bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pharmacological characterization of β2‐adrenoceptor in PGT‐β mouse pineal gland tumour cells
Authors: Suh Byung‐Chang , Chae Hee‐Don , Chung Joo‐Ho , Kim Kyong‐Tai 
Published: January 2005

The adrenoceptor in a mouse pineal gland tumour cell line (PGT‐β) was identified and characterized using pharmacological and physiological approaches.
Adrenaline and noradrenaline, adrenoceptor agonists, stimulated cyclic AMP generation in a concentration‐dependent manner, but had no effect on inositol 1,4,5‐trisphosphate production. Adrenaline was a more potent activator of cyclic AMP generation than noradrenaline, with half maximal‐effective concentrations (EC50) seen at 175±22 nM and 18±2 μM for adrenaline and noradrenaline, respectively.
The addition of forskolin synergistically stimulated the adrenaline‐mediated cyclic AMP generation in a concentration‐dependent manner.
The pA2 value for the specific β2‐adrenoceptor antagonist ICI‐118,551 (8.7±0.4) as an antagonist of the adrenaline‐stimulated cyclic AMP generation were ∼3 units higher than the value for the βI‐adrenoceptor antagonist atenolol (5.6±0.3).
Treatment of the cells with adrenaline and forskolin evoked a ∼3 fold increase in the activity of serotonin N‐acetyltransferase with the peak occurring 6 h after stimulation.
These results suggest the presence of β2‐adrenoceptors in mouse pineal cells and a functional relationship between the adenylyl cyclase system and the regulation of N‐acetyltransferase expression.

British Journal of Pharmacology (1999) 126, 399–406; doi:10.1038/sj.bjp.0702248
Brain‐to‐blood partition and in vivo inhibition of 5‐hydroxytryptamine reuptake and quipazine‐mediated behaviour of nefazodone and its main active metabolites in rodents
Authors: Nacca Angelo , Guiso Giovanna , Fracasso Claudia , Cervo Luigi , Caccia Silvio 
Published: January 2005

The brain/plasma partition of nefazodone, hydroxynefazodone (OHNFZ) and m‐chlorophenyl‐piperazine (mCPP) and their antagonism of p‐chloroamphetamine (PCA)‐induced 5‐hydroxytryptamine (5‐HT) depletion and quipazine‐induced head twitches were compared in rodents.
Nefazodone (30 mg kg−1, i.p.) rapidly entered the brain but concentrations were exceeded by mCPP, the metabolic ratio being 47 and 10 in the mouse and rat respectively. OHNFZ was detectable in plasma but never in brain.
Brain concentrations of OHNFZ in the mouse (30 mg kg−1, i.p.) were less than 10% of those in plasma, confirming a poor blood‐brain barrier penetration. Concentrations of its metabolite mCPP were similar to those after 5 mg kg−1(i.p.) mCPP.
In the mouse, nefazodone (30 mg kg−1) antagonized the 5‐HT depleting effect of PCA 2 h after dosing, when it had disappeared from brain but when mCPP concentrations were similar to those after 5 mg kg−1 (i.p.) mCPP. However, mCPP antagonized PCA less than nefazodone.
In the rat, nefazodone pretreatment (30 mg kg−1, 15 min) prevented (97% of inhibition) quipazine‐induced head twitches. The effect was weaker (65% of inhibition) but significant when only mCPP was detected in brain. Analysis of brain concentrations of the two compounds after their ED50 against quipazine indicated that both contributed to the effect, although nefazodone was more active than mCPP in terms of concentrations required to obtain a comparable reduction of twitches.
These findings show that mCPP concentrates in the brain following injection of nefazodone and may play a role in preventing quipazine‐induced behaviour and PCA‐induced 5‐HT depletion. In contrast OHNFZ poorly enters the brain and its in vivo activity is mostly due to its biotransformation to mCPP.

British Journal of Pharmacology (1998) 125, 1617–1623; doi:10.1038/sj.bjp.0702251
Mechanisms involved in the metabotropic glutamate receptor‐enhancement of NMDA‐mediated motoneurone responses in frog spinal cord
Authors: Holohean Alice M , Hackman John C , Davidoff Robert A 
Published: January 2005

The metabotropic glutamate receptor (mGluR) agonist trans‐(±)‐1‐amino‐1,3‐cyclopentanedicarboxylic acid (trans‐ACPD) (10–100 μM) depolarized isolated frog spinal cord motoneurones, a process sensitive to kynurenate (1.0 mM) and tetrodotoxin (TTX) (0.783 μM).
In the presence of NMDA open channel blockers [Mg2+; (+)‐5‐methyl‐10,11‐dihydro‐5H‐dibenzo[a,d]cyclohepten‐5,10‐imine hydrogen maleate (MK801); 3,5‐dimethyl‐1‐adamantanamine hydrochloride (memantine)] and TTX, trans‐ACPD significantly potentiated NMDA‐induced motoneurone depolarizations, but not α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐proprionate (AMPA)‐ or kainate‐induced depolarizations.
NMDA potentiation was blocked by (RS)‐α‐methyl‐4‐carboxyphenylglycine (MCPG) (240 μM), but not by α‐methyl‐(2S,3S,4S)‐α‐(carboxycyclopropyl)‐glycine (MCCG) (290 μM) or by α‐methyl‐(S)‐2‐amino‐4‐phosphonobutyrate (L‐MAP4) (250 μM), and was mimicked by 3,5‐dihydroxyphenylglycine (DHPG) (30 μM), but not by L(+)‐2‐amino‐4‐phosphonobutyrate (L‐AP4) (100 μM). Therefore, trans‐ACPD's facilitatory effects appear to involve group I mGluRs.
Potentiation was prevented by the G‐protein decoupling agent pertussis toxin (3–6 ng ml−1, 36 h preincubation). The protein kinase C inhibitors staurosporine (2.0 μM) and N‐(2‐aminoethyl)‐5‐isoquinolinesulphonamide HCl (H9) (77 μM) did not significantly reduce enhanced NMDA responses. Protein kinase C activation with phorbol‐12‐myristate 13‐acetate (5.0 μM) had no effect.
Intracellular Ca2+ depletion with thapsigargin (0.1 μM) (which inhibits Ca2+/ATPase), 1,2‐bis(O‐aminophenoxy)ethane‐N,N,N′,N′‐tetracetic acid acetyl methyl ester (BAPTA‐AM) (50 μM) (which buffers elevations of [Ca2+]i), and bathing spinal cords in nominally Ca2+‐free medium all reduced trans‐ACPD's effects.
The calmodulin antagonists N‐(6‐aminohexyl)‐5‐chloro‐1‐naphthalenesulphonamide (W7) (100 μM) and chlorpromazine (100 μM) diminished the potentiation.
In summary, group I mGluRs selectively facilitate NMDA‐depolarization of frog motoneurones via a G‐protein, a rise in [Ca2+]i from the presumed generation of phosphoinositides, binding of Ca2+ to calmodulin, and lessening of the Mg2+‐produced channel block of the NMDA receptor.

British Journal of Pharmacology (1999) 126, 333–341; doi:10.1038/sj.bjp.0702263
Dual actions of the metabolic inhibitor, sodium azide on KATP channel currents in the rat CRI‐G1 insulinoma cell line
Authors: Harvey J , Hardy S C , Ashford M L J 
Published: January 2005

The effects of various inhibitors of the mitochondrial electron transport chain on the activity of ATP‐sensitive K+ channels were examined in the Cambridge rat insulinoma G1 (CRI‐G1) cell line using a combination of whole cell and single channel recording techniques.
Whole cell current clamp recordings, with 5 mM ATP in the pipette, demonstrate that the mitochondrial uncoupler sodium azide (3 mM) rapidly hyperpolarizes CRI‐G1 cells with a concomitant increase in K+ conductance. This is due to activation of KATP channels as the sulphonylurea tolbutamide (100 μM) completely reversed the actions of azide. Other inhibitors of the mitochondrial electron transport chain, rotenone (10 μM) or oligomycin (2 μM) did not hyperpolarize CRI‐G1 cells or increase K+ conductance.
In cell‐attached recordings, bath application of 3 mM sodium azide (in the absence of glucose) resulted in a rapid increase in KATP channel activity, an action readily reversible by tolbutamide (100 μM). Application of sodium azide (3 mM), in the presence of Mg‐ATP, to the intracellular surface of excised inside‐out patches also increased KATP channel activity, in a reversible manner.
In contrast, rotenone (10 μM) or oligomycin (2 μM) did not increase KATP channel activity in either cell‐attached, in the absence of glucose, or inside‐out membrane patch recordings.
Addition of sodium azide (3 mM) to the intracellular surface of inside‐out membrane patches in the presence of Mg‐free ATP or the non‐hydrolysable analogue 5′‐adenylylimidodiphosphate (AMP‐PNP) inhibited, rather than increased, KATP channel activity.
In conclusion, sodium azide, but not rotenone or oligomycin, directly activates KATP channels in CRI‐G1 insulin secreting cells. This action of azide is similar to that reported previously for diazoxide.

British Journal of Pharmacology (1999) 126, 51–60; doi:10.1038/sj.bjp.0702267
Homologous regulation of the α2C‐adrenoceptor subtype in human hepatocarcinoma, HepG2
Authors: Cayla Cécile , Schaak Stéphane , Roquelaine Cyril , Gales Céline , Quinchon Françoise , Paris Hervé 
Published: January 2005

Previous studies of the regulation of the α2C‐adrenoceptor in OK and in transfected cells have led to discrepant conclusions. In the present work, we examined the homologous regulation of the human α2C‐adrenoceptor in the hepatocarcinoma cell‐line, HepG2; a model which expresses this subtype spontaneously.
Short‐period treatment of the cells with UK14304 provoked neither a diminution of the potency of the α2‐agonist to inhibit forskolin‐induced cyclic AMP‐accumulation nor a change in the degree of receptor coupling to G‐proteins.
Long‐period exposure to UK14304 resulted in a large reduction of [3H]MK912 binding sites (55% decrease). The action of UK14304 was dose‐dependent (EC50=190±45 nM), rapid (t1/2 =4.2 h) and reversible. Receptor down‐regulation was also observed with clonidine or (−)adrenaline (38 and 36% decrease, respectively) and was blocked by the addition of α2‐antagonists.
Conversely to that observed with α2‐agonists, treatment of the cells with RX821002 or yohimbine alone, but not with phentolamine, promoted a significant increase of the receptor expression.
The observed alterations of receptor density are not the reflection of changes at the α2C4 mRNA level. Estimation of the receptor protein turnover and measurement of its half‐life demonstrated that down‐regulation by α2‐agonists and up‐regulation by α2‐antagonists, with inverse‐agonist efficacy, are respectively the consequence of increased and decreased rate of receptor degradation.
In conclusion, our data show that α2C‐adrenoceptor does not undergo desensitization but is down‐regulated in HepG2. The lack of desensitization agrees with previous results obtained in cells transfected with the α2C4 gene, but not with observations made in OK cells. Inversely, down‐regulation fits with results obtained in OK but not in transfected cells. The reasons for these discrepancies are discussed. Our results also demonstrated that certain α2‐antagonists behave as inverse agonist on the HepG2 model and thus provide for the first time evidence of inverse efficacy of antagonists on a cellular model expressing physiological level of a wild‐type α2‐adrenoceptor.

British Journal of Pharmacology (1999) 126, 69–78; doi:10.1038/sj.bjp.0702269
Modulation of chloride, potassium and bicarbonate transport by muscarinic receptors in a human adenocarcinoma cell line
Authors: Holliday Nicholas D , Cox Helen M 
Published: January 2005

Short‐circuit current (ISC) responses to carbachol (CCh) were investigated in Colony 1 epithelia, a subpopulation of the HCA‐7 adenocarcinoma cell line. In Krebs‐Henseleit (KH) buffer, CCh responses consisted of three ISC components: an unusual rapid decrease (the 10 s spike) followed by an upward spike at 30 s and a slower transient increase (the 2 min peak). This response was not potentiated by forskolin; rather, CCh inhibited cyclic AMP‐stimulated ISC.
In HCO3− free buffer, the decrease in forskolin‐elevated ISC after CCh was reduced, although the interactions between CCh and forskolin remained at best additive rather than synergistic. When Cl− anions were replaced by gluconate, both Ca2+‐ and cyclic AMP‐mediated electrogenic responses were significantly inhibited.
Basolateral Ba2+ (1–10 mM) and 293B (10 μM) selectively inhibited forskolin stimulation of ISC, without altering the effects of CCh. Under Ba2+‐ or 293B‐treated conditions, CCh responses were potentiated by pretreatment with forskolin.
Basolateral charybdotoxin (50 nM) significantly increased the size of the 10 s spike of CCh responses in both KH and HCO3− free medium, without affecting the 2 min peak. The enhanced 10 s spike was inhibited by prior addition of 5 mM apical Ba2+. Charybdotoxin did not affect forskolin responses.
In epithelial layers prestimulated with forskolin, the muscarinic antagonists atropine and 4‐diphenylacetoxy‐N‐methylpiperidine methiodide (4‐DAMP, both at 100 nM) abolished subsequent 10 μM CCh responses. Following addition of p‐fluoro hexahydro‐sila‐difenidol (pF‐HHSiD, 10 μM) or pirenzepine (1 μM), qualitative changes in the CCh response time‐profile also indicated a rightward shift of the agonist concentration‐response curve; however, 1 μM gallamine had no effect. These results suggest that a single M3‐like receptor subtype mediates the secretory response to CCh.
It is concluded that CCh and forskolin activate discrete populations of basolateral K+ channels gated by either Ca2+ or cyclic AMP, but that the Cl− permeability of the apical membrane may limit their combined effects on electrogenic Cl− secretion. In addition, CCh activates a Ba2+‐sensitive apical K+ conductance leading to electrogenic K+ transport. Both agents may also modulate HCO3− secretion through a mechanism at least partially dependent on carbonic anhydrase.

British Journal of Pharmacology (1999) 126, 269–279; doi:10.1038/sj.bjp.0702270
Rate‐dependent blockade of a potassium current in human atrium by the antihistamine loratadine
Authors: Crumb William J 
Published: January 2005

The antihistamine loratadine is widely prescribed for the treatment of symptoms associated with allergies. Although generally believed to be free of adverse cardiac effects, there are a number of recent reports suggesting that loratadine use may be associated with arrhythmias, in particular atrial arrhythmias.
Nothing is known regarding the potassium channel blocking properties of loratadine in human cardiac cells. Using the whole‐cell patch clamp technique, the effects of loratadine on the transient outward K current (Ito), sustained current (Isus), and current measured at −100 mV (IK1 and Ins), the major inward and outward potassium currents present in human atrial myocytes, were examined in order to provide a possible molecular mechanism for the observed atrial arrhythmias reported with loratadine use.
Loratadine rate‐dependently inhibited Ito at therapeutic concentrations with 10 nM loratadine reducing Ito amplitude at a pacing rate of 2 Hz by 34.9±6.0%. In contrast, loratadine had no effect on either Isus or current measured at −100 mV.
These results may provide a possible mechanism for the incidences of supraventricular arrhythmias reported with the use of loratadine.

British Journal of Pharmacology (1999) 126, 575–580; doi:10.1038/sj.bjp.0702273
Beneficial effects of raxofelast (IRFI 016), a new hydrophilic vitamin E‐like antioxidant, in carrageenan‐induced pleurisy
Authors: Cuzzocrea Salvatore , Costantino Giuseppina , Mazzon Emanuela , Caputi Achille P 
Published: January 2005

Peroxynitrite is a strong oxidant that results from reaction between NO and superoxide. It has been recently proposed that peroxynitrite plays a pathogenetic role in inflammatory processes. Here we have investigated the therapeutic efficacy of raxofelast, a new hydrophilic vitamin E‐like antioxidant agent, in rats subjected to carrageenan‐induced pleurisy.
In vivo treatment with raxofelast (5, 10, 20 mg kg−1 intraperitoneally 5 min before carrageenan) prevented in a dose dependent manner carrageenan‐induced pleural exudation and polymorphonuclear migration in rats subjected to carrageenan‐induced pleurisy. Lung myeloperoxidase (MPO) activity and malondialdehyde (MDA) levels, as well as histological organ injury were significantly reduced by raxofelast.
Immunohistochemical analysis for nitrotyrosine, a footprint of peroxynitrite, revealed a positive staining in lungs from carrageenan‐treated rats. No positive nitrotyrosine staining was found in the lungs of the carrageenan‐treated rats, which received raxofelast (20 mg kg−1) treatment.
Furthermore, in vivo raxofelast (5, 10, 20 mg kg−1) treatment significantly reduced peroxynitrite formation as measured by the oxidation of the fluorescent dihydrorhodamine 123, prevented the appearance of DNA damage, the decrease in mitochondrial respiration and partially restored the cellular level of NAD+ in ex vivo macrophages harvested from the pleural cavity of rats subjected to carrageenan‐induced pleurisy.
In conclusion, our study demonstrates that raxofelast, a new hydrophilic vitamin E‐like antioxidant agent, exerts multiple protective effects in carrageenan‐induced acute inflammation.

British Journal of Pharmacology (1999) 126, 407–414; doi:10.1038/sj.bjp.0702275
Role of iNOS in the vasodilator responses induced by L‐arginine in the middle cerebral artery from normotensive and hypertensive rats
Authors: Briones Ana M , Alonso María J , Marín Jesús , Salaices Mercedes 
Published: January 2005

The substrate of nitric oxide synthase (NOS), L‐arginine (L‐Arg, 0.01 μM−1 mM), induced endothelium‐independent relaxations in segments of middle cerebral arteries (MCAs) from normotensive Wistar‐Kyoto (WKY) and hypertensive rats (SHR) precontracted with prostaglandin F2α (PGF2α). These relaxations were higher in SHR than WKY arteries.
L‐NG‐nitroarginine methyl ester (L‐NAME) and 2‐amine‐5,6‐dihydro‐6‐methyl‐4H‐1,3‐tiazine (AMT), unspecific and inducible NOS (iNOS) inhibitors, respectively, reduced those relaxations, specially in SHR.
Four‐ and seven‐hours incubation with dexamethasone reduced the relaxations in MCAs from WKY and SHR, respectively.
Polymyxin B and calphostin C, protein kinase C (PKC) inhibitors, reduced the L‐Arg‐induced relaxation.
Lipopolysaccharide (LPS, 7 h incubation) unaltered and inhibited these relaxations in WKY and SHR segments, respectively. LPS antagonized the effect polymyxin B in WKY and potentiated L‐Arg‐induced relaxations in SHR in the presence of polymyxin B.
The contraction induced by PGF2α was greater in SHR than WKY arteries. This contraction was potentiated by dexamethasone and polymyxin B although the effect of polymyxin B was higher in SHR segments. LPS reduced that contraction and antagonized dexamethasone‐ and polymyxin B‐induced potentiation, these effects being greater in arteries from SHR.
These results suggest that in MCAs: (1) the induction of iNOS participates in the L‐Arg relaxation and modulates the contraction to PGF2α; (2) that induction is partially mediated by a PKC‐dependent mechanism; and (3) the involvement of iNOS in such responses is greater in the hypertensive strain.

British Journal of Pharmacology (1999) 126, 111–120; doi:10.1038/sj.bjp.0702281
Two affinities for a single antagonist at the neuronal NK1 tachykinin receptor: evidence from quantitation of receptor endocytosis
Authors: Jenkinson Karl M , Southwell Bridget R , Furness John B 
Published: January 2005

In smooth muscle contractility assays, many NK1 receptor (NK1r) antagonists inhibit responses to the neurotransmitter, substance P (SP), and its analogue, septide, with markedly different potency, leading to the proposal that there is a septide‐preferring receptor related to the NK1r.
We used fluorescence immunohistochemistry and confocal microscopy to visualize agonist‐induced NK1r endocytosis and analyse agonist/antagonist interactions at native NK1r in neurons of the myenteric plexus of guinea‐pig ileum.
SP and septide gave sigmoid log concentration‐response curves and were equipotent in inducing NK1r endocytosis.
The NK1r antagonists, CP‐99994 (2S,3S)‐3‐(2‐methoxybenzyl)amino‐2‐phenylpiperidine dihydrochloride and MEN‐10581, cyclo(Leuψ[CH2NH]Lys(benzyloxycarbonyl)‐Gln‐Trp‐Phe‐βAla) were both more potent in inhibiting endocytosis (50× and 8× greater respectively) against septide than against SP.
The results suggest that SP and septide interact differently with the NK1r, and that a single antagonist can exhibit different affinities at a single NK1r population, depending on the agonist with which it competes. Thus it may not be necessary to posit a separate septide‐preferring tachykinin receptor.

British Journal of Pharmacology (1999) 126, 131–136; doi:10.1038/sj.bjp.0702285
A comparison of an A1 adenosine receptor agonist (CVT‐510) with diltiazem for slowing of AV nodal conduction in guinea‐pig
Authors: Snowdy Stephen , Liang Hui Xiu , Blackburn Brent , Lum Robert , Nelson Marek , Wang Lisa , Pfister Jürg , Sharma Bhavender P , Wolff Andrew , Belardinelli Luiz 
Published: January 2005

The purpose of this study was to compare the pharmacological properties (i.e. the AV nodal depressant, vasodilator, and inotropic effects) of two AV nodal blocking agents belonging to different drug classes; a novel A1 adenosine receptor (A1 receptor) agonist, N‐(3(R)‐tetrahydrofuranyl)‐6‐aminopurine riboside (CVT‐510), and the prototypical calcium channel blocker diltiazem.
In the atrial‐paced isolated heart, CVT‐510 was approximately 5 fold more potent to prolong the stimulus‐to‐His bundle (S–H interval), a measure of slowing AV nodal conduction (EC50=41 nM) than to increase coronary conductance (EC50=200 nM). At concentrations of CVT‐510 (40 nM) and diltiazem (1 μM) that caused equal prolongation of S–H interval (∼10 ms), diltiazem, but not CVT‐510, significantly reduced left ventricular developed pressure (LVP) and markedly increased coronary conductance. CVT‐510 shortened atrial (EC50=73 nM) but not the ventricular monophasic action potentials (MAP).
In atrial‐paced anaesthetized guinea‐pigs, intravenous infusions of CVT‐510 and diltiazem caused nearly equal prolongations of P–R interval. However, diltiazem, but not CVT‐510, significantly reduced mean arterial blood pressure.
Both CVT‐510 and diltiazem prolonged S–H interval, i.e., slowed AV nodal conduction. However, the A1 receptor‐selective agonist CVT‐510 did so without causing the negative inotropic, vasodilator, and hypotensive effects associated with diltiazem. Because CVT‐510 did not affect the ventricular action potential, it is unlikely that this agonist will have a proarrythmic action in ventricular myocardium.

British Journal of Pharmacology (1999) 126, 137–146; doi:10.1038/sj.bjp.0702287
Effects of tumour necrosis factor‐α on left ventricular function in the rat isolated perfused heart: possible mechanisms for a decline in cardiac function
Authors: Edmunds N J , Lal H , Woodward B 
Published: January 2005

The cardiac depressant actions of TNF were investigated in the isolated perfused rat heart under constant flow (10 ml min−1) and constant pressure (70 mmHg) conditions, using a recirculating (50 ml) mode of perfusion.
Under constant flow conditions TNF (20 ng ml−1) caused an early (<25 min) decrease in left ventricular developed pressure (LVDP), which was maintained for 90 min (LVDP after 90 min: control vs TNF; 110±4 vs 82±10 mmHg, P<0.01).
The depression in cardiac function seen with TNF under constant flow conditions, was blocked by the ceramidase inhibitor N‐oleoylethanolamine (NOE), 1 μM, (LVDP after 90 min: TNF vs TNF with NOE; 82±10 vs 111±5 mmHg, P<0.05).
In hearts perfused at constant pressure, TNF caused a decrease in coronary flow rate (change in flow 20 min after TNF: control vs TNF; −3.0±0.9 vs −8.7±1.2 ml min−1, P<0.01). This was paralleled by a negative inotropic effect (change in LVDP 20 min after TNF: control vs TNF; −17±7 vs −46±6 mmHg, P<0.01). The decline in function was more rapid and more severe than that seen under conditions of constant flow.
These data indicate that cardiac function can be disrupted by TNF on two levels, firstly via a direct, ceramidase dependant negative inotropic effect, and secondly via an indirect coronary vasoconstriction.

British Journal of Pharmacology (1999) 126, 189–196; doi:10.1038/sj.bjp.0702294