bluuebunny/crossref_metadata_2025_split huggingface dataset:
Functional analysis of desensitization of the β‐adrenoceptor signalling pathway in rat cardiac tissues following chronic isoprenaline infusion
Authors: McMartin L , Summers R J 
Published: January 2005

This study examined β‐adrenoceptor signalling in cardiac tissues following infusion of isoprenaline (400 μg kg−1 h−1) or vehicle to rats for 14 days.
Isoprenaline infusion caused marked hypertrophy of atria and ventricles and reduced the resting rate of spontaneously beating right atria and the basal force of left atrial contraction.
In spontaneously beating right atria, concentration‐response curves to isoprenaline and forskolin were shifted 7.9 and 3.2 fold to the right following treatment whereas responses to the cyclic AMP analogue 5,6‐dichloro‐1‐ß‐D‐ribofuranosylbenzimidazole‐3′, 5′‐cyclic monophosphorothioate were unchanged.
In electrically driven left atria, concentration‐response curves to isoprenaline and forskolin were shifted 4 fold to the right and maximum responses reduced. Responses to dibutyryl cyclic AMP were shifted 3.2 fold to the right but those to Ca2+ were unchanged.
Inotropic responses of left and right ventricular papillary muscles to isoprenaline were abolished and markedly reduced respectively by isoprenaline treatment. Responses to forskolin were shifted 5 fold to the right. Responses to dibutyryl cyclic AMP were shifted to the right 3.2 and 2 fold in left and right ventricular papillary muscles. Responses to isobutyl methyl xanthine were shifted to the right 15.8 and 6.3 fold in left and right papillary muscles whereas those to Ca2+ were not significantly altered.
This study indicates differences in β‐adrenoceptor desensitization in different regions of the heart following chronic infusion of isoprenaline. Chronotropic responses showed impaired signalling between the receptor and adenylate cyclase whereas inotropic responses exhibited additional desensitization at the level of cyclic AMP dependent protein kinase.

British Journal of Pharmacology (1999) 127, 1012–1020; doi:10.1038/sj.bjp.0702618
Induction of prostanoid, nitric oxide, and cytokine formation in rat bone marrow derived macrophages by activin A
Authors: Nüsing Rolf M , Barsig Johannes 
Published: January 2005

In this study we describe that activin A, a transforming growth factor (TGF) β‐like polypeptide affects the expression of inflammatory response genes and their products.
In rat bone marrow derived macrophages 15 nM activin A caused the stimulation of prostaglandin (PG) E2 and thromboxane (TX) A2 formation, production of nitrite as a marker for nitric oxide (NO) and the release of the cytokines tumour necrosis factor (TNF) α and interleukin (IL) ‐1β. As shown by mRNA analysis induction of cyclo‐oxygenase‐2 and inducible nitric oxide synthase by activin A gave rise to the enhanced release of prostanoids and NO.
Costimulation of bone marrow derived macrophages with 15 nM activin A and 100 nM 12‐O‐tetradecanoyl‐phorbol 13‐acetate (TPA) potentiated the synthesis of prostanoids in a synergistic manner. With respect to NO formation the effect of activin A and TPA was additive.
In contrast to the nitrite production activin A induced PGE2 synthesis was susceptible to tyrosine kinase inhibition by genistein and tyrphostin 46 (IC50 was 10 and 20 μM, respectively). This observed inhibition was caused by the selective suppression of activin A induced cyclo‐oxygenase‐2 mRNA expression. Further, the release of TNFα in the presence of activin A was potentiated by tyrosine kinase inhibition.
In summary, we report that activin A exerts proinflammatory activity which results in the formation of prostanoids, NO and cytokines in rat bone marrow derived macrophages. Tyrosine kinase dependent and independent signalling pathways are involved leading to the increased synthesis of these metabolites. Based upon these results, we speculate that activin A may be considered as a possible component of inflammatory processes affecting at least the haematopoietic system.

British Journal of Pharmacology (1999) 127, 919–926; doi:10.1038/sj.bjp.0702626
The structural requirements for phorbol esters to enhance serotonin and acetylcholine release from rat brain cortex
Authors: Iannazzo L , Kotsonis P , Majewski H 
Published: January 2005

The effects of various phorbol‐based protein kinase C (PKC) activators on the electrical stimulation‐induced (S‐I) release of serotonin and acetylcholine was studied in rat brain cortical slices pre‐incubated with [3H]‐serotonin or [3H]‐choline to investigate possible structure‐activity relationships.
4β‐Phorbol 12,13‐dibutyrate (4βPDB, 0.1–3.0 μM), enhanced S‐I release of serotonin in a concentration‐dependent manner whereas the structurally related inactive isomer 4α‐phorbol 12, 13‐dibutyrate (4αPDB) and phorbol 13‐acetate (PA) were without effect. Another group of phorbol esters containing a common 13‐ester substituent (phorbol 12,13‐diacetate, PDA; phorbol 12‐myristate 13‐acetate, PMA; phorbol 12‐methylaminobenzoate 13‐acetate, PMBA) also enhanced S‐I serotonin release with PMA being least potent.
The deoxyphorbol monoesters, 12‐deoxyphorbol 13‐acetate (dPA), 12‐deoxyphorbol 13‐angelate (dPAng), 12‐deoxyphorbol 13‐phenylacetate (dPPhen) and 12‐deoxyphorbol 13‐isobutyrate (dPiB) enhanced S‐I serotonin release but 12‐deoxyphorbol 13‐tetradecanoate (dPT) was without effect. The 20‐acetate derivatives of dPPhen and dPAng were less effective in enhancing S‐I serotonin release compared to the parent compounds.
With acetylcholine release all phorbol esters tested had a far lesser effect when compared to their facilitatory action on serotonin release with only 4βPDB, PDA, dPA, dPAng and dPiB having significant effects.
The effects of the phorbol esters on serotonin release were not correlated with their reported in vitro affinity and isozyme selectivity for PKC. A comparison across three transmitter systems (noradrenaline, dopamine, serotonin) suggests basic similarities in the structural requirements of phorbol esters to enhance transmitter release with short chain substituted mono‐ and diesters of phorbol being more potent facilitators of release than the long chain esters. Some compounds notably PDA, PMBA, dPPhen, dPPhenA had different potencies across noradrenaline, dopamine and serotonin.

British Journal of Pharmacology (1999) 127, 1177–1189; doi:10.1038/sj.bjp.0702627
Role of tachykinin NK2‐receptor activation in the allergen‐induced late asthmatic reaction, airway hyperreactivity and airway inflammatory cell influx in conscious, unrestrained guinea‐pigs
Authors: Schuiling Martin , Zuidhof Annet B , Meurs Herman , Zaagsma Johan 
Published: January 2005

In a guinea‐pig model of allergic asthma, we investigated the involvement of the tachykinin NK2 receptors in allergen‐induced early (EAR) and late (LAR) asthmatic reactions, airway hyperreactivity (AHR) after these reactions and inflammatory cell influx in the airways, using the selective non‐peptide NK2 receptor antagonist SR48968.
On two different occasions, separated by a 1 week interval, ovalbumin (OA)‐sensitized guinea‐pigs inhaled either vehicle (3 min) or SR48968 (100 nM, 3 min) at 30 min before as well as at 5.5 h after OA provocation (between the EAR and LAR) in a random crossover design.
SR48968 had no significant effect on the EAR, but significantly attenuated the LAR by 44.2±16.4% (P<0.05) compared to saline control.
The NK2 receptor antagonist did not affect the OA‐induced AHR to histamine after the EAR at 5 h after OA challenge (3.59±0.59 fold increase in histamine reactivity vs 3.79±0.61 fold increase in the controls, NS), but significantly reduced the AHR after the LAR at 23 h after OA challenge (1.59±0.24 fold increase vs 1.93±0.15 fold increase, respectively, P<0.05).
Bronchoalveolar lavage studies performed at 25 h after the second OA provocation showed that SR48968 significantly inhibited the allergen‐induced infiltration of neutrophils (P<0.05) and lymphocytes (P<0.01) in the airways.
These results indicate that NK2 receptor activation is importantly involved in the development of the allergen‐induced late (but not early) asthmatic reaction and late (but not early) AHR to histamine, and that NK2 receptor‐mediated infiltration of neutrophils and lymphocytes in the airways may contribute to these effects.

British Journal of Pharmacology (1999) 127, 1030–1038; doi:10.1038/sj.bjp.0702628
Role of N‐type calcium channels in autonomic neurotransmission in guineapig isolated left atria
Authors: Serone Adrian P , Angus James A 
Published: January 2005

Calcium entry via neuronal calcium channels is essential for the process of neurotransmission. We investigated the calcium channel subtypes involved in the operation of cardiac autonomic neurotransmission by examining the effects of selective calcium channel blockers on the inotropic responses to electrical field stimulation (EFS) of driven (4 Hz) guineapig isolated left atria. In this tissue, a previous report (Hong & Chang, 1995) found no evidence for N‐type channels involved in the vagal negative inotropic response and only weak involvement in sympathetic responses.
The effects of cumulative concentrations of the selective N‐type calcium channel blocker, ω‐conotoxin GVIA (GVIA; 0.1–10 nM) and the nonselective N‐, P/Q‐type calcium channel blocker, ω‐conotoxin MVIIC (MVIIC; 0.01–10 nM) were examined on the positive (with atropine, 1 μM present) and negative (with propranolol, 1 μM and clonidine, 1 μM present) inotropic responses to EFS (eight trains, each train four pulses per punctate stimulus).
GVIA caused complete inhibition of both cardiac vagal and sympathetic inotropic responses to EFS. GVIA was equipotent at inhibiting positive (pIC50 9.29±0.08) and negative (pIC50 9.13±0.17) inotropic responses. MVIIC also mediated complete inhibition of inotropic responses to EFS and was 160 and 85 fold less potent than GVIA at inhibiting positive (pIC50 7.08±0.10) and negative (pIC50 7.20±0.14) inotropic responses, respectively. MVIIC was also equipotent at inhibiting both sympathetic and vagal responses.
Our data demonstrates that N‐type calcium channels account for all the calcium current required for cardiac autonomic neurotransmission in the guinea‐pig isolated left atrium.

British Journal of Pharmacology (1999) 127, 927–934; doi:10.1038/sj.bjp.0702629
Naloxone blocks endomorphin‐1 but not endomorphin‐2 induced inhibition of tachykinergic contractions of guinea‐pig isolated bronchus
Authors: Fischer Axel , Undem Bradley J 
Published: January 2005

The recently identified endogenous agonists on the μ‐opioid‐receptor (μOR), endomorphin‐1 (EM‐1) and endomorphin‐2 (EM‐2), induce a concentration dependent inhibition of electrical field stimulation (EFS)‐induced tachykinin‐mediated contractions of the guinea‐pig bronchus (ED50s <10 nM for both compounds). Surprisingly, only endomorphin‐1 effects could be blocked by naloxone (10 μM), whereas endomorphin‐2 effects were not affected by specific antagonists for the μ‐, κ‐, and δ‐opioid‐receptor.British Journal of Pharmacology (1999) 127, 605–608; doi:10.1038/sj.bjp.0702630
RS‐127445: a selective, high affinity, orally bioavailable 5‐HT2B receptor antagonist
Authors: Bonhaus Douglas W , Flippin Lee A , Greenhouse Robert J , Jaime Saul , Rocha Cindy , Dawson Mark , Van Natta Kristine , Chang L K , Pulido‐Rios Tess , Webber Andrea , Leung Edward , Eglen Richard M , Martin Graeme R 
Published: January 2005

Efforts to define precisely the role of 5‐HT2B receptors in normal and disease processes have been hindered by the absence of selective antagonists. To address this deficiency, we developed a series of naphthylpyrimidines as potentially useful 5‐HT2B receptor antagonists.
RS‐127445 (2‐amino‐4‐(4‐fluoronaphth‐1‐yl)‐6‐isopropylpyrimidine) was found to have nanomolar affinity for the 5‐HT2B receptor (pKi=9.5±0.1) and 1,000 fold selectivity for this receptor as compared to numerous other receptor and ion channel binding sites.
In cells expressing human recombinant 5‐HT2B receptors, RS‐127445 potently antagonized 5‐HT‐evoked formation of inositol phosphates (pKB=9.5±0.1) and 5‐HT‐evoked increases in intracellular calcium (pIC50=10.4±0.1). RS‐127445 also blocked 5‐HT‐evoked contraction of rat isolated stomach fundus (pA2=9.5±1.1) and (±)α‐methyl‐5‐HT‐mediated relaxation of the rat jugular vein (pA2=9.9±0.3). RS‐127445 had no detectable intrinsic activity in these assays.
In rats, the fraction of RS‐127445 that was bioavailable via the oral or intraperitoneal routes was 14 and 60% respectively. Intraperitoneal administration of RS‐127445 (5 mg kg−1) produced plasma concentrations predicted to fully saturate accessible 5‐HT2B receptors for at least 4 h.
In conclusion, RS‐127445 is a selective, high affinity 5‐HT2B receptor antagonist suitable for use in vivo. The therapeutic potential of this molecule is being further evaluated.

British Journal of Pharmacology (1999) 127, 1075–1082; doi:10.1038/sj.bjp.0702632
Characterization of the inflammatory response to proteinase‐activated receptor‐2 (PAR2)‐activating peptides in the rat paw
Authors: Vergnolle Nathalie , Hollenberg Morley D , Sharkey Keith A , Wallace John L 
Published: January 2005

In the present study, we have observed the development of an inflammatory reaction in the rat hindpaw, following the injection of specific agonists of PAR2 (two PAR2 activating peptides). This inflammation was characterized by oedema and granulocyte infiltration.
Two selective PAR2 activating peptides, SLGRL‐NH2 and trans‐cinnamoyl‐LIGRLO‐NH2 induced significant oedema in the rat hindpaw from 1–6 h following subplantar injection. Six hours after the PAR2‐activating peptide injection, the paw tissues showed a complete disruption of tissue architecture along with an inflammatory cell infiltrate.
In the inflamed paw, PAR2‐immunoreactivity was expressed on endothelial cells as well as on the infiltrating inflammatory cells.
The oedema induced by the injection of the two PAR2 activating peptides was slightly reduced in rats pre‐treated with compound 48/80, but was not modified by pre‐treatment of rats with cromolyn, a mast cell stabilizer. Pre‐treatment of rats with a cyclo‐oxygenase inhibitor (indomethacin) or a nitric oxide synthase inhibitor (L‐Nω‐nitro‐L‐arginine methyl ester) had no effect on the oedema induced by the PAR2‐activating peptides.
These results demonstrate that the administration of PAR2‐activating peptides into the rat paw induced an acute inflammatory response characterized by a persistent oedema (at least 6 h) and granulocyte infiltration. The PAR2‐induced inflammatory response occurred through a mechanism largely independent of mast cell activation, and of the production of prostanoids and nitric oxide.

British Journal of Pharmacology (1999) 127, 1083–1090; doi:10.1038/sj.bjp.0702634
The antiplatelet activity of PMC, a potent α‐tocopherol analogue, is mediated through inhibition of cyclo‐oxygenase
Authors: Sheu Joen R , Lee Cheng R , Lin Chang C , Kan Ya C , Lin Chien H , Hung Wei C , Lee Yen M , Yen Mao H 
Published: January 2005

PMC, a potent α‐tocopherol derivative, dose‐dependently (5–25 μM) inhibited the ATP‐release reaction and platelet aggregation in washed human platelets stimulated by agonists (collagen and ADP).
PMC also dose‐dependently inhibited the intracellular Ca2+ mobilization, whereas it did not inhibit phosphoinositide breakdown in human platelets stimulated by collagen.
PMC (10 and 25 μM) significantly inhibited collagen‐stimulated thromboxane A2 (TxA2) formation in human platelets. On the other hand, PMC (25 and 100 μM) did not increase the formation of cyclic AMP or cyclic GMP in platelets. Moreover, PMC (25, 100, and 200 μM) did not affect the thromboxane synthetase activity of aspirin‐treated platelet microsomes.
PMC (10 and 25 μM) markedly inhibited the exogenous arachidonic acid (100 μM)‐induced prostaglandin E2 (PGE2) formation in the presence of imidazole (600 μM) in washed human platelets, indicating that PMC inhibits cyclo‐oxygenase activity.
We conclude that PMC may exert its anti‐platelet aggregation activity by inhibiting cyclo‐oxygenase activity, which leads to reduced prostaglandin formation; this, in turn, is followed by a reduction of TxA2 formation, and finally inhibition of [Ca2+]i mobilization and ATP‐release.

British Journal of Pharmacology (1999) 127, 1206–1212; doi:10.1038/sj.bjp.0702637
Blockade by N‐3 polyunsaturated fatty acid of the Kv4.3 current stably expressed in Chinese hamster ovary cells
Authors: Singleton C B , Valenzuela S M , Walker B D , Tie H , Wyse K R , Bursill J A , Qiu M R , Breit S N , Campbell T J 
Published: January 2005

The Kv4.3 gene is believed to encode a large proportion of the transient outward current (Ito), responsible for the early phase of repolarization of the human cardiac action potential. There is evidence that this current is involved in the dispersion of refractoriness which develops during myocardial ischaemia and which predisposes to the development of potentially fatal ventricular tachyarrhythmias.
Epidemiological, clinical, animal, and cellular studies indicate that these arrhythmias may be ameliorated in myocardial ischaemia by n‐3 polyunsaturated fatty acids (n‐3 PUFA) present in fish oils.
We describe stable transfection of the Kv4.3 gene into a mammalian cell line (Chinese hamster ovary cells), and using patch clamp techniques have shown that the resulting current closely resembles human Ito.
The current is rapidly activating and inactivating, with both processes being well fit by double exponential functions (time constants of 3.8±0.2 and 5.3±0.4 ms for activation and 20.0±1.2 and 96.6±6.7 ms for inactivation at +45 mV at 23°C). Activation and steady state inactivation both show voltage dependence (V1/2 of activation=−6.7±2.5 mV, V1/2 of steady state inactivation=−51.3±0.2 mV at 23°C). Current inactivation and recovery from inactivation are faster at physiologic temperature (37°C) compared to room temperature (23°C).
The n‐3 PUFA docosahexaenoic acid blocks the Kv4.3 current with an IC50 of 3.6 μmol L−1. Blockade of the transient outward current may be an important mechanism by which n‐3 PUFA provide protection against the development of ventricular fibrillation during myocardial ischaemia.

British Journal of Pharmacology (1999) 127, 941–948; doi:10.1038/sj.bjp.0702638
Dual mode of stimulation by the β‐carboline ZK 91085 of recombinant GABAA receptor currents: molecular determinants affecting its action
Authors: Thomet Urs , Baur Roland , Scholze Petra , Sieghart Werner , Sigel Erwin 
Published: January 2005

In electrophysiological measurements the β‐carboline ethyl 6‐benzyloxy‐β‐carboline‐3‐carboxylate (ZK 91085) acts as a positive allosteric modulator on rat recombinant α1β2γ2 GABAA receptors and binds with high affinity (IC50=1.5 nM) to the [3H]‐flunitrazepam site. Flumazenil was able to partially counteract the current modulation. These observations indicate an action of ZK 91085 at the benzodiazepine binding site.
At the dual subunit combination α1β2, which lacks the γ subunit required for benzodiazepine modulation, we still observed a potentiation of GABA currents. Thus ZK 91085 acts via an additional site on the channel. At the subunit combination α1β1, ZK 91085 potentiation is strongly reduced as compared to α1β2. In binding studies, ZK 91085 was able to decrease [35S]‐TBPS binding in α1β2γ2 and α1β2 but not in α1β1. This selectivity of ZK 91085 for receptors containing the β2 isoform over those containing the β1 isoform is reminiscent of the action of loreclezole.
To identify amino acid residues important for the second type of modulation, we functionally compared wild type α1β2 and mutant receptors for stimulation by ZK 91085. The mutation β2N265S, that abolishes loreclezole effects, also abolishes ZK 91085 stimulation. The mutation β2Y62L increased stimulation by ZK 91085 3–4 fold, locating an influencing entity of the second type of action of ZK 91085 at an α/β subunit interface.
Structural intermediates of ZK 91085 and the β‐carboline abecarnil, the latter of which only slightly potentiated GABA currents in α1β2, were analysed to determine structural requirements for modulation.
ZK 91085 thus allosterically stimulates the GABAA receptor through two sites of action: the benzodiazepine site and the loreclezole site in contrast to classical β‐carbolines, that confer negative allosteric modulation through the benzodiazepine site.

British Journal of Pharmacology (1999) 127, 1231–1239; doi:10.1038/sj.bjp.0702639
Treatment with inverse agonists enhances baseline atrial contractility in transgenic mice with chronic beta2‐adrenoceptor activation
Authors: Nagaraja Savitha , Iyer Srinivas , Liu Xiushi , Eichberg Joseph , Bond Richard A 
Published: January 2005

In this study, we investigate whether chronic treatment with β‐adrenoceptor (βAR) ligands with inverse agonist activity enhances myocardial β2AR‐mediated atrial tension more than neutral antagonists in transgenic mice (TG35). These mice exhibit chronic adrenoceptor activation because they possess a greater number of constitutively active receptors than wild type mice due to cardiac‐specific overexpression of human β2ARs. TG35 and wild type mice were chronically treated for 90 h with three inverse agonists, ICI‐118,551, propranolol, and carvedilol, and one neutral antagonist, alprenolol. After 96 h, we compared the basal and isoprenaline‐stimulated (10 μM) increase in atrial tension in treated or untreated TG35 mice and wild type mice. In parallel, to determine the effect of chronic βAR ligand treatment on the amounts of G protein receptor kinase‐2 (GRK‐2) and G proteins, we performed Western blotting on myocardial cytosolic and membrane proteins.
Atria from the TG35 mice treated with inverse agonists showed increases in the baseline tension compared to those from alprenolol/vehicle‐treated mice. ICI‐118,551 and propranolol treatment restored the elevated myocardial G‐inhibitory protein (Giα) levels to that of wild type. Also, treatment with inverse agonists upregulated G‐stimulatory protein (Gsα) levels and GRK2 above those levels in vehicle‐treated TG35 or wild type mice. The increased baseline atrial tension was reversed by the addition of ICI‐118,551.
Overall, our data suggests that inverse agonists enhance baseline atrial tension more than neutral antagonists. Based on this, we propose that upregulation of the active conformation of the β2ARs, Gsα protein and restoration of Giα as three possible mechanisms to explain this enhanced receptor activity.
Therefore, the favourable effects of some ligands used in pathological conditions involving chronic adrenoceptor activation may be due to the inverse agonist activity of the ligand.

British Journal of Pharmacology (1999) 127, 1099–1104; doi:10.1038/sj.bjp.0702645