bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential effects of nitric oxide donors on basal and electrically evoked release of acetylcholine from guinea‐pig myenteric neurones
Authors: Hebeiß Katalina , Kilbinger Heinz 
Published: July 2012

The effects of the nitric oxide (NO) donors, 3‐morpholino‐sydnonimine (SIN‐1), S‐nitroso‐N‐acetylpenicillamine (SNAP) and sodium nitroprusside on basal and electrically evoked release of [3H]‐acetylcholine were studied in myenteric plexus longitudinal muscle preparations of the guinea‐pig small intestine preincubated with [3H]‐choline.
The NO donors concentration‐dependently increased basal release of [3H]‐acetylcholine. The increase in release was calcium‐dependent and was prevented in the presence of tetrodotoxin. Superoxide dismutase (150 u ml−1) potentiated the effect of SIN‐1. The selective inhibitor of soluble guanylyl cyclase, 1H‐[1,2,4]oxadiazolo[4,3‐α]quinoxalin‐1‐one (ODQ, 0.01‐1 μm), antagonized the facilitatory effect of SNAP. 8‐Bromo cyclic GMP and the cyclic GMP‐specific phosphodiesterase inhibitor, zaprinast (both 0.1‐1 mM), also enhanced basal [3H]‐acetylcholine release. The effect of 10 μm SNAP was significantly enhanced in the presence of zaprinast.
The NO donors concentration‐dependently inhibited the electrically evoked release of [3H]‐acetylcholine, whereas 8‐bromo cyclic GMP and zaprinast enhanced the evoked release. The inhibition of acetylcholine release by SNAP was not affected by ODQ (0.01‐1 μm).
It is concluded that NO stimulates basal acetylcholine release from myenteric neurones through activation of guanylyl cyclase. In addition, NO inhibits the depolarization evoked release of acetylcholine by a presynaptic mechanism unrelated to cyclic GMP. The data imply that NO is not only an inhibitory transmitter to intestinal smooth muscles but also a modulator of cholinergic neurotransmission in the myenteric plexus.
Involvement of prostaglandins in the down‐regulation of allergic plasma leakage observed in rats undergoing pleural eosinophilia
Authors: Bandeira‐Melo Christianne , Singh Yajaira , Cordeiro Renato S.B. , e Silva Patrícia M.R. , Martins Marco A. 
Published: July 2012

Recent evidence has implicated eosinophils in the inhibition of allergen‐induced rat pleurisy, but the mechanism of this negative modulation is not completely understood. This study was undertaken in order to define the potential role of prostaglandins in this phenomenon.
Wistar rats were actively sensitized by subcutaneous injection of a mixture of ovalbumin and Al(OH)3 and challenged with an intrapleural (i.pl.) injection of ovalbumin (12 μg/cavity) 14 days later.
Analysis of the pleural fluid effluent revealed a massive mast cell degranulation and plasma protein extravasation 4 h post‐challenge. We confirmed that concurrently with selective pleural fluid eosinophilia caused by platelet‐activating factor (PAF), the pleural cavity became hyporesponsive to allergen‐induced protein exudation and to the parallel reduction in the number of intact mast cells.
These hyporesponsive animals presented a significant augmentation in the pleural effluent level of prostaglandin E2 (PGE2), which increased with increasing numbers of eosinophils in the pleural cavity. Furthermore, pretreatment with either indomethacin or aspirin failed to modify allergen‐induced exudation but reversed the exudatory hyporesponsiveness associated with eosinophil recruitment.
Allergic exudation was clearly down‐regulated by the following pretreatments: (i) PGE2 (10 μg/cavity, i.pl.) plus rolipram (40 μg/cavity, i.pl.), (ii) misoprostol (200 μg kg−1, p.o.) or (iii) dibutyryl cyclic AMP (80 μg/cavity, i.pl.).
We conclude that prostaglandins may be implicated in the eosinophil‐mediated inhibition of allergic pleurisy, probably acting via cyclic AMP signalling pathway activation.
Characterization of the P2Y‐purinoceptor involved in the ATP‐induced rise in cytosolic Ca2+ concentration in rat ileal myocytes
Authors: Pacaud Pierre , Feolde Erick , Frelin Christian , Loirand Gervaise 
Published: July 2012

The P2‐purinoceptor subtype and the intracellular signalling mechanism(s) involved in the rise in the free cytosolic Ca2+ concentration ([Ca2+]i) induced by ATP and analogues were analyzed in myocytes isolated from the longitudinal muscle layer of rat ileum by means of molecular and physiological techniques.
The P2‐purinoceptor expressed by ileal smooth muscle cells shared 100% amino acid identity with the rat P2Y1‐receptor.
Short applications of the purinoceptor agonists induced a transient rise in [Ca2+]i in an all‐or‐nothing manner. The rank order of potency of the analogues of ATP and ADP, determined by measuring the percentage of responding cells was 2‐methylthioATP = 2‐chloro‐ATP > ADP > ATP, with concentrations giving [Ca2+]i response in 50% of cells ranging between 3 nM and 0.6 μm. The concentration‐response curves to ADP and ATP were shifted to the right by 10 μm pyridoxal phosphate‐6‐azophenyl‐2′,4′‐disulphonic acid (PPADS).
Although the rise in [Ca2+]i induced by stimulation of the ileal P2Y‐purinoceptor was inhibited by heparin (5 mg ml−1), we were not able to detect stimulation of phospholipase C under conditions (37°C) where muscarinic cholinoceptor activation markedly increased inositol phosphate (InsP) accumulation. However, the carbachol (CCh)‐induced increase in InsP accumulation was suppressed when the agonist was applied at 20°C while a CCh‐induced [Ca2+]i rise similar to that obtained in response to the P2‐purinoceptor agonist was still observed.
Our results indicate that the rat ileal myocytes express a PPADS‐sensitive P2‐purinoceptor similar to the P2Y1‐receptor subtype. Although there is no detectable increase in InsP production, stimulation of these receptors leads to a rise in [Ca2+]i by activation of the inositol 1,4,5‐trisphosphate receptor‐channel of the intracellular Ca2+ store, indicating that they couple to phospholipase C.
Effect of selective blockade of endothelin ETB receptors on the liver dysfunction and injury caused by endotoxaemia in the rat
Authors: Ruetten Hartmut , Thiemermann Christoph 
Published: July 2012

We investigated the effects of the selective endothelin (ET)A receptor antagonist BQ‐485 and the selective ETB receptor antagonist BQ‐788 on circulatory failure, multiple organ dysfunction syndrome (MODS) and the alterations in acid base balance caused by endotoxaemia in the anaesthetized rat.
Male Wistar rats were anaesthetized (thiopentone sodium; 120 mg kg−1, i.p.) and received a continuous infusion of vehicle (saline, 0.6 ml kg−1h−1, i.v.), BQ‐485 (10 nmol kg−1 min−1, i.v.) or BQ‐788 (10 nmol kg−1 min−1, i.v.). Fifteen min later, animals received a bolus injection of either saline (0.9% NaCl, 1 ml kg−1, i.v.) or E. coli lipopolysaccharide (LPS, 10 mg kg−1, i.v.).
Injection of LPS resulted in a fall in blood pressure from 115 ± 4 mmHg (time 0) to 82 ± 4 mmHg at 360 min (n = 15) as well as a hyporeactivity to the pressor responses to noradrenaline (NA, 1 μm kg−1, i.v.). Infusion of BQ‐788 attenuated the delayed hypotension (at 360 min: 100 ± 4 mmHg, n = 7; P < 0.05) and significantly enhanced the pressor responses elicited by NA (at 60 to 240 min). In contrast, treatment of LPS‐rats with BQ‐485 augmented the hypotension (at 360 min), but did not affect the vascular hyporeactivity elicited by endotoxaemia.
Endotoxaemia for 360 min resulted in rises in the serum levels of urea and creatinine (indicators of renal failure), glutamate‐oxalate‐transferase (GOT) and glutamate‐pyruvate‐transferase (GPT) (indicators of hepatocellular injury), and bilirubin and γ‐glutamyl transferase (γGT) (indicators of liver failure) as well as nitrite (indicator of the induction of nitric oxide synthase; iNOS). Treatment of LPS‐rats with BQ‐788, but not with BQ‐485, attenuated the degree of liver injury and failure, while neither BQ‐788 nor BQ‐485 affected the acute renal failure or the induction of iNOS caused by endotoxin.
Endotoxaemia also caused (within 15 min) an acute metabolic acidosis (falls in pH, HCO3− and base excess) which was compensated by hyperventilation (fall in Paco2). Treatment of LPS‐rats with BQ‐788 or BQ‐485 did not affect the metabolic acidosis caused by LPS.
Thus, the selective ETB receptor antagonist BQ‐788 attenuated (i) the delayed hypotension, (ii) the vascular hyporeactivity to NA as well as (iii) the degree of hepatocellular injury and dysfunction caused by endotoxin in the anaesthetized rat. In contrast, the selective ETA receptor antagonist did neither attenuate the circulatory failure nor the liver or renal dysfunction associated with endotoxaemia. We propose that the prevention of the hepatocellular dysfunction and injury caused BQ‐788 in endotoxaemia is due to an improvement in oxygen delivery to the liver secondary to (i) inhibition of pre‐sinusoidal constriction, (ii) inhibition of sinusoidal constriction, and (iii) improvement in perfusion pressure.
A novel antagonist, No. 7943, of the Na+/Ca2+ exchange current in guinea‐pig cardiac ventricular cells
Authors: Watano Tomokazu , Kimura Junko , Morita Tominori , Nakanishi Hironori 
Published: July 2012

The effects of No. 7943 on the Na+/Ca2+ exchange current and on other membrane currents were investigated in single cardiac ventricular cells of guinea‐pig with the whole‐cell voltage‐clamp technique.
No. 7943 at 0.1–10 μm suppressed the outward Na+/Ca2+ exchange current in a concentration‐dependent manner. The suppression was reversible and the IC50 value was approximately 0.32 μm.
No. 7943 at 5–50 μm suppressed also the inward Na+/Ca2+ exchange current in a concentration‐dependent manner but with a higher IC50 value of approximately 17 μm.
In a concentration‐response curve, No. 7943 raised the KmCa2+ value, but did not affect the Imax value, indicating that No. 7943 is a competitive antagonist with external Ca2+ for the outward Na+/Ca2+ exchange current.
The voltage‐gated Na+ current, Ca2+ current and the inward rectifier K+ current were also inhibited by No. 7943 with IC50s of approximately 14, 8 and 7 μm, respectively.
In contrast to No. 7943, 3′,4′‐dichlorobenzamil (DCB) at 3–30 μm suppressed the inward Na+/Ca2+ exchange current with IC50 of 17 μm, but did not affect the outward exchange current at these concentrations.
We conclude that No. 7943 inhibits the outward Na+/Ca2+ exchange current more potently than any other currents as a competitive inhibitor with external Ca2+. This effect is in contrast to DCB which preferentially inhibits the inward rather than the outward Na+/Ca2+ exchange current.
In vivo microdialysis study of a specific inhibitor of soluble guanylyl cyclase on the glutamate receptor/nitric oxide/cyclic GMP pathway
Authors: Fedele Ernesto , Jin Ying , Varnier Giorgia , Raiteri Maurizio 
Published: July 2012

Nitric oxide (NO) is known to stimulate soluble guanylyl cyclase, thereby eliciting an elevation of guanosine 3′:5′‐cyclic monophosphate (cyclic GMP) in target cells. Recently, a selective inhibitor of soluble guanylyl cyclase, 1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ), has been identified and characterized in vitro. We have investigated the in vivo effects of ODQ on the glutamate receptor/NO/cyclic GMP pathway by monitoring extracellular cyclic GMP during microdialysis of the cerebellum or the hippocampus of freely‐moving adult rats.
Intracerebellar administration of ODQ (1–100 μm) via the microdialysis probe inhibited, in a concentration‐dependent manner, the basal extracellular level of cyclic GMP. The maximal inhibition, measured after a 20 min perfusion with 100 μm ODQ, amounted to 80% and persisted unchanged as long as ODQ was perfused. When ODQ was removed from the perfusion stream after 20 min, the levels of cyclic GMP started to recover, suggesting reversibility of guanylyl cyclase inhibition by ODQ.
The cyclic GMP response evoked in the cerebellum by NMDA (200 μm) or by α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionate (AMPA; 100 μm) was largely attenuated by 100 μm ODQ. The pattern of the inhibition curves suggests competition for guanylyl cyclase between ODQ and the NO generated by NMDA or AMPA receptor activation.
ODQ (100 μm) prevented the elevation of extracellular cyclic GMP levels provoked by intracerebellar infusion of the NO generator S‐nitroso‐N‐acetylpenicillamine (SNAP; 1 mM). The inhibition of the SNAP effect was rapidly relieved when ODQ was removed from the perfusion fluid. However, ODQ (100 μm) was unable to affect the cyclic GMP response elicited by 5 mM SNAP, in keeping with the proposed idea that ODQ binds to the ‘NO receptor’ in a reversible and competitive manner.
Infusion of ODQ (10, 100 or 300 μm) into the hippocampus of freely‐moving rats diminished the basal extracellular level of cyclic GMP. The maximal inhibition amounted to 50% and was produced by 100 μm ODQ.
The cyclic GMP response observed when 1 mM SNAP was perfused in the hippocampus, similar in percentage terms to that seen in cerebellum, was dramatically reduced during co‐infusion of 100 μm ODQ.
ODQ appears to act in vivo as a selective, reversible and possibly competitive inhibitor of the soluble guanylyl cyclase targeted by NO. This enzyme may generate most (about 80%) of the cyclic GMP found under basal conditions in the extracellular space of the cerebellum. In the hippocampus, about 50% of the basal cyclic GMP does not seem to originate from the ODQ‐sensitive soluble guanylyl cyclase.
Contrast between effects of aminobisphosphonates and non‐aminobisphosphonates on collagen‐induced arthritis in mice
Authors: Nakamura Masanori , Ando Takanobu , Abe Mastaka , Kumagai Katsuo , Endo Yasuo 
Published: July 2012

Bisphosphonates (BPs) are inhibitors of bone resorption, and many derivatives have been developed for the treatment of enhanced bone resorption. Aminobisphosphonates (aminoBPs) are particularly potent in this respect. We have shown previously that aminoBPs, such as 4‐amino‐1‐hydroxybutylidene‐1,1‐bisphosphonic acid (AHBuBP), induce histidine decarboxylase, the enzyme forming histamine, and increase macrophages, granulocytes and osteoclast numbers. Non‐aminoBPs do not show this activity.
In the present study, an additional aminoBP, cycloheptyl‐aminomethylene bisphosphonate (CHAMBP), was shown to have similar properties to AHBuBP suggesting that these actions are common among aminoBPs.
In experiments carried out to determine if aminoBPs affect immune responses, we found that CHAMBP and AHBuBP each exacerbated the arthritis induced in mice by the co‐injection of type II collagen and an adjuvant, a model for rheumatoid arthritis. In contrast, dichloromethylene bisphosphonate (C12MBP), a typical non‐aminoBP, did suppress the arthritis.
On the basis of these results, and those obtained previously, we propose that the exacerbating effects of CHAMBP and AHBuBP may be related to their ability to stimulate the synthesis of histamine and to increase macrophages and granulocytes. Conversely, we propose that the suppressive effect of C12MBP on arthritis is related to its cytotoxic action on macrophages or granulocytes.
Renal effects of TAPP, a highly selective μ‐opioid agonist
Authors: Gutkowska Jolanta , Schiller Peter W. 
Published: July 2012

The effect of i.v. administration of TAPP, a highly selective and exclusively peripherally‐acting μ‐opioid receptor agonist, on urine output, urinary sodium, potassium and cyclic GMP, and on plasma immunoreactive atrial natriuretic factor (IR‐ANF) levels was studied in conscious normally hydrated female rats (200–250 g).
TAPP treatment produced a significant dose‐dependent increase of urine output and urinary sodium, potassium and cyclic GMP excretion during the first hour. The highest TAPP dose used (2.5 mg kg−1 body weight) elicited a 10 fold elevation of urine output from 0.23 ± 0.06 ml h−1 to 2.5 ± 0.3 ml h−1 (n = 18) accompanied by augmented sodium [from 17.0 ± 4.7 μEq h−1 to 79 ± 12.7 μEq h−1, n = 18 (P < 0.001)], potassium [from 9.5 ± 2.5 μEq h−1 to 39.4 ± 6.6 μEq h−1, n = 18 (P < 0.005)], and cyclic GMP excretion [from 191 ± 21 pmol h−1 to 1340 ± 322 pmol h−1, n = 18 (P < 0.001)]. Plasma IR‐ANF rose from 22 ± 4 pg ml−1 to 508 ± 22 pg ml−1 (n = 18) (P < 0.001) 5 min after administration of TAPP (2500 μg kg−1).
TAPP lowered systemic blood pressure, also in a dose‐related manner, 1–5 min after injection. This decrease in blood pressure was transient and did not last more than 10 min.
Pretreatment with the opioid antagonist naloxone (0.8 mg per rat) abolished the diuretic, natriuretic and kaliuretic effect of TAPP (250 μg kg−1): urine output dropped from 1.16 ± 0.15 ml h−1, n = 12, to the control value of 0.15 ± 0.06 ml h−1, n = 12 (P < 0.001), sodium excretion fell from 57.5 ± 11 μEq h−1, to 21.3 ± 8.5 μEq h−1, n = 12 (P < 0.001), and potassium excretion decreased from 45.4 ± 9.7 μEq h−1, n = 12, to 16.1 ± 7.0 μEq h−1, (P < 0.001).
Pretreatment with anti‐ANF serum (0.4 ml) abolished the diuretic effect of TAPP: urine output diminished significantly from 1.93 ± 0.28 to 0.88 ± 0.29 ml h−1 (P < 0.01) (n = 6). The TAPP‐induced diuretic action, increased sodium/potassium excretion and elevated urinary cyclic GMP levels were also reversed by anti‐ANF antibodies.
Since TAPP is totally unable to cross the blood‐brain barrier, the ensemble of these observations led to the conclusion that the diuretic, natriuretic, kaliuretic and hypotensive effects produced by this μ‐opioid agonist through interaction with peripheral μ‐opioid receptors occur via ANF release.
Modulation of carbachol‐induced [Ca2+]i oscillations by Ca2+ influx in single intestinal smooth muscle cells
Authors: Komori S. , Iwata M. , Unno T. , Ohashi H. 
Published: July 2012

Oscillations of cytosolic Ca2+ concentration ([Ca2+]i) evoked by carbachol (CCh; 2 μm), a muscarinic agonist, were detected as oscillatory changes of muscarinic receptor‐coupled cationic current (Icat) in guinea‐pig ileal smooth muscle cells by the whole cell patch‐clamp technique.
Reduction of extracellular Ca2+ from 2 mM to 0.2 or 0.05 mM, during CCh‐induced Icat oscillations, caused them to disappear or to decrease markedly in frequency. A return to 2 mM Ca2+ concentration restored the initial Icat oscillations.
Application of nifedipine (1–3 μm) or D600 (2–5 μm) to block the voltage‐gated Ca2+ channel (VGCC) decreased the frequency of the ongoing Icat oscillations in the cells held at −20 mV, but it was without effect in cells held at −60 mV.
Displacement of the holding potential of −20 mV to −60 mV to deactivate VGCC produced a decrease, an increase or no noticeable change in the frequency of the Icat oscillations in different cells. Displacement to 20 mV to inactivate VGCC invariably produced a decrease in the frequency. In nifedipine‐treated cells, the Icat oscillations varied in frequency voltage‐dependently in a reverse and linear way within the range −80 to 40 mV.
Application of thapsigargin (1 or 2 μm), an inhibitor of Ca2+‐ATPase in the membrane of internal Ca2+ stores, caused CCh‐induced Icat oscillations to disappear with a progressing phase during which their amplitude, but not frequency, declined.
The results suggest that membrane Ca2+ entry has a crucial role to play in regulation of the frequency of CCh‐induced [Ca2+]i oscillations in addition to persistence of their generation, and that the effect is brought about by a potential mechanism independent of Ca2+ store replenishment. They also provide evidence that two types of Ca2+ permeant channels, VGCC and an as yet unidentified channel, are involved in the Ca2+ entry responsible for modulation of [Ca2+]i oscillations.
Pyrimidinoceptor‐mediated activation of phospholipase C and phospholipase A2 in RAW 264.7 macrophages
Authors: Lin W.W. , Lee Y.T. 
Published: July 2012

As well as the presence of P2Z purinoceptors previously found in macrophages, we identified pyrimidinoceptors in RAW 264.7 cells, which activate phospholipase C (PLC) and phospholipase A2 (PLA2).
The relative potency of agonists to stimulate inositol phosphate (IP) formation and arachidonic acid (AA) release was UTP = UDP >> ATP, ATPγS, 2MeSATP. For both signalling pathways, the EC50 values for UTP and UDP (3 μm) were significantly lower than that for ATP and all other analogues tested (> 100 μm).
UTP and UDP displayed no additivity in terms of IP formation and AA release at maximally effective concentrations.
UTP‐, but not ATP‐, evoked AA release was 60% inhibited by pertussis toxin (PTX), while stimulation of IP formation by both agonists was unaffected. Short‐term treatment with phorbol 12‐myristate 13‐acetate (PMA) led to a dose‐dependent inhibition of IP responses to UTP and UDP, but failed to affect the AA responses. Removal of extracellular Ca2+ inhibited the PI response to UTP, but abolished its AA response.
ATP‐induction of these two transmembrane signal pathways was decreased in high Mg2+‐containing medium but potentiated by the removal of extracellular Mg2+.
Suramin and reactive blue displayed equal potency to inhibit the IP responses of UTP and ATP.
Both UTP and UDP (0.1–100 μm) induced a sustained increase in [Ca2+]i which lasted for more than 10 min.
Taken together, these results indicate that in mouse RAW 264.7 macrophages, pyrimidinoceptors with specificity for UTP and UDP mediate the activation of PLC and cytosolic (c) PLA2. The activation of PLC is via a PTX‐insensitive G protein, whereas that of cPLA2 is via a PTX‐sensitive G protein‐dependent pathway. The sustained Ca2+ influx caused by UTP contributes to the activation of cPLA2. RAW 264.7 cells also possess P2Z purinoceptors which mediate ATP4‐‐induced PLC and PLA2 activation.
Characterization of α1D‐adrenoceptor subtype in rat myocardium, aorta and other tissues
Authors: Deng Xing Fei , Chemtob Sylvain , Varma Daya R. 
Published: July 2012

This study was done to characterize the functional role of α1D‐adrenoceptors in rat myocardium, aorta, spleen, vas deferens and prostate by use of the selective antagonist BMY 7378.
BMY 7378 inhibited [3H]‐prazosin binding to aortic membranes with a potency (pKi 9.8 ± 0.40) approximately 100 fold higher than in right ventricular membranes (pKi 7.47 ± 0.11) and approximately 1,000 fold higher than that in plasma membranes of the prostate (pKi 6.62 ± 0.39), vas deferens (pKi 6.67 ± 0.15), salivary gland (pKi 6.46 ± 0.38) and liver (6.58 ± 0.06).
BMY 7378 antagonized the positive inotropic effects of phenylephrine (in the presence of 1 μm propranolol) on right ventricles (pA2 7.0 ± 0.11), left atria (pKB 7.04 ± 0.18) and papillary muscles (pKB 6.9 ± 0.1) and inhibited phenylephrine‐induced increase in inositol phosphates.
BMY 7378 was approximately 100 fold more potent as an antagonist of phenylephrine on aortic strips (pA2 9.0 ± 0.13) than on vas deferens (pKB 7.17 ± 0.08) and spleen (pKB 7.16 ± 0.21); it was ineffective on the prostate.
Chloroethylclonidine suppressed the maximal effects of phenylephrine on spleen; 5‐methylurapidil antagonized the effects of phenylephrine on aortic strips (pA2 7.98 ± 0.08), vas deferens (pKB 8.89 ± 0.07) and prostate (pKB 8.85 ± 0.21).
BMY 7378 caused a dose (0.1–100 nmol kg−1)‐dependent decrease in mean blood pressure of urethane‐anaesthetized rats and its hypotensive efficacy was equal to that of hexamethonium.
The data suggest that α1D‐adrenoceptors play a significant role in rat aorta, a minor role in the heart, vas deferens and spleen and virtually no role in the prostate.