bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rapid decrease in neuropeptide Y gene expression in rat adrenal gland induced by the α2‐adrenoceptor agonist, clonidine
Authors: Higuchi Hiroshi , Iwasa Atsushi , Miki Naomasa 
Published: July 2012

The mechanism of regulation of the neuropeptide Y (NPY) gene by pharmacological treatment with the α2‐adrenenoceptor agonist, clonidine, was investigated by quantitative Northern blot analysis of the effects of this drug on the NPY mRNA levels in rat adrenal gland and medulla oblongata/pons.
In the adrenal gland, clonidine‐treatment (50 μg kg−1, s.c., once daily) resulted in decrease in the amount of NPY mRNA to 44 ± 10% of the control level in 24 h and then its increase to 162 ± 16% of the control level after 5 days. Concomitant changes in putative NPY pre‐mRNA species (7.0 and 3.3 kb) were observed, probably due to changes at the level of NPY gene transcription.
The short‐term (24 h) effect of clonidine was blocked by yohimbine (5 mg kg−1, i.p., once daily). Yohimbine alone tended to increase the NPY mRNA level after 24 h.
The recovery/increase in the NPY mRNA level in the adrenal gland after 5 days treatment with clonidine was similar to its increase after treatment with reserpine (0.5 mg kg−1, i.p., once daily).
NPY gene expression in the medulla oblongata/pons was not changed by short‐ or long‐term treatment with clonidine.
These results suggest that clonidine suppresses NPY gene expression in the adrenal gland, probably at the level of transcription, by activation of the α2‐adrenoceptor.
The effect of E. coli STa enterotoxin on the absorption of weakly dissociable anti‐malarial drugs from rat intestine in vivo
Authors: Rawlings J.M. , Lynch J. , Lucas M.L. 
Published: July 2012

The effect of E. coli heat stable (STa) enterotoxin on the absorption of radiolabelled anti‐malarial weak bases and their appearance in peripheral blood was assessed in vivo by a recirculation procedure in rat intestinal loops.
Enterotoxin increased the jejunal disappearance of quinine (P < 0.05), trimethoprim (P < 0.05), proguanil (P < 0.05) and chloroquine (P < 0.001) and left pyrimethamine disappearance unaltered. Peripheral blood levels of trimethoprim (P < 0.02) and proguanil (P < 0.05) were higher after STa exposure.
In the ileum, enterotoxin increased the luminal disappearance (P < 0.05) and peripheral blood appearance (P < 0.001) of chloroquine. The luminal disappearance rate of trimethoprim was reduced (P < 0.05) and that of pyrimethamine unchanged.
The increased jejunal absorption of the anti‐malarial drugs occurred despite STa causing a reduction in the amount of net fluid absorption. It seems likely that the enhanced absorption with STa exposure is related to the effect of STa on the microclimate pH. An elevation in the microclimate pH would increase the amount of undissociated weak base available for non‐ionic diffusion.
The favourable elevation of microclimate pH by STa seemed to be outweighed by the reduced fluid absorption in the ileum. Only chloroquine still showed enhanced absorption in the ileum and this may have been because unlike the other antimalarial drugs, chloroquine has two dissociable groups likely to be affected by the mucosal surface pH changes.
Evidence that acetylcholine‐mediated hyperpolarization of the rat small mesenteric artery does not involve the K+ channel opened by cromakalim
Authors: McPherson Grant A. , Angus James A. 
Published: July 2012

Acetylcholine causes a concentration‐dependent hyperpolarization of the rat small mesenteric artery (diameter at 100 mmHg, 200–400 μm). In the absence of tone the average potential change was from approximately −60 to −75 mV. In the presence of tone induced by endothelin‐1 (20 nm), acetylcholine caused vasorelaxation in association with a marked hyperpolarization; from approximately −32 to −71 mV.
A number of compounds known to antagonize the actions of cromakalim were tested for their ability to block responses to acetylcholine. Glibenclamide (0.1–3 μm), phentolamine (10–100 μm) and alinidine (1–30 μm) caused a concentration‐dependent depolarization of the rat small mesenteric artery which was not dependent on an intact endothelium. Glibenclamide was approximately 10 times more potent than either phentolamine or alinidine, a similar ratio to their potency as antagonists of cromakalim.
In the presence of concentrations of the cromakalim antagonists which functionally inhibited responses to cromakalim, only phentolamine and alinidine had a significant effect on the hyperpolarization and functional responses to acetylcholine. Glibenclamide was without effect at the concentrations used.
Experiments on pig coronary artery, where acetylcholine causes vasoconstrictor responses, showed that phentolamine and alinidine have some anti‐muscarinic activity which could account for their ability to affect vasorelaxant/hyperpolarization responses to acetylcholine in the rat small mesenteric artery.
The results suggest that the acetylcholine‐mediated hyperpolarization observed in the rat small mesenteric artery does not involve K+ channels opened by cromakalim. This finding differs from other studies performed on the rabbit middle cerebral artery which show hyperpolarizing responses to acetylcholine to be glibenclamide‐sensitive. It is likely therefore that the hyperpolarization response observed to acetylcholine can be initiated through a number of mechanisms, only one of which utilizes K+ channels opened by cromakalim.
Facilitatory effects of tachykinins and guanethidine on the acetylcholine output stimulated by nicotine from guinea‐pig bladder
Authors: Shinkai Michiko , Takayanagi Issei , Kato Teruko 
Published: July 2012

Contractile responses and acetylcholine release evoked by nicotine in guinea‐pig detrusor strips were determined by isotonic transducer and radioimmunoassay, respectively. Nicotine stimulated acetylcholine release and a contractile response in guinea‐pig detrusor strips treated with the cholinesterase inhibitor, methanesulphonyl fluoride (MSF). Both actions evoked by nicotine were antagonized by the nicotinic receptor antagonist, hexamethonium but were insensitive to tetrodotoxin.
A sympathetic nerve blocker, guanethidine and a tachykinin antagonist, [d‐Arg1, d‐Pro2, d‐Trp7,9, Leu11]‐substance P (rpwwL‐SP) partially inhibited the acetylcholine release evoked by nicotine to much the same degree. The inhibitory effects of guanethidine and rpwwL‐SP on acetylcholine release were significantly greater than corresponding effects on the contraction evoked by nicotine.
In preparations treated with rpwwL‐SP to block the tachykinin receptors, guanethidine had no effect on the response to nicotine. Conversely, after treatment with guanethidine to block release of a mediator from sympathetic nerve endings, nicotine‐induced responses were not affected by rpwwL‐SP.
Nicotine‐induced contraction was reduced to 30% by the muscarinic cholinoceptor antagonist, atropine and completely abolished after desensitization of P2‐purinoceptors with α,β‐methylene ATP in the presence of atropine.
A concentration‐contractile response curve to neurokinin A (NKA) was shited to the left after cholinesterase inhibition with MSF. Atropine abolished the facilitatory effect of MSF and partially inhibited contractions induced by NKA at 100 nm to 1 μm. The contractile responses to substance P methyl ester (SPOMe) and Tyro‐neurokinin B (Tyro‐NKB) were not influenced by MSF or atropine.
After desensitization of NR1 tachykinin receptors with SPOMe or preincubation with senktide, the cholinergic component of the nicotine‐induced contraction was the same as the control value (100%).
Our findings give further support to our previous results: nicotine stimulates acetylcholine release in a tetrodotoxin‐resistant manner in guinea‐pig bladder and acetylcholine release evoked by nicotine is increased by the coordinated action of sympathetic nerves and tachykinin(s). It is suggested that the tachykinin receptor subtype involved in acetylcholine release is NK2.
Endothelium‐dependent and endothelium‐independent vasodilatation of the hepatic artery of the rabbit
Authors: Brizzolara Antonia L. , Burnstock Geoffrey 
Published: July 2012

The isolated hepatic artery of the rabbit contracted to exogenously applied noradrenaline (NA). There was no significant difference in the maximal contraction or the EC50 value in vessels where the endothelium was present and in endothelium‐denuded preparations.
Acetylcholine (ACh) induced a vasodilatation of vessels preconstricted with NA which was entirely dependent on the endothelium.
Adenosine 5′‐triphosphate (ATP), 2‐methylthio ATP, adenosine and sodium nitroprusside induced concentration‐dependent, sustained relaxations of vessels in which tone had been induced with NA. The relaxation responses were not reduced after removal of the endothelium. 8‐Phenyltheophylline antagonized the relaxation response produced by adenosine, but not that due to ATP at lower concentrations. The maximum response to ATP was reduced in the presence of 8‐phenyltheophylline.
α,β‐Methylene ATP produced further contraction of vessels preconstricted with NA in both endothelium‐denuded preparations and in vessels where the endothelium remained intact.
Immunohistochemical analysis was used to show the presence of nerve fibres containing substance P (SP), calcitonin gene‐related peptide (CGRP) and vasoactive intestinal polypeptide (VIP) in the hepatic artery. Application of SP induced a concentration‐dependent relaxation which was entirely dependent on the presence of an intact endothelium. CGRP and VIP, however, elicited concentration‐dependent relaxations which were independent of the endothelium.
It is concluded that in the rabbit hepatic artery, responses to ACh are dependent on the presence of intact endothelium. P1‐, P2x‐ and P2y‐purinoceptors, mediating relaxation to adenosine, vasoconstriction to ATP and vasodilatation to ATP respectively, are located on vascular smooth muscle. Furthermore, CGRP and VIP mediate a direct vasodilatation of smooth muscle both in the absence and the presence of the endothelium, whereas SP produces a relaxation via receptors located on the endothelium.
Demethoxyviridin and wortmannin block phospholipase C and D activation in the human neutrophil
Authors: Bonser R.W. , Thompson N.T. , Randall R.W. , Tateson J.E. , Spacey G.D. , Hodson H.F. , Garland L.G. 
Published: July 2012

The fungal metabolite, wortmannin, has recently been shown to inhibit fMet‐Leu‐Phe‐stimulated superoxide production and phospholipase D (PLD) activation in the human neutrophil.
We have found that a close structural analogue of wortmannin, demethoxyviridin, has a similar inhibitory profile but in addition blocks phosphatidylinositol 4,5‐bisphosphate‐specific phospholipase C and hence inositol 1,4,5‐trisphosphate (IP3) formation.
Inhibition of fMet‐Leu‐Phe‐stimulated PLD by demethoxyviridin was characteristically non‐competitive (IC50 = 31 ± 10 nm).
Inhibition of fMet‐Leu‐Phe‐stimulated IP3 formation required concentrations almost 10 times higher (IC50 = 250 ± 130 nm).
Surprisingly, demethoxyviridin only inhibited fMet‐Leu‐Phe‐induced intracellular calcium mobilization at concentrations 100 times greater than those needed to block IP3 formation.
Demethoxyviridin also inhibited PLD activation induced by sodium fluoride or phorbol myristate acetate (PMA) but the concentrations required were 100 times those needed to block fMet‐Leu‐Phe‐stimulated PLD.
These observations support the contention that PLD plays an important role in signal transduction in the human neutrophil and indicate that wortmannin and demethoxyviridin inhibit PLD activation at a common step in the signalling pathway.
Furthermore, these results suggest that demethoxyviridin may block the interaction between the chemotactic peptide receptor and a GTP‐binding protein that is intimately involved in PLD activation.
Endothelin modulates calcium channel current in neurones of rabbit pelvic parasympathetic ganglia
Authors: Nishimura T. , Akasu T. , Krier J. 
Published: July 2012

The effects of endothelin were studied, in vitro, on neurones contained in the rabbit vesical pelvic ganglion by use of intracellular and single‐electrode voltage clamp techniques under conditions where sodium and potassium channels were blocked.
In the current‐clamp experiments, endothelin (1 μm) caused a depolarization followed by a hyperpolarization of the membrane potential. In the voltage‐clamp experiments, endothelin (0.01–1 μm) caused an inward current followed by an outward current in a concentration‐dependent manner.
Membrane conductance was increased during the endothelin‐induced depolarization and inward current. Membrane conductance was decreased during the endothelin‐induced hyperpolarization and outward current.
The endothelin‐induced inward and outward currents were not altered by lowering external sodium concentration or raising external potassium concentration.
The endothelin‐induced inward current was depressed (mean 72%) in a Krebs solution containing nominally zero calcium and high magnesium. These results suggest that a predominent component of the endothelin‐induced inward current is mediated by calcium ions.
The calcium‐insensitive component of the inward current was abolished by a chloride channel blocker, 4‐acetamide‐4′‐isothiocyanostilbene‐2,2′‐disulphonic acid. The mean reversal potential for the calcium‐insensitive component of the inward current was −18 mV. This value is near the equilibrium potential for chloride. Thus, it is presumed that the calcium‐insensitive component of the inward current is carried by chloride ions.
Endothelin caused an initial depression followed by a long lasting facilitation of both rapidly and slowly decaying components of high‐threshold calcium channel currents (N‐ and L‐type).
In summary, the data show that for neurones in the vesical pelvic ganglia, endothelin causes membrane depolarization and activates an inward current. The ionic mechanisms involve receptor‐operated calcium and chloride currents. Also, endothelin causes an initial depression followed by a long‐lasting facilitation of the voltage‐dependent calcium current.
Specific neurokinin receptors mediate plasma extravasation in the rat knee joint
Authors: Lam F.Y. , Ferrell W.R. 
Published: July 2012

Plasma extravasation in the rat knee joint was induced by intra‐articular injection of neurokinins and specific neurokinin receptor agonists.
Pronounced plasma extravasation was produced by substance P (SP, 4–185 μm) and to a lesser extent by neurokinin‐B (NKB, 83–413 μm), whereas neurokinin‐A (NKA, 88–440 μm) and calcitonin gene‐related peptide (CGRP, 26–130 μm) had no significant effect.
The specific neurokinin1 receptor agonist [Sar9, Met(O2)11]‐substance P (NR1 agonist) in doses of 0.4–70 μm appeared to be more potent than SP in eliciting plasma extravasation. The neurokinin2 receptor agonist [Nle10]‐neurokinin A4–10 (NK2 agonist) was not effective at 70 μm but produced a small and significant effect at 330 μm, whereas the neurokinin3 receptor agonist [MePhe7]‐neurokinin B (NK3 agonist) was without effect at 40 μm or 400 μm.
Injections of SP or NKA into the synovial cavity of the rat knee were equally effective in producing marked plasma extravasation in remote sites such as the forelimb and hindlimb paws.
Co‐administration experiments showed that the effects of SP were synergistic with NKA or the NK1 receptor agonist, but not with CGRP or the NK2 receptor agonist.
The rank order of potency was NK1 agonist ≥ SP > NKB > NK2 agonist suggesting that NK1 receptors mediate plasma extravasation in the rat knee joint.
Kinetic studies on stereospecific recognition by the thromboxane A2/prostaglandin H2 receptor of the antagonist, S‐145
Authors: Kishino Junji , Hanasaki Kohji , Nagasaki Tohru , Arita Hitoshi 
Published: July 2012

The mechanism for the stereospecific recognition of the antagonist S‐145 by the thromboxane A2 (TXA2)/prostaglandin H2 (PGH2) receptor was examined by ligand‐binding techniques in rat vascular smooth muscle cells (VSMCs) and in human platelet membranes.
Scatchard analysis revealed the existence of a single class of binding sites with the same maximum number for both [3H]‐(+)‐S‐145 and [3H]‐(−)‐S‐145 in both cell types. The dissociation constants (Kd) for the binding of the (+)‐isomer in rat VSMCs and human platelet membranes were, respectively, 0.40 ± 0.03 and 0.20 ± 0.02 nm, each value being lower than that for the (−)‐isomer (3.57 ± 0.74 and 2.87 ± 0.08 nm, respectively).
The rank orders of potency (Ki) for a series of TXA2/PGH2 ligands at inhibiting [3H]‐(+)‐S‐145 binding were highly correlated with those determined for [3H]‐(−)‐S‐145 binding in both cell preparations.
Kinetic analysis of the binding of both radioligands revealed a much lower dissociation rate constant (k−1) and a slightly greater association rate constant (k1) for the (+)‐isomer compared to those for the (−)‐isomer.
These results suggest that it is at the stage of dissociation from the TXA2/PGH2 receptor that the stereochemistry of the optical isomers of S‐145 confers their difference in affinity for these receptors in rat VSMCs and human platelet membranes.
Nitroglycerin relaxes coronary artery of the pig with no change in glutathione content or glutathione S‐transferase activity
Authors: Sakanashi Matao , Matsuzaki Toshihiro , Aniya Yoko 
Published: July 2012

The role of glutathione content and glutathione S‐transferase activity in vascular relaxant responses to nitroglycerin was evaluated in potassium (30 mm)‐contracted coronary artery strips of the pig by measuring changes in tension, glutathione content and glutathione S‐transferase activity.
Prior exposure of coronary artery strips to nitroglycerin (10−5 m or 10−4 m for 20 min) resulted in tachyphylaxis to subsequent relaxation to nitroglycerin (10−8–10−5 m).
The glutathione content and glutathione S‐transferase activity of the arterial strips rendered tachyphylactic by prior exposure to nitroglycerin (10−5 m for 20 min or 10−3 m for 120 min) were not significantly different from those of control strips.
Treatment with diethyl maleate (10−4 m or 10−3 m for 60 min) markedly depleted arterial glutathione content in a concentration‐dependent manner with no change in glutathione S‐transferase activity.
The relaxant response of coronary artery strips to nitroglycerin (10−8–10−5 m) was completely unaffected following treatment with diethyl maleate (10−4 m or 10−3 m for 60 min).
The results suggest that vascular glutathione content does not play an important role in vascular relaxation or tolerance development to nitroglycerin, at least in pig isolated coronary artery.
Inhibitory effects of guanosine 3′: 5′‐cyclic monophosphate on the synthesis of dopamine in the rat kidney
Authors: Soares‐da‐Silva P. , Fernandes M. Helena 
Published: July 2012

In the present study the effects of M&B 22,948, a guanosine 3′: 5′‐cyclic monophosphate (cyclic GMP) selective phosphodiesterase inhibitor and of 8‐bromo cyclic GMP were examined on the synthesis of dopamine from l‐3,4‐dihydroxyphenylalanine (l‐DOPA) in rat cortical slices and in whole kidney homogenates. The deamination of newly‐formed dopamine into 3,4‐dihydroxyphenylacetic acid (DOPAC) was also studied. The assay of l‐DOPA, dopamine, noradrenaline and DOPAC was performed by high performance liquid chromatography (h.p.l.c.) with electrochemical detection.
Incubation of renal slices and homogenates of whole kidney with exogenous l‐DOPA (0.1–10.0 μm) resulted in a concentration‐dependent formation of both dopamine and DOPAC.
The addition of M&B 22,948 (10 μm) to the incubation medium resulted in a marked reduction in the accumulation of both newly‐formed dopamine and DOPAC in kidney slices; the inhibitory effect of M&B 22,948 on DOPAC formation was greater than that on dopamine. 8‐Bromo cyclic GMP (250 μm) produced only a slight decrease in the tissue levels of newly‐formed dopamine (5–13% reduction), but was found to decrease significantly (51–68% reduction) the formation of DOPAC in kidney slices. The addition of 8‐bromo cyclic GMP plus M&B 22,498 to the incubation medium resulted in similar effects to those described for M&B 22,948 alone.
In kidney homogenates, in contrast to results observed in kidney slices, M&B 22,948 (10 μm) and 8‐bromo cyclic GMP (250 μm) were found to affect neither the formation of dopamine nor its deamination to DOPAC.
In conclusion, the results presented here suggest that cyclic GMP may be involved in the regulation of dopamine synthesis, probably through the control of the entry of l‐DOPA into the tubular epithelial cells.
In vitro vascular effects of cicletanine in pregnancy‐induced hypertension
Authors: Ebeigbe A.B. , Cabanie M. 
Published: July 2012

The vascular effects of cicletanine have been studied in vitro on ring preparations of inferior epigastric arteries from normotensive human females and human females with pregnancy‐induced hypertension (preeclampsia).
Cicletanine (10−7–10−3 m) elicited concentration‐dependent relaxation of vessels precontracted with 10−7 m noradrenaline (NA) or 60 mm K+ but was more potent in the former. Relaxation was significantly greater in rings from preeclamptic patients and was uninfluenced by endothelium removal.
The intracellular Ca‐dependent contractile responses to 10−5 m NA in Ca‐free medium as well as the subsequent extracellular Ca‐dependent contractions (on restoration of external Ca) were significantly attenuated dose‐dependently by cicletanine (10−5 m, 3 × 10−4 m) in arterial rings from both normotensive and preeclamptic patients. Cicletanine also relaxed rings precontracted by 25 mm K+ but was ineffective against 80 mm K+‐induced contractions.
The inhibition of intracellular Ca‐dependent contractions was significantly greater in rings from preeclamptic than from normotensive patients whereas extracellular Ca‐dependent contractions were comparably inhibited in both groups. Nifedipine, on the other hand, had little effect on the intracellular Ca‐dependent contractions but significantly depressed extracellular Ca‐dependent contractions.
Cicletanine‐induced relaxation was uninfluenced by pretreatment with propranolol, ouabain, tetraethylammonium, procaine, indomethacin, cimetidine or tetrodotoxin but was antagonized by glibenclamide.
The results show that cicletanine inhibits contractile responses of human isolated inferior epigastric arteries by a mechanism unrelated to endothelial factors but associated with inhibition of calcium metabolism. An action of cicletanine on glibenclamide‐sensitive K+ channels is also suggested. Cicletanine‐induced inhibition was significantly greater in arteries from preclamptic patients.
Pharmacology of the putative M4 muscarinic receptor mediating Ca‐current inhibition in neuroblastoma × glioma hybrid (NG 108–15) cells
Authors: Caulfield M.P. , Brown D.A. 
Published: July 2012

We have assessed the potency of a range of agonists and antagonists on the muscarinic receptor responsible for inhibiting the Ca‐current (ICa) in NG 108–15 hybrid cells.
Acetylcholine (ACh), oxotremorine‐M and carbachol were potent ‘full’ agonists (EC50 values were 0.11 μm, 0.14 μm and 2 μm, respectively). Maximum inhibition of peak high‐threshold ICa by these agonists was 39.5%. (±)‐Muscarine, methylfurmethide and arecaidine propargyl ester (APE) were ‘partial’ agonists, with EC50 values of 0.54 μm, 0.84 μm and 0.1 μm, respectively.
Atropine, pirenzepine and himbacine were potent antagonists of muscarinic inhibition of ICa, with apparent pKB values of 9.8, 7.74 and 8.83, respectively. Methoctramine was relatively weak (pKB = 7.63). Atropine and pirenzepine depressed maximum responses to agonists, probably because these antagonists have relatively slow dissociation rates.
The characteristic pharmacological profile found for the M4 receptors in these functional experiments (himbacine high affinity, pirenzepine moderate to high affinity, methoctramine low affinity) corresponds well with data from earlier binding experiments (Lazareno et al., 1990). Since mRNA hybridising to probes for the m4 receptor genotype can be detected in these cells, it is suggested that these pharmacological characteristics identify the equivalent expressed receptor subtype M4.