bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of P1060 and aprikalim on whole‐cell currents in rat portal vein; inhibition by glibenclamide and phentolamine
Authors: Ibbotson T. , Edwards G. , Noack Th. , Weston A.H. 
Published: July 2012

Smooth muscle cells of the rat portal vein were dispersed by enzymatic treatment and recordings of whole‐cell currents were made by the voltage‐clamp technique. The effects of the potassium (K) channel openers, P1060 (0.3–10 μm) and aprikalim (3–30 μm) on these currents were investigated. Antagonism of these agents by glibenclamide and phentolamine was also studied.
When cells were clamped at — 10 mV, P1060 (1 μm) and aprikalim (3 μm) each induced a slowly‐developing K‐current (IKCO), the noise of which gradually increased. The rate of onset of IKCO was greater for P1060 than for aprikalim. Current‐voltage plots showed that P1060 and aprikalim each caused an approximately 25 mV negative shift of the reversal potential at zero current.
P1060 (1 μm) and aprikalim (3 μm) each inhibited the slowly activating, slowly inactivating delayed rectifier current, ITO.
Addition of MgATP (5 mm) to the recording pipette inhibited the generation of IKCO by P1060 (1 μm) and reduced the accompanying inhibition of ITO.
Stationary fluctuation analysis of the current noise associated with IKCO induced by P1060 (1 μm) or aprikalim (3 μm) at a holding potential of — 10 mV indicated that the unitary conductance of the underlying K‐channels was 10.5 pS at 0 mV under the quasi‐physiological conditions of the experiment.
In the absence of K‐channel openers, neither phentolamine (30–100 μm) nor glibenclamide (1 μm) affected the magnitude of control non‐inactivating currents. However, phentolamine (30–100 μm), but not glibenclamide (1 μm) inhibited the control delayed rectifier current, ITO.
After induction of IKCO by P1060 (1 μm) or aprikalim (3 μm), subsequent exposure to glibenclamide (1 μm) or phentolamine (30 μm) inhibited this current. After aprikalim‐induced reduction of ITO had developed, subsequent exposure to glibenclamide was able partially to reverse the inhibition of ITO whereas phentolamine was without effect. Pre‐exposure to glibenclamide (1 μm) prevented both the generation of IKCO by aprikalim (3 μm) and the inhibitory effect of this agent on ITO.
It is concluded that P1060 and aprikalim each induce the current IKCO by opening the same small conductance, ATP‐sensitive K‐channel (KATP), an effect which can be inhibited by glibenclamide or phentolamine. The opening of KATP by both P1060 and aprikalim probably involves competition between these agents and ATP for the ATP‐control site associated with the channel. Inhibition of the delayed rectifier current, ITO, by P1060 and aprikalim was glibenclamide‐sensitive and may be caused by the induction of a state of run‐down in the channel which underlies this current.
Modulation of adjuvant arthritis by endogenous nitric oxide
Authors: Ialenti Armando , Moncada Salvador , Di Rosa Massimo 
Published: July 2012

The role of endogenous nitric oxide (NO) in adjuvant arthritis in Lewis rats has been studied by use of l‐arginine, the amino acid from which NO is synthesized, and NG‐nitro‐l‐arginine methyl ester (l‐NAME), an inhibitor of NO synthase. Prolonged modulation (35 days) of the l‐arginine: NO pathway in rats was achieved by dissolving test compounds in the drinking water (l‐arginine: 3, 10 and 30 mg ml−1; l‐NAME: 0.1, 1 and 10 mg ml−1).
Arthritis was exacerbated by l‐arginine and suppressed by l‐NAME in a dose‐related fashion. Combined treatment with l‐NAME (1 mg ml−1) and l‐arginine (30 mg ml−1) did not modify the arthritis.
Reduced weight gain, which is a feature of adjuvant arthritis, was modified by these compounds so that l‐arginine reduced weight gain whereas l‐NAME increased weight gain compared with that in control animals.
d‐Arginine (30 mg ml−1), NG‐nitro‐d‐arginine methyl ester (d‐NAME: 1 mg ml−1) and l‐lysine (30 mg ml−1), an amino acid not involved in the generation of NO, were without effect on either arthritis or body weight gain.
. Antigen‐stimulated proliferation of T‐lymphocytes as well as generation of nitrite (NO2−) and release of acid phosphatase from macrophages were all enhanced in l‐arginine‐treated arthritic rats and reduced in l‐NAME‐treated animals.
These results suggest that endogenous NO modulates adjuvant arthritis, possibly by interfering with the activation of T‐lymphocytes and/or macrophages.
The role of nitric oxide in cholinergic neurotransmission in rat trachea
Authors: Sekizawa Kiyohisa , Fukushima Takeyasu , Ikarashi Yasushi , Maruyama Yuji , Sasaki Hidetada 
Published: July 2012

We have investigated the role of nitric oxide (NO) in cholinergic contraction in rat trachea.
Methylene blue (10 nm to 30 μm) potentiated cholinergic contraction induced by electrical field stimulation (EFS) at 5 Hz in a concentration‐dependent fashion. At a concentration of 30 μm, methylene blue decreased responses to log EFS frequency, producing 50% of maximum contraction from a control value of 0.74 ± 0.09 Hz to 0.30 ± 0.05 Hz without a significant effect on concentration‐response curves to acetylcholine (ACh).
NG‐monomethyl‐l‐arginine (l‐NMMA; 100 μm) also potentiated cholinergic contraction induced by EFS at 5 Hz (131.5 ± 4.6% of control) without having any effect against ACh (3 μm)‐induced contractions. Likewise, l‐NMMA (100 μm) significantly increased EFS (5 Hz)‐evoked release of ACh from tracheal segments into the bath solution (51.4 ± 4.0 pmol ml−1 in the presence of l‐NMMA and 35.0 ± 1.8 pmol ml−1 in the absence of l‐NMMA, respectively).
Administration of NO (present in acidified soluton of NaNO2) (1 nm to 10 μm) and sodium nitroprusside (100 nm to 10 μm) concentration‐dependently reduced EFS (5 Hz)‐induced cholinergic contractions without having a significant effect on ACh (3 μm)‐induced contractions. These results were unaffected by prior exposure of the tissues to l‐NMMA (100 μm).
Dibutyryl cyclic GMP (3 mm) also reduced cholinergic contractions induced by EFS at 5 Hz (70.1 ± 3.6% of control) without any significant effect on ACh (3 μm)‐induced contractions.
Pretreatment of tissues with capsaicin (30 μm) or α‐chymotrypsin (1 u ml−1) failed to inhibit methylene blue (30 μm)‐induced potentiation of responses to EFS at 5 Hz.
These results suggest that an endogenous NO‐like factor may mediate prejunctional inhibition of cholinergic contraction through a cyclic GMP‐dependent mechanism in rat trachea.
The effects of a converting enzyme inhibitor (Captopril) and angiotensin II on fetal renal function
Authors: Lumbers E.R. , Burrell J.H. , Menzies R.I. , Stevens A.D. 
Published: July 2012

Renal function was studied in chronically catheterized fetal sheep (119–128 days gestation), before and during treatment of the ewe with the angiotensin converting enzyme (ACE) inhibitor, Captopril, which crosses the placenta and blocks the fetal renin angiotensin system.
An i.v. dose of 15 mg (about 319 μg kg−1) of Captopril to salt‐replete ewes followed by an infusion to the ewe of 6 mg h−1 (about 128 μg kg−1 h−1) caused a fall in fetal arterial pressure (P < 0.01), and a rise in fetal renal blood flow (RBF) from 67.9 ± 5.6 to 84.9 ± 8.3 ml min−1 (mean ± s.e.mean) (P < 0.05). Renal vascular resistance and glomerular filtration rate (GFR) fell (P < 0.01); fetal urine flow (P < 0.01) and sodium excretion declined (P < 0.05).
Ewes were treated for the next 2 days with 15 mg Captopril twice daily. On the 4th day, 15 mg was given to the ewe and fetal renal function studied for 2 h during the infusion of Captopril (6 mg h−1) to the ewe. Of the 9 surviving fetuses, 3 were anuric and 3 had low urine flow rates. When 6 μg kg−1 h−1 of angiotensin II was infused directly into the fetus RBF fell from 69 ± 10.1 ml min−1 to 31 ± 13.9 ml min−1, GFR rose (P < 0.05) and urine flow (P < 0.01) and sodium excretion increased in all fetuses.
It is concluded that the small fall in fetal arterial pressure partly contributed to the fall in fetal GFR but in addition, efferent arteriolar tone fell so that the filtration pressure fell further. Thus maintenance of fetal renal function depends on the integrity of the fetal renin angiotensin system. These findings explain why use of ACE inhibitors in human pregnancy is associated with neonatal anuria.
A comparison of intravenous NBQX and GYKI 53655 as AMPA antagonists in the rat spinal cord
Authors: Chizh Boris A. , Cumberbatch Michael J. , Headley P. Max 
Published: July 2012

The effects of intravenous administration of two α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionic acid (AMPA) antagonists were studied on responses of single neurones to iontophoretically applied excitatory amino acids. The tests were performed on spinal neurones in α‐chloralose anaesthetized, spinalized rats.
Both the quinoxaline, NBQX (2–16 mg kg−1) and the 2,3‐benzodiazepine, GYKI 53655 (2–8 mg kg−1) dose‐dependently decreased responses to AMPA.
Both compounds were short acting, with half‐recovery times of 15 min for NBQX and 7 min for GYKI 53655.
The selectivity for responses to AMPA over those to N‐methyl‐d‐aspartate (NMDA) was significantly poorer for systemic NBQX than for either systemic GYKI 53655 or iontophoretic NBQX, suggesting that systemic NBQX may be converted to a less selective metabolite.
GYKI 53655 is therefore likely to be a more valuable tool than NBQX for the study of AMPA receptor‐mediated processes in vivo.
Pharmacological characterization of the human histamine H2 receptor stably expressed in Chinese hamster ovary cells
Authors: Leurs Rob , Smit Martine J. , Menge Wiro M.B.P. , Timmerman Hendrik 
Published: July 2012

The gene for the human histamine H2 receptor was stably expressed in Chinese hamster ovary (CHO) cells and characterized by [125I]‐iodoaminopotentidine binding studies. In addition, the coupling of the expressed receptor protein to a variety of signal transduction pathways was investigated.
After cotransfection of CHO cells with pCMVhumH2 and pUT626, a phleomycine‐resistant clonal cell line (CHOhumH2) was isolated that expressed 565 ± 35 fmol kg−1 protein binding sites with high affinity (0.21 ± 0.02 nm) for the H2 antagonist, [125I]‐iodoaminopotentidine.
Displacement studies with a variety of H2 antagonists indicated that the encoded protein was indistinguishable from the H2 receptor identified in human brain membranes and guinea‐pig right atrium. The Ki‐values observed in the various preparations correlated very well (r2 = 0.996–0.920).
Displacement studies with histamine showed that a limited fraction (32 ± 6%) of the binding sites showed a high affinity for histamine (2 ± 1.2 μm); the shallow displacement curves were reflected by a Hill‐coefficient significantly different from unity (nH = 0.58 ± 0.09). The addition of 100 μm Gpp(NH)p resulted in a steepening of the displacement curve (nH = 0.79 ± 0.02) and a loss of high affinity sites for histamine.
Displacement studies with other agonists indicated that the recently developed specific H2 agonists, amthamine and amselamine, showed an approximately 4–5 fold higher affinity for the human H2 receptor than histamine.
Stimulation of CHOhumH2 cells with histamine resulted in a rapid rise of the intracellular cyclic AMP levels. After 10 min an approximately 10 fold increase in cyclic AMP could be measured. The EC50 value for this response was 7 ± 1 nm for histamine. This response was effectively blocked by tiotidine and cimetidine, resulting in Ki values of 8 ± 1 nm and 0.56 ± 0.24 μm respectively.
Stimulation of CHOhumH2 cells with histamine neither inhibited the A23187‐induced release of [3H]‐arachidonic acid nor changed the intracellular IP3 levels.
These results show that the cloned human gene encodes a histamine H2 receptor that is indistinguishable from the H2 receptor identified in human brain tissue. This receptor is functionally coupled to the adenylate cyclase in CHO cells, but does not influence the inositolphosphate turnover or arachidonic acid release.
Poly‐l‐arginine‐mediated release of acetylcholine from parasympathetic nerves in rat and guinea‐pig airways
Authors: Spina D. , Goldie R.G. 
Published: July 2012

The synthetic cationic polypeptide, poly‐l‐arginine (0.03–1 mg ml−1) induced concentration‐dependent contraction of guinea‐pig and rat isolated trachea. In guinea‐pig isolated trachea, this response was attenuated in the presence of the muscarinic cholinoceptor antagonist, atropine (0.1 μm) and augmented by the acetylcholinesterase inhibitor, ecothiophate (0.1 μm). The neuronal sodium channel blocker, tetrodotoxin (3 μm) failed to alter the contractile response to poly‐l‐arginine and acetylcholine.
The contractile response to poly‐l‐arginine in rat isolated trachea was inhibited in the presence of atropine (0.1 μm) and the 5‐hydroxytryptamine (5‐HT) receptor antagonist, methysergide (1 μm). Treatment of rat tracheal preparations with capsaicin (100 μm) or tetrodotoxin (3 μm) failed to alter the contractile response to poly‐l‐arginine. In contrast, ecothiophate (0.1 μm) augmented the contractile response to poly‐l‐arginine in rat isolated trachea.
Electrical field stimulation (5 Hz, 2 min) of epithelium‐denuded guinea‐pig tracheal preparations preloaded with [3H]‐choline resulted in a contractile response and the simultaneous efflux of radioactivity into the superfusate. Both these responses were abolished in the presence of tetrodotoxin (1.5 μm). Poly‐l‐arginine (1 mg ml−1) also increased the efflux of total radioactivity from epithelium‐denuded guinea‐pig isolated tracheal preparations preloaded with [3H]‐choline, but this response was tetrodotoxin‐insensitive. The negatively charged polyanion, heparin (1 mg ml−1) failed to increase significantly the efflux of radioactivity from epithelium‐denuded preparations.
In conclusion, the synthetic cationic polypeptide, poly‐l‐arginine, caused contraction of guinea‐pig isolated tracheal preparations via the release of acetylcholine from parasympathetic nerves. Similarly, poly‐l‐arginine‐induced contraction of rat isolated trachea is secondary to the release of acetylcholine from parasympathetic nerves and/or the release of mast cell‐derived 5‐HT.
Stereoselective and non‐stereoselective actions of isoflurane on the GABAA receptor
Authors: Hall A.C. , Lieb W.R. , Franks N.P. 
Published: July 2012

Acutely dissociated cerebellar Purkinje neurones from 8–14 day old rats were studied under voltage clamp in the whole‐cell patch‐clamp configuration. Cl− currents induced by bath application of γ‐aminobutyric acid (GABA) were measured (using symmetrical Cl− solutions) at both low (2 μm) non‐desensitizing and high (300 μm) desensitizing concentrations of GABA.
At 2 μm GABA, the bicuculline‐sensitive Cl− currents were potentiated by racemic isoflurane and both of its optical isomers. Isoflurane had no effect on membrane current in the absence of GABA. The dose‐response data for potentiation by racemic isoflurane could be fitted with a Hill equation with an EC50 = 320 ± 20 μm isoflurane and a Hill coefficient of h = 2.7 ± 0.4 (means ± s.e.mean).
The potentiations produced by the optical isomers of isoflurane at 2 μm GABA were stereoselective at moderate and high anaesthetic concentrations. The maximum stereoselectivity, about two fold, occurred at the EC50 concentration for general anaesthesia (310 μm isoflurane), with S(+)‐isoflurane being more effective than R(−)‐isoflurane. At sub‐anaesthetic concentrations, the stereoselectivity was less marked and vanished at the lowest concentration used (77 μm isoflurane).
The sustained residual current remaining after exposure of neurones to a desensitizing concentration of GABA (300 μm) was inhibited non‐stereoselectively, but only at high concentrations of isoflurane. The ratio of inhibitions by S(+)‐ and R(−)‐isoflurane (mean ± s.e.mean) was 1.14 ± 0.21 at 770 μm isoflurane. At the EC50 concentration for general anaesthesia, however, the inhibition was barely significant.
The above results are discussed in relation to the possible role of the GABAA receptor channel in general anaesthesia.
Involvement of apamin‐sensitive K+ channels in antigen‐induced spasm of guinea‐pig isolated trachea
Authors: Yamauchi Hideyuki , Miura Motohiko , Ichinose Masakazu , Ishikawa Jun , Nakajima Natsuko , Tomaki Masafumi , Inoue Hiroshi , Maeyama Kazutaka , Watanabe Takehiko , Shirato Kunio 
Published: July 2012

In order to examine whether K+ channels play a role in antigen‐induced airway responses, the effect of K+ channel blockers on antigen‐induced airway smooth muscle contraction and mediator release was examined in vitro in guinea‐pigs actively sensitized with ovalbumin (OA).
Tracheal strips from sensitized animals were suspended in organ baths under a resting tension of 1 g and isometric tension was continuously measured. Cumulative concentration‐response curves to OA (0.1–1000 ng ml−1) or histamine (10 nm‐1 mm) were obtained in the presence and absence of K+ channel blockers.
OA (10, 100 or 1000 ng ml−1) was incubated with minced lung tissues from the same animals for 15 min in the presence and absence of K+ channel blockers, and released histamine and leukotriene C4 (LTC4) in the incubating medium were measured.
Apamin, a small conductance Ca2+‐activated K+ channel (PK,Ca) blocker, (0.1, 0.3 and 1 μm) significantly inhibited OA‐induced smooth muscle contraction, while charybdotoxin (ChTX, 10 nm), an intermediate and large conductance PK,Ca blocker, and iberiotoxin (IbTX, 3 nm), a large conductance PK,Ca blocker, were without effect. Apamin (0.3 μm) had no effect on exogenously administered histamine‐induced airway smooth muscle contraction, suggesting that the inhibition of OA‐induced contraction by apamin did not occur at the smooth muscle level.
The inhibition of OA‐induced contraction by apamin (0.3 μm) was not significantly affected by pretreatment with a leukotriene antagonist, ONO‐1078 (10 μm), but was abolished by pretreatment with a histamine H1‐receptor blocker, pyrilamine (1 μm).
Apamin by itself (up to 0.1 μm) had no effect on spontaneous histamine release from minced lung tissues. Histamine release induced by low and intermediate concentrations of OA (10 and 100 ng ml−1) was significantly suppressed by apamin pretreatment (P < 0.05 and P < 0.001), whereas LTC4 release was not affected. ChTX (0.1 μm) and IbTX (10 nm) had no significant effect on either spontaneous or OA (100 ng ml−1)‐induced histamine release.
These results suggest that apamin partially but substantially inhibits antigen‐induced smooth muscle contraction, presumably by inhibiting antigen‐induced histamine release from airway mast cells through small conductance PK,Ca. closure.
Pharmacological properties of the cloned α1A/D‐adrenoceptor subtype are consistent with the α1A‐adrenoceptor characterized in rat cerebral cortex and vas deferens
Authors: Kenny B.A. , Naylor A.M. , Greengrass P.M. , Russell M.J. , Friend S.J. , Read A.M. , Wyllie M.G. 
Published: July 2012

The pharmacological characteristics of cloned mammalian α1A/D‐, α1B‐ and α1C‐adrenoceptor subtypes expressed in rat 1 fibroblasts were determined in comparison to the binding and functional properties of these subtypes in rat tissues.
Analysis of [3H]‐prazosin binding to membrane homogenates from rat 1 fibroblast cells expressing each of the α1‐subtypes indicated high affinity binding to a single population of binding sites. Binding affinities were similar for α1A/D‐, α1B‐ and α1C‐subtypes (Kds: 0.13, 0.10 and 0.15 nm respectively) although a higher density of α1B‐ and α1C‐receptors (Bmax: 4068 and 10,323 fmol mg−1 protein respectively) were expressed in comparison to α1A/D (838 fmol mg−1).
Displacement of [3H]‐prazosin from membranes expressing cloned α1‐adrenoceptor subtypes revealed that 5‐methyl‐urapidil, WB 4101, benoxathian and phentolamine displayed high affinity and selectivity for α1A/D‐ over α1B‐subtypes. These compounds also had high affinity and selectivity for α1C‐ over α1B‐subtypes. 5‐Methyl‐urapidil showed selectivity for α1C (Ki 0.60 ± 0.16 nm) over both α1A/D (Ki, 9.8 ± 2.8 nm) and α1B (Ki 57.2 ± 12 nm) subtypes. Prazosin and doxazosin were not subtype selective.
In comparison to [3H]‐prazosin a similar pharmacological profile was obtained with [125I]‐HEAT using cloned α1A/D‐, α1B‐ and α1C‐adrenoceptors expressed in rat 1 fibroblasts.
The affinities of prazosin, WB 4101, 5‐methyl‐urapidil, phentolamine and benoxathian at cloned α1A/D‐receptors were consistent with α1A affinities determined with chlorethylclonidine‐treated rat cortical membranes. Affinities at cloned α1B‐receptors were consistent with α1B affinities determined with rat liver membranes.
Using the epididymal rat vas deferens as a functional measure of α1A affinity, prazosin (pA2 9.23 ± 0.28), WB 4101 (pA2 9.58 ± 0.12), phentolamine (pKB 7.90 ± 0.16), benoxathian (pKB 9.21 ± 0.21) and 5‐methyl‐urapadil (pKB 8.51 ± 0.16) were potent antagonists of noradrenaline‐induced contractions.
At present, evidence from cloning studies suggests the existence of at least three α1‐adrenoceptor subtypes. In contrast to the recent proposal for α1‐adrenoceptor classification, the pharmacology of the cloned α1A/D (or α1D)‐adrenoceptor is more consistent with that of an α1A‐adrenoceptor characterized in rat cerebral cortex and vas deferens.
Replacement of salt by a novel potassium‐ and magnesium‐enriched salt alternative improves the cardiovascular effects of ramipril
Authors: Mervaala Eero M.A. , Paakkari Ilari , Laakso Juha , Nevala Riikka , Teräväinen Tertt M‐Lüsa , Fyhrquist Frej , Vapaatalo Heikki , Karppanen Heikki 
Published: July 2012

The influence of salt (sodium chloride; NaCl) (an additional 6% in the diet) and that of a novel sodium‐reduced, potassium‐, magnesium‐, and l‐lysine‐enriched salt alternative on the cardiovascular effects of ramipril was studied in stroke‐prone spontaneously hypertensive rats in a 6‐week study. The intake of sodium chloride was adjusted to the same level by adding the salt alternative at a 1.75 times higher amount than regular salt.
Salt produced a marked rise in blood pressure and induced cardiac hypertrophy and significant mortality, while the salt alternative neither increased blood pressure nor caused any mortality and produced less cardiac hypertrophy than salt.
Ramipril treatment at a daily dose of 3 mg kg−1normalized blood pressure and prevented the development of cardiac hypertrophy of rats on control diet. These effects of ramipril were blocked by the addition of salt but were only slightly attenuated by the addition of the salt alternative. The mortality in the salt group was prevented by ramipril.
Responses of mesenteric arterial rings in vitro were examined at the end of the study. Salt, but not the salt alternative, increased vascular contractile responses to noradrenaline. Ramipril treatment improved the arterial relaxation responses to acetylcholine and to sodium nitroprusside. The vascular relaxation enhancing effect of ramipril was blocked by salt but only slightly attenuated by the salt alternative.
Ramipril treatment did not significantly increase plasma renin activity in the presence or in the absence of salt supplementation. The salt alternative did not cause hyperkalaemia, either alone or in combination with ramipril treatment.
Both salt supplementations, irrespective of ramipril treatment, induced a six to eight fold increase in the urinary excretion of calcium. There was an expected 90 to 140% rise in the urinary excretion of magnesium and 200% rise in the urinary excretion of potassium in the salt alternative group. Salt also produced an approximately 50% increase in magnesuria.
Our findings suggest that replacement of salt by the potassium‐, magnesium‐ and l‐lysine‐enriched salt alternative improves the cardiovascular effects of ramipril. In the present study the beneficial effect was related to the increased intakes of potassium and/or magnesium and l‐lysine from the salt alternative because the amount of sodium chloride was the same.