bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of the effects of lithium on phosphatidylinositol (PI) cycle activity in human muscarinic ml receptor‐transfected CHO cells
Authors: Atack John R. , Prior Angela M. , Griffith Douglas , Ragan C. Ian 
Published: July 2012

The effects of lithium on [3H]‐inositol and [3H]‐cytidine incorporation into [3H]‐inositol monophosphates ([3H]‐InsP1) and [3H]‐cytidine monophosphorylphosphatidate ([3H]‐CMP‐PA), respectively, and inositol 1,4,5‐trisphosphate (InsP3) and inositol 1,3,4,5‐tetrakisphosphate (InsP4) mass were studied in carbachol‐stimulated human ml muscarinic receptor‐transfected Chinese hamster ovary cells (ml CHO cells).
Lithium alone (10 mm) had no appreciable effects on any of the four parameters measured; it was only in carbachol‐stimulated cells that the effects of lithium became apparent.
In the presence of carbachol (1 mm), lithium (10 mm) caused a relatively rapid (within 5 min) accumulation of [3H]‐InsP1 and [3H]‐CMP‐PA which continued up to about 20–30 min, after which accumulation slowed down. On the other hand, the elevation in InsP3 and InsP4 levels produced by carbachol was not altered by lithium in the short‐term and only at later times (> 20–30 min) was the response attenuated, with InsP3 and InsP4 levels approaching basal.
The effects of lithium on carbachol‐stimulated [3H]‐InsP1 and [3H]‐CMP‐PA accumulation and the attenuation of the carbachol‐induced elevation of InsP3 and InsP4 were all dose‐dependent, with EC50s in the region of 1 mm.
The lithium‐induced effects on [3H]‐CMP‐PA and InsP3 and InsP4 in carbachol‐stimulated cells could be reversed, in a dose‐dependent manner, by preincubation with exogenous myo‐inositol (EC50 = 2–3 mm) but not by the inactive analogue scyllo‐inositol, indicating that these effects occur as a consequence of depletion of inositol.
The temporal effects of lithium are consistent with lithium inhibiting inositol monophosphatase, causing accumulation of InsP1, resulting in lower free inositol levels. This leads to accumulation of CMP‐PA and reduced PI synthesis which, once agonist‐linked membrane inositol phospholipids are depleted, produces attenuated InsP3 and InsP4 responses.
These results in ml CHO cells support the hypothesis that lithium affects the PI cycle cell signalling pathway by depletion of inositol due to inhibition of inositol monophosphatase.
Evidence that depletion of internal calcium stores sensitive to noradrenaline elicits a contractile response dependent on extracellular calcium in rat aorta
Authors: Noguera M. Antonia , D'Ocon M. Pilar 
Published: July 2012

Noradrenaline 1 μm induced a contractile response in rat isolated aorta in the presence or in the absence of extracellular Ca2+ with depletion of intracellular Ca2+ stores. Thereafter, during incubation in the presence of Ca2+, an increase in the resting tone was observed. Such a contractile response did not occur after exposure to caffeine or 5‐hydroxytryptamine.
This increase in tension was inhibited in a concentration‐dependent manner by α‐adrenoceptor antagonists (prazosin, phentolamine and yohimbine), the non‐specific relaxing compound, papaverine and by the Ca2+‐entry blocker, nifedipine. Therefore, this contractile process is related to depletion of Ca2+ stores sensitive to noradrenaline and is linked to Ca2+ entry through voltage‐operated Ca2+ channels and α‐adrenoceptors.
Phentolamine and yohimbine did not block the Ca2+ refill pathway; prazosin and nifedipine inhibited the reuptake of Ca2+ by an internal store sensitive only to noradrenaline; papaverine inhibited the refilling of caffeine‐ and noradrenaline‐sensitive Ca2+‐stores.
Evidence that M1 muscarinic receptors enhance noradrenaline release in mouse atria by activating protein kinase C
Authors: Costa Mary , Barrington Michelle , Majewski Henryk 
Published: July 2012

The M1 selective muscarinic agonist, McNeil A 343, enhanced the electrically evoked release of noradrenaline from postganglionic sympathetic nerves in mouse atria. This has been found previously to be due to activation of muscarinic receptors of the M1 subtype, probably located on sympathetic nerve terminals. The present study investigated the signal transduction mechanisms involved in the release‐enhancing effects of McNeil A 343. The release of noradrenaline from mouse atria was assessed by measuring the electrically‐induced (3 Hz, 60 s) outflow of radioactivity from atria which had been pre‐incubated with [3H]‐noradrenaline.
8‐Bromo cyclic AMP in the presence of IBMX was used to enhance maximally S‐I noradrenaline release through cyclic AMP‐dependent mechanisms. However, the facilitatory effect of McNeil A 343 (10 μm) was not different from the effect in the absence of these drugs, suggesting that McNeil A 343 enhances noradrenaline release independently of the cyclic AMP system. Furthermore, the release‐enhancing effect of McNeil A 343 (10 μm) on noradrenaline release was also not altered by the 5‐lipoxygenase inhibitor, BW A4C.
The facilitatory effect of McNeil A 343 was not altered in the presence of drugs (trifluoperazine, W7, and calmidazolium) which inhibit calmodulin‐dependent processes, suggesting that the mechanisms of action of McNeil A 343 does not depend on calmodulin.
It was considered likely that the facilitatory effect of McNeil A 343 on noradrenaline release may be due to activation of protein kinase C, since activators of protein kinase C enhance noradrenaline release. The facilitatory effect of McNeil A 343 was abolished by the non‐selective protein kinase C inhibitor, K‐252a. To investigate further the involvement of protein kinase C, mouse atria were chronically incubated (9–10 h) with the protein kinase C activator, 4β‐phorbol dibutyrate (1.0 μm) in order to down‐regulate protein kinase C activity. In protein kinase C‐down‐regulated atria, the facilitatory effect of McNeil A 343 (30 μm) was abolished. Incubation with 4α‐phorbol dibutyrate which does not affect protein kinase C did not reduce the facilitatory effect of McNeil A 343. This provides evidence that activation of protein kinase C is involved in the signal transduction process of McNeil A 343.
Pharmacology of high‐threshold calcium currents in GH4C1 pituitary cells and their regulation by activation of human D2 and D4 dopamine receptors
Authors: Seabrook G.R. , Knowles M. , Brown N. , Myers J. , Sinclair H. , Patel S. , Freedman S.B. , McAllister G. 
Published: July 2012

The objective of this study was to characterize the pharmacology of calcium currents in GH4C1 pituitary cells and determine whether activation of heterologously expressed human dopamine receptors can regulate their function. Human D2(short), D3 and D4,2 receptor cDNA's were separately transfected into GH4C1 cells and whole cell calcium currents were recorded by use of nystatin‐perforated patch clamp techniques.
High‐threshold calcium currents were antagonized in a biphasic manner by the dihydropyridine, nisoldipine. The half‐maximally effective concentration for each site was 0.2 nm (pIC50 = 9.78 ± 0.21, n = 4) and 339 nm (pIC50 = 6.47 ± 0.12, n = 4). The component of current inhibited by 10 nm nisoldipine was also blocked by ω‐conotoxin GVIA (30 ± 9% at 30 nm, n = 6) or by ω‐agatoxin IVA (34 ± 7% at 100 nm, n = 4).
Activation of either D2 or D4 receptors by dopamine (10 μm) or quinpirole (0.1 to 10 μm) reduced the peak calcium current by ca. 20% in the majority of cells studied. No inhibition was observed in control or D3 transfected GH4C1 cell lines.
The mobilisation of intracellular calcium by thyrotropin releasing hormone in hD4‐GH4C1 cells was also studied using Fura‐2 AM microspectrofluorimetry. Thyrotropin releasing hormone caused a concentration‐dependent increase in calcium mobilisation with an EC50 of 7 nm. D4 receptor activation had no effect upon either basal or hormone‐induced [Ca2+]i transients.
These results demonstrate that GH4C1 pituitary cells have at least two types of dihydropyridine‐sensitive high‐threshold calcium currents and that like D2 receptors, human D4 receptors can also regulate calcium channel function.
Moguisteine: a novel peripheral non‐narcotic antitussive drug
Authors: Gallico L. , Borghi A. , Rosa C. Dalla , Ceserani R. , Tognella S. 
Published: July 2012

The antitussive effects of moguisteine have been compared with codeine in several experimental models of cough in guinea‐pigs and dogs.
Moguisteine and codeine dose‐dependently (respective ED50 values are given in parentheses) inhibited cough induced in guinea‐pigs by 7.5% citric acid aerosol (25.2 and 29.2 mg kg−1, p.o.), by 30 μm capsaicin aerosol (19.3 and 15.2 mg kg−1, p.o.), by mechanical stimulation (22.9 and 26.4 mg kg−1, p.o.) and by tracheal electrical stimulation (12.5 and 13.9 mg kg−1, p.o.).
Moguisteine was effective against cough induced by tracheal electrical stimulation in dogs (ED50 17.2 mg kg−1, p.o.); codeine was not tested because of its emetic effect.
After repeated dosing (12–15 days), moguisteine did not induce tolerance in either guinea‐pigs or dogs.
Moguisteine did not interact with opiate receptors, since it did not show affinity for [3H]‐naloxone binding sites and furthermore naloxone (5mg kg−1, s.c.) did not antagonize its antitussive effects.
Moguisteine had no antitussive effect after i.c.v. administration (20 μg), whilst codeine (2–10 μg) and dextromethorphan (2.5–20 μg) were highly effective.
Our findings demonstrate that moguisteine is a novel peripherally acting non‐narcotic antitussive agent, the mode of action of which remains to be elucidated fully.
Covariation of α2‐adrenoceptor density and function following irreversible antagonism with EEDQ
Authors: Durcan Michael J. , Morgan Philip F. , Van Etten Michelle L. , Linnoila Markku 
Published: July 2012

Administration of the irreversible antagonist, N‐ethoxycarbonyl‐2‐ethoxy‐1,2‐dihydroquinoline, (EEDQ, 2 mg kg−1, i.p.) to mice reduced binding of [3H]‐RX 821002 (2‐methoxy‐idazoxan) to α2‐adrenoceptors in whole mouse brain by 75% 24 h later. The receptor binding returned over time only being reduced by 25% by 16 days post administration; the time taken for binding to return to 50% of control levels was estimated to be 5.25 days.
EEDQ administration also resulted in the loss of the sedative effect of the α2‐adrenoceptor agonist, medetomidine, measured by the holeboard test of directed exploration and locomotor activity. Agonistinduced sedation returned to control values by 8 days post EEDQ administration.
EEDQ administration also resulted in the loss of the hypothermic response to medetomidine (0.1 mg kg−1, i.p.). Medetomidine‐induced hypothermia returned to control values by 12 days post EEDQ administration.
Pretreatment with the selective α2‐adrenoceptor antagonist, RX 821002 (0.1–3.0 mg kg−1, i.p.) 45 min before EEDQ prevented the loss of α2‐adrenoceptors as well as the blockade of medetomide‐induced sedation and hypothermia by EEDQ.
The results of these experiments indicate that there is significant receptor reserve for α2‐adrenoceptor‐mediated behavioural and physiological responses.
Mediation of most atypical effects by species homologues of the β3‐adrenoceptor
Authors: Blin Nathalie , Nahmias Clara , Drumare Marie F. , Strosberg A. Donny 
Published: July 2012

A wide panel of compounds acting on β‐adrenoceptors active either in mammalian heart or in rodent digestive tract and adipose tissues, were investigated for their effects on Chinese hamster ovary cells transfected with the human or murine β3‐adrenoceptor gene.
The β3‐agonists, bucindolol, CGP 12177A and pindolol exhibited the highest binding affinities; BRL 37344, LY 79771, ICI 201651 and SR 58611A presented high potencies in stimulating adenylyl cyclase; bupranolol appeared as the most efficient β3‐antagonist.
This pharmacological analysis further established that the β3‐adrenoceptor is the prototype of the adipose tissue atypical β‐adrenoceptor, since these receptors share a number of pharmacological properties which differ strikingly from those of β1‐ and β2‐adrenoceptors: low affinities for conventional β‐adrenoceptor agonists and antagonists, high potencies for novel compounds active in adipose tissues, partial agonistic activites for several β1/β2‐antagonists.
Although the pharmacological profiles of the human and murine β3‐receptor were very similar, some quantitative or even qualitative differences were observed for particular compounds such as propranolol, which exhibited weak and partial agonistic effects at the human β3‐receptors and antagonistic effects at the murine β3‐receptors. These differences may result from key amino‐acid substitutions between the human and the murine β3‐receptor sequences, which may alter the binding site or signal processing.
Compounds active on atypical β‐sites of other tissues such as heart and digestive tract were also potent on the β3‐adrenoceptor expressed in Chinese hamster ovary cells, suggesting that this receptor mediates most of the atypical properties described in various tissues, and that differences in ligand effects may result from tissue‐related specificities.
Blockade by oral or parenteral RPR 100893 (a non‐peptide NK1 receptor antagonist) of neurogenic plasma protein extravasation within guinea‐pig dura mater and conjunctiva
Authors: Lee Won S. , Moussaoui Saliha M. , Moskowitz Michael A. 
Published: July 2012

The ability of an NK1 receptor antagonist, RPR 100893, and its enantiomer, RPR 103253 to block neurogenic plasma protein extravasation in guinea‐pig dura mater and conjunctiva was assessed following 125I‐labelled bovine serum albumin ([125I]‐BSA, 50 μCi kg−1, i.v.) and unilateral electrical stimulation of the trigeminal ganglion (0.6 mA, 5 ms, 5 Hz, 5 min) or capsaicin administration (150 μg kg−1, i.v.).
When administered p.o. 60 min prior to electrical stimulation, RPR 100893 (≥ 0.1 μg kg−1) decreased plasma protein extravasation in dura mater in a dose‐dependent manner, whereas the enantiomer (10 or 100 μg kg−1, p.o.) was inactive.
When given i.v. 30 min prior to electrical stimulation, RPR 100893 (≥ 0.5 ng kg−1) significantly inhibited plasma protein extravasation in the dura mater evoked by electrical stimulation in a dose‐dependent manner.
RPR 100893 (100 μg kg−1, p.o.) also reduced the leakage when given 45 min before the guinea‐pigs were killed and 10, 40 and 80 min after electrical trigeminal stimulation.
RPR 100893 given p.o. dose‐dependently inhibited capsaicin‐induced plasma protein extravasation with ID50s of 7.4 μg kg−1 and 82 μg kg−1 for dura mater and conjunctiva, respectively.
These results are consistent with the contention that NK1 receptors mediate neurogenic plasma protein leakage following trigeminal stimulation, and suggest that NK1 receptor antagonists of the perhydroisoindolone series may be useful for treating migraine and cluster headaches.
Des‐Arg9‐bradykinin‐induced increases in intracellular calcium ion concentration in single bovine tracheal smooth muscle cells
Authors: Marsh Katrina A. , Hill Stephen J. 
Published: July 2012

Dynamic video imaging was used to measure the des‐Arg9‐bradykinin‐induced changes in the intracellular free calcium ion concentration ([Ca2+]i) of single bovine tracheal smooth muscle (BTSM) cells.
In the presence of extracellular calcium ions, des‐Arg9‐bradykinin (1 nm–10 μm) produced a concentration‐dependent increase in the [Ca2+]i over basal levels yielding an EC50 value of 316 nm. The percentage of cells responding to each concentration of des‐Arg9‐bradykinin also increased in a concentration‐dependent manner (from 9% to 100%).
The bradykinin B2 receptor antagonist, d‐Arg[Hyp3,Thi5,8,d‐Phe7]‐bradykinin (10 μm), was without effect on the calcium response of the cells when added 2 min prior to des‐Arg9‐bradykinin (100 nm). However, the B1 receptor antagonist, des‐Arg9Leu8‐bradykinin (10 μm), completely abolished the des‐Arg9‐bradykinin‐induced response.
Under calcium‐free conditions, des‐Arg9‐bradykinin induced an increase in [Ca2+]i at concentrations of 1 μm and 10 μm. The response to 10 μm des‐Arg9‐bradykinin was reduced by preincubation of either d‐Arg[Hyp3,Thi5,8,d‐Phe7]‐bradykinin (10 μm) or des‐Arg9Leu8‐bradykinin (10 μm).
We conclude that bradykinin B1 receptors are expressed by cultured BTSM cells and mediate the des‐Arg9‐bradykinin‐induced influx of calcium ions at low agonist concentrations (< 1 μm). At higher concentrations, des‐Arg9‐bradykinin (1 μm and 10 μm) can stimulate both B1 and B2 receptors to effect intracellular calcium release under calcium‐free conditions.
The P2Z‐purinoceptor of human lymphocytes: actions of nucleotide agonists and irreversible inhibition by oxidized ATP
Authors: Wiley James S. , Chen Joan R. , Snook Marie B. , Jamieson Gary P. 
Published: July 2012

Extracellular adenosine triphosphate (ATP) is known to open a receptor‐operated ion channel (P2Z class) in human lymphocytes which conducts a range of cationic permeants. The activity of a range of different agonists and inhibitors towards the P2Z‐purinoceptor was investigated by measuring the agonist‐induced influx of Ba2+ into fura‐2 loaded lymphocytes.
The most potent agonist was 2′ & 3′‐0‐(4‐benzoylbenzoyl)‐ATP (benzoylbenzoic ATP) which gave 2 fold greater maximum Ba2+ influx and had a 10 fold lower EC50 than for ATP. The rank order of agonist potency in K+‐media was benzoylbenzoic ATP>>ATP = 2‐methylthio ATP = 2‐chloro ATP>ATP‐γ‐S. ADP, UTP and α,β‐methylene ATP were unable to stimulate Ba2+ influx.
Extracellular Na+ inhibited the increment of Ba2+ influx induced by all concentrations of ATP, 2‐methylthio ATP, 2‐chloroATP and ATP‐γ‐S. This inhibitory effect of extracellular Na+ is also reflected in the different EC50s for benzoylbenzoic ATP (8 μm in K+‐media, 18 μm in Na+‐media) but the maximal response to this agonist was the same in the presence or absence of Na+.
Treatment of lymphocytes with 2,3 dialdehyde ATP (oxidized ATP) at 300 μm for 60 min gave total and irreversible inhibition of ATP‐induced Ba2+ influx. 5′‐p‐Fluorosulphonyl benzoyladenosine (FSBA) also was an irreversible inhibitor but the maximal inhibition achieved was 90%.
It is concluded that the P2Z‐purinoceptor of human lymphocytes has a rank order of agonist potency which clearly distinguishes it from other P2‐receptors and that oxidized ATP is a convenient irreversible inhibitor for the P2Z‐purinoceptor.
Production of PGE2 by bovine cultured airway smooth muscle cells and its inhibition by cyclo‐oxygenase inhibitors
Authors: Delamere F. , Holland E. , Patel S. , Bennett J. , Pavord I. , Knox A. 
Published: July 2012

Prostaglandin E2 (PGE2) is thought to be an important inhibitory modulator of inflammatory processes in the airway. It inhibits inflammatory cell function and cholinergic neurotransmission in vitro and roles have been postulated in vivo in refractoriness and in the mechanism of action of the diuretic agent, frusemide.
The production of PGE2 by bovine cultured airway smooth muscle cells has been studied under a range of conditions. The effects of cyclo‐oxygenase inhibitors (flurbiprofen, indomethacin, acetyl salicylic acid) on serum‐induced production of PGE2 were assessed over a range of concentrations (10−7–10−4 m).
Serum‐stimulated production of PGE2 in control wells ranged from 350 to 800 ng PGE2 ml−1 in cells from different animals. All three cyclo‐oxygenase inhibitors inhibited PGE2 production with an order of potency, flurbiprofen > indomethacin > acetyl salicylic acid. Log IC50 values were − 6.24 for flurbiprofen, − 5.23 for indomethacin and − 3.50 for acetyl salicylic acid.
PGE2 production was stimulated by arachidonic acid (10−5 m) or addition of the proinflammatory mediator, bradykinin (10−8–10−5 m).
Incubation of cells for 24 h with 5 bromo deoxyuridine (BRDU) (10−4 m) to prevent DNA synthesis did not alter PGE2 production in response to serum, suggesting that it was not a function of proliferation per se.
Our study suggests that airway smooth muscle may be an important source of PGE2. Production of PGE2 may be a novel feedback mechanism whereby airway smooth muscle cells can negatively modulate airways inflammation. The differing potencies of the cyclo‐oxygenase inhibitors may explain the contrasting effect of these drugs in recent studies in asthma.
Characterization of the capsaicin‐sensitive component of cyclophosphamide‐induced inflammation in the rat urinary bladder
Authors: Ahluwalia A. , Maggi C.A. , Santicioli P. , Lecci A. , Giuliani S. 
Published: July 2012

Cyclophosphamide (CYP) (150 mg kg−1, i.p. 0.5–48 h before) caused a time‐dependent plasma protein extravasation in the rat urinary bladder with the maximal extravasation occuring at between 2 and 4 h after administration of the drug.
Prior capsaicin desensitization of capsaicin‐sensitive primary afferent neurones (CSPANs) (50 mg kg−l, s.c., 4 days before) resulted in approximately 50% inhibition of the magnitude of the extravasation response at the 2 h time‐point.
Intraperitoneal (i.p.) pretreatment with the tachykinin NK1 receptor antagonist, RP 67,580 (0.44 mg kg−1) or the bradykinin B2 receptor antagonist, Hoe 140 (0.13 mg kg−1) had significant inhibitory effects, giving responses of 56 ± 6% and 39 ± 4% of the control extravasation response to CYP treatment after 2 h. Pretreatment with the tachykinin NK2 receptor antagonist, SR 48,968 (0.3 mg kg−1, i.p.), the histamine H1 receptor blocker, chlorpheniramine (10 mg kg−1, i.p.), the 5‐HT receptor blocker, methysergide (6 mg kg−l, i.p.) or the cyclo‐oxygenase inhibitor indomethacin (5 mg kg−1, i.p.) had no significant effect upon the development of the extravasation response at this same time‐point.
In rat isolated urinary bladder strips, the active metabolite of CYP, acrolein (1–300 μm) produced a concentration‐dependent contraction that was significantly reduced by in vitro capsaicin desensitization (10 μm for 15 min) indicating direct stimulation of CSPANs. CYP was without appreciable effect.
The effect of acrolein in vitro was significantly reduced by pretreatment of the bladder with a combination of tachykinin NK1 and NK2 receptor antagonists, RP 67,580 (3 μm) and SR 48,968 (1 μm). The dose‐response curve to acrolein was also significantly inhibited by treatment with indomethacin (10 μm) and slightly affected by Hoe 140 (1 μm).
These findings demonstrate the contribution of CSPANs to the development of CYP‐induced cystitis. Plasma protein extravasation involves activation of tachykinin NK1 and bradykinin B2 receptors. Activation of CSPANs in the urinary bladder is likely to be due to the conversion of CYP into its active metabolite, acrolein, and not to a direct effect of CYP upon these nerve‐endings.