bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bradykinin‐induced activation of nociceptors: receptor and mechanistic studies on the neonatal rat spinal cord‐tail preparation in vitro
Authors: Dray A. , Patel I.A. , Perkins M.N. , Rueff A. 
Published: July 2012

The effects of bradykinin on nociceptors have been characterized on a preparation of the neonatal rat spinal cord with functionally connected tail maintained in vitro. Administration of bradykinin to the tail activated capsaicin‐sensitive peripheral fibres and evoked a concentration‐dependent (EC50 = 130 nm) depolarization recorded from a spinal ventral root (L3‐L5).
The response to bradykinin was unaffected by the peptidase inhibitors, bestatin (0.4 mm), thiorphan (1 μm), phosphoramidon (1 μm) and MERGETPA (10 μm) or by the presence of calcium blocking agents, cadmium (200 μm) and nifedipine (10 μm).
Inhibition of cyclo‐oxygenase with indomethacin (1–5 μm), aspirin (1–10 μm) and paracetamol (10–50 μm) consistently attenuated responses to bradykinin.
The effect of bradykinin was mimicked by the phorbol ester PDBu, an activator of protein kinase C. The response to bradykinin was attenuated following desensitization to PDBu but desensitization to bradykinin did not induce a cross‐desensitization to PDBu. The protein kinase C inhibitor staurosporine (10–500 nm) consistently attenuated the effects of PDBu and bradykinin.
Bradykinin responses were reversibly enhanced by dibutyryl cyclic AMP (100 μm). However dibutyryl cyclic GMP (0.5 mm) and nitroprusside (10 μm) produced prolonged block of responsiveness to bradykinin. Prolonged superfusion with pertussis toxin did not affect responses to bradykinin.
The B1‐receptor agonist des Arg9‐bradykinin (10–100 μm) was ineffective alone or after prolonged exposure of the tail to lipopolysaccharide (100 ng ml−1) or epidermal growth factor (100 ng ml−1) to induce B1 receptors. The B1‐receptor antagonist, des Arg9 Leu8‐bradykinin (10 μm) did not attenuate the response to bradykinin. A number of bradykinin B2 antagonists selectively and reversibly attenuated the response to bradykinin. The rank order potency was Hoe 140 > LysLys [Hyp3,Thi5,8,d‐Phe7]‐bradykinin > d‐Arg[Hyp3, Thi5,8, d‐Phe7]‐bradykinin = d‐Arg[Hyp2,Thi5,8, d‐Phe7]‐bradykinin.
These data show that bradykinin produces concentration‐dependent activation of peripheral nociceptors in the neonatal rat tail. The responses were unaffected by calcium channel block and were partially dependent on the production of prostanoids. Bradykinin‐evoked responses were consistent with the activation of protein kinase C‐dependent mechanisms. Cyclic GMP‐dependent mechanisms may be involved in bradykinin‐receptor desensitization whereas cyclic‐AMP dependent mechanisms increase fibre excitability and facilitate bradykinin‐induced responses. The effects of bradykinin were mediated by a B2 receptor.
Endothelium‐dependent relaxation of rabbit middle cerebral artery to a histamine H3‐agonist is reduced by inhibitors of nitric oxide and prostacyclin synthesis
Authors: Kim L. Ea , Javellaud J. , Oudart N. 
Published: July 2012

The possible involvement of prostanoids and endothelium‐derived relaxing factor (EDRF) in the vasodilatation induced by a histamine H3‐agonist was examined in the rabbit perfused middle cerebral artery preconstricted with K+ (50 mm).
The endothelium‐dependent relaxation to (R)‐α‐methylhistamine [(R)‐α‐MeHA] was competitively antagonized by thioperamide (an H3‐antagonist) with a pA2 of 9.05, but unaffected by propranolol, atropine, l‐ and d‐sulpiride. This effect was stereoselective since the (S)‐isomer was 100 times less potent than the (R)‐isomer.
Two inhibitors of nitric oxide synthesis, NG‐nitro‐l‐arginine methyl ester (l‐NAME) and NG‐monomethyl‐l‐arginine (l‐NMMA), inhibited the relaxation induced by (R)‐α‐methylhistamine. The inhibitory effects of 10−5 m NG‐nitro‐l‐arginine methyl ester and 10−5 m NG‐monomethyl‐l‐arginine were reversed by equimolar concentrations of l‐arginine, but strongly enhanced by 10−4 m tranylcypromine. Tranylcypromine alone (10−5 m−10−4 m) partially reduced the (R)‐α‐methylhistamine‐induced relaxation. Both dexamethasone and indomethacin also inhibited this relaxation.
The results suggest that the H3‐mediated relaxation of the rabbit middle cerebral artery may involve release of both a prostanoid, probably prostacyclin, and endothelium‐derived relaxing factor. The relaxant effects of these two endogenous compounds appear to be synergistic.
Interaction of the central analgesic, tramadol, with the uptake and release of 5‐hydroxytryptamine in the rat brain in vitro
Authors: Driessen B. , Reimann W. 
Published: July 2012

Tramadol is a centrally acting analgesic with low opioid receptor affinity and therefore presumably other mechanisms of analgesic action. Tramadol inhibits noradrenaline uptake but since 5‐hydroxytryptamine (5‐HT) is also involved in the modulation of pain perception, we tested the effects of tramadol on 5‐HT uptake and release in vitro.
Tramadol inhibited the uptake of [3H]‐5‐HT into purified rat frontal cortex synaptosomes with an IC50 of 3.1 μm. The (+)‐enantiomer was about four times more potent than the (−)‐enantiomer; the main metabolite of tramadol, O‐desmethyltramadol, was about ten times less potent.
Rat frontal cortex slices were preincubated with [3H]‐5‐HT, then superfused and stimulated electrically. Tramadol facilitated the basal outflow of [3H]‐5‐HT, at concentrations greater than 1 μm, while the uptake inhibitor 5‐nitroquipazine enhanced both basal and stimulation‐evoked overflow. Effects of the (+)‐enantiomer were more potent than either the racemate, the (−)‐enantiomer or the principal metabolite.
The effects of tramadol on the basal outflow of [3H]‐5‐HT were almost completely abolished when the superfusion medium contained a high concentration of the selective 5‐HT uptake blocker, 6‐nitroquipazine.
The results provide evidence for an interaction of tramadol with the neuronal 5‐HT transporter. An intact uptake system is necessary for the enhancement of extraneuronal 5‐HT concentrations by tramadol indicating an intraneuronal site of action.
The effects of dietary treatment with essential fatty acids on sciatic nerve conduction and activity of the Na+/K+ pump in streptozotocin‐diabetic rats
Authors: Lockett M.J. , Tomlinson D.R. 
Published: July 2012

This study examined the effects of dietary essential fatty acid supplementation (5% (w/w) evening primrose oil) upon sciatic motor nerve conduction velocity and 86Rb+ pumping in sciatic nerve endoneurial preparations in rats with 4 to 5 weeks of streptozotocin‐induced diabetes.
Control diabetic rats (dietary supplementation with 5% (w/w) hydrogenated coconut oil) exhibited a reduction in motor nerve conduction velocity (16%; P < 0.05) compared to similarly‐fed non‐diabetic controls, but there was no significant alteration in ouabain‐sensitive 86Rb+ pumping, a parameter reflecting activity of the Na+/K+ pump.
Treatment of diabetic rats with evening primrose oil prevented completely the development of the motor nerve conduction velocity deficit without affecting the severity of diabetes. Evening primrose oil treatment did not significantly affect motor nerve conduction velocity of non‐diabetic animals.
Evening primrose oil treatment caused a significant reduction in activity of the Na+/K+ pump in sciatic nerves of diabetic animals (45%; P < 0.05).
These results suggest that the acute conduction velocity defect arising in streptozotocin‐diabetic rats, and the actions of evening primrose oil upon this, are independent of any effect on activity of the Na+/K+ pump. Other putative mechanisms are discussed.
The electrical and mechanical responses of the rabbit saphenous artery to nerve stimulation and drugs
Authors: Nally Jane E. , Muir T.C. 
Published: July 2012

Electrical and mechanical responses to field stimulation (1–64 Hz, 0.5 ms supramaximal voltage) were recorded simultaneously in the rabbit saphenous artery. The electrical response consisted entirely of excitatory junction potentials (e.j.ps) which were abolished by α, β methylene ATP (α,β MeATP, 10−6 m) and by tetrodotoxin (TTX, 10−6 m) but were unaffected by the α1‐adrenoceptor antagonist, prazosin (10−6 m). No additional electrical response was evoked by field stimulation, even in the presence of normetanephrine (NMN) and desmethylimipramine (DMI, each 10−6 m), which block neuronal and extraneuronal uptake of noradrenaline (NA) respectively. Action potentials to field stimulation were produced only in the presence of tetraethylammonium (10−3 m) which also enhanced the contraction.
Contractions to field stimulation were reduced (by some 50%) by prazosin (10−6 m) and abolished by the additional presence of α,β MeATP (10−6 m), which blocks purinoceptors by desensitization, suggesting the involvement of both NA and an ATP‐like substance in the contractile response.
Idazoxan (10−6 m) which blocks prejunctional α2‐adrenoceptors, significantly increased the amplitude of both e.j.ps and the contraction to field stimulation (10 pulses, 1–4 Hz, 0.5 ms, supramaximal voltage).
NA (10−2 m by pressure ejection) did not alter membrane potential even in the presence of NMN and DMI (each 10−6 m). ATP (10−2 m by pressure ejection) produced a concentration‐dependent, α,β MeATP‐sensitive depolarization.
In tissues desensitized by constant infusion of α,β MeATP (10−6 m) contractions to NA (10−7−3 × 10−5 m), histamine (10−7 − 3 × 10−5 m) and KCl (1–1.6 × 10−2 m) were unaffected.
Following restoration of the membrane potential, after an initial depolarization, α,β MeATP (4 × 10−6 m) did not change the amplitude of electrotonic hyperpolarizing current pulses significantly but abolished evoked e.j.ps. The rates of recovery of evoked e.j.ps and the depolarization to ATP (10−2 m by pressure ejection) following desensitization to α,β MeATP (10−6 m) were comparable. These results suggest that the effects of α,β MeATP are mediated selectively via receptors (purinoceptors).
Suramin (10−3 m) abolished e.j.ps and the prazosin (10−6 m), insenstive component of the contractile response and antagonized contractions to α,β MeATP (10−7−10−5 m), ATP (10−5−10−3 m), histamine (10−7−3 × 10−5 m) and 5‐hydroxytryptamine (10−7−10−5 m) but those to NA (10−7−10−5 m) and KCl (1−1.6 × 10−2 m) were unaffected. Suramin is insufficiently selective, under these conditions, as a purinoceptor antagonist.
Adenosine receptors in rat basophilic leukaemia cells: transductional mechanisms and effects on 5‐hydroxytryptamine release
Authors: Abbracchio Maria P. , Paoletti Anna M. , Luini Alberto , Cattabeni Flaminio , DE Matteis M. Antonietta 
Published: July 2012

The presence of adenosine receptors linked to adenylate cyclase activity and their functional role in calcium‐evoked 5‐hydroxytryptamine (5‐HT) release was investigated in rat basophilic leukaemia (RBL) cells, a widely used model for studying the molecular mechanisms responsible for stimulus‐secretion coupling.
In [3H]‐5‐HT‐loaded cells triggered to release by the calcium ionophore A23187, a biphasic modulation of 5‐HT secretion was induced by adenosine analogues, with inhibition of stimulated release at nm and potentiation at μm concentrations, suggesting the presence of adenosine receptor subtypes mediating opposite effects on calcium‐dependent release. This was also confirmed by results obtained with other agents interfering with adenosine pharmacology, such as adenosine deaminase and the non‐selective A1/A2 antagonist 8‐phenyl‐theophylline.
Similar biphasic dose‐response curves were obtained with a variety of adenosine analogues on basal adenylate cyclase activity in RBL cells, with inhibition and stimulation of adenosine 3′:5′‐cyclic monophosphate (cyclic AMP) production at nm and μm concentrations, respectively. The rank order of potency of adenosine analogues for inhibition and stimulation of adenylate cyclase activity and the involvement of G‐proteins in modulation of cyclic AMP levels suggested the presence of cyclase‐linked A1 high‐affinity and A2‐like low‐affinity adenosine receptor subtypes. However, the atypical antagonism profile displayed by adenosine receptor xanthine antagonists on cyclase stimulation suggested that the A2‐like receptor expressed by RBL cells might represent a novel cyclase‐coupled A2 receptor subtype.
Micromolar concentrations of adenosine analogues could also increase inositol phospholipid hydrolysis and inositol tris‐phosphate formation in both unstimulated cells and in cells triggered to release by the calcium ionophore. The stimulation was constant, small and additive to that exerted by the calcium ionophore.
It is concluded that RBL cells express both A1 and A2‐like adenosine receptors which exert opposite effects on 5‐HT release and intracellular cyclic AMP levels. However, besides modulation of cyclic AMP levels, additional transduction pathways, such as modulation of phospholipase C activity, may contribute to the release response evoked by adenosine analogues in this cell‐line.
Nedocromil sodium prevents in vivo generation of the eosinophilotactic substance induced by PAF but fails to antagonize its effects
Authors: e Silva Patrícia M.R. , Martins Marco A. , Castro‐Faria‐Neto Hugo C. , Bozza Patricia T. , Pires Ana L.A. , Renato  , Cordeiro S.B. , Vargaftig B. Boris 
Published: July 2012

The intrathoracic injection of platelet activating factor (PAF) into rats induced a decrease in the pleural leucocyte numbers within 15 min, accompanied by a marked exudation, maximal 1 h later. After 6 h, concomitantly with the reduction of exudation, a marked increase in the number of mononuclear cells, neutrophils and eosinophils was observed. Within 24 h, the pleural eosinophil accumulation peaked and persisted up to 96 h.
Topical treatment with nedocromil sodium affected pleural exudation by PAF under conditions where systemic meclizine was ineffective. Nedocromil sodium blocked, dose‐dependently, the increase in the pleural content of mononuclear cells, neutrophils and eosinophils, observed 6 h after PAF administration, as well as the eosinophilia 24 h later. Moreover, the co‐incubation of peritoneal eosinophils with nedocromil sodium did not interfere with the migration triggered by PAF.
The transfer of the 6 h‐PAF pleural washings from donor to recipient rats caused a selective pleural eosinophilia, which was clearly inhibited when nedocromil sodium was administered to donor, but not to recipient animals, showing that this drug interferes with the generation rather than with the expression of the eosinophilotactic activity(ies).
These findings indicate that the nedocromil sodium interferes with PAF‐induced exudation and leucocyte accumulation, by a mechanism other than its ability to reduce the local effects of histamine and which may relate to suppression of the eosinophilotactic principle generation.
Reduced α1‐ and β2‐adrenoceptor‐mediated positive inotropic effects in human end‐stage heart failure
Authors: Steinfath Markus , Danielsen Wiebke , von der Leyen Heiko , Mende Ulrike , Meyer Wilfried , Neumann Joachim , Nose Monika , Reich Torsten , Schmitz Wilhelm , Scholz Hasso , Starbatty Jutta , Stein Birgitt , Döring Volker , Kalmar Peter , Haverich Axel 
Published: July 2012

α1‐Adrenoceptor (phenylephrine in the presence of propranolol) and β2‐adrenoceptor (fenoterol)‐mediated positive inotropic effects were investigated in human ventricular preparations isolated from five nonfailing (prospective organ donors) and from eight explanted failing hearts with end‐stage idiopathic dilative cardiomyopathy (NYHA IV).
For comparison, the nonselective β‐adrenoceptor agonist isoprenaline, the phosphodiesterase (PDE) inhibitor 3‐isobutyl‐1‐methylxanthine (IBMX), the cardiac glycoside dihydroouabain, and calcium were studied.
Furthermore, the influence of IBMX on adenosine 3′: 5′‐cyclic monophosphate (cyclic AMP) PDE activity as well as total β‐adrenoceptor density, β1‐ and β2‐adrenoceptor subtype distribution, and α1‐adrenoceptor density were compared in nonfailing and failing human heart preparations. The radioligands (−)‐[125I]‐iodocyanopindolol for β‐adrenoceptor binding and [3H]‐prazosin for α1‐adrenoceptor binding were used.
The inotropic responses to calcium and dihydroouabain in failing human hearts were unchanged, whereas the maximal α1‐ and β2‐adrenoceptor‐mediated positive inotropic effects were greatly reduced. The inotropic effects of the other cyclic AMP increasing compounds, i.e. isoprenaline and IBMX, were also reduced to about 60% of the effects observed in nonfailing controls. The potency of these compounds was decreased by factors 4–10.
The basal PDE activity and the PDE inhibition by IBMX were similar in nonfailing and failing preparations.
The total β‐adrenoceptor density in nonfailing hearts was about 70 fmol mg−1 protein. In failing hearts the total number of β‐adrenoceptors was markedly reduced by about 60%. The β1/β2‐adrenoceptor ratio was shifted from about 80/20% in nonfailing to approximately 60/40% in failing hearts which was due to a selective reduction of β1‐adrenoceptors. The β2‐adrenoceptor population remaining unchanged. α1‐Adrenoceptor density was increased from about 4 fmol mg−1 protein in nonfailing to 10 fmol mg−1 protein in failing hearts.
Changes in PDE activity and adrenoceptor downregulation cannot completely explain the reduced positive inotropic effects of α1‐ and β2‐adrenoceptor agonists in failing human hearts. This supports the hypothesis that impairment of other processes such as the coupling between receptor and effector system, i.e. the respective G‐proteins, are equally important in end‐stage heart failure.
Penicillin‐induced potentiation of glycine receptor‐operated choride current in rat ventro‐medial hypothalamic neurones
Authors: Tokutomi Naofumi , Agopyan Nadia , Akaike Norio 
Published: July 2012

Effects of penicillin G (PCN) on glycine (Gly)‐evoked Cl− current (IGly) were investigated in acutely dissociated rat ventro‐medial hypothalamic (VMH) neurones by the whole cell mode of patch clamp technique.
When PCN was applied simultaneously with Gly, PCN depressed IGly like a Cl− channel blocker.
The PCN‐induced blocking action was clearly observed at a low PCN concentration (30 u), while the maximal blockade was achieved by 600 u (units per 10 ml) PCN.
When tested solution containing both PCN and Gly was quickly substituted with one containing Gly only, a new rebound‐like transient current (IT) which also passed through Cl− channel, was elicited.
The peak amplitude of IT induced by PCN at concentrations higher than 100 u was greater than that induced by glycine alone. We termed this phenomenon PCN‐induced potentiation of IGly. In all cells tested, PCN potentiated IGly.
At a lower PCN concentration below 30 u, IT generation was not clear in the presence of 10−5 m γ‐aminobutyric acid. With PCN a higher concentration than 300 u, IT amplitude was treater than that of the original peak IGly. This was observed in 18 neurones out of 21. The maximal amplitude of the IT was achieved with 600 u PCN.
Intervascular and stimulus selectivity of nitrendipine and related derivatives in KCl and prostaglandin F2α precontracted porcine arteries
Authors: Kojda Georg , Klaus Wolfgang , Werner Günther , Fricke Uwe 
Published: July 2012

Dihydropyridine‐type calcium entry blockers exhibit a different vasodilator potency depending on the arterial tissue (intervascular selectivity) as well as on the precontracting stimulus used (stimulus selectivity). In addition, the structure of their ester side chains seems to influence their activity.
Vascular activity of nitrendipine and six related 3‐ester side chain derivatives was investigated in isolated coronary, ulnar and basilar arteries of the pig following precontraction with KCl or prostaglandin F2α (PGF2α).
After depolarization, all dihydropyridines exhibited a weak preferential action on coronary arteries. Bay E 6927 produced the strongest effect in all vessel types. By contrast, precontraction with PGF2α resulted in a marked preferential action in basilar arteries, although higher concentrations of the dihydropyridines were required for half maximal vasorelaxation. In each case, ulnar arteries were less sensitive.
Except with Bay O 5572, the most bulky substituted and least active derivative, only moderate differences were observed within the dihydropyridines studied. On the other hand, there was a pronounced increase in the ratios of the half maximal active concentrations required after precontraction of the vessels with PGF2α compared to KCl (stimulus selectivity) following a limited prolongation of the 3‐ester side chain up to an isopropyl‐group.
It is suggested that the observed shift in the intervascular selectivity after precontraction with PGF2α is a consequence of different contractile mechanisms in the three vessel types studied. The degree of the stimulus selectivity may also depend on the structure of the dihydropyridines.
Comparison of the contractile effects of endothelin‐1 and sarafotoxin S6b in goat isolated cerebral arteries
Authors: Salom Juan B. , Torregrosa Germán , Miranda Francisco J. , Alabadí José A. , Alborch Enrique 
Published: July 2012

The effects of endothelium‐derived endothelin‐1 and snake venom‐derived sarafotoxin S6b, peptides with striking structural and functional similarities, were examined and compared in isolated middle cerebral arteries of goats.
Endothelin‐1 and sarafotoxin S6b contracted cerebral arteries in a concentration‐dependent manner. The potency of endothelin‐1 (EC50 = 4.9 (3.9–6.2) × 10−10 m) was about ten times higher than that of sarafotoxin S6b (EC50 = 5.5 (4.4–6.9) × 10−9 m). The tension returned to basal values after repeated washings and contraction with endothelin‐1 could be reproduced. Endothelin‐1 and sarafotoxin S6b induced further contraction in arteries precontracted with prostaglandin F2α (10−5 m).
Mechanical removal of the endothelium or incubation with indomethacin (10−5 m) displaced the concentration‐response curves to endothelin‐1 and, more pronouncedly, to sarafotoxin S6b to the left. The maximum response to sarafotoxin S6b was also increased by either of these two treatments.
Incubation in ‘nominally’ Ca2+‐free medium attenuated the vasoconstrictor response to endothelin‐1 but not to sarafotoxin S6b, which was inhibited after incubation in Ca2+‐free medium to which EGTA (10−4 m) had been added. Pretreatment with caffeine (2 × 10−2 m) in Ca2+‐free medium abolished responses to endothelin‐1 and sarafotoxin S6b.
Bay K 8644 (10−10 m, 10−8 m) enhanced and nicardipine (10−10 m, 10−8 m) inhibited in a concentration‐dependent manner vasoconstrictor response to endothelin‐1. Response to sarafotoxin S6b was only affected by 10−8 m Bay K 8644 or nicardipine.
It is concluded that endothelin‐1 and sarafotoxin S6b are potent vasoconstrictors of goat cerebral arteries, having direct effects on smooth muscle which are counteracted by the endothelium through the release of a vasodilatator substance, probably prostacyclin. Both endothelin‐1 and sarafotoxin S6b depend on extracellular Ca2+ and on intracellular, caffeine‐sensitive Ca2+ stores to develop vasoconstriction. However, endothelin‐1 depends to a larger extent than sarafotoxin S6b on free extracellular Ca2+.