bluuebunny/crossref_metadata_2025_split huggingface dataset:
PAF‐induced muscarinic cholinoceptor hyperresponsiveness of ferret tracheal smooth muscle and gland secretion in vitro
Authors: Webber S.E. , Morikawa T. , Widdicombe J.G. 
Published: July 2012

The effects of exposure of the ferret trachea in vitro to platelet activating factor (PAF) were examined on methacholine‐induced smooth muscle contraction, mucus volume and lysozyme outputs, and albumin transport across the tracheal epithelium.
Methacholine (0.1–30 μm) produced concentration‐dependent increases in tracheal smooth muscle tone and mucus volume, lysozyme and albumin outputs from the trachea.
The concentration‐response curves for methacholine‐induced smooth muscle contraction, mucus volume and lysozyme outputs were all shifted upwards after exposure of the trachea to PAF (1 μm) with a significant increase in maximum response for each variable. The EC50 values for methacholine‐induced smooth muscle contraction and mucus volume output were significantly reduced after PAF exposure suggesting an increase in the potency of methacholine. The concentration‐response curve for methacholine‐induced albumin output was shifted downwards after PAF exposure with a greatly reduced maximum but no change in the EC50 for methacholine.
PAF‐induced hyperresponsiveness of methacholine‐induced smooth muscle contraction, mucus volume and lysozyme outputs was not affected by indomethacin, FPL55712, or mepyramine and cimetidine, but was prevented by catalase and superoxide dismutase (SOD), and by WEB2086. Similarly, PAF‐induced inhibition of methacholine‐stimulated albumin output was prevented by catalase and SOD, and by WEB2086.
We conclude that PAF induces hyperresponsiveness of ferret tracheal smooth muscle and submucosal gland secretion (including lysozyme secretion from serous cells) to methacholine. This hyperresponsiveness is probably produced by receptor‐mediated release of oxygen free‐radicals. The inhibition of methacholine‐induced albumin flux suggests a loss of epithelial function which is also probably mediated by release of free‐radicals. The mechanism by which the free‐radicals produce the changes in responsiveness to methacholine, and the cellular source of the free‐radicals, remain to be established.
Adenosine receptors in post‐mortem human brain
Authors: James Stephen , Xuereb John H. , Askalan Rand , Richardson Peter J. 
Published: July 2012

Adenosine A2‐like binding sites were characterized in post‐mortem human brain membranes by examining several compounds for their ability to displace [3H]‐CGS 21680 (2[p‐(2 carboxyethyl)‐phenethylamino]‐5′‐N‐ethylcarboxamido adenosine) binding.
Two A2‐like binding sites were identified in the striatum.
The more abundant striatal site was similar to the A2a receptor previously described in rat striatum, both in its pharmacological profile and striatal localization.
The less abundant striatal site had a pharmacological profile similar to that of the binding site characterized in the other brain regions examined. This was intermediate in character between A1 and A2 and may represent another adenosine receptor subtype.
The co‐purification of [3H]‐CGS 21680 binding during immunoisolation of human striatal cholinergic membranes was used to assess the possible cholinergic localization of A2‐like binding sites in the human striatum. Only the more abundant striatal site co‐purified with cholinergic membranes. This suggests that this A2a‐like site is present on cholinergic neurones in the human striatum.
Effect of neuropeptide Y on adrenergic and non‐adrenergic, non‐cholinergic responses in the rat anococcygeus muscle
Authors: Vila E. , Tabernero A. , Fernandes F. , Salaices M. 
Published: July 2012

The effects of neuropeptide Y (NPY) were examined on adrenergic and non‐adrenergic, non‐cholinergic (NANC) neurotransmission in the rat anococcygeus muscle.
NPY (0.1–0.3 μm) greatly potentiated the contractile responses induced by field stimulation. Prazosin (0.1 μm) completely abolished the stimulation‐induced responses either in the absence or presence of NPY.
NPY (0.1–0.3 μm) enhanced only the contractile responses to low doses of noradrenaline (NA, 0.003–0.01 μm). Responses to tyramine were unaffected by the same concentrations of NPY.
In superfused anococcygeus, previously loaded with [3H]‐NA, NPY (0.1–0.3 μm) failed to modify the basal, as well as the stimulation‐evoked, release of tritium at 2 and 4 Hz.
NANC relaxations induced by electrical stimulation were significantly reduced, in a concentration‐related manner, by 0.1–0.3 μm NPY.6 l‐NG‐nitro‐arginine (l‐NOARG, 30 μm) enhanced the stimulation (0.25–1 Hz)‐induced motor responses. In the presence of l‐NOARG (30 μm), NPY (0.1 μm) did not modify the motor responses induced by field stimulation (0.25–0.5 Hz). l‐Arginine did not reverse the NPY‐induced potentiation of stimulation‐induced motor responses.7 The relaxations of anococcygeus muscle induced by sodium nitroprusside (SNP, 0.01–0.3 μm) were diminished by NPY (0.1–0.3 μm).8 Our study suggests that NPY, at concentrations devoid of contractile effect, potentiates the motor responses of rat anococcygeus muscle as a consequence, at least in part, of the inhibition of NANC relaxing responses by a different mechanism from l‐NOARG.
Vasopressin‐stimulated [3H]‐inositol phosphate and [3H]‐phosphatidylbutanol accumulation in A10 vascular smooth muscle cells
Authors: Plevin Robin , Stewart Allison , Paul Andrew , Wakelam Michael J.O. 
Published: July 2012

The characteristics of vasopressin‐stimulated phosphatidylinositol 4,5 bisphosphate (PtdIns(4,5)P2) and phosphatidylcholine (PtdCh) hydrolysis were examined in A10 vascular smooth muscle cells (VSMC), by assessing the formation of [3H]‐inositol phosphates ([3H]‐IP) and the accumulation of the phospholipase D (PLD) specific product, [3H]‐phosphatidylbutanol ([3H]‐PtdBuOH).
Vasopressin ([Arg8]‐VP) and a number of related analogues stimulated the accumulation of [3H]‐IP and [3H]‐PtdBuOH with similar EC50 values, generating the same rank order of potency for each response (Arg8‐VP = vasotocin = Lys8‐VP ≫ oxytocin).
Inhibition of vasopressin‐stimulated [3H]‐IP and [3H]‐PtdBuOH accumulation by the V1a receptor antagonists, Des‐Gly9[β‐mercapto‐β,β,‐cyclopentamethylene propionyl, O‐Et‐Tyr2,Val4,Arg8]‐vasopressin generated similar IC50 values suggesting that both these responses are mediated through the activation of a single V1a receptor subtype.
The onset of vasopressin‐stimulated inositol‐1,4,5‐trisphosphate (Ins(1,4,5)P3) mass formation proceeded [3H]‐PtdBuOH accumulation indicating that PtdCh hydrolysis was activated subsequent to PtdIns(4,5)P2 breakdown.
The protein kinase C (PKC) activator, tetradecanoylphorbol acetate (TPA) also stimulated [3H]‐PtdBuOH accumulation. Preincubation with the PKC inhibitor Ro‐31–8220 abolished both TPA‐ and vasopressin‐stimulated [3H]‐PtdBuOH, suggesting that the intermediate activation of protein kinase C is involved in the regulation of PLD by vasopressin.6 Pretreatment of the A10 VSMC with Ro‐31–8220 (100 μm) also potentiated vasopressin‐stimulated Ins(1,4,5)P3 mass formation. Therefore stimulation of PKC may have opposing roles in the regulation of agonist activation of PLC and PLD.7 Preincubation of the cells with EGTA, verapamil, or the receptor‐operated calcium channel antagonist, SK&F 96365, reduced vasopressin‐stimulated [3H]‐PtdBuOH accumulation by approximately 30%, suggesting that influx of calcium has a significant role to play in the regulation of vasopressin‐stimulated PLD activity.
GH4ZD10 cells expressing rat 5‐HT1A receptors coupled to adenylyl cyclase are a model for the postsynaptic receptors in the rat hippocampus
Authors: Fowler C.J. , Ahlgren P.C. , Brännström G. 
Published: July 2012

Vasoactive intestinal polypeptide (VIP) stimulated adenosine 3′:5′‐cyclic monophosphate (cyclic AMP) production by cultured GH4ZD10 cells with an EC50 value of about 7 nm. The extracellularly recovered cyclic AMP predominated, and was reduced by co‐incubation with 8‐hydroxy‐2‐(di‐n‐propylamino) tetralin (8‐OH‐DPAT) and 5‐hydroxytryptamine (5‐HT), whereas dopamine (0.1–30 μm) did not reduce VIP‐stimulated cyclic AMP production.
The responses to 5‐HT and 8‐OH‐DPAT were blocked by (−)‐alprenolol and NAN 190. The antagonism by (−)‐alprenolol was competitive in nature with a pA2 value of 7.0.
The responsiveness of the cells to 5‐HT agonists was highly dependent upon the culturing conditions used. Thus, 8‐OH‐DPAT inhibition of VIP (30 nm)‐stimulated cyclic AMP production decreased with increasing passage number of the cells. Reduction of the zinc concentration used to promote expression of the 5‐HT1A receptor gene produced a greater sensitivity of the cells to 5‐HT agonists.
Under such conditions, the following efficacies (5‐HT = 100) were found: lisuride 106, (+)‐lysergic‐acid diethylamide 100, 5‐methoxy‐N,N‐dimethyltryptamine 98, RU 24949 98, 5‐carboxamidotryptamine 97, (±)‐8‐OH‐DPAT 90, (+)‐8‐OH‐DPAT 87, 1‐[2‐(4‐aminophenyl)ethyl]‐4‐(3‐trifluoromethylphenyl)‐piperazine 86, flesinoxan 79/88, (−)‐8‐OH‐DPAT 62, buspirone 43/50, ipsapirone 46. Spiroxatrine and spiperone had a low intrinsic activity, but reduced the response to 5‐HT. These efficacies are similar to those reported in the literature for post‐synaptically localized 5‐HT1A receptors in the rat hippocampus. Thus, the GH4ZD10 cells serve as a useful in vitro model system for these receptors.
Characterization of adrenoceptors involved in the electrogenic chloride secretion by cultured rat epididymal epithelium
Authors: Leung A.Y.H. , Yip W.K. , Wong P.Y.D. 
Published: July 2012

Short‐circuit current (SCC) technique was used to study the adrenoceptors involved in the electrogenic chloride secretion by cultured cauda epididymal epithelium of rats. Stimulation of the epithelium with noradrenaline (primarily β1‐adrenoceptor selective agonist), salbutamol (β2‐adrenoceptor selective agonist) and adrenaline (non‐selective β‐adrenoceptor agonist) led to a rise in SCC. At a low chart‐speed (2 mm min−1), the response profile to these agonists consisted of a peak followed by a sustained response considerably higher than the basal SCC.
The EC50s (doses of agonist producing 50% maximum response) of noradrenaline, salbutamol and adrenaline were 300, 115 and 10 nm respectively. Pretreating the tissues with 1 μm atenolol (β1‐selective antagonist) and 10 μm butoxamine (β2‐selective antagonist) shifted the dose‐response curves of noradrenaline (shifted EC50 = 4000 nm) and salbutamol (shifted EC50 = 1050 nm) to the right. Atenolol (1 μm) and butoxamine (10 μm) shifted the dose‐response curve of adrenaline to the right with new EC50s of 30 nm and 115 nm, respectively.
The rapidly rising phase of the SCC response to noradrenaline and adrenaline observed at low chart‐speed consisted of a brief and transient retraction followed by a rebound increase in SCC. At a high chart‐speed (1 mm s−1), the retraction and rebound phenomenon manifested as a fast initial spike which could be blocked by phentolamine (non‐specific α‐adrenoceptor antagonist) in a dose‐dependent fashion. Similar initial spikes were observed when the tissues were stimulated with phenylephrine (α1‐selective agonist) but not with isoprenaline (non‐selective β‐agonist) or forskolin (activator of adenylate cyclase). The response of the initial spike triggered by noradrenaline was dose‐dependent and the EC50 was 2000 nm.
The present study showed that the electrogenic chloride secretion by rat epididymis could be stimulated by α1, β1‐ and β2‐adrenoceptor agonists. The α1‐mediated response had a faster onset and more transient action than the β‐counterpart. It is postulated that epididymal chloride secretion might be regulated by neural (noradrenaline‐mediated) and humoral (adrenaline‐mediated) controls and that the stimulus‐secretion coupling mechanisms might involve both Ca2+ (α1‐mediated response) and adenosine 3′:5′‐cyclic monophosphate (β‐mediated response) as intracellular second messengers.
Involvement of nitric oxide pathway in the PAF‐induced relaxation of rat thoracic aorta
Authors: Moritoki Hideki , Hisayama Tetsuhiro , Takeuchi Shougo , Miyano Hiroaki , Kondoh Wataru 
Published: July 2012

The mechanism of the vasorelaxant effect of platelet activating factor (PAF) on rat thoracic aorta and the effect of aging on the PAF‐induced relaxation were investigated.
PAF at concentrations causing relaxation induced marked increases in guanosine 3′:5′‐cyclic monophosphate (cyclic GMP) production, but did not induce an increase in adenosine 3′:5′‐cyclic monophosphate (cyclic AMP).
Removal of the endothelium by mechanical rubbing, and treatment with the PAF antagonists CV‐3988, CV‐6209 and FR‐900452, the nitric oxide biosynthesis inhibitor, NG‐nitro l‐arginine, the radical scavenger, haemoglobin, and the soluble guanylate cyclase inhibitor, methylene blue, inhibited PAF‐induced relaxation and abolished or attenuated PAF‐stimulated cyclic GMP production.
The relaxation was greatest in arteries from rats aged 4 weeks. With an increase in age, the response of the arteries to PAF was attenuated.
Endothelium‐dependent cyclic GMP production also decreased with increase in age of the rats.6 These results suggest that PAF stimulates production of nitric oxide from l‐arginine by acting on the PAF receptors in the endothelium, which in turn stimulates soluble guanylate cyclase in the smooth muscle cells, and so increases production of cyclic GMP, thus relaxing the arteries. Age‐associated decrease in PAF‐induced relaxation may result from a reduction of cyclic GMP formation.
Activation of the human neutrophil 5‐lipoxygenase by leukotriene B4
Authors: McDonald Patrick P. , McColl Shaun R. , Naccache Paul H. , Borgeat Pierre 
Published: July 2012

In the present study, we demonstrate that leukotriene B4 (LTB4) has the ability to activate the human neutrophil 5‐lipoxygenase (5‐LO).
Stimulation of neutrophils with 30 nm 14,15‐dideuterio‐LTB4 (D2‐LTB4) failed to induce the synthesis of LTB4 from endogenous arachidonic acid (AA), but stimulated the formation of LTB4 from 3.3 μm exogenous AA, as determined by GC‐MS analysis.
The stimulatory effect of LTB4 on 5‐LO activity was further examined with an alternative substrate; LTB4 time‐ and dose‐dependently stimulated the 5‐LO‐mediated conversion of exogenous 15(S)‐hydroperoxy‐5,8,11,13‐(Z,Z,Z,E)‐eicosatetraenoate (15‐HpETE) into 5(S), 15(S)‐dihydroxy‐6,8,11,13,‐(E,Z,Z,E)‐eicosatetraenoate (5,15‐DiHETE), with a threshold effect at 300 pm.
The ability of LTB4 to activate the 5‐LO showed structural specificity, since LTB4 was found to be 100 times more potent than ω‐hydroxy‐LTB4, and 300 times more potent than its Δ6‐trans‐12‐epi‐ isomer.
The LTB4‐induced 5‐LO activation was effectively inhibited by MK‐886 (an inhibitor of 5‐LO translocation), by pertussis toxin, and by the LTB4 receptor antagonist, LY‐223982.6 These results demonstrate that the binding of LTB4 to its cell‐surface receptor results in 5‐LO activation in a process mediated by pertussis toxin‐sensitive guanine nucleotide‐binding proteins. Our data also suggest that the underlying mechanism involves a translocation of the 5‐LO to the membrane. These findings raise the possibility that LTB4 produced by phagocytes may positively feedback on its own synthesis.
Cardiovascular effects of substituted tetrahydroisoquinolines in rats
Authors: Dong Hui , Lee Chi‐Ming , Huang Wen‐Long , Peng Si‐Xun 
Published: July 2012

A series of substituted tetrahydroisoquinolines derived from the cleavage products of tetrandrine were found to inhibit [3H]‐nitrendipine binding to rat cerebral cortical membranes. Those compounds which displaced [3H]‐nitrendipine binding were also able to inhibit high KCl‐induced contraction of rat aorta in vitro.
There was a significant correlation between the ability of these tetrahydroisoquinolines to inhibit [3H]‐nitrendipine binding and KCl‐induced contraction (r = 0.99, P < 0.001).
CPU‐23 (1‐{1‐[(6‐methoxy)‐naphth‐2‐yl]}‐propyl‐2‐(1‐piperidine)‐acetyl‐6,7‐dimethoxy‐1,2,3,4,‐tetrahydroisoquinoline), one of the most potent compounds identified in this series, behaved as a simple competitive inhibitor at the [3H]‐nitrendipine binding site and reduced the apparent affinity but not the maximal number of binding sites in saturation analysis.
In contrast to nifedipine which caused hypotension and tachycardia, CPU‐23 induced both hypotension and bradycardia in a dose‐dependent manner in pentobarbitone‐anaesthetized Sprague‐Dawley rats, spontaneously hypertensive and age‐matched normotensive WKY rats.
It is suggested that CPU‐23 may exert its cardiovascular effects via interaction with the dihydropyridine binding site on the L‐type calcium channel.
Effects of cholinoceptor and 5‐hydroxytryptamine3 receptor antagonism on erythromycin‐induced canine intestinal motility disruption and emesis
Authors: Qin Xin Yu , Pilot Marie‐Anne , Thompson Hilary , Scott Mark 
Published: July 2012

Erythromycin administration is associated with gastrointestinal problems, disturbed gastrointestinal motility and emesis. This study in the dog investigates the underlying mechanisms.
Intestinal myoelectrical activity and the occurrence and latency of emesis were recorded in eight conscious dogs. All drugs were administered intravenously.
Erythromycin (7 mg kg−1) increased contractions of the proximal small intestine, and caused emesis in all fasted dogs and in 5 dogs after food. Atropine (50 mg kg−1 min−1) and hexamethonium (10 mg kg−1 h−1) partially inhibited the GI motility effects but did not significantly reduce emesis.
Metoclopramide at a high dose (2 mg kg−1 h−1) reduced the incidence of emesis in the presence of increased intestinal motility, but a low dose (150 μg kg−1 h−1) was ineffective.
A 5‐hydroxytryptamine3 (5‐HT3) receptor antagonist, MDL 72222 (1 mg kg−1), reduced emesis when given alone and combined with metoclopramide (low dose). The 5‐HT4 receptor agonist BRL24924 (Renzapride, 1 mg kg−1) had no effect on emesis either alone in combination with metoclopramide.
In conclusion, erythromycin‐induced GI motility disturbances and emesis are not causally related. Whereas the increase in intestinal smooth muscle activity is possibly cholinergically mediated, emesis occurs at least in part via a 5‐hydroxytryptaminergic mechanism, but does not involve the dopamine system.
Na+/H+ exchange inhibitors reverse lactate‐induced depression in postischaemic ventricular recovery
Authors: Karmazyn Morris 
Published: July 2012

By use of pharmacological approaches, the present study examined the hypothesis that the deleterious effect of lactate on postischaemic ventricular recovery may be mediated, at least in part, by enhanced activation of the Na+/H+ exchanger at the time of reperfusion.
Spontaneously beating isolated hearts of the rat were subjected to 15 min zero‐flow global ischaemia followed by 30 min reperfusion. The effects of lactate (10, 20 or 40 mm) were studied by adding it 20 min before ischaemia whereas reperfusion was carried out with lactate‐free buffer.
Pretreatment with 20 or 40 mm lactate significantly reduced postischaemic recovery of developed force to 17 ± 3% and 16 ± 4% of preischaemic values (P < 0.05) compared to a 78 ± 4% recovery in control hearts. Similarly, recovery in ventricular rate was significantly reduced to 34 ± 7.6% and 38 ± 12% with 20 and 40 mm lactate, respectively compared to 97.5 ± 6.4% recovery in control hearts. At a concentration of 10 mm, lactate was without effect on either force or ventricular rate recovery.
Coadministration of either of two Na+/H+ exchange inhibitors, amiloride (174 μm) or 5‐N,N‐hexamethylene amiloride (HMA, 1 μm) with lactate and inclusion of the two drugs during the first 5 min of reperfusion resulted in reversal of lactate‐induced inhibition of force recovery with observed recoveries of 69 ± 6.7% and 64 ± 5% with amiloride and HMA, respectively. Similarly, recovery in ventricular rate was significantly enhanced to 92 ± 10% and 89 ± 6% with amiloride and HMA, respectively compared to 38 ± 12% recovery in control hearts.
In electrically paced hearts (5 Hz) subjected to 15 min ischaemia and 30 min reperfusion, 40 mm lactate significantly reduced force recovery to 36 ± 5.5% compared to 57 ± 6% in control hearts. In the presence of amiloride or HMA, force recovery in lactate‐treated hearts was significantly increased to 68 ± 16% and 72 ± 4.7% of preischaemic values, respectively.
In spontaneously beating hearts, resting tension changes during both ischaemia and reperfusion were not statistically different between treatment groups. However, in paced hearts pretreated with 40 mm lactate the elevation in resting tension during the first 5 min of reperfusion, was significantly reduced by both amiloride and HMA.
Changes in functional recoveries produced by either lactate or Na+/H+ exchange inhibitors were unrelated to alterations in high energy phosphate depletion during ischaemia or to repletion of these compounds after 30 min reperfusion either in spontaneously beating or electrically paced hearts.
The results suggest that stimulated Na+/H+ exchange activation at reflow contributes, at least partially, to lactate‐induced depression of postischaemic recovery.
Effect of an intracellular calcium chelator on the regulation of electrically evoked [3H]‐noradrenaline release from rat hippocampal slices
Authors: Fredholm Bertil B. , Hu Ping‐Sheng 
Published: July 2012

The electrically (3 Hz, 5 min) evoked [3H]‐noradrenaline ([3H]‐NA) release from rat hippocampal slices was reduced by prior treatment of the slices with 1,2‐bis(2‐aminophenoxy)ethane‐N,N,N′N′‐tetraacetomethylester (BAPTA/AM) in a concentration‐(10 to 500 μm) dependent manner (40% at 30 μm). Reduction of medium calcium from 1.3 to 0.5 mm caused a larger (70%) decrease. BAPTA free acid (100 mm), a non‐permeable Ca2+‐chelator had no significant effect.
Basal [3H]‐noradrenaline release was reduced by BAPTA/AM in a concentration‐dependent manner (50% at 30 μm), but reduction of external Ca2+ from 1.3 to 0.5 mm did not alter basal release.
About 10% of total [3H]‐NA in the slices was released at 3 Hz stimulation in 1.3 mm Ca2+ buffer. Addition of the α2‐adrenoceptor antagonist, idazoxan (1 μm), increased electrically evoked [3H]‐NA release to 26% but stimulated release was not altered by the adenosine A1‐receptor antagonist, 8‐cyclopentyl theophylline (8‐CPT) (1 μm).
Evoked release was reduced by the α2‐receptor agonist, UK 14,304, in a concentration‐dependent manner in the presence of 8‐CPT (1 μm). The magnitude of this effect was not altered by the treatment of slices with 30 μm BAPTA/AM.
The adenosine A1 receptor agonist, N6‐cyclohexyl adenosine (CHA) (1 μm) inhibited electrically evoked [3H]‐NA release by about 40% in the presence of idazoxan (1 μm). The effect of CHA was not significantly altered by treatment of slices with BAPTA/AM.
The N‐type Ca2+ ‐channel antagonist, ω‐conotoxin (30 nm), inhibited electrically evoked [3H]‐NA release by 30–50% and this was not altered by treatment of the slices with BAPTA/AM.
The present results show that spontaneous [3H]‐NA release is affected by reduction of intracellular Ca2+, but not by reduction of extracellular Ca2+ or by the presynaptic agonists or ω‐conotoxin. By contrast, electrically evoked release was affected more strongly by alterations of extracellular Ca2+ than by buffering intracellular Ca2+. The reduction of electrically evoked [3H]‐NA release by agonists at the adenosine A1‐receptor and α2‐adrenoceptor is probably mediated through the control of Ca2+ entry via membrane ion channels or at a low affinity Ca2+‐site governing evoked release.