bluuebunny/crossref_metadata_2025_split huggingface dataset:
Functional dopamine D2 receptors on rat vagal afferent neurones
Authors: Lawrence Andrew J. , Krstew Elena , Jarrott Bevyn 
Published: July 2012

1 In the present study in vitro electrophysiology and receptor autoradiography were used to determine whether rat vagal afferent neurones possess dopamine D2 receptors.2 Dopamine (10–300 μm) elicited a temperature‐ and concentration‐dependent depolarization of the rat isolated nodose ganglion preparation. When applied to the tissue 15 min prior to agonist, raclopride (10 μm), clozapine (10 μm) or a mixture of raclopride and clozapine (10 μm each) all produced a threefold parallel shift to the right of the dopamine concentration‐response curve. In contrast, SCH 23390 (100 nM), phentolamine and propranolol (1 μm each) failed to antagonize the dopamine‐mediated depolarization.3 [125I]‐NCQ 298 (0.5 nM), a D2 selective radioligand, bound topographically to sections of rat brainstem. Densitometric quantification of autoradiograms revealed 93.8 ± 0.5% specific binding of this salicylamide radioligand, as determined by raclopride (10 μm, n = 10 animals). Binding was highest in the nucleus tractus solitarius (NTS), particularly the medial and gelatinous subnuclei. In addition, specific binding was also observed in the interpolar spinal trigeminal nucleus and the inferior olive.4 Unilateral nodose ganglionectomy caused a 36.6 ± 3.0% reduction in specific binding in the denervated NTS compared to the contralateral NTS. Furthermore, the loss of binding was confined to the dorsal aspect of the medial subnucleus of the NTS. Sham surgery had no effect on the binding of [125I]‐NCQ 298 in rat brainstem.5 The present data provide evidence for the presence of functionally relevant dopamine D2 receptors on both the soma and central terminals of rat vagal afferent neurones. In addition, the majority of D2 receptors in the rat NTS appear to be located postsynaptically with respect to vagal terminals, and are presumably located either on ascending glossopharyngeal terminals, descending terminals from higher brain regions or on neuronal cell bodies within the NTS.
Selective modification of rat hepatic microsomal fatty acid chain elongation and desaturation by fibrates: relationship with peroxisome proliferation
Authors: Alegret Marta , Cerqueda Enric , Ferrando Rosa , Vazquez Manuel , Sánchez Rosa M. , Adzet Tomás , Merlos Manuel , Laguna Juan C. 
Published: July 2012

1 The time‐course of the effect of clofibrate (CFB), bezafibrate (BFB) and gemfibrozil (GFB) on lipid plasma levels and palmitoyl‐, palmitoleoyl‐ and γ‐linolenoyl‐CoA elongase, Δ‐9, Δ‐6 and Δ‐5 desaturase activities, and microsomal electron transport chains, as well as the correlation with the peroxisomal proliferation phenomenon have been studied in male Sprague‐Dawley rats.2 As reported in our previous work, the three drugs behave as peroxisomal proliferators (the order of potency was BFB> CFB ≤ GFB) and induced a clear reduction in both plasma cholesterol and triglyceride levels.3 Palmitoyl‐CoA elongation activity was increased by the three drugs (BFB = GFB> CFB), whereas palmitoleoyl‐CoA elongation activity was only enhanced by GFB. Elongation activity was not modified by fibrates when γ‐linolenoyl‐CoA was used as substrate. These results are in accordance with the existence of three different elongation systems for saturated, mono‐ and polyunsaturated fatty acids.4 Δ‐9, Δ‐6 and Δ‐5 desaturase activities were increased by the three fibrates, with an order of potency BFB>CFB = GFB for Δ‐9 and Δ‐5, and GFB>BFB = CFB for Δ‐6.5 Of the enzyme activities integrated in the microsomal electron transport chains, NADH cytochrome b5 reductase was not affected by fibrate treatment, NADPH cytochrome c reductase activity was enhanced (BFB = GFB> CFB), whereas NADH cytochrome c reductase activity was reduced by CFB and BFB.6 The increase in Δ‐9 and Δ‐5 desaturase activities was highly dependent on the peroxisomal proliferation phenomena, whereas the increase in Δ‐6 desaturase activity and the decrease in NADH cytochrome c reductase was mainly independent. The modifications of palmitoyl‐CoA elongase and NADPH cytochrome c reductase activities, as well as plasma lipid levels, were partially correlated with peroxisomal β‐oxidation, but the r2 values obtained point to the existence of additional independent mechanisms.7 As man is assumed to be a species refractory to peroxisomal proliferation, only those fibrate effects not absolutely related to this phenomenon are expected to appear after fibrate therapy.
Blockade by polyamine NMDA antagonists related to ifenprodil of NMDA‐induced synthesis of cyclic GMP, increases in calcium and cytotoxicity in cultured neurones
Authors: Beart Philip M. , Schousboe Arne , Frandsen Aase 
Published: July 2012

1 Antagonists acting at the polyamine site of the N‐methyl‐D‐aspartate (NMDA) subtype of glutamate receptor, including a number of heterocyclic aminoalcohols related to ifenprodil, were investigated to establish their functional interaction at the NMDA receptor and their neuroprotective profile.2 In murine cultured neocortical neurones, NMDA (100μm)‐stimulated production of guanosine 3′:5′‐cyclic monophosphate (cyclic GMP) was blocked by N‐l([thienyl]‐cyclohexyl)‐piperidine (1 μm) and by the nitric oxide (NO) synthase inhibitor NG‐nitro‐L‐arginine (100 μm). Ifenprodil and structurally related heterocyclic aminoalcohols inhibited in a concentration‐dependent manner the NMDAstimulated, NO‐dependent production of cyclic GMP; rank potency order was: ifenprodil > 2309 BT > tibalosine > threo‐tibalosine > 840S.3 All of the polyamine NMDA antagonists blocked NMDA (300 μm)‐stimulated increases in intracellular calcium concentrations as measured by changes in the fluorescence of pre‐loaded fluo‐3‐acetoxy methyl ester. Rank potency order was: ifenprodil > 2309 BT > 840S > tibalosine > threotibalosine.4 In a series of experiments to evaluate the effectiveness of the polyamine NMDA antagonists as blockers of NMDA‐induced cytotoxicity, all of the drugs were found to inhibit the leakage of lactate dehydrogenase after the exposure of the murine neocortical cultures to NMDA (100 μm, 5 h). Rank potency order was: 2309 BT > ifenprodil > tibalosine > threo‐tibalosine > 840S.5 These results provide direct evidence that polyamine NMDA antagonists produce a functional blockade of the NMDA receptor complex. The heterocyclic aminoalcohols described herein, like ifenprodil, block NMDA‐mediated elevation of intracellular NO and calcium, two key events in the excitotoxic cascade, and are cytoprotective.
Effects of acute and chronic ethanol on cyclic AMP accumulation in NG108‐15 cells: differential dependence of changes on extracellular adenosine
Authors: Kelly E. , Williams RJ. , Harrison P.K. 
Published: July 2012

1 This study investigated the effects of acute and chronic ethanol on basal, agonist‐ and forskolin‐stimulated cyclic AMP formation in NG108‐15 mouse neuroblastoma x rat glioma hybrid cells, and examined the role of changes in extracellular adenosine concentrations on the effects observed.2 NG108‐15 cells incubated acutely with ethanol (1–200 mM) displayed concentration‐dependent increases in basal and iloprost‐stimulated (300 nM; a prostanoid IP receptor agonist) cyclic AMP accumulation but a concentration‐dependent decrease in forskolin‐stimulated (10 μm) accumulation.3 Cells treated chronically with ethanol (200 mM) for 48 h displayed increases over control in basal, iloprost‐ (0.001–10 μm) and forskolin (0.01–100 μm)‐stimulated cyclic AMP formation. However, chronic ethanol did not affect [3H]‐iloprost binding to cell membranes.4 Inclusion of adenosine deaminase (ADA; 1 unit ml−1) during the incubation period to measure cyclic AMP accumulation completely abolished the increase in basal accumulation following chronic ethanol, but did not affect the increase in iloprost stimulation. On the other hand ADA partially reversed the increase in forskolin stimulation following chronic ethanol, but even in the presence of high concentrations of ADA (5 units ml−1) the forskolin stimulation remained elevated above control.5 Cells treated chronically with the adenosine receptor agonist 5′‐(N‐ethylcarboxamido)‐adenosine (NEC A; 10 μm for 48 h) displayed a reduction in subsequent NEC A‐ and forskolin‐stimulated cyclic AMP accumulation, but iloprost stimulation was not affected. ADA included acutely during the incubation period to measure cyclic AMP accumulation abolished the reduction in forskolin but not NECA stimulation produced by the chronic NECA pretreatment.6 We have previously noted that ethanol inhibits NG108‐15 cell proliferation and alters cell morphology. To mimic this, cells were incubated in the absence of foetal calf serum for 48 h. Following this time, basal, iloprost‐ and forskolin‐stimulated cyclic AMP formation was enhanced over that in cells grown in the presence of serum.7 These results indicate that chronic ethanol enhances cyclic AMP formation in intact NG108‐15 cells by more than one mechanism: one involves increased extracellular adenosine concentrations and the other a change in the transduction system beyond the receptor, possibly involving the adenylyl cyclase enzyme. Furthermore the ethanol‐induced changes in cyclic AMP accumulation may relate to alterations in NG108‐15 cell growth and development.
Inhibition of serum‐induced proliferation of bovine tracheal smooth muscle cells in culture by heparin and related glycosaminoglycans
Authors: Kilfeather S.A. , Tagoe S. , Perez A.C. , Okona‐Mensa K. , Matin R. , Page C.P. 
Published: July 2012

1 The effect of heparin and related glycosaminoglycans on bovine airway smooth muscle proliferation has been investigated.2 Foetal bovine serum stimulated division of bovine trachealis smooth muscle cells in a concentration‐dependent fashion at concentrations between 1 and 30%.3 Heparin (0.1–100 μg ml‐1), heparan sulphate (0.1–100 μg ml−1) and fragmin (0.1–100 μg ml−1) inhibited smooth muscle division in a concentration‐dependent fashion between 0.1–100 μg ml−1. A heparin disaccharide did not exhibit inhibition of division at 100 μg ml−1.4 Dextran sulphate at molecular weights of 5 × 103 and 5 × 105 concentration‐dependently inhibited division between 0.1–100 μg ml−1. Dextran without sulphation did not exhibit inhibition of division at 100 μg ml−1.5 The magnitude of inhibition of proliferation did not reach 100% for any compounds examined at concentrations up to 100 μg ml−1 during incubations for 5 and 14 days. IC50 values for inhibition of proliferation ranged between 1–5 μg ml−1.6 These findings suggest that heparin and related glycosaminoglycans inhibit bovine airway smooth muscle cell division.
Characterization of histamine H3 receptors regulating acetylcholine release in rat entorhinal cortex
Authors: Arrang J.M. , Drutel G. , Schwartz J.‐C. 
Published: July 2012

1 The pharmacological properties and location of H3 receptors modulating acetylcholine release have been investigated in non‐superfused slices and synaptosomes of rat entorhinal cortex preloaded with [3H]‐choline.2 (R)α‐methylhistamine, an H3‐receptor agonist, potently inhibited the K+‐evoked tritium release from slices, an effect antagonized by thioperamide, an H3‐receptor antagonist, with nanomolar potency.3 The K+‐evoked tritium release from synaptosomes remained unaltered in the presence of the potent and selective H3‐receptor agonists, imetit and (R)α‐methylhistamine, suggesting that H3 receptors modulating acetylcholine release are not presynaptically located on cholinergic nerve terminals.4 Phenylbutanoylhistamine and phenylpropylhistamine, two H3‐receptor antagonists of moderate potency, failed to antagonize the inhibitory effects of (R)α‐methylhistamine observed in slices. Unexpectedly, both compounds when used alone, inhibited tritium release from slices and synaptosomes with micromolar potency and to the same extent (by approximately 50% when added at a final concentration of 200 μm). This inhibitory effect did not involve H1, H2 or H3 receptors and was not mediated by an unknown histamine receptor site, since histamine used at a high concentration neither reproduced nor antagonized the effect of phenylbutanoylhistamine. It remained unaltered in the presence of scopolamine and was neither mimicked nor antagonized by vasoactive intestinal peptide, previously shown to be colocalized with acetylcholine in some neurones.5 It is concluded that acetylcholine release in rat entorhinal cortex is modulated by H3 receptors presumably not located on cholinergic axon terminals. It remains to be established whether these H3 receptors belong to a receptor subtype different from those previously described since the potency of phenylbutanoylhistamine and phenylpropylhistamine as H3‐receptor antagonists was probably greatly underestimated by additional properties of both drugs.
The role of nitric oxide in cardiac depression induced by interleukin‐1β and tumour necrosis factor‐α
Authors: Schulz Richard , Panas Donna L. , Catena Robert , Moncada Salvador , Olley Peter M. , Lopaschuk Gary D. 
Published: July 2012

Myocardial dysfunction during septic shock is associated with enhanced production of cytokines such as interleukin‐1β (IL‐1β) and tumour necrosis factor‐α (TNF‐α). These cytokines depress cardiac mechanical function by a mechanism which is not well defined.
Bacterial endotoxin or cytokines cause the expression of Ca2+‐independent nitric oxide (NO) synthase in cardiac myocytes, vascular endothelial cells and endocardial endothelial cells, causing enhanced production of NO. As NO has negative inotropic actions on cardiac muscle, we tested the sum effects of IL‐1β plus TNF‐α in the intact heart to determine whether enhanced expression of NO synthase activity in the cells that comprise the heart is involved in cardiac depression associated with cytokine stimulation.
Rat isolated working hearts perfused with IL‐1β plus TNF‐α showed a markedly greater depression in contractile function, measured as cardiac work, after 2 h of perfusion compared with time‐matched control hearts. The depressant action of IL‐1β plus TNF‐α was first apparent after 1 h of perfusion; no early (15 min) cardiac depressant actions were seen.
The competitive inhibitor of Ca2+‐dependent and Ca2+‐independent NO synthases, NG‐nitro‐l‐arginine methyl ester (l‐NAME, 3 μm) when given concurrently with IL‐1β plus TNF‐α prevented the loss in contractile function such that these hearts after 2h of perfusion had similar function to time‐matched controls. l‐NAME did not acutely reverse the loss of contractile function in hearts exposed for 2 h to IL‐1β plus TNF‐α. The protective action of l‐NAME in the presence of cytokines was concentration‐dependent and was not seen at a higher concentration (10 μm) due to the significant reduction in coronary flow observed at this concentration.
In contrast, when l‐NAME (3 μm) was given in the absence of IL‐1β plus TNF‐α it depressed contractile function over the 2h perfusion period by significantly reducing coronary flow.
Inhibition of protein synthesis with cycloheximide (Cx) abolished the loss in function that occurred over 2h in both control and IL‐1β plus TNF‐α‐treated hearts.
Inducible, Ca2+‐independent NO synthase activity was not observed in freshly isolated hearts but was observed in control hearts perfused for 2 h in vitro and was doubled in hearts perfused with IL‐1β plus TNF‐α. Cx prevented the expression of Ca2+‐independent NO synthase in both control and cytokine‐treated hearts.
In summary, these results suggest that the depression of myocardial function by IL‐1β plus TNF‐α is mediated, at least in part, by induction of Ca2+‐independent NO synthase activity in the heart.
Involvement of B2 receptors in the bradykinin‐induced relaxation of guinea‐pig isolated trachea
Authors: Da Silva A. , Amrani Y. , Trifilieff A. , Landry Y. 
Published: July 2012

The aim of this study was to determine the receptor type and involvement of arachidonic acid metabolites in bradykinin‐induced relaxation of the guinea‐pig isolated trachea.
In the resting tracheal preparation, bradykinin (0.1 nm − 30 μm induced a concentration‐related contractile response (pD2 = 8.8 ± 0.3). The maximal tension (1056 ± 321 mg) was observed at 0.3 μm bradykinin. In contrast, when tracheal preparations were pre‐contracted with histamine (30 μm leading to a half‐maximum response), a concentration‐related relaxation was observed with bradykinin. At the highest concentration of bradykinin used (3 μm), a reversal of 63 ± 13% of the contractile response to histamine was observed. Both effects of bradykinin were inhibited by the cyclo‐oxygenase inhibitor, indomethacin (1 μm). In concentration‐response curves, melittin (10 nm − 1 μm), a direct activator of phospholipase A2, mimicked both effects of bradykinin. The highest concentration of melittin used (1 μm), induced a tension of 813 ± 120 mg and led to the reversal of 41 ± 8% of the contractile response to histamine. The contractile effect of melittin was inhibited in the presence of both indomethacin (1 μm) and AA861 (1 μm), a 5‐lipoxygenase inhibitor.
[Des Arg9]‐bradykinin (1 nm‐3 μm), a B1‐receptor agonist, was unable to relax precontracted guinea‐pig tracheal preparations. The relaxation induced by bradykinin was antagonized by the B2 receptor antagonists, Hoe 140 (d‐Arg0[Hyp3, Thi5, d‐Tic7, Oic8]bradykinin) and NPC 17761 (d‐Arg0[Hyp3, d‐HypE(trans‐thiophenyl)7, Oic8]bradykinin). Hoe 140 (0.1 μm to 0.6 μm) behaved as a non‐competitive antagonist with an apparent pA2 = 7.2 ± 0.4, whereas NPC 17761 (0.3 to 1 μm) competitively antagonized bradykinin‐induced relaxation with a pKB = 7.3 ± 0.2. The Schild regression slope did not differ from unity, 0.96 ± 0.20, P < 0.05.
These data demonstrate that bradykinin‐induced relaxation of guinea‐pig trachea occurs via the activation of bradykinin B2‐receptors. The stimulation of B2‐bradykinin receptors induces the activation of the cyclo‐oxygenase pathway, leading either to contraction or relaxation depending on the tone of the trachea.
The kinin B1 receptor antagonist des‐Arg9‐[Leu8]bradykinin: an antagonist of the angiotensin AT1 receptor which also binds to the AT2 receptor
Authors: Pruneau D. , Duvoid A. , Luccarini J.M. , Bélichard P. , Bonnafous J.C. 
Published: July 2012

Agonists and antagonists of kinin B1 and B2 receptors were evaluated in vitro for their effects against angiotensin II (AII)‐induced contractile responses in the rabbit aorta and for their binding properties to angiotensin AT1 and AT2 receptors from purified membrane of rat liver and lamb uterus respectively.
In aortic rings, the kinin B1 receptor antagonist, des‐Arg9‐[Leu8]bradykinin (BK) (3–100 μm) caused a concentration‐dependent decrease in sensitivity and a depression of the maximum response to AII. Des‐Arg10‐[Leu9]kallidin (KD), des‐Arg9‐BK, des‐Arg10‐KD, BK or KD at 3 μm had no effect against All‐induced contractions.
Des‐Arg9‐[Leu8]BK (3 or 100 μm) did not affect contractions of aortic rings to histamine, potassium chloride, endothelin‐1, 5‐hydroxytryptamine, noradrenaline and the thromboxane A2‐mimetic, U46619.
Des‐Arg9‐[Leu8]BK displaced [125I]‐Sar1‐AII binding to the AT1 subtype in rat liver membranes with a Ki value of 1.1 ± 0.4 μm. Values of Ki for des‐Arg9‐BK and KD were 45 ± 13 μm and 25 ± 22 μm, respectively. The other kinin derivatives des‐Arg10‐KD, BK and des‐Arg10‐[Leu9]KD at concentrations up to 100 μm did not bind to the AT1 receptor.
All the kinin derivatives except BK bound to AT2 receptors in lamb uterus membranes. Values of Ki for des‐Arg9‐[Leu8]BK, des‐Arg10‐[Leu9]KD, des‐Arg9‐BK, des‐Arg10‐KD and KD were 0.3 ± 0.1, 0.7 ± 0.1, 1.2 ± 0.3, 1.5 ± 0.3 and 7.0 ± 1.6 μm, respectively.
In conclusion, des‐Arg9‐[Leu8]BK is an insurmountable antagonist of All‐induced contractions in the rabbit aorta and also binds with a relatively high affinity to AT1 and AT2 receptors in isolated membrane fractions. These additional properties of des‐Arg9‐[Leu8]BK should be considered when it is used as an antagonist to characterize kinin B1 receptors.
Differential effects of phosphoramidon on contractile responses to angiotensin II in rat blood vessels
Authors: Chen Lihua , McNeill J. Robert , Wilson Thomas W. , Gopalakrishnan Venkat 
Published: July 2012

Cumulative concentration‐tension response (C‐R) curves to angiotensin II (AII), big endothelin‐1 (big ET‐1), ET‐1 and arginine vasopressin (AVP) were determined in endothelium intact‐ring preparations of aorta, mesenteric artery and tail artery isolated from adult male Sprague‐Dawley rats in the presence or absence of the neutral metalloprotease inhibitor, phosphoramidon.
The order of sensitivity of the three rat vascular smooth muscle preparations to AII, big ET‐1 and ET‐1 was aorta> mesenteric artery> tail artery whereas that for AVP was reversed, namely, tail artery> mesenteric artery> aorta.
Phosphoramidon blocked the responses to AII in a concentration‐dependent manner, whereas even very high concentrations of phosphoramidon (100 μm) failed to affect the tension responses evoked by ET‐1 and AVP in all three preparations. Low concentrations of phosphoramidon (10 μm) produced significant increases in EC50 values for AII in tail artery (P<0.01) and mesenteric artery (P<0.05) but not in aorta. The rank order of sensitivity to the inhibition by phosphoramidon was tail artery< mesenteric artery< aorta. Phosphoramidon‐evoked rightward shifts in the C‐R curves to AII were much higher than those to big ET‐1 in both mesenteric artery and tail artery.
In endothelium‐denuded preparations, AII failed to evoke any increases in tension in tail artery while the responsiveness of the mesenteric artery to AII was reduced significantly relative to endothelium‐intact tissues with a rightward shift in the C‐R curve and a decrease in the maximal response. On the other hand, the C‐R curve to AII was shifted to the left in aorta following removal of the endothelium. Importantly, ET‐1 and AVP evoked vasoconstrictor responses were unaffected by the inclusion of a high concentration of phosphoramidon (100 μm) in endothelium‐denuded aorta and mesenteric artery.
The results suggest that AII‐evoked tension responses of blood vessels such as tail artery are completely endothelium‐dependent; in relatively larger blood vessels such as mesenteric artery they are partially endothelium‐dependent while in much bigger conduit type blood vessel such as aorta, they are endothelium‐independent. It is concluded that the vasoconstrictor responses to AII in mesenteric artery and tail artery may be mediated by the release of endothelins from the endothelium by increased formation from big ET, an effect that is blocked by phosphoramidon.