bluuebunny/crossref_metadata_2025_split huggingface dataset:
Attenuation of vasoconstriction by endogenous nitric oxide in rat caudal artery
Authors: Vo Phuong A. , Reid Julianne J. , Rand Michael J. 
Published: July 2012

The effects of NG‐nitro‐l‐arginine (l‐NNA), NG‐nitro‐l‐arginine methyl ester (l‐NAME), haemoglobin and methylene blue have been examined on vascular reactivity in the rat isolated caudal artery. The effects of l‐NNA and sodium nitroprusside were also investigated on the stimulation‐induced (S‐I) efflux of noradrenaline in the rat caudal artery.
l‐NNA (10 μm) and l‐NAME (10 μm) significantly attenuated the vasodilator responses to acetylcholine (1 nm − 1 μm), but had no effect on vasodilator responses to papaverine (1–100 μm).
Vasoconstrictor responses to sympathetic nerve stimulation (3 Hz, 10 s), noradrenaline (0.01–1 μm), methoxamine (1–10 μm), 5‐hydroxytryptamine (0.01–0.3 μm), phenylephrine (0.1–10 μm), endothelin‐1 (10 nm) and KCl (40 mm) were significantly enhanced by 10 μm l‐NNA. l‐NAME (10 μm) caused a significant enhancement of vasoconstrictor responses to noradrenaline and sympathetic nerve stimulation in endothelium‐intact, but not in endothelium‐denuded tissues.
Haemoglobin and methylene blue (both 10 μm) enhanced the vasoconstrictor responses to sympathetic nerve stimulation and noradrenaline. The enhancements were absent in endothelium‐denuded arterial segments.
In endothelium‐denuded arterial segments precontracted with phenylephrine, the vasodilator responses to the nitric oxide donor, sodium nitroprusside (0.1–300 nm), were decreased by increasing the level of precontraction.
l‐NNA (10 μm) had no effect on the S‐I efflux of radioactivity from arteries in which transmitter stores had been labelled with [3H]‐noradrenaline.
These results suggest that endothelial nitric oxide attenuates vasoconstrictor responses in the rat caudal artery through activation of soluble guanylate cyclase to decrease smooth muscle contractility. Therefore, the findings provide evidence that nitric oxide acts as a functional antagonist to oppose vasoconstriction.
Role of protein kinase C in the regulation of histamine and bradykinin stimulated inositol polyphosphate turnover in adrenal chromaffin cells
Authors: Boarder Michael R. , Challiss R.A. John 
Published: July 2012

The possibility that bradykinin‐ or histamine‐stimulated inositol polyphosphate accumulation may be regulated by protein kinase C (PKC) in bovine adrenal chromaffin cells has been addressed.
Initial experiments confirmed that the phorbol ester 12‐O‐tetradecanoyl‐phorbol 13‐acetate (TPA) dramatically inhibited agonist‐stimulated [3H]‐inositol phosphate accumulations in [3H]‐inositol prelabelled cells. In contrast, the PKC inhibitor, Ro 31–8220, did not affect this response.
Histamine (100 μm) or bradykinin (100 nm) evoked rapid increases in inositol 1,4,5‐trisphosphate (Ins(1,4,5)P3) and inositol 1,3,4,5‐tetrakisphosphate (Ins(1,3,4,5)P4) mass accumulations (maximal accumulations within 10 s and 30 s, respectively) which declined towards basal values over a 10 min incubation period. TPA (1 μm) significantly attenuated the peak Ins(1,4,5)P3 response to bradykinin and histamine by 30% and 70% respectively. In contrast, TPA did not significantly affect agonist‐stimulated Ins(1,3,4,5)P4 responses.
Ro 31–8220 (10 μm) significantly enhanced the maximal Ins(1,4,5)P3 accumulations elicited by both bradykinin and histamine.
The results indicate that the initial Ins(1,4,5)P3 response to either bradykinin or histamine in bovine adrenal chromaffin cells can be attenuated by PKC activation by phorbol ester and enhanced by PKC inhibition by Ro 31–8220. In contrast, agonist‐stimulated Ins(1,3,4,5)P4 accumulation does not appear to be affected by these manipulations of PKC activity. Possible bases for differential modulation of Ins(1,4,5)P3 and Ins(1,3,4,5)P4 are discussed.
Non‐competitive inhibition of GABAA responses by a new class of quinolones and non‐steroidal anti‐inflammatories in dissociated frog sensory neurones
Authors: Yakushiji Takashi , Shirasaki Tetsuya , Akaike Norio 
Published: July 2012

The interaction of a new class of quinolone antimicrobials (new quinolones) and non‐steroidal anti‐inflammatory agents (NSAIDs) with the GABAA receptor‐Cl− channel complex was investigated in frog sensory neurones by use of the internal perfusion and ‘concentration clamp’ techniques.
The new quinolones and the NSAIDs (both 10−6−10−5 m) had little effect on the GABA‐induced chloride current (ICl) when applied separately. At a concentration of 10−4 m the new quinolones, and to a lesser degree the NSAIDs, produced some suppression of the GABA response.
The co‐administration of new quinolones and some NSAIDs (10−6−10−14 m) resulted in a marked suppression of the GABA response. The size of this inhibition was dependent on the concentration of either the new quinolone or the NSAID tested. The inhibitory potency of new quinolones in combination with 4‐biphenylacetic acid (BPAA) was in rank order norfloxacin (NFLX) ≫ enoxacin (ENX) > ciprofloxancin (CPFX) ≫ ofloxacin (OFLX), and that of NSAIDs in combination with ENX was BPAA ≫ indomethacin = ketoprofen > naproxen > ibuprofen > pranoprofen. Diclofenac, piroxicam and acetaminophen did not affect GABA responses in the presence of ENX.
In the presence of ENX or BPAA, there was a small shift to the right of the concentration‐response curve for GABA without any effect on the maximum response. However, the co‐administration of these drugs suppressed the maximum of the GABA concentration‐response curve, indicating a non‐competitive inhibition, for which no voltage‐dependency was observed.
Simultaneous administration of ENX and BPAA also suppressed pentobarbitone (PB)‐gated ICl. On the other hand, both PB and phenobarbitone reversed the inhibition of GABA‐induced ICl by co‐administration of ENX and BPAA.
The effect on GABAA responses of co‐administration of new quinolones and NSAIDs was not via an interaction with benzodiazepine receptors coupled to the GABAA receptor, since this effect was not reversed by Ro15–1788 or diazepam.
It is concluded that the co‐administration of new quinolones and some of the NSAIDs inhibit GABAergic transmission, and could result in convulsions.
Effect of milacemide on extracellular and tissue concentrations of dopamine and 5‐hydroxytryptamine in rat frontal cortex
Authors: Semba Jun'ichi , Doheny Mary , Patsalos Philip N. , Sarna Gurcharan , Curzon Gerald 
Published: July 2012

Milacemide is a glycine prodrug which is both an inhibitor and a substrate for monoamine oxidase‐type B (MAO‐B) and also an inhibitor of MAO‐type A (MAO‐A). Its effects on dopamine and 5‐hydroxytryptamine (5‐HT) metabolism in rat frontal cortex tissue and dialysate were evaluated.
Dialysate dopamine concentrations increased linearly and dose‐dependently after milacemide administration (100, 200, 400 mg kg−1, i.p.), peaking at 1 h. A concomitant dose‐dependent decrease in dialysate 3,4‐dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) concentrations was observed but these changes were smaller (27% and 40% respectively) than the change in dopamine (125% after 400 mg kg−1 milacemide).
Dialysate 5‐HT was significantly increased only at 1.5 h after giving milacemide 400 mg kg−1. Dialysate 5‐hydroxyindoleacetic acid (5‐HIAA) concentration was not affected.
Milacemide (400 mg kg−1) at 1.5 h post‐administration significantly increased frontal cortex tissue concentrations of dopamine and 5‐HT; the percentage increase in dopamine being about four times that of 5‐HT. Metabolite concentrations, including 5‐HIAA, decreased. Changes in tissue and dialysate dopamine, DOPAC and HVA were approximately proportionate to each other.
The results are explicable in terms of an inhibition by milacemide of MAO‐A.
Neuropeptide Y (NPY) receptors in HEL cells: comparison of binding and functional parameters for full and partial agonists and a non‐peptide antagonist
Authors: Feth Friedhelm , Rascher Wolfgang , Michel Martin C. 
Published: July 2012

We have compared the binding and Ca2+ mobilizing properties of various full agonists, partial agonists and a non‐peptide antagonist at the neuropeptide Y (NPY) receptor of human erythroleukemia (HEL) cells.
[125I]‐NPY binding to intact HEL cells was rapid, saturable, of high affinity and with a specificity typical for the Y1‐like subtype: NPY, peptide YY (PYY) and [Pro34]‐NPY competed for [125I]‐NPY binding with high affinity whereas NPY13–36 and NPY18–36 had only low affinity.
NPY, PYY and [Pro34]‐NPY potently increased intracellular Ca2+ in HEL cells and had equal efficacy. NPY13–36, vasoactive intestinal peptide (VIP) and pancreatic polypeptide (PP) increased intracellular Ca2+ only poorly.
Whereas VIP and PP did not significantly affect NPY‐stimulated Ca2+ mobilization, NPY13–36 inhibited NPY‐stimulated Ca2+ increases and shifted the NPY concentration‐response curve to the right without altering its maximal effect.
The agonist (pEC50) potencies of the various peptides corresponded well with the affinities of these compounds in the binding assay (pKi), whereas the antagonist potencies (pKb) of the peptide partial agonists and the pA2 value of the non‐peptide NPY antagonist (He 90481), calculated from functional data, were lower than the respective affinities determined in the binding studies.
A plot of the fractional Ca2+ response vs the fractional receptor occupancy did not reveal any nonlinear receptor‐effector coupling for NPY or [Pro34]‐NPY; a small receptor reserve might exist for PYY.
We conclude that the binding and functional properties of HEL cell NPY receptors are very similar. NPY, PYY and [Pro34]NPY are full agonists at these receptors, whereas NPY13–36 is a partial agonist.
The role of platelet‐activating factor and peptidoleukotrienes in the vascular changes of rat passive anaphylaxis
Authors: Fernández‐Gallardo Sagrario , Gijón Miguel Angel , García Carolina , Furió Vicente , Liu Fu‐Tong , Crespo Mariano Sánchez 
Published: July 2012

The role of platelet‐activating factor (PAF) and peptidoleukotrienes as putative mediators of some of the vascular changes triggered by antigen was investigated in rats passively sensitized with monoclonal anti‐DNP (2,4‐dinitrophenyl) IgE.
Lethal anaphylaxis with respiratory distress, systemic hypotension, detachment of the intestinal mucosa, leukopenia and extravasation of protein‐rich plasma was observed after antigen challenge of rats sensitized with partially purified monoclonal IgE at concentrations of 15 mg protein kg−1.
Analysis of the peritoneal fluid obtained after i.v. challenge with DNP‐BSA (bovine serum albumin) showed the presence of significant amounts of PAF (101 ± 8 pg/rat), whereas this mediator was undetectable in control animals. Leukotriene D4 was the predominant peptidoleukotriene that could be recovered after antigen challenge, and showed an extremely high concentration (92 ± 15 ng/rat) as compared to PAF levels.
Extravasation of protein‐rich plasma was observed shortly after challenge and reached a maximum at 30 min. Treatment of animals with i.v. PCA 4248 (1–2 mg kg−1) and WEB 2086 (1 mg kg−1), two chemically unrelated compounds which are antagonists of the PAF‐receptor, produced a significant reduction of the extravasation of protein‐rich plasma.
The same degree of protection could be afforded by MK‐886, an inhibitor of leukotriene biosynthesis. Combined treatment with WEB 2086 and MK‐886 provided greater inhibition of protein‐rich plasma extravasation than either compound alone. PCA 4248 was also found to inhibit in a dose‐dependent manner the systemic hypotension observed upon DNP‐BSA challenge.
These data indicate that the lipid mediators PAF and peptidoleukotrienes are major effectors of the vascular disturbances observed in rat passive IgE‐mediated anaphylaxis.
Changes in plasma catecholamine and neuropeptide Y levels after sympathetic activation in dogs
Authors: Poncet Marie‐France , Damase‐Michel Christine , Tavernier Genevieve , Tran Marie‐Antoinette , Berlan Michel , Montastruc Jean‐Louis , Montastruc Paul 
Published: July 2012

Plasma levels of noradrenaline (NA) and neuropeptide Y (NPY) were evaluated in two experimental models associated with an increase in sympathetic tone: conscious dogs which were subject to either sinoaortic denervation or acute administration of the α2‐adrenoceptor antagonist yohimbine.
Dogs that had undergone sinoaortic denervation exhibited a two fold increase in plasma NA without any change in NPY levels.
Yohimbine (0.05 mg kg−1 i.v. as a bolus) produced similar effects. A higher dose of yohimbine (0.5 mg kg−1 i.v.) increased both plasma NA (7 fold) and NPY (6.5 fold) levels.
The present results indicate that changes in plasma catecholamines and NPY are not always concomitant. They suggest that the simultaneous release of NA and NPY is only observed under in vivo conditions for a marked increase in sympathetic tone.
Diazoxide‐sensitivity of the adenosine 5′‐triphosphate‐dependent K+ channel in mouse pancreatic β‐cells
Authors: Schwanstecher Christina , Dickel Corinna , Ebers Imke , Lins Sabine , Zünkler B.J. , Panten U. 
Published: July 2012

. In mouse pancreatic β‐cells the regulation of the diazoxide‐sensitivity of the adenosine 5′‐triphosphate‐dependent K+ channel (K‐ATP‐channel) was examined by use of the patch‐clamp technique.
. In intact β‐cells incubated at 37°C in the presence of 3 mm d‐glucose, diazoxide did not affect the single channel conductance but stimulated channel‐opening activity. Diazoxide produced half‐maximal effects at 82 μm and 13 fold activation at maximally effective concentrations (300–400 μm). The response to diazoxide (300 μm) was not completely suppressed by saturating tolbutamide concentrations (1 or 5 mm).
. Inside‐out patch‐clamp experiments were carried out using an experimental protocol favouring phosphorylation of membrane proteins. Under these conditions diazoxide was ineffective in the absence of any nucleotides, weakly effective in the presence of MgATP (26 or 87 μm) and strongly effective in the presence of the Mg complexes of adenosine 5′‐diphosphate, 2′‐deoxyadenosine 5′‐diphosphate or guanosine 5′diphosphate (MgADP, MgdADP or MgGDP).
. In inside‐out patches exposed to nucleotide‐free solutions, saturating concentrations of tolbutamide did not cause complete block of K‐ATP‐channels. When the channels were activated by MgdADP (48 μm), tolbutamide was even less effective. Sensitization of MgdADP‐induced channel activation by diazoxide further weakened the effects of tolbutamide.
. Diazoxide (50 or 300 μm) prevented the complete channel block induced by saturating tolbutamide concentrations in the presence of Mg2+ and ADP (1 mm).6. In the presence of Mg2+, the K‐ATP‐channel‐blocking potency of cytosolic ATP decreased in the order inside‐out > outside‐out > whole‐cell configuration of the patch‐clamp technique.7. It is concluded that the K‐ATP‐channel is controlled via four separate binding sites for inhibitory nucleotides (e.g. free ATP and ADP), stimulatory nucleotides (MgADP, MgdADP, MgGDP), sulphonylureas and diazoxide. Strong inhibition of the channel openings by sulphonylureas results from occupation of both sites for nucleotides. Diazoxide is only effective when the site for stimulatory nucleotides is occupied.
The effects of β2‐adrenoceptor agonists and a corticosteroid, budesonide, on the secretion of inflammatory mediators from monocytes
Authors: Linden Margareta 
Published: July 2012

The in vitro effects of the β2‐adrenoceptor agonists (1 × 10−9−10−5 m), terbutaline, salmeterol, and formoterol, on the release of inflammatory mediators, i.e. the eicosanoids leukotriene B4 (LTB4) and prostaglandin E2 (PGE2) and the cytokine interleukin‐1β (IL‐1β), were assessed in cultures of human blood monocytes. For comparison, the effects of a 5‐lipoxygenase inhibitor, BW A4C (1 × 10−9−10−5 m), and a corticosteroid, budesonide (1 × 10−10−10−5 m) were also examined. Sotalol was used to investigate whether the actions of β2‐agonists were mediated through β‐adrenoceptors.
Terbutaline, like budesonide, had no significant effect on LTB4 release, whereas BW A4C (IC50 = 2 × 10−8 m) was a potent inhibitor. All concentrations of formoterol approximately halved the LTB4 secretion, whereas high concentrations (1 × 10−7−10−5 m) only, of salmeterol, inhibited release. Only salmeterol, at high concentrations (> 1 × 10−6 m), lowered the secretion of PGE2 in monocyte cultures. Formoterol and salmeterol reduced the secretion of IL‐1β only at the highest dose (1 × 10−5 m). In contrast, budesonide (≥ 1 × 10−9 m) was a potent suppressant of this secretion.
Treatment of monocyte cultures with sotalol (1 × 10−5 m) did not significantly antagonize the inhibitory effects of salmeterol and formoterol. These results suggest that the inhibitory action of these β2‐agonists on the release of eicosanoids or IL‐1β, is not mediated via β2‐adrenoceptors.
This study does not support a therapeutic importance of the anti‐release effects of β2‐agonists since high concentrations were generally required. Furthermore, the anti‐secretory action of β2‐agonists was distinct from that of corticosteroids.
Effect of nucleotides on the cytosolic free calcium activity and inositol phosphate formation in human glomerular epithelial cells
Authors: Pavenstädt H. , Späth M. , Schlunck G. , Nauck M. , Fischer R. , Wanner C. , Schollmeyer P. 
Published: July 2012

Glomerular epithelial cells (GEC) were cultured from human kidneys and immunologically characterized.
The effect of extracellular nucleotides on the cytosolic free calcium activity [Ca2+]i was investigated with the fura‐2 microfluorescence method. Extracellular UTP, UDP, UMP, ATP, adenosine 5′‐O‐(3‐thio)‐trisphosphate (ATP‐γ‐S), inosine‐triphosphate (ITP), guanyltriphosphate (GTP), 2‐methylthio‐ATP, AMP, α,β‐methylene‐ATP and adenosine led to a rapid, transient, concentration‐dependent increase of [Ca2+]i, followed by a plateau above the baseline level.
In a calcium‐free extracellular solution, the rapid increase of [Ca2+]i was still present, whereas the plateau level was abolished.
ATP and UTP (ED50 both: 10−5 m) stimulated inositol trisphosphate (InsP3) formation in GEC.
The order of potency for the purine nucleotides in stimulating InsP3 formation was ATP = ATP‐γ‐S > ADP > 2‐methylthio‐ATP > AMP = a,β methylene‐ATP = adenosine.6 The increase of InsP3 induced by ATP (10−5 m) could be inhibited by the P2 receptor blocker suramin (> 10−4 m). Reactive blue 2 exhibited a weak stimulating effect on the InsP3 formation and only a weak inhibitory effect at a concentration of 10−3 m was observed.7 Protein kinase C activation by preincubation of GEC with phorbol 12‐myristate 13‐acetate (PMA, 100 ng ml−1, 15 min) abolished the effect of ATP (10−5 m) on InsP3 formation. Downregulation of protein kinase C by long term incubation (18 h) with PMA had no significant effect on the phosphoinositol turnover induced by ATP.8 The results indicate that an increase of [Ca2+]i and inositol phosphate breakdown can be mediated via activation of a P2 receptor in human GEC.
Elevation of cytosolic calcium by cholinoceptor agonists in SH‐SY5Y human neuroblastoma cells: estimation of the contribution of voltage‐dependent currents
Authors: Forsythe Ian D. , Lambert David G. , Nahorski Stefan R. , Linsdell Paul 
Published: July 2012

Muscarinic but not nicotinic receptor stimulation in SH‐SY5Y human neuroblastoma cells induces a concentration‐dependent increase in [3H]‐inositol phosphate formation and a biphasic increase in [Ca2+]i. The latter involves release from both an intracellular store and Ca2+ entry across the plasma membrane. Here we examine the possibility that this agonist‐stimulated Ca2+ entry occurs indirectly, as a consequence of depolarization.
Electrophysiological characterization, by whole cell patch‐clamp techniques revealed that SH‐SY5Y cells possess a tetrodotoxin‐sensitive inward sodium current, a dihydropyridine‐insensitive calcium current and an outward potassium current which was blocked by tetraethylammonium, 4‐aminopyridine and intracellular caesium ions. The outward potassium current showed voltage‐dependent activation and inactivation, similar to that seen for A‐currents.
Application of nicotinic agonists evoked an inward current in cells voltage‐clamped at negative holding potentials, but this current rectified, resulting in little or no outward current flow at positive potentials. The mean amplitude at a holding potential of — 60 mV was — 1.14 nA. Extrapolation of the current‐voltage relation gave a reversal potential of +8mV, indicative of a non‐specific cationic permeability.
Application of muscarinic agonists had no detectable effect in most of the cells tested. However, in one third of cells studied, a small slowly activating inward current was observed. The mean amplitude of this current at a holding potential of — 60 mV was — 8.3 pA.
This study confirms that SH‐SY5Y cells possess voltage‐dependent sodium, potassium and calcium currents. In addition, these cells are strongly depolarized by nicotinic agonists, which produce little change in [Ca2+]i. On the other hand, muscarinic agonists produce profound changes in [Ca2+]i with only a small inward current (depolarization). The contrasting effects of these two cholinoceptor agonists strongly implies that the Ca2+ entry after muscarinic receptor activation is not primarily due to activation of voltage‐dependent calcium channels.
Differential modulation of extracellular levels of 5‐hydroxytryptamine in the rat frontal cortex by (R)‐ and (S)‐zacopride
Authors: Barnes N.M. , Cheng C.H.K. , Costall B. , Ge J. , Naylor R.J. 
Published: July 2012

The ability of various anxiolytic and potential anxiolytic agents to modify 5‐hydroxytryptamine (5‐HT) release in the frontal cortex of the rat was assessed by the microdialysis technique.
The benzodiazepine receptor agonist, diazepam (2.5 mg kg−1, i.p.), the 5‐HT1A receptor agonist 8‐hydroxy‐2‐(di‐n‐propylamino) tetralin (8‐OH‐DPAT, 0.32 mg kg−1, s.c.) and the 5‐HT1A receptor partial agonist buspirone (4.0 mg kg−1, i.p.) maximally reduced extracellular levels of 5‐HT in the rat frontal cortex by approximately 50–60%, 70–80% and 30–40%, respectively.
(R)‐zacopride (1.0–100 μg kg−1, i.p.) dose‐dependently reduced extracellular levels of 5‐HT in the rat frontal cortex (approximately 80% maximal reduction) whereas the other 5‐HT3 receptor antagonists ondansetron (10 μg kg−1, i.p.) and (S)‐zacopride (10–100 μg kg−1, i.p.) were ineffective.
In contrast to (S)‐zacopride (100 nm; administered via the microdialysis probe), (R)‐zacopride (1.0–100 nm; administered via the microdialysis probe) induced a concentration‐dependent reduction in extracellular levels of 5‐HT in the rat frontal cortex (approximately 70% maximal reduction).
In contrast to ondansetron (100 μg kg−1, i.p.), (S)‐zacopride (10–100 μg kg−1, i.p.) dose‐dependently reversed the (R)‐zacopride (10 μg kg−1, i.p.) induced reduction in extracellular levels of 5‐HT in the rat frontal cortex. The highest dose of (S)‐zacopride (100 μg kg−1, i.p.) completely prevented the (R)‐zacopride response. In addition, (S)‐zacopride (100 nm; administered via the microdialysis probe) attenuated the inhibitory action of (R)‐zacopride (10 nm; administered via the microdialysis probe) on extracellular levels of 5‐HT in the rat frontal cortex.6 In conclusion, the present study provides further evidence of the ability of diazepam, 8‐OH‐DPAT and buspirone to reduce the activity of the central 5‐hydroxytryptaminergic system in vivo. Furthermore, the results indicate that the ability of (R)‐zacopride to reduce the in vivo release of 5‐HT in the rat frontal cortex does not correlate with its 5‐HT3 receptor antagonism. However, the differential affinity of (R)‐ and (S)‐zacopride for a (S)‐zacopride‐insensitive (R)‐zacopride site in rat cerebral cortex mirrors the relative activity of the two zacopride stereoisomers to modify the in vivo release of 5‐HT in the frontal cortex of the rat and their ability to release suppressed behaviour in animal models of anxiety.