acid (GABA) on the intramural neurones of 14–18 day old rats were studied in situ by use of intracellular current‐ and voltage‐clamp techniques. The ionic conductance changes and the effects of various GABA‐receptor agonists and antagonists on these neurones were also investigated.
Prolonged application of GABA either by ionophoresis (10 pC‐10 nC) or superfusion (10–100 μm), evoked a biphasic membrance depolarization in over 90% of all paratracheal neurones studied. Typically, the response consisted of an initial rapid depolarization (18–45 ms) that subsequently faded over a period of 15–25 s to reveal a second smaller depolarization which was maintained for the duration of GABA application. Both components of the evoked response resulted in an increase in membrane conductance and an inward flow of current.
The amplitude of the transient inward current, recorded during the initial phase of the response, was linearly related to the membrane potential at which it was elicited and reversed symmetrically at a membrane potential of −32.7 mV. The underlying increase in conductance was largely independent of membrane potential. The equilibrium potential for the sustained inward current was −38.7 mV. Replacement of extracellular chloride with gluconate ions initially enhanced the GABA‐evoked inward current. With successive applications of GABA in low chloride, the evoked current and conductance changes declined markedly.
Muscimol superfusion (1–10 μm) or ionophoresis (10 pC‐10 nC) mimicked both the initial and late phases of the GABA‐induced conductance change and inward current. Baclofen (1–100 μm) had no effect upon either resting membrane potential or conductance in any of the cells tested.
The large transient initial phase of the GABA‐evoked inward current and depolarization were potently inhibited by picrotoxin (1–50 μm), whereas the smaller sustained inward current was largely resistant to picrotoxin.
All of the observed actions of GABA and muscimol were antagonized by bicuculline (0.1–10 μm) in an apparently competitive manner.
It is concluded that GABA acts via GABAA receptors present on the soma of paratracheal neurones to produce an increase in membrane chloride conductance. Prolonged application of GABA results in a decline in the observed current due to a combination of two processes: receptor desensitization and shifts in the chloride equilibrium potential. The possible roles for GABA in neural regulation of airway excitability are discussed.
Cerebrovascular responses to capsaicin in vitro and in situ
Authors: Edvinsson Lars , Jansen Inger , Kingman Tom A. , McCulloch James 
Published: July 2012

The cerebrovascular effects of capsaicin have been examined in vitro, in feline isolated cerebral arteries (circular segments, 2–3 mm long, 300–400 μm extended diameter) and, in situ, in pial arterioles (diameter 40–200 μm) on the cortical surface of chloralose‐anaesthetized cats.
In isolated middle cerebral arteries, low concentrations of capsaicin (10−14‐10−10m) effected a concentration‐dependent relaxation of vessels precontracted with prostaglandin F2α. This relaxant response was markedly attenuated by repeated administration of capsaicin but was minimally affected by the presence of atropine, propranolol, cimetidine or spantide in the tissue bath.
In isolated middle cerebral arteries, higher concentrations of capsaicin effected a marked concentration‐dependent contraction. This contraction was not modified by 10−6 μ phentolamine or 10−6m ketanserin. A markedly reduced contraction by capsaicin was found upon the removal of calcium ions from the buffer solution. Also the calcium entry blocker nimodipine reversed the capsaicin‐induced contraction.
Subarachnoid perivascular microapplication of capsaicin around individual pial arterioles in situ elicited a biphasic response (an immediate vasoconstriction followed by a sustained vasodilatation). The maximum vasoconstriction was a 60 ± 6% reduction in diameter from base line and the maximum vasodilatation a 38 ± 7% increase in diameter. Vasodilatation occurred at lower concentrations of capsaicin (EC50, approximately 5 × 10−8 μ) than those required for vasoconstriction (EC50 3 × 10−7 μ).
Trigeminal ganglionectomy 10–16 days before the microapplication abolished the in situ vasodilator effects of capsaicin (10−6m) applied perivascularly, but was without effect on the vasoconstrictor actions of this agent.
Repeated administration of capsaicin (10−6m) around the same arteriole resulted in a progressive attenuation of the vasodilator phase of the response, with no modification of the vasoconstrictor phase.
The present study suggests that capsaicin‐induced cerebral vasodilatation is due to the release of vasoactive agents from cerebrovascular trigeminal nerve fibres, whereas the vasoconstrictor effect of capsaicin is due to a direct effect on the cerebral vasculature which is mediated via the transmembrane passage of extracellular calcium.
δ‐Opioid receptor binding sites in rodent spinal cord
Authors: Traynor J.R. , Hunter J.C , Rodriguez R.E. , Hill R.G. , Hughes J. 
Published: July 2012

The δ‐opioid receptor agonist [d‐Pen2,d‐Pen5]enkephalin showed an antinociceptive effect in the mouse tail‐flick test, following intrathecal administration. This action was reversed by naloxone and by the selective δ‐opioid receptor antagonist ICI 174864.
High affinity, saturable binding of [3H]‐[d‐Pen2,d‐Pen5]enkephalin has been demonstrated in spinal cord homogenates from guinea‐pig, hamster, rat and both adult and young (18–20 g) mice. The binding was shown by autoradiography to be concentrated in the superficial laminae of the dorsal horn.
Competition studies confirmed that the binding of [3H]‐[d‐Pen2,d‐Pen5]enkephalin was to the δ‐opioid site. However, anomalies were seen with displacement assays using μ‐ligands, which may suggest some common high affinity site for δ‐ and μ‐opioid receptor agonists in the spinal cord.
The results add further evidence for a role of the δ‐opioid receptor in spinally‐mediated antinociception.
Antagonism by nifedipine of contraction and Ca2+ ‐influx evoked by ATP in guinea‐pig urinary bladder
Authors: Katsuragi T. , Usune S. , Furukawa T. 
Published: July 2012

The effects of Ca2+‐antagonists, especially nifedipine, on contraction and increase of intracellular Ca2+ (Fura‐2/AM method) evoked by ATP were evaluated in a thin outer layer segment of guinea‐pig urinary bladder.
The ATP‐evoked contraction was markedly inhibited by dihydropyridine‐type Ca2+‐antagonists, such as nifedipine and nitrendipine, but not by D‐600, ω‐conotoxin and tetramethrin.
This antagonism by nifedipine of ATP‐evoked contractions was competitive from the Schild plot analysis, the pA2 value being 8.23. The reduction of ATP‐evoked contraction by nifedipine (0.1 μm) was fully reversed by administration of Bay K 8644 (0.1 μm).
ATP (100 μm) caused an increase of fluorescence brightness after loading Fura‐2/AM, which was coupled with a contraction of the bladder. Both the contraction and the elevation of intracellular Ca2+ evoked by the nucleotide were completely antagonized by nifedipine.
These results suggest that ATP may activate the dihydropyridine‐sensitive, voltage‐dependent Ca2+‐channels in a direct or indirect fashion and, thereby, elicit a contraction of the bladder.
Mechanism of endothelin‐induced contraction in guinea‐pig trachea: comparison with rat aorta
Authors: Hay D.W.P. 
Published: July 2012

Endothelin (1nm‐0.3 μm) produced a concentration‐dependent contraction of guinea‐pig epithelium‐containing (intact) trachea (EC50 = 30.9 nm). Endothelin was a less potent agonist than leukotriene D4 (LTD4; EC50 = 0.77 nm), but was more potent than carbachol (EC50 = 0.15 μm) or substance P (EC50 = 1.4 μm). Endothelin was a more potent contractile agent in rat endothelium‐denuded aorta (EC50 = 2.1 nm) than in guinea‐pig trachea.
Endothelin‐induced contraction in guinea‐pig trachea was unaffected by mepyramine (10 μm), atropine (1 μm), SK&F 104353 (10 μm), a leukotriene receptor antgonist, or SQ 29,548 (1 μm), a thromboxane receptor antagonist. The contraction produced by 0.3 μm endothelin was potentiated by cyclo‐oxygenase inhibition with 5 μm indomethacin.
Nicardipine (0.01 or 0.1 μm) or incubation in calcium‐free medium +0.1 mm EGTA for 30 min had a relatively minor or no effect on endothelin concentration‐response curves in guinea‐pig intact trachea, but markedly inhibited responses produced by endothelin in endothelium‐denuded aorta of the rat. Increasing the EGTA concentration in calcium‐free medium to 1 mm abolished endothelin‐induced contraction in guinea‐pig trachea.
In guinea‐pig trachea, ryanodine (10 μm) produced a 2.1 fold shift to the right of endothelin concentration‐response curves and reduced the maximum response elicited by 0.3 μm endothelin.
Staurosporine (0.01 μm and 0.1 μm), a protein kinase C inhibitor, was without effect on endothelin‐ or carbachol‐induced contraction in guinea‐pig trachea, but markedly inhibited the response produced by endothelin in rat aorta.
Endothelin (3 nm‐0.3 μm) produced a concentration‐dependent stimulation of phosphatidylinositol (PI) turnover in guinea‐pig intact trachea, with an EC50 value of 45.9 nm.
Removal of the epithilium markedly potentiated endothelin‐induced contraction in guinea‐pig trachea, producing a 4.7 fold leftward shift in endothelin concentration‐response curves and an increase in the contractile response elicited by 0.3 μm endothelin.
These data indicate that endothelin is a potent agonist in guinea‐pig trachea whose response is markedly enhanced by removal of the airway epithelium. Endothelin‐induced contraction is not mediated to a marked extent by calcium influx via dihydropyridine‐sensitive calcium channels and does not involve the release of histamine, acetylcholine, leukotrienes or thromboxane. Rather, endothelin appears to produce contraction of guinea‐pig trachea via a direct action which involves stimulation of PI turnover and utilization of calcium from intracellular stores and, also, calcium influx via a pathway that is not sensitive to dihydropyridine calcium channel inhibitors. Endothelin‐induced contraction of rat aorta was more sensitive to the effects of incubation in Ca2+‐free medium, nicardipine or staurosporine, suggesting that differences exist in the relative mechanisms whereby endothelin produces contraction in different tissues.
Inhibition of eosinophil cyclic nucleotide PDE activity and opsonised zymosan‐stimulated respiratory burst by ‘type IV’‐selective PDE inhibitors
Authors: Dent Gordon , Giembycz Mark A. , Rabe Klaus F. , Barnes Peter J. 
Published: July 2012

The cyclic nucleotide phosphodiesterase (PDE) of guinea‐pig eosinophils was partially characterized and the effects of selective inhibitors of PDE isoenzymes upon opsonized zymosan (OZ)‐stimulated respiratory burst were studied.
PDE activity in eosinophil lysates appeared to be membrane‐associated, displayed substrate specificity for adenosine 3′: 5′ cyclic monophosphate (cyclic AMP) versus guanosine 3′: 5′ cyclic monophosphate (cyclic GMP) and was insensitive to cyclic GMP or Ca2+ and calmodulin.
The non‐selective PDE inhibitor, 3‐isobutyl‐1‐methylxanthine caused a concentration‐dependent inhibition of both OZ‐stimulated hydrogen peroxide (H2O2) generation and cyclic AMP hydrolysis. The type IV‐selective PDE inhibitors, rolipram and denbufylline, also inhibited H2O2 generation and cyclic AMP hydrolysis in a concentration‐dependent manner whilst SK&F 94120 and Org 9935 (type III‐selective) and zaprinast (type Ia or V‐selective) were ineffective.
Dibutyryl cyclic AMP, a cell‐permeable, non‐hydrolysable analogue of cyclic AMP, caused a concentration‐dependent inhibition of H2O2 generation stimulated by OZ. Dibutyryl cyclic GMP was ineffective.
It is concluded that eosinophil respiratory burst activity induced by OZ can be regulated by intracellular cyclic AMP and that the levels of cyclic AMP are controlled exclusively by a rolipram‐ and denbufylline‐sensitive PDE isoenzyme that resembles a type IV species.
The pharmacological specificity of N‐methyl‐d‐aspartate receptors in rat cerebral cortex: correspondence between radioligand binding and electrophysiological measurements
Authors: Grimwood Sarah , Foster Alan C. , Kemp John A. 
Published: July 2012

The pharmacological specificity of N‐methyl‐d‐aspartate (NMDA) receptors has been investigated in the rat cerebral cortex by use of radioligand binding and electrophysiological techniques.
A comparison was made between a functional assay (NMDA‐induced depolarizations in a rat cortical slice preparation) and NMDA‐sensitive l‐[3H]‐glutamate binding in the same brain region and species, to provide accurate affinity values for agonists and antagonists at the NMDA recognition site.
In a preparation of crude postsynaptic densities (PSD) from rat cortex, l‐[3H]‐glutamate bound with high affinity to an NMDA‐sensitive population of sites with KD (geometric mean (–s.e.mean, +s.e.mean) = 120 (114, 126) nm, Bmax (mean ± s.e.mean) = 11.4 ± 0.8 pmol mg−1 protein and Hill coefficient (mean ± s.e.mean) = 1.2 ± 0.17 (n = 3).
There was a good agreement between the relative affinities in radioligand binding and electrophysiological assays for the receptor agonists NMDA, N‐methyl‐l‐aspartate, quinolinate and trans‐2,3‐piperidine dicarboxylate, which are poor substrates of acidic amino acid transport systems. However, agonists which are good substrates for high affinity uptake systems (l‐ and d‐glutamate, l‐ and d‐aspartate, d‐aspartate‐β‐hydroxamate and l‐glutamate‐γ‐hydroxamate) were much weaker in the electrophysiological experiments.
Schild analysis of the antagonism of NMDA responses in the rat cortical slice by dl‐3‐(2‐carboxypiperazin‐4‐yl)propyl‐1‐phosphonate, d‐ and dl‐2‐amino‐5‐phosphonovalerate, d‐ and dl‐2‐amino‐ 7‐phosphonoheptanoate, d‐β‐aspartylaminomethylphosphonate, d‐γ‐glutamylglycine and d‐α‐aminoadipate (d‐AA) indicated a competitive interaction with respective pA2 values of 6.17, 5.62, 5.24, 5.28, 5.20, 5.00, 4.43 and 3.97.
In the radioligand binding experiments the same antagonists inhibited only the NMDA‐sensitive component of l‐[3H]‐glutamate binding. IC50 values showed a good correlation with the pA2 values (correlation coefficient = 0.96), with the exception of d‐AA which was more potent than anticipated in the binding experiments (IC50 = 9.8 μm).
These results confirm that NMDA‐sensitive l‐[3H]‐glutamate binding sites represent the NMDA recognition site of the NMDA receptor and provide affinity values for both agonists and antagonists in the rat cerebral cortex, agreeing well with previous estimates in this and other tissues.
Mechanical responses to catecholamines in the longitudinal muscle of guinea‐pig gastric fundus
Authors: Parekh A.B. , Syed M. Md , Tomita T. 
Published: July 2012

In the longitudinal muscle of guinea‐pig gastric fundus, adrenaline and phenylephrine (1–30 μm) both produced a slow contraction preceded by a relaxation. The slow contraction was strongly inhibited by prazosin (0.1 μm), but only weakly by yohimbine (1μm), suggesting main contribution of α1‐adrenoceptors.
Most of the slow contraction was blocked by meclofenamate or indomethacin (0.1–0.3 μm). Both these drugs also inhibited spontaneously generated muscle tone. In some preparations, obtained from the apical fundus, a small contraction remained in the presence of meclofenamate.
During contraction induced by prostaglandin E2, adrenaline produced sustained relaxation and phenylephrine often transient relaxation, in the presence of meclofenamate. The transient relaxation, but not the sustained relaxation, was suppressed by prazosin.
In the presence of prostaglandin E2 (5 nm), after treating with phenoxybenzamine (30 μm) for 30 min, isoprenaline and adrenaline produced concentration‐dependent relaxation, with IC50s of 3.9 nm and 64 nm, respectively. Propranolol shifted these concentration‐response curves to the right, with apparent pA2s of 8.15 and 7.34, respectively.
It is suggested that in the fundic longitudinal muscle, adrenaline‐induced contraction is mediated mainly by an increase in endogenous prostaglandin production through activation of α1 ‐adrenoceptors and that adrenaline produces transient relaxation through α1‐adrenoceptors and sustained relaxation through β‐adrenoceptors. The β‐adrenoceptors in the longitudinal muscle are more sensitive to adrenaline and isoprenaline than those in the circular muscle.
Renal handling and effects of S(+)‐ibuprofen and R(–)‐ibuprofen in the rat isolated perfused kidney
Authors: Cox P.G.F. , Moons W.M. , Russel F.G.M. , van Ginneken C.A.M. 
Published: July 2012

The renal handling and effects of S(+)‐ and R(–)‐ibuprofen have been studied in the isolated perfused kidney (IPK) of the rat.
Both ibuprofen enantiomers were extensively reabsorbed and accumulated in the kidney in a concentration‐dependent manner. No pharmacokinetic differences were observed between the two enantiomers.3 S(+)‐ibuprofen concentrations ranging from 0.25 to 25 μg ml−1 (1.2 to 120 μm) caused a decrease in urinary flow, glomerular filtration rate (GFR) and electrolyte excretion. Urinary pH and excretion of glucose were not influenced. R(–)‐ibuprofen concentrations ranging from 2.5 to 25 μg ml−1 (12 to 120 μm) also decreased urinary flow and electrolyte excretion. This decrease, however, was less than observed with S(+)‐ibuprofen. GFR, urinary pH and glucose excretion were not affected by R(–)‐ibuprofen. Prostaglandin E2 (PGE2) concentrations of 133 ng ml−1 reversed the effects on renal function of both enantiomers.
Very high S(+)‐ and R(–)‐ibuprofen concentrations (> 400 μg ml−1) resulted in an increase in urinary flow and fractional excretion of sodium, chloride, potassium, glucose and calcium.
It is concluded that the pharmacokinetic behaviour of ibuprofen in the kidney is not stereoselective. Relatively high concentrations of both enantiomers increased the urinary flow and electrolyte excretion in a nonstereoselective manner. Lower concentrations of S(+)‐ibuprofen decreased urinary flow and electrolyte excretion. The pharmacologically inactive R(–)‐ibuprofen was also able to affect renal function in a similar way, but at different concentrations. These effects on renal function are probably caused by inhibition of PGE2 synthesis.
Modulation of the structure‐binding relationships of antagonists for muscarinic acetylcholine receptor subtypes
Authors: Pedder E. Kristina , Eveleigh Phike , Poyner David , Hulme Edward C. , Birdsall Nigel J.M. 
Published: July 2012

Membranes from rat cerebral cortex, myocardium and extraorbital lacrimal gland were used as sources of M1 M2 and M3 muscarinic acetylcholine receptors respectively and the affinities of seven antagonists for the three subtypes were examined under different experimental conditions.
The affinities for the membrane‐bound receptors were measured at different ionic strengths and temperatures and compared with those determined on the receptor solubilised in the neutral detergent digitonin or the zwitterionic detergent, CHAPSO.
The range of measured affinity constants of a given antagonist for a specific subtype varied from 2 (atropine at M1 receptors) to 1000 (AF‐DX 116 at M2 receptors).
As a consequence of these changes in affinity, which were dependent on the drug, the subtype and the experimental conditions, both the structure‐binding relationships of a given subtype can be markedly changed as well as the selectivity of a drug for the different subtypes. For example it is possible to change the relative affinities of AF‐DX 116 and gallamine at membrane‐bound M1 receptors from 50:1 to 1:60.
Experimental conditions for the observation of high selectivity of pirenzepine, AF‐DX 116, gallamine and hexahydrosiladiphenidol for the three subtypes are given.
When the receptors are removed from their membrane environment by solubilisation in detergent, antagonist affinities are changed but the subtypes still retain different structure‐binding relationships.
In general, AF‐DX 116 and the allosteric antagonist, gallamine, behave differently from the other antagonists, suggesting that they bind in different ways to muscarinic receptors.
Careful attention should therefore be paid to the experimental conditions in binding assays used to assess the affinities and selectivities of new muscarinic antagonists in order to avoid misleading results.
The ability to produce enhanced or attenuated affinities and selectivities of antagonists, resulting from the induction of different conformations of the receptor by a variety of physical, chemical or molecular biological perturbations may lead to a better understanding of the structural basis of drug receptor interactions.
Nitric oxide is the mediator of ATP‐induced dilatation of the rabbit hepatic arterial vascular bed
Authors: Mathie R.T. , Ralevic V. , Alexander B. , Burnstock G. 
Published: July 2012

Livers of 10 New Zealand White rabbits were perfused in vitro with Krebs‐Bülbring buffer via the hepatic artery (HA) and portal vein (PV) at constant flows of 23 ± 1 and 77 + 1 ml min−1 100 g−1 respectively. The tone of the preparation was raised with noradrenaline (concentration: 10 μm).
Dose‐response curves for the vasodilatation produced by adenosine 5′‐triphosphate (ATP), acetylcholine (ACh), adenosine, and sodium nitroprusside (SNP) were obtained following injection into the HA supply. Injections were then repeated in the presence of the l‐arginine to nitric oxide pathway inhibitors N‐monomethyl‐l‐arginine (l‐NMMA, n = 6) and N‐nitro‐l‐arginine methyl ester (l‐NAME, n = 4) at concentrations of 30 μm and 100 μm for each inhibitor.
Both l‐NMMA and l‐NAME antagonized the responses to ATP and ACh; l‐NAME was 2–3 times more potent than l‐NMMA as an inhibitor of these endothelium‐dependent vasodilatations. Neither l‐NMMA nor l‐NAME attenuated responses of the endothelium‐independent vasodilators, adenosine and SNP.
These results indicate that nitric oxide is the mediator of ATP‐induced vasodilatation in the HA vascular bed of the rabbit and that the receptor responsible for the release of nitric oxide, the P2y‐purinoceptor, is located predominantly on the endothelium.