bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of macrophage depletion on the induction of histidine decarboxylase by lipopolysaccharide, interleukin 1 and tumour necrosis factor
Authors: Endo Yasuo , Nakamura Masanori , Nitta Yasutaka , Kumagai Katsuo
Published: July 2012

Our previous work has shown that injection into mice of lipopolysaccharide (LPS) and the cytokines interleukin 1 (IL‐1) and tumour necrosis factor (TNF) induces histidine decarboxylase (HDC), the enzyme forming histamine, in various tissues such as liver, lung, spleen and bone marrow, but not in the blood. The induction of HDC also occurs in nude mice and mast cell‐deficient mice. On the other hand, haematopoietic cytokines such as IL‐3, granulocyte colony‐stimulating factor (G‐CSF) and granulocyte – macrophage CSF (GM‐CSF) only induce HDC in the haematopoietic organs, i.e. bone marrow and spleen. In the present study, the effect of macrophage depletion on the induction of HDC was examined.

On day 1 after a single intravenous injection of a macrophage depletor (liposomes encapsulating dichloromethylene diphosphonate, which is toxic when ingested into macrophages), macrophages were almost completely depleted in the liver and reduced by about 50% in the spleen and bone marrow, but not significantly affected in the lung. On day 3, the degrees of the depletion were similar to those of day 1. In the spleen, macrophages were depleted in the red pulp, and there was a structural destruction.

In macrophage‐depleted mice, the induction of HDC by LPS, IL‐1α or TNF‐α was not impaired in the liver, and was potentiated in the lung and bone marrow. The induction of HDC was decreased only in the spleen at day 3.

HDC was not induced by LPS in the spleen of the adult rat, which is correspondingly inactive in haematopoiesis.

These results indicate that the major cells in which HDC activity is induced in response to LPS, IL‐1 and TNF are not circulating granulocytes, circulating monocytes, T cells derived from thymus, mast cells or phagocytic macrophages. Based on these results, we discuss the possibility that the major cells in which HDC was induced in non‐haematopoietic and haematopoietic organs were endothelial cells and haematopoietic precursor cells respectively.
Pharmacology of the octopamine receptor from locust central nervous tissue (OAR3)
Authors: Roeder Thomas
Published: July 2012

The present study characterized highly effective agonists from different classes of compounds for the neuronal octopamine receptor (OAR3) of the migratory locust (Locusta migratoria L.). Biogenic amines and phenyliminoimidazolidines (PIIs) were employed for the study of structure‐activity relationships.

The highest affinity PIIs were predominantly those with substitutions at the positions 2 and 4 of the phenolic ring (e.g. NC 7, KI = 0.3 nm, NC 8, KI = 0.81 nm). Substitutions at these positions always had positive effects on the affinity of the respective agonists.

Substitutions at the positions 3, 5 and 6, however, always had negative effects on the affinity. At the position one of the phenolic ring, heterocyclic substituents are preferred.

Some PIIs had a more than 30 times higher affinity for OARs than for α‐adrenoceptors which are the vertebrate homologues of the insect octopamine receptors.

The only non‐PII with subnanomolar affinity was the aminooxazoline derivative AC 6 (KI = 0.92 nm).

A variety of substances with known insecticidal activity such as chlordimeform, demethylchlor‐dimeform, amitraz or AC 6 had high affinity for the locust neuronal octopamine receptor.
Functional evidence for a 5‐HT2B receptor mediating contraction of longitudinal muscle in human small intestine
Authors: Borman R.A. , Burleigh D.E.
Published: July 2012

Application of 5‐hydroxytryptamine induces contraction of longitudinal muscle strips from human terminal ileum. The response was resistant to antagonism by ketanserin, ondansetron or DAU6285, but was non‐surmountably antagonized by methysergide. The selective 5‐HT2B/2C receptor antagonist, SB 200646A evoked a concentration‐dependent, parallel and dextral displacement of the concentration‐response curve to 5‐HT, yielding a pA2 estimate of 7.17. Application of yohimbine, a 5‐HT1 and 5‐HT2B receptor antagonist, also induced a rightward shift of the response curve to 5‐HT, yielding a pA2 estimate of 8.10. In conclusion, it appears that a 5‐HT2B receptor mediates the contractile response of the longitudinal muscle of human small intestine to 5‐HT.
Mechanisms of bradykinin‐induced contraction of the guinea‐pig gallbladder in vitro
Authors: Cabrini Daniela A. , Silva Ana M. , Calixto João B.
Published: July 2012

The mechanisms underlying bradykinin (BK)‐mediated contractions in strips of guinea‐pig gallbladder (GPG) were examined by use of selective bradykinin (BK) receptor agonists and antagonists.

Addition of BK and related kinins (0.1 pM‐10μm) after 2 h of equilibration of the preparation caused graded contractions characterized by two distinct phases: high affinity (0.1 pM‐1 nM) and low affinity (3 nM‐10 μm). The rank order of potency for the first phase (mean EC50, PM) was: BK (1.36) = Hyp3‐BK (1.44) = Lys‐BK (1.54)>Tyr8‐BK (2.72)> Met‐Lys‐BK (4.30). The rank order of potency for the second phase (mean EC50, nM, at concentration producing 50% of the contraction caused by 80 mM KC1) was: Hyp3‐BK (8.95)> Met‐Lys‐BK (12.78)>Tyr8‐BK (33.75)> Lys‐BK (60.92)> BK (77.35). The contractile responses (g of tension) to 3 μm of BK (the highest concentration tested) were: Hyp3‐BK, 1.76 ±0.09; BK, 1.65 ±0.12; Lys‐BK, 1.45 ±0.13; Tyr8‐BK, 1.36 ±0.15 and Met‐Lys‐BK, 1.36 ±0.15. The selective B1 agonist, des‐Arg9‐BK, caused only a weak contraction with maximal response (0.21 ± 0.05 g), which corresponded to approximately 10% of that induced by BK.

BK‐induced contraction in GPG was inhibited by indomethacin (3 μm) or ibuprofen (30 μm), and was partially reduced by phenidone (30 μm), but was not affected by atropine (1 μm), nicardipine (1 μm), Ca2+‐free medium plus EGTA, dazoxiben (30 μm), L‐655,240 (10 nM, a selective receptor antagonist of thromboxane A2), MK‐571 (0.1 μm, a selective leukotriene D4 receptor antagonist), tetrodotoxin (0.3 μm), CP 96,345 (0.3 μm, a NK1 receptor antagonist), mepyramine (1 μm), glibenclamide (1 μm), H‐7 (3 μm), staurosporine (100 nM), or phorbol 12‐myristate 13‐acetate (1 μm). However, BK‐induced contractions in GPG maintained in Ca2+‐free medium were markedly attenuated by ryanodine (10 μm).

Prostaglandin E2, prostaglandin F2α or U46619 (0.1 nM to 100 μm), caused concentration‐dependent contractions in GPG with mean EC50S of 3.1 μm; 1.7 μm and 0.47 nM and maximal responses of 1.36 ±0.15; 1.32 ±0.20 and 0.96 ± 0.09 g, respectively.

The selective B2 receptor antagonists, Hoe 140, NPC 17731 and NPC 17761 (0.01‐1 μm), caused concentration‐dependent displacements to the right of the contractile concentration‐response curve for BK. The selective B1 receptor antagonist, des‐Arg9‐[Leu8]‐BK (1 μm), did not affect BK‐induced GPG contraction.

These data suggest that both high and low affinity BK responses in GPG are mediated by activation of B2 receptors, and that BK‐mediated contraction in GPG depends on the release of intracellular Ca2+ sources sensitive to ryanodine. In addition, BK‐induced contraction in GPG is mediated by release of proinflammatory eicosanoid(s) derived from the cyclo‐oxygenase pathway from arachidonic acid metabolism unrelated to thromboxane A2, and seems not to be coupled to activation of a protein kinase C‐dependent mechanism.
Functional interaction between losartan and central tachykinin NK3 receptors in the conscious rat
Authors: Picard Pierre , Chretien Louise , Couture Réjean
Published: July 2012

The cardiovascular and behavioural effects elicted by the intracerebroventricular (i.c.v.) injection of substance P (SP), neurokinin A (NKA), [MePhe7]neurokinin B ([MePhe7]NKB) or angiotensin II (All) in the conscious rat were assessed before and 5 min after i.c.v. pretreatment with antagonists selective for angiotensin AT1 (losartan and its active metabolite EXP 3174), angiotensin AT2 (PD 123,319) or tachykinin NK3 (R 486) receptors.

I.c.v. administration of 25 pmol All evoked an increase in mean arterial blood pressure (MAP) and water intake behaviour, accompanied by a transient bradycardia, whereas 25 pmol [MePhe7]NKB caused a transient increase in MAP and heart rate (HR) concurrently with marked wet dog shake behaviour. At the same dose, SP and NKA were more potent than [MePhe7]NKB in increasing MAP and HR, but did not produce water intake or wet dog shake behaviours.

Losartan (650 pmol, i.c.v.) reduced significantly the cardiovascular and behavioural responses to All or [MePhe7]NKB, but not to SP or NKA. While 65 pmol losartan was inactive, 260 pmol inhibited selectively the central effects of AII Whereas EXP 3174 (6.5 nmol) blocked both All and [MePhe7]NKB‐mediated responses, the dose of 650 pmol blocked only the responses to AII.

The central responses to All and [MePhe7]NKB were not affected by PD 123,319 (650 pmol). On the other hand, the [MePhe7]NKB‐induced central effects were significantly reduced by R 486 (650 pmol). The NK3‐selective antagonist had no effect against AII.

This study provides functional evidence, to support earlier binding data, that losartan (and to some extent its active metabolite EXP 3174) interact with the tachykinin NK3 receptor in rat brain. However, the cardiovascular and behavioural responses induced by central tachykinin agonists (SP, NKA and [MePhe7]NKB) and All are mediated by unrelated mechanisms.
Cardiovascular actions of the furoxan CAS 1609, a novel nitric oxide donor
Authors: Bohn Helmut , Brendel Joachim , Martorana Piero A. , Schönafinger Karl
Published: July 2012

This study examines the cardiovascular effects of CAS 1609 (4‐hydroxymethyl‐furoxan‐3‐carboxamide) in vitro as well as in vivo in various animal models.

CAS 1609 relaxed guinea‐pig pulmonary artery strips without endothelium with IC50‐values of 0.9 μm (phenylephrine contracted) and 15 μ (KCl‐depolarized). This effect was inhibited by oxyhaemoglobin. In these arteries CAS 1609 significantly increased (+ 192%) guanosine 3′:5′‐cyclic monophosphate levels, which indicates that the compound acts as a donor of nitric oxide (NO).

In the anaesthetized pig, CAS 1609 (0.3‐1.0 mg kg−1, i.d.) significantly lowered blood pressure and left ventricular end‐diastolic pressure. Left ventricular contractility was slightly reduced and heart rate remained almost unchanged.

In anaesthetized dogs, i.v. or i.d. administration of CAS 1609 (0.3‐3.0 mg kg−1) decreased, in a dose‐related fashion, preload and afterload of the heart, cardiac output, left ventricular work and myocardial oxygen consumption. This haemodynamic profile is similar to that of known NO‐donors.

In anaesthetized dogs with acute heart failure due to intracoronary injection of microspheres, CAS 1609 (0.3mgkg−1, i.v.) improved the haemodynamic condition and reduced mortality by 80%.

In conscious dogs, oral treatment with a dose of 0.5 mg kg−1 given twice daily at 07 h 00 min and 19 h 00 min (each dose had a duration of action ≤ 12 h) for 5 days showed no signs of tolerance to the haemodynamic effects of the drug.

All these data indicate that CAS 1609 is a potent, long‐lasting orally active donor of NO, devoid of tolerance development.
Conversion of inhaled nitric oxide to nitrate in man
Authors: Westfelt Ulla Nathorst , Benthin Günther , Lundin Stefan , Stenqvist Ola , Wennmalm Åke
Published: July 2012

Nitric oxide (NO) is potentially useful as a selective vasodilator drug in infants and adults with pulmonary hypertension. In vitro and in vivo observations demonstrate that NO may be converted to nitrate in the blood, to be further excreted into the urine. The aim of the present study was to assess quantitatively the importance of this pathway for inhaled NO in human subjects.

Healthy subjects inhaled 15NO (25 p.p.m.) for 1 h. The plasma and urine levels of 15NO3‐ were followed for 2 and 48 h, respectively.

The measured retention of 15NO in the lungs was 224 ± 13 μmol, corresponding to 90 ± 2% of the inhaled amount. Plasma 15NO3‐ increased during the inhalation of 15NO, to about 15μmoll_1, and fell when inhalation of 15NO was terminated.

Urinary excretion of 15NO3‐ during the first 24 h after inhalation was 154 ± 12μmol. During the following 24 h another 8 ± 2 μmol of 15NO3 appeared in the urine.

We conclude that conversion of inhaled NO to nitrate is a major metabolic pathway in man, covering more than 70% of its inactivation. The metabolic fate of the remaining NO inhaled requires further study.
Comparative effects of activation of soluble and particulate guanylyl cyclase on cyclic GMP elevation and relaxation of bovine tracheal smooth muscle
Authors: Ijioma Samuel C. , Challiss R.A. John , Boyle John P.
Published: July 2012

The effects of nitric oxide‐donating compounds and atrial natriuretic peptide on cyclic GMP accumulation and mechanical tone were compared with the effects of isoprenaline in bovine tracheal smooth muscle.

Sodium nitroprusside, glyceryl trinitrate, S‐nitroso‐N‐acetylpenicillamine (SNAP), atrial natriuretic peptide and isoprenaline each caused concentration‐dependent inhibitions of histamine‐maintained tone (EC50 values 320 ±80, 150 ±45, 14,000 ±4,000, 2.8 ±0.8 and 6.6 ±4.3 nM respectively).

When compared with their effects on histamine‐induced tone, sodium nitroprusside was equally potent and effective in causing relaxation of methacholine‐supported tone (EC50 290 ± 90 nM) while isoprenaline was as effective, but less potent (EC50 30 ± 7 nM). SNAP was more potent and equi‐effective as a relaxant of methacholine‐supported tone (EC50 340 ± 140 nM). At the maximum concentrations of glyceryl trinitrate and atrial natriuretic peptide tested against methacholine‐supported tone, relaxations of 52% and 14% of the isoprenaline maximum were seen.

Sodium nitroprusside, glyceryl trinitrate and atrial natriuretic peptide each induced concentration‐dependent increases in cyclic GMP accumulation. The time‐courses of accumulation correlated closely with the relaxant actions of these compounds.

Pretreatment of tracheal smooth muscle with sodium nitroprusside or SNAP caused a rightward shift of the concentration‐effect curve for histamine while reducing the maximum response.

LY 83583, a putative guanylyl cyclase inhibitor, caused a concentration‐dependent reduction in basal cyclic GMP accumulation in tracheal smooth muscle and inhibited the effects of sodium nitroprusside on cyclic GMP accumulation.

LY 83583 also inhibited the relaxation of histamine‐supported tone by glyceryl trinitrate, sodium nitroprusside, SNAP and atrial natriuretic peptide, and also sodium nitroprusside‐ and SNAP‐induced relaxation of methacholine‐supported tone. However, it had no significant effect on glyceryl trinitrate‐induced relaxation of methacholine‐supported tone.

It is concluded that the relaxant actions of sodium nitroprusside, glyceryl trinitrate, SNAP and atrial natriuretic peptide follow as a result of their ability to activate either soluble or particulate guanylyl cyclase leading to cyclic GMP accumulation. Although there does not seem to be any functional difference in the relaxant response to cyclic GMP generated by the particulate as opposed to soluble form(s) of guanylyl cyclase, atrial natriuretic peptide receptor/guanylyl cyclase activation was much less effective in causing relaxation of methacholine‐supported tone when compared to activators of soluble guanylyl cyclase.
A role for endothelin in bicuculline‐induced neurogenic pulmonary oedema in rats
Authors: Herbst C. , Tippler B. , Shams H. , Simmet Th.
Published: July 2012

The possible contribution of endogenous endothelin (ET) to the pathogenesis of seizure‐associated pulmonary oedema was examined in mechanically ventilated rats after intravenous bolus injection of the γ‐aminobutyric acid (GABA) antagonist, bicucuiline (1.2 mg kg−1).

Recurrent seizure activity elicited by bicucuiline injection led to rapidly developing pulmonary oedema. Within 4 min after bicucuiline application (1.2mg kg_1), arterial O2 partial pressure (PaO2) significantly dropped from 17.49±1.20 kPa to 7.51 ±2.21 kPa (P<0.01) and arterial CO2 partial pressure (PaCO2) significantly increased from 4.64±0.56 kPa to 8.15±0.99 kPa (P<0.01). Gradually a progressive acidosis developed. Moreover, mean arterial blood pressure (MABP) and end‐inspiratory airway pressure (Paw) rapidly increased.

Concomitantly there was a time‐dependent increase of big ET‐1 and ET‐1 levels in bronchoalveolar lavage (BAL) as determined by combined reverse phase high performance liquid chromatography (h.p.l.c.) and radioimmunoassay. BAL levels of both peptides increased up to 8 min after bicucuiline injection and slowly decreased subsequently. In contrast, BAL from animals injected with vehicle did not contain detectable amounts of ET.

Pretreatment with the endothelin‐converting enzyme inhibitor, phosphoramidon (5.4 mg kg−1, i.v.) for 5 min significantly (P< 0.001) reduced peak ET‐1 levels in BAL fluid by 65.4 ±9.9% at 8 min after bicucuiline injection. Simultaneously it afforded protection from hypoxia. PacO2 did not increase and PaO2 decreased only slightly from 14.63 ±1.00 kPa to 12.97 ±0.61 kPa (P>0.05) after phosphoramidon pretreatment. In contrast, vehicle‐treated animals that received bicucuiline showed both significant hypercapnia as well as profound hypoxia. Phosphoramidon significantly diminished the maximum increase in Paw by 76.7 ±12.4% (P< 0.005), but only slightly affected the MABP. Phosphoramidon pretreatment had no effect on the acidosis.

Pretreatment with the ETA receptor antagonist, BQ‐123 (1 mg kg−1, i.v.), for 5 min did not affect the levels of ET‐1 in the BAL fluid at 8 min after bicucuiline injection but did ameliorate the development of hypoxia. No hypercapnia developed and Pao2 decreased only moderately from 16.65 ± 0.25 kPa to 14.19 ±2.15 kPa (P>0.05) in BQ‐123‐treated animals. In contrast, vehicle‐treated animals that received bicuculline exhibited significant hypercapnia as well as profound hypoxia. BQ‐123 significantly reduced the increase in Paw by 51.3 ± 12.8% (P<0.01). It affected MABP only slightly and had no effect on the acidosis.

These results suggest that ET peptides play a significant role in this model of neurogenic pulmonary oedema and may act as mediators of respiratory distress. The deleterious effects of endogenous ET in this model are primarily mediated via the ETA receptor, for they were inhibited by the ETA receptor antagonist, BQ‐123. ETA receptor antagonists may therefore be of potential therapeutic value in respiratory distress.
Adenosine A1 receptor‐mediated changes in basal and histamine‐stimulated levels of intracellular calcium in primary rat astrocytes
Authors: Peakman Marie‐Claire , Hill Stephen J.
Published: July 2012

The effects of adenosine A1 receptor stimulation on basal and histamine‐stimulated levels of intracellular free calcium ion concentration ([Ca2+]i) have been investigated in primary astrocyte cultures derived from neonatal rat forebrains.

Histamine (0.1 μm‐l mM) caused rapid, concentration‐dependent increases in [Ca2+]i over basal levels in single type‐2 astrocytes in the presence of extracellular calcium. A maximum mean increase of 1,468 ±94 nM over basal levels was recorded in 90% of type‐2 cells treated with 1 mM histamine (n = 49). The percentage of type‐2 cells exhibiting calcium increases in response to histamine appeared to vary in a concentration‐dependent manner. However, the application of 1 mM histamine to type‐1 astrocytes had less effect, eliciting a mean increase in [Ca2+]i of 805 ± 197 nM over basal levels in only 30% of the cells observed (n = 24).

In the presence of extracellular calcium, the A1 receptor‐selective agonist, N6‐cyclopentyladenosine (CPA, 10 μm), caused a maximum mean increase in [Ca2+]i of 1,110 ± 181 nM over basal levels in 30% of type‐2 astrocytes observed (n = 53). The size of this response was concentration‐dependent; however, the percentage of type‐2 cells exhibiting calcium increases in response to CPA did not appear to vary in a concentration‐dependent manner. A mean calcium increase of 605 ± 89 nM over basal levels was also recorded in 23% of type‐1 astrocytes treated with 10 μm CPA (n = 30).

In the absence of extracellular calcium, in medium containing 0.1 mM EGTA, a mean increase in [Ca2+]i of 504 ±67 nM over basal levels was recorded in 41% of type‐2 astrocytes observed (n = 41) after stimulation with 1 μm CPA. However, in the presence of extracellular calcium, pretreatment with the A1 receptor‐selective antagonist, 8‐cyclopentyl‐1,3‐dipropylxanthine, for 5–10 min before stimulation with 1 μm CPA, completely antagonized the response in 100% of the cells observed.

In type‐2 astrocytes, prestimulation with 10 nM CPA significantly increased the size of the calcium response produced by 0.1 μm histamine and the percentage of responding cells. Treatment with 0.1 μm histamine alone caused a mean calcium increase of 268 ±34 nM in 41% of the cells observed (n = 34). After treatment with 10 nM CPA, mean calcium increase of 543 ±97 nM was recorded in 100% of the cells observed (n = 33).

These data indicate that adenosine A1 receptors couple to intracellular calcium mobilization and extracellular calcium influx in type‐1 and type‐2 astrocytes in primary culture. In addition, the simultaneous activation of adenosine A1 receptors on type‐2 astrocytes results in an augmentation of the calcium response to histamine H1 receptor stimulation.
Regenerative caffeine‐induced responses in native rabbit aortic endothelial cells
Authors: Rusko J. , Wang X. , van Breemen C.
Published: July 2012

Single native aortic endothelial cells obtained by enzymatic dispersion of the rabbit aortic endothelium were held under voltage clamp using patch pipette and whole‐cell membrane currents were measured. In parallel experiments performed on cells from the same batches, the free internal calcium concentration, [Ca2+]i, in the cell was estimated by use of the Ca2+‐sensitive fluorescent dye, fura‐2.

Caffeine (20 mM) applied to the cell evoked an outward current and an initial peak in [Ca2+]1 followed by a lower sustained rise (plateau). Ca2+‐free, EGTA‐containing solution applied outside the cells did not reduce these responses.

Following caffeine stimulation there was a biphasic rising phase of outward current both in the presence and absence of extracellular Ca2+.

Application of graded doses of caffeine revealed all‐or‐none type responses of both the outward current and the rise in [Ca2+]i.

Preincubation with lower doses of caffeine reduced the magnitude of both the outward current and the [Ca2+]i transient evoked by 20 mM caffeine.

Tetraethylammonium (3 mM) applied to the bathing solution blocked unitary and spontaneous transient outward currents (STOCs) stimulated by Ca2+‐free solution, but only reduced the outward current evoked by caffeine (20 mM).

In conclusion, our results reveal the all‐or‐none nature of Ca2+ release from the endoplasmic reticulum (ER) in native aortic endothelial cells. Lower concentrations of caffeine (0.4‐0.5 mM) may deplete intracellular Ca2+ stores. Extracellular Ca2+ is not necessary for maintaining the activity of spontaneous and caffeine‐induced outward currents in native aortic endothelial cells. Spontaneous outward currents are believed to represent the sporadic release of calcium from store sites independent of both extracellular Ca2+ and the caffeine‐sensitive Ca2+ stores which stimulate the outward current.
Ramipril‐induced decrease in renal lithium excretion in the rat
Authors: Barthelmebs Mariette , Grima Michele , Imbs Jean‐Louis
Published: July 2012

The interaction of ramipril, an inhibitor of angiotensin I converting enzyme, with renal lithium handling was analysed in conscious normotensive Wistar rats and compared with the known increase in renal tubular lithium reabsorption induced by the non‐steroidal anti‐inflammatory drug, indomethacin.

The rats were treated for five days with ramipril (1 mg kg−1 day−1 orally), indomethacin (2.5 mg kg−1 day−1 intramuscularly) or their solvents. Lithium chloride (16.7 mg kg−1 intraperitonealy) was given as a single dose on the fifth day and renal functions were measured.

Ramipril induced a decrease in renal lithium clearance which was correlated with the decrease in the quantity of filtered lithium and the increase in the tubular fractional reabsorption of the metal. Ramipril also reduced the systolic blood pressure of the rats by about 15 mmHg.

In the absence of any effect on creatinine clearance or systolic blood pressure, indomethacin increased renal fractional lithium reabsorption and led to an increase in plasma lithium levels, as previously reported by our group. 5 In conclusion, our results indicate that ramipril decreases renal lithium excretion in Wistar rats, when given orally at a dose of 1 mg kg−1 day−1 over five days.
Central cardiovascular effects of acetylcholine in the conscious dog
Authors: Brefel C. , Lazartigues E. , Tran M.A. , Gauquelin G. , Geelen G. , Gharib C. , Montastruc J.L. , Montastruc P. , Rascol O.
Published: July 2012

The effects of central cholinomimetic drugs on cardiovascular and vasoactive hormonal responses (blood pressure, heart rate, catecholamines, vasopressin, atrial natriuretic factor, neuropeptide Y plasma levels and plasma renin activity) were investigated in conscious Beagle dogs. For this purpose a catheter was chronically implanted into each dog's cisterna magna to allow repeated central injections in the awake animals.

Intracisternal acetylcholine (20 μg kg−1) significantly increased systolic and diastolic blood pressure. These changes were accompanied by an initial short term tachycardia followed by a long lasting bradycardia. Intracisternal acetylcholine also increased noradrenaline, adrenaline and vasopressin plasma levels, decreased plasma renin activity but did not modify plasma levels of neuropeptide Y and atrial natriuretic factor.

The effects of acetylcholine were completely abolished by pretreatment with intracisternal injection of the muscarinic antagonist, atropine (5 μg kg−1) but not by the intracisternal injection of the nicotinic antagonist, mecamylamine (25 μg kg−1).

The present results demonstrate that there are qualitative and quantitative differences between the central cardiovascular effects of acetylcholine in conscious dogs compared to what we previously reported, using a comparable protocol, in anaesthetized dogs. Under both conditions, we observed a central cholinergically mediated increase in blood pressure secondary to an increase in sympathetic tone and vasopressin release but these responses were shorter (less than 10 min) in the conscious dogs than in anaesthetized dogs (more than 10 min). Moreover, we detected in the response to the central cholinergic stimulation in the conscious dogs a significant increase in plasma adrenaline levels and biphasic changes in heart rate which were not described previously in the anaesthetized dog.
Induction of nitric oxide synthase and microvascular injury in the rat jejunum provoked by indomethacin
Authors: Whittle Brendan J.R. , László Ferenc , Evans Steven M. , Moncada Salvador
Published: July 2012

The role of nitric oxide (NO) formed by the inducible isoform of NO synthase (NOS) in the generation of indomethacin‐induced intestinal microvascular leakage was investigated in the rat. 2 Indomethacin (10 mg kg−1, s.c.) provoked an elevation of vascular leakage of radiolabelled human serum albumin in the jejunum over 48 h, commencing 18 h after its administration. This was associated with the induction of a calcium‐independent NOS, as assessed by the conversion of radiolabelled L‐arginine to citrulline. 3 Pretreatment with the glucocorticoid, dexamethasone (1 mg kg−1 day−1, s.c.) inhibited the induction of NOS and reduced jejunal microvascular leakage, determined 24 and 48 h after indomethacin. 4 Administration of the broad‐spectrum antibiotic, ampicillin (800 mg kg−1 day−1, p.o.) likewise inhibited both the induction of NOS and the plasma leakage observed 24 and 48 h after indomethacin. 5 Ampicillin pretreatment did not, however, inhibit the induction of NOS, determined 5 h following endotoxin (3 mg kg−1 i.v.) challenge. Furthermore, incubation with ampicillin (1 mM, 10 min) did not inhibit the activity of the calcium‐independent isoform in vitro. 6 Administration of the NOS inhibitor, NG‐nitro‐L‐arginine methyl ester (L‐NAME, 2–10 mg kg−1, s.c.), at the time of the detectable expression of the inducible NOS (18 h after indomethacin), dose‐dependently attenuated the plasma leakage, determined 6 later. This effect was reversed by pretreatment with L‐arginine (300 mg kg−1, s.c.) 15 min before L‐NAME. 7 These findings suggest that induction of a calcium‐independent NOS following indomethacin administration involves gut bacteria and leads to microvascular injury in the rat jejunum.
Inhibition by halothane of potassium‐stimulated acetylcholine release from rat cortical slices
Authors: Griffiths R. , Greiff J.M.C. , Haycock J. , Elton C.D. , Rowbotham D.J. , Norman R.I.
Published: July 2012

Cholinergic neurones in the basal forebrain are linked to cortical activation and arousal.

The present study was designed to examine the hypothesis that clinically relevant doses of halothane (0.1 to 5%) would significantly reduce depolarization‐evoked acetylcholine (ACh) release from rat cortical slices.

ACh release was measured from rat cortical slices by a chemiluminescent technique.

Depolarization‐evoked ACh release was inhibited significantly by halothane with an IC50 of 0.38%. This value equates to 0.3 MAC (the minimum alveolar concentration at which no movement occurs to a standard surgical stimulus in 50% of subjects) for the rat.

The potent effect of halothane on ACh release suggests that this mechanism may be a target for the action of volatile anaesthetic agents. This in vitro effect on ACh release is consistent with effects of halothane reported in vivo.
Regulation by phosphodiesterase isoenzymes of non‐adrenergic non‐cholinergic contraction in guinea‐pig isolated main bronchus
Authors: Spina D. , Harrison S. , Page C.P.
Published: July 2012

We have investigated the role of phosphodiesterase isoenzymes in modulating electric field stimulation (EFS), substance P and capsaicin‐induced contraction of the guinea‐pig isolated main bronchus.

Non‐adrenergic non‐cholinergic contractile responses were elicited by EFS (3 Hz, 20 s) in the guinea‐pig isolated main bronchus in the presence of the non‐selective muscarinic antagonist, atropine (0.1 μm), the non‐selective, β‐adrenoceptor antagonist, propranolol (1 μm), the neutral endopeptidase inhibitor, thiorphan (10 μm) and the cyclooxygenase inhibitor, indomethacin (5 PM). The type III, type III/IV, type IV and type V phosphodiesterase isoenzyme inhibitor, SKF 94836, benzafentrine, Ro‐20–1724 and zaprinast respectively, significantly attenuated the contractile response to EFS. The IC50 (95% confidence limits) value for SKF 94836, benzafentrine, Ro‐20–1724 and zaprinast was 8.3 μm (0.89‐78); 0.7, μm (0.1–4.5); 0.5 μm (0.2‐1.2) and 13 μm (2–87) respectively.

The phosphodiesterase isoenzyme inhibitors, SKF 94836, Ro‐20–1724 and zaprinast, partially attenuated the contractile response to substance P (10 nM). Benzafentrine significantly inhibited the contractile response to substance P. yielding an IC50 value of 1.9 μm (0.9‐3.8).

The phosphodiesterase isoenzyme inhibitor, Ro‐20–1724 (0.1–100 μm) failed to reduce significantly the contractile potency of capsaicin (P>0.05). In contrast, SKF 94836 (1 μm), benzafentrine (10 μm) and zaprinast (100 μm) significantly reduced the contractile potency of capsaicin (P<0.05).

The selective phosphodiesterase isoenzyme inhibitors, SKF 94836, benzafentrine, Ro‐20–1724 and zaprinast (0.01–100 μm) reversed in a concentration‐dependent manner the contractile response to exogenously administered capsaicin (EC50) yielding IC50 values of 3.91 μm (0.68‐22); 3.37 μm (1.86‐6.11); 0.366 μm (0.201‐0.564) and 50.1, μm (18.6–135) respectively.

In conclusion, phosphodiesterase isoenzymes appear to regulate the contractile response to electrical field stimulation and our results provide circumstantial evidence for a regulatory role of phosphodiesterase type IV isoenzyme on sensory nerve function in vitro.
Mediation by prostaglandins of the nitric oxide‐induced neurogenic vasodilatation in rat skin
Authors: Holzer Peter , Jociĉ Milana , Peskar Bernhard A.
Published: July 2012

Intraplantar administration of the nitric oxide (NO) donor, sodium nitroprusside (SNP), induces hyperaemia in the rat paw skin, which is in part due to release of calcitonin gene‐related peptide (CGRP) from afferent nerve fibres. The present study examined whether prostaglandins or other inflammatory mediators participate in the neurogenic vasodilatation caused by SNP. Blood flow in the plantar hindpaw skin of urethane‐anaesthetized rats was measured by laser Doppler flowmetry.

The hyperaemic responses to intraplantar administration of the NO donors SNP (150 pmol) and 3‐morpholinosydnonimine (SIN‐1, 15 nmol) were attenuated by 45% and 61%, respectively, after injection of the CGRP antagonist, CGRP8–37 (50 nmol kg−1, i.v.) which did not significantly change baseline blood flow.

The NO synthase inhibitor NG‐nitro‐L‐arginine methyl ester (L‐NAME, 15 mg kg−1, i.v.), the bradykinin antagonist Hoe‐140 (100 nmol kg−1, i.v.) and the histamine antagonists, pyrilamine (2 mg kg−1, i.v.) plus cimetidine (10 mg kg−1, i.p.) were without effect on baseline blood flow and the vasodilatation caused by SNP.

The cyclooxygenase inhibitors, indomethacin (10 mg kg−1, i.p.) and flurbiprofen (5 mg kg−1, i.p.) depressed the SNP‐induced hyperaemia by 65% and 42%, respectively, without altering baseline blood flow. The ability of CGRP8–37 to inhibit the vasodilator response to SNP was lost in indomethacin‐treated rats. 5 Intraplantar administration of prostaglandin E2 (PGE2, 15 pmol) evoked cutaneous vasodilatation which was attenuated by 66% after administration of CGRP8–37 but remained unaltered by indomethacin or L‐NAME. 6 These data indicate that the neurogenic hyperaemia which in rat skin is induced by intraplantar administration of NO donors involves the formation of prostaglandins which in turn cause release of the vasodilator peptide, CGRP, from perivascular afferent nerve fibres.
Nitric oxide synthase in dog urethra: a histochemical and pharmacological analysis
Authors: Takeda Masayuki , Lepor Herbert
Published: July 2012

To examine the presence of nitric oxide synthase (NOS) activity in female dog urethra, pharmacological experiments were performed using electrical field stimulation (EFS), guanethidine, atropine, NG‐nitro‐L‐arginine methyl ester and L‐arginine, NOS immunohistochemistry using specific anti‐NOS antibody, and reduced nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase staining were also performed.

EFS caused frequency‐dependent contractions in all urethral preparations, but in the presence of guanethidine and atropine, EFS caused significant relaxation in the proximal urethra and was without effect on the distal urethra.

In the presence of guanethidine, atropine, and NG‐nitro‐L‐arginine methyl ester, small contractions to EFS were re‐established in the proximal urethra, but not in the distal urethra. NG‐nitro‐D‐arginine methyl ester had no such effect.

In the presence of guanethidine, atropine, and NG‐nitro‐L‐arginine methyl ester, the addition of L‐arginine, restored the EFS‐elicited relaxant responses previously seen with guanethidine and atropine alone in the proximal urethra (at 30 Hz; 12.89 ± 5.27% to −2.44 ± 4.43%, mean ± s.e., P<0.05). D‐Arginine had no such effect.

In the distal urethra, the addition of NG‐nitro‐L‐arginine methyl ester and then L‐arginine had no effect on responses to EFS in preparations treated with guanethidine and atropine.

Sodium nitroprusside caused relaxation in both the proximal and distal urethra. The relaxant responses per cm2 cross sectional area in the proximal and distal urethra were 1.23 ± 0.29, and 2.02 ± 0.54 g cm−2 cross sectional area (mean ± s.e.), respectively: there was no significant difference between them.

Both NOS and NADPH diaphorase‐positive neurones were present in dog urethra, the densities of both being higher in the proximal urethra than in the distal urethra.

These results show that female dog urethra possesses NOS nerves and that endogenous NO may play a role in relaxation in the proximal but not the distal urethra.
Calcium homeostasis in mouse fibroblast cells: affected by U‐73122, a putative phospholipase Cβ blocker, via multiple mechanisms
Authors: Grierson Jeremy P. , Meldolesi Jacopo
Published: July 2012

The inhibitory effects of the putative phospholipase Cβ inhibitor, U‐73122, on ligand‐induced and thapsigargin‐induced [Ca2+]i transients were investigated in mouse fibroblast cells (the L line).

Ca2+ release from intracellular stores was stimulated either by ATP (and also by UTP or ADP) working through the activation of a P2U receptor, or by lysophosphatidic acid, which elicited a more pronounced response.

U‐73122 inhibited the Ca2+ mobilization produced by all the agonists in a dose‐dependent manner, consistent with a mode of action involving phospholipase C inhibition.

In addition, however, U‐73122 slowed the kinetics of intracellular Ca2+ release induced by the Ca2+‐ATPase inhibitor, thapsigargin, and reduced the influx of Ca2+ across the plasma membrane, following stimulation of store‐dependent influx by the latter.

We conclude that U‐73122 has multiple sites of action, all of which can lead to a change in Ca2+ homeostasis. Thus, particular caution is recommended when employing this agent and when interpreting the results obtained.
Subtypes of tachykinin receptors on tonic and phasic neurones in coeliac ganglion of the guinea‐pig
Authors: Zhao F.‐Y. , Saito K. , Yoshioka K. , Guo J.‐Z. , Murakoshi T. , Konishi S. , Otsuka M.
Published: July 2012

Intracellular recording techniques were used to investigate the characteristics of tachykinin receptors and their subtypes in tonic and phasic neurones, which constituted two major neuronal populations in the coeliac ganglion of the guinea‐pig.

In 95% of phasic neurones a long‐lasting after‐hyperpolarization (LAH), 5–8s in duration and 10–20 mV in amplitude, was observed following action potentials evoked by passing a train of depolarizing current pulses into the neurones. In contrast, LAH was observed in only 4% of tonic neurones.

In most tonic neurones, substance P (SP), neurokinin A (NKA) and senktide induced depolarizations, whereas in phasic neurones they usually inhibited LAH but rarely induced depolarization.

Tonic and phasic neurones were further classified into three groups based on their responses (depolarization for tonic neurones and LAH inhibition for phasic neurones) to these tachykinin receptor agonists: (1) neurones responsive to SP, NKA and senktide (71–78%); (2) those responsive to senktide but not to SP and NKA (12–23%) and (3) those not responsive to any of the three agonists (7–11%).

GR71251 (5 μM), an NK1‐selective tachykinin receptor antagonist, depressed the depolarization in tonic neurones and the LAH inhibition in phasic neurones induced by SP and NKA, but not those induced by senktide.

Selective NK2 receptor agonists, [Nle10]NKA4‐10, [β‐Ala8]NKA4‐10 and GR64349, were without effect in both tonic and phasic neurones. Furthermore, an NK2 receptor antagonist, L659,877, did not inhibit the depolarization induced by NKA, SP or senktide in tonic neurones.

It is suggested that NK1 and NK3 receptors are present on a large proportion of coeliac ganglion neurones. In tonic neurones both subtypes of tachykinin receptors are coupled to membrane depolarization, whereas in phasic neurones activation of these receptors leads to inhibition of LAH. The present study also suggests that NKA evokes the depolarization in tonic neurones and the LAH inhibition in phasic neurones via NK1, but not NK2 receptors.
Involvement of tachykinins in plasma extravasation induced by bradykinin and low pH medium in the guinea‐pig conjunctiva
Authors: Figini Michela , Javdan Panthea , Cioncolini Fabio , Geppetti Pierangelo
Published: July 2012

The effect of bradykinin, capsaicin, substance P and low pH medium on plasma extravasation in the guinea‐pig conjunctiva has been studied. Evans blue dye was measured in the conjunctiva after local instillation of the agents into the conjunctival sac.

Bradykinin (2–50 nmol), capsaicin (20–50 nmol) and substance P (0.5‐5 nmol) caused a dose‐dependent increase in plasma extravasation with the following order of potency: substance P> bradykinin = capsaicin. The effect of capsaicin (50 nmol) and substance P (5 nmol) was abolished by the tachykinin NKX receptor antagonist, CP‐99,994 (8umolkg−1, i.v.) (P<0.01), whereas CP‐100,263 (8 umol kg−1, i.v.) the inactive enantiomer of CP‐99, 994 was without effect. CP‐99,994 inhibited by 70% (P<0.01) the effect of bradykinin.

The kinin B2 receptor antagonist, Hoe 140 (icatibant, 10 nmol kg−1, i.v.) abolished the response to bradykinin (50 nmol) (P<0.01), but did not affect the responses to capsaicin (50 nmol) or substance P (5 nmol). Plasma extravasation induced by low pH medium (pH 1) was abolished by CP‐99,994 (P<0.01) and by Hoe 140 (P<0.01).

The present findings suggest that: endogenous or exogenous tachykinins increase plasma extravasation in the guinea‐pig conjunctiva by activation of NK1 receptors; bradykinin‐induced plasma extravasation is mediated by tachykinin release from sensory nerve endings; low pH media cause plasma extravasation via release of kinins that by activation of B2 receptors release tachykinins from sensory nerve endings.
Effects of GTPγS on muscarinic receptor‐stimulated inositol phospholipid hydrolysis in permeabilized smooth muscle from the small intestine
Authors: Prestwich S.A. , Miyazaki H. , Bolton T.B.
Published: July 2012

Smooth muscle fragments from the longitudinal layer of the small intestine of the guinea‐pig were permeabilized with Staphylococcus aureus alpha toxin (a‐toxin) and used to investigate the role of G‐protein activation in the regulation of muscarinic acetylcholine receptor (AChR)‐stimulated inositol phospholipid hydrolysis.

The efficiency of α‐toxin permeabilization was estimated by the release of [3H]‐2‐deoxyglucose ([3H]‐2DG) after prior loading or lactate dehydrogenase (LDH) enzyme release from the smooth muscle fragments.

In a‐toxin‐permeabilized smooth muscle, but not in non‐permeabilized muscle, GTPγS induced time‐and concentration‐dependent increases in labelled inositol phosphates. Carbachol (CCh) increased labelled inositol phosphates in both permeabilized and non‐permeabilized muscle, although the increases were greater in non‐permeabilized smooth muscle. The response to 100 γM CCh was severely reduced by 0.5 γM atropine.

In permeabilized muscle the effects of GTPγS or CCh on inositol phosphate levels were reduced by treatment with pertussis toxin (PTX) and completely inhibited by GDPβS.

GTPγS caused a concentration‐dependent inhibition of the CCh‐induced increases in the levels of labelled inositol phosphates. Dibutyryl cyclic AMP or Sp‐cAMPs (adenosine‐3′,5′‐cyclic phosphoro‐thiolate‐Sp) reduced the effects of CCh on inositol phosphate levels.

The results suggest that muscarinic AChR activation induces inositol phospholipid hydrolysis via more than one G‐protein in this smooth muscle and that several mechanisms may contribute to the modulation of both stimulatory and inhibitory responses observed.
Prevention by α‐tocopherol and rutin of glutathione and ATP depletion induced by oxidized LDL in cultured endothelial cells
Authors: Schmitt Anne , Salvayre Robert , Delchambre Jean , Négre‐Salvayre Anne
Published: July 2012

Oxidized low density lipoproteins (LDL) are thought to play an important role in atherogenesis. Mildly oxidized LDL are cytotoxic to cultured endothelial cells. Toxic doses of oxidized LDL promote the peroxidation of cellular lipids (beginning at 6 h and being maximal after 12 h of pulse with oxidized LDL) and glutathione and ATP depletion (beginning after 15 h of pulse and evolving concurrently with the cytotoxicity).

Antioxidants from 3 different classes (rutin, ascorbic acid and α‐tocopherol) were compared as to their ability to inhibit the cytotoxic effect of oxidized LDL to endothelial cells.

Effective concentrations of α‐tocopherol inhibited cellular lipid peroxidation, glutathione and ATP depletion and the cytotoxic effect.

Ascorbic acid was less effective than α‐tocopherol and rutin, and exhibited a dose‐dependent biphasic effect in the presence of oxidized LDL.

Effective concentrations of rutin inhibited glutathione and ATP depletion as well as cytotoxicity, but did not block cellular lipid peroxidation. This suggests that the glutathione and ATP depletion is directly correlated to the cytotoxicity of oxidized LDL, whereas cellular lipid peroxidation is probably not directly the cause of cellular damage leading to cell death.

The association of antioxidants of 3 different classes allowed the suppression of the biphasic effect of ascorbic acid and increased the efficacy of the protective effect. The potential consequences for prevention of the pathogenic role of oxidized LDL in endothelial injury are discussed.
The formation of nitric oxide donors from peroxynitrite
Authors: Moro María Ángeles , Darley‐Usmar Victor M. , Lizasoain Ignacio , Su Yunchao , Knowles Richard G. , Moncada Salvador , Radomski Marek W.
Published: July 2012

Administration of peroxynitrite (ONOO−, 30–300 μM) caused relaxation of rabbit aortic strips superfused in series in a cascade. The compound responsible for this effect had a half‐life greater than 20 s and could not therefore be either nitric oxide (NO) or ONOO− which have half‐lives in the order of 1–2 s under these conditions. However the relaxation was inhibited by oxyhemoglobin, suggesting that the compound could be converted to NO in the vascular tissues or in the superfusate.

The products of the reaction between ONOO− and Krebs buffer containing 11 mM glucose, but not glucose‐free Krebs buffer, caused relaxation of the bioassay tissues. These data suggest that stable NO donor(s) were formed from the reaction of ONOO− with glucose. We therefore prepared these NO donor(s) by the reaction of glucose solutions with ONOO− in order to characterize their pharmacological actions both in the cascade bioassay and on platelets and to study their ability to release NO.

These reaction product(s) caused relaxation in the cascade and inhibition of platelet aggregation. Both effects were dependent on the concentration of D‐glucose, were equally effective if L‐glucose was used as a reactant and were reversed by oxyhaemoglobin.

The products of the reaction between ONOO− and glucose or other biological molecules containing an alcohol functional group, such as fructose, glycerol, or glyceraldehyde, released NO in the presence of Cu2+ and L‐cysteine.

These results indicate that ONOO− reacts with sugars or other compounds containing an alcohol functional group(s) to form NO donor(s) with the characteristics of organic nitrate/nitrites. This may represent a further detoxification pathway for ONOO− in vivo.