bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of descarboethoxyloratadine, the major metabolite of loratadine, on the human cardiac potassium channel Kv1.5
Authors: Caballero Ricardo , Delpón Eva , Valenzuela Carmen , Longobardo Mónica , Franqueza Laura , Tamargo Juan 
Published: January 2005

The effects of descarboethoxyloratadine (DCL), the major metabolite of loratadine, were studied on a human cardiac K+ channel (hKv1.5) cloned from human ventricle and stably expressed in a mouse cell line by means of the patch‐clamp technique. DCL (1–100 μM) inhibited hKv1.5 current in a concentration‐dependent manner with an apparent affinity constant of 12.5±1.2 μM. The blockade increased steeply over the voltage range of channel opening, which indicated that DCL binds preferentially to the open state of the channel. At more depolarized potentials a weaker voltage‐dependence was observed consistent with a binding reaction sensing ∼amp;20% of the transmembrane electrical field. DCL, 20 μM, increased the time constant of deactivation of tail currents, thus inducing a ‘crossover’ phenomenon. The present results demonstrated that DCL blocked hKv1.5 channels in a concentration‐, voltage‐, and time‐dependent manner.British Journal of Pharmacology (1997) 122, 796–798; doi:10.1038/sj.bjp.0701468
Reversal of tolerance to the antitransit effects of morphine during acute intestinal inflammation in mice
Authors: Pol Olga , Puig Margarita M. 
Published: January 2005

The aim of investigation was to establish and compare the reversibility of tolerance to the antitransit effects of morphine by three different procedures: (a) acute inflammation of the gut, (b) lorglumide a cholecystokininA (CCKA) receptor antagonist, or (c) MK‐801, an N‐methyl‐D‐aspartate (NMDA) receptor ion channel blocker. The type of interaction between morphine and lorglumide or MK‐801 on the inhibition of gastrointestinal transit (GIT) in naive animals was also evaluated.
Male Swiss CD‐1 mice were implanted with 75 mg of morphine base or placebo pellets. Gastrointestinal transit was assessed with a charcoal meal and results expressed as % inhibition of GIT. Inflammation was induced by the intragastric (p.o.) administration of croton oil (CO), while controls received castor oil (CA) or saline (SS). Morphine was administered by subcutaneous (s.c.) or intracerebroventricular (i.c.v.) injection, to naive and tolerant animals treated with CO, CA or SS. Dose‐response curves for s.c. morphine were also perforrmed in naive and tolerant mice receiving 5.2 or 7.4 nmol (s.c.) lorglumide or MK‐801, respectively.
The ED50 values for inhibition of GIT by s.c. morphine were: 45.9±2.7 and 250.1±3.1 nmol in naive and tolerant animals, respectively, demonstrating a five fold decrease in the potency of morphine. In naive animals, inflammation (CO) decreased the ED50 of morphine three times (14.4±2.2 nmol). However, no tolerance to s.c. morphine (ED50 16.4±2.6 nmol) was manifested during intestinal inflammation. After i.c.v. administration, a similar degree of tolerance to morphine was observed (4.8 fold decrease in potency). Intestinal inflammation had no effect on the ED50 values of i.c.v. morphine in naive and tolerant animals, showing that reversal of tolerance is related to local mechanism/s. Mean values for intestinal pH were 6.9±0.04 and 6.2±0.04 in SS and CO treated mice, respectively. In addition, morphine was 74 times more potent by the i.c.v. than by the s.c. route (naive‐SS).
Morphine and lorglumide interacted synergistically in naive animals; in addition, the administration of lorglumide reversed tolerance to s.c. morphine. No interaction (additivity) was observed in naive animals when morphine and MK‐801 were administered in combination. However, the drug completely reversed tolerance to the antitransit effects of morphine.
The present investigation shows that acute inflammation of the gut reverses tolerance to the antitransit effects of s.c. morphine by a peripheral mechanism. Qualitatively similar results were obtained after the administration of lorglumide or MK‐801. Our results suggest that a local decrease in pH could play an important role during inflammation, while antagonism of endogenous compensatory systems would explain the reversal of tolerance induced by lorglumide or MK‐801.

British Journal of Pharmacology (1997) 122, 1216–1222; doi:10.1038/sj.bjp.0701472
The pacemaker current If in single human atrial myocytes and the effect of β‐adrenoceptor and A1‐adenosine receptor stimulation
Authors: Porciatti Francesco , Pelzmann Brigitte , Cerbai Elisabetta , Schaffer Peter , Pino Roberto , Bernhart Eva , Koidl Bernd , Mugelli Alessandro 
Published: January 2005

We used single human atrial myocytes to study If occurrence, properties and pharmacological modulation. Cells were obtained by chunk enzymatic digestion from samples of right atrial appendages of patients undergoing corrective cardiac surgery.
Patch‐clamped cells in the whole‐cell configuration were superfused with a modified Tyrode solution to reduce contamination by interfering currents and to amplify If. The average cell membrane capacitance was 85.06±2.41 pF (n=531). Data were consistent with the geometrical dimensions of the cells (length 94.2±1.89 μm, width 17.9±0.42 μm, n=126).
When hyperpolarizing to −120 mV from a holding potential of −40 mV, 252 of 306 tested cells (82%) expressed a hyperpolarization‐activated inward current (If density =3.77±0.25 pA pF−1); the current was considered to be present in a given cell if its density at −120 mV was larger than 0.5 pA pF−1.
Current activation was sigmoidal and fitted a Boltzmann model; the average activation curve (n=25) showed a maximum current amplitude of 205.97±19.94 pA, corresponding to 3.87±0.63 pA pF−1, voltage of half‐maximal activation (V1/2) at −86.68±2.19 mV and a slope of −11.39±0.69 mV. The reversal potential of If measured by tail‐current analysis was −13.07±1.92 mV (n=6). The addition of CsCl (5 mM) fully and reversibly blocked the current.
In the presence of the β‐adrenoceptor agonist isoprenaline (Iso, 1 μM), V1/2 was significantly shifted toward less negative potentials by 6.06±1.96 mV (n=16, P=0.0039). The selective A1‐adenosine receptor agonist cyclopentyladenosine (CPA, 1 μM) caused a statistically significant shift of V1/2 toward more negative potentials with respect to the control curve, both in the absence (−7.37±1.83 mV, P=0.0005, n=11) and in the presence of 1 μM Iso (−4.97±1.78, P=0.031, n=6).
These results demonstrate that a current with the properties of If described in cardiac primary and secondary pacemakers occurs in the majority of human atrial cells. While the pathophysiological relevance of If in human atrial tissue remains to be defined, our data clearly show that it is modulated through stimulation of β‐adrenoceptors and A1‐adenosine receptors.

British Journal of Pharmacology (1997) 122, 963–969; doi:10.1038/sj.bjp.0701473
Fidelity in functional coupling of the rat P2Y1 receptor to phospholipase C
Authors: Schachter Joel B. , Boyer José L. , Li Qing , Nicholas Robert A. , Harden T. Kendall 
Published: January 2005

The rat homologue of the P2Y1 receptor has been heterologously expressed in 1321N1 human astrocytoma cells and in C6 rat glioma cells.
As has been shown previously for the turkey and human P2Y1 receptors, the rat P2Y1 receptor expressed in either cell type responded to 2MeSATP with increases in inositol phosphate accumulation that were competitively blocked by the antagonist PPADS. Neither of the wild type cell lines exhibited inositol phosphate responses to P2Y1 receptor agonists.
Expression of the rat P2Y1 receptor did not confer a capacity of 2MeSATP to inhibit adenylyl cyclase activity in 1321N1 cells. Moreover, the inhibition of adenylyl cyclase mediated by an endogenous P2Y receptor of C6 glioma cells was not enhanced by expression of the rat P2Y1 receptor. The P2Y receptor‐mediated inhibition of adenylyl cyclase in C6 glioma cells expressing both the endogenous P2Y receptor and the rat P2Y1 receptor remained unaffected by PPADS.
Since the P2Y receptor responsible for inhibition of adenylyl cyclase in C6 glioma cells does not share the pharmacological or functional properties of the P2Y1 receptor, even when both receptors originate from the same species and are simultaneously expressed in the same cell line, it is concluded that the P2Y1 receptor is distinct from an endogenous P2Y receptor in C6 cells that couples to inhibition of adenylyl cyclase.

British Journal of Pharmacology (1997) 122, 1021–1024; doi:10.1038/sj.bjp.0701479
Activation of the cAMP transduction cascade contributes to the mechanical hyperalgesia and allodynia induced by intradermal injection of capsaicin
Authors: Sluka Kathleen A. 
Published: January 2005

The spinal role of the cAMP transduction cascade in nociceptive processing was investigated in awake behaving rats (male, Sprague‐Dawley) by activating or inhibiting this pathway spinally. Microdialysis fibres were implanted into the dorsal horn to infuse drugs directly to the spinal cord.
Animals, without peripheral tissue injury, were tested for responses to repeated applications (10 trials) of von Frey filaments and threshold to mechanical stimulation before and after infusion of 8‐bromo‐cAMP. In this group of animals treated spinally with 8‐br‐cAMP (1–10 mM) a dose‐dependent hyperalgesia and allodynia were produced. This was manifested as an increased number of responses to 10 trials of von Frey filaments (10, 50, 150, 250 mN) and a decrease in mechanical threshold.
A second series of experiments studied the manipulation of the cAMP pathway spinally in a model of tissue injury induced by intradermal injection of capsaicin. Animals were either pre‐ or post‐treated spinally with the adenylate cyclase inhibitor, tetrahydrofuryl adenine (THFA) or the protein kinase A inhibitor, myrosilated protein kinase (14–22) amide (PKI). Injection of capsaicin resulted in an increased number of responses to repeated applications of von Frey filaments and a decrease in threshold to mechanical stimuli outside the site of injection, secondary mechanical hyperalgesia and allodynia.
Pre‐treatment with either THFA (1 mM) or PKI (5 mM) had no effect on the capsaicin‐evoked secondary hyperalgesia and allodynia.
In contrast, post‐treatment spinally with THFA (0.01–1 mM) or PKI (0.05–50 mM) dose‐dependently reduced the mechanical hyperalgesia and allodynia produced by capsaicin injection. Furthermore, the mechanical hyperalgesia and allodynia blocked by the adenylate cyclase inhibitor, THFA (1 mM), was reversed by infusion of 8‐bromo‐cAMP (0.01–10 mM) in a dose‐dependent manner.
Thus, this study demonstrates that activation of the cAMP transduction cascade at the spinal cord level results in mechanical hyperalgesia and allodynia and that the secondary mechanical hyperalgesia and allodynia following intradermal injection of capsaicin is mediated by this same transduction cascade.

British Journal of Pharmacology (1997) 122, 1165–1173; doi:10.1038/sj.bjp.0701486
Effects of a novel guanylate cyclase inhibitor on nitric oxide‐dependent inhibitory neurotransmission in canine proximal colon
Authors: Franck H. , Sweeney K. M. , Sanders K. M. , Shuttleworth C. W. R. 
Published: January 2005

Previous studies suggested that nitric oxide (NO) may cause hyperpolarization and relaxation of canine colonic smooth muscle by both cGMP‐dependent and cGMP‐independent mechanisms. This hypothesis was tested using 1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxaline‐1‐one (ODQ), a novel inhibitor of NO‐stimulated guanylate cyclase.
In the presence of histamine (30 μM), atropine and indomethacin (both at 1 μM), electrical field stimulation of intrinsic neurons (EFS; 5 Hz) produced inhibition of phasic contractile activity that is due to NO synthesis. ODQ caused a concentration‐dependent block of this response (10 nM to 10 μM).
Inhibitory junction potentials (IJPs) due to NO synthesis were recorded from muscle cells located near the myenteric border of the circular muscle layer, using intracellular microelectrodes. IJPs were abolished by ODQ (1–10 μM).
EFS (10–20 Hz) produced frequency‐dependent inhibition of electrical slow waves recorded from cells located near the submucosal surface of the circular muscle layer. This inhibition is due to NO synthesis, and it was abolished by ODQ (1–10 μM).
Hyperpolarization and relaxation produced by an NO donor, sodium nitroprusside, were abolished by ODQ pretreatment (1–10 μM). In contrast, inhibitory responses to 8‐Br‐cGMP (1 mM) were unaffected by ODQ.
ODQ alone (1–10 μM) had no significant effect on spontaneous electrical or phasic contractile activity. In tissues pre‐treated with L‐NAME (300 μM), ODQ decreased the amplitude of spontaneous or histamine‐stimulated phasic contractile activity.
These results suggest that electrical and mechanical effects of endogenously released and exogenously applied NO in canine colon are largely due to cGMP synthesis by ODQ‐sensitive soluble guanylate cyclase. No evidence to support a direct (cGMP‐independent) mechanism of NO action was found. ODQ also appears to cause a non‐specific inhibition of muscle contractile activity; however, this effect does not contribute to block of NO‐dependent effects.

British Journal of Pharmacology (1997) 122, 1223–1229; doi:10.1038/sj.bjp.0701487
Structural requirements for roxatidine in the stimulant effect of rat gastric mucin synthesis and the participation of nitric oxide in this mechanism
Authors: Ichikawa Takafumi , Ishihara Kazuhiko , Saigenji Katsunori , Hotta Kyoko 
Published: January 2005

The structural requirements of the histamine H2‐receptor antagonist, roxatidine (2‐acetoxy‐N‐(3‐[m‐(1‐piperidinylmethyl)phenoxy]‐propyl)acetamide hydrochloride), for the stimulant effect on mucin biosynthesis and their relation to histamine H2‐receptor antagonism were identified by considering the structural analogues of this drug using an organ culture system of the rat stomach and competition studies with [125I]iodoaminopotentidine ([125I]‐APT) binding to membranes of the guinea pig striatum.
[3H]Glucosamine incorporation into mucin during 5 h incubation period was stimulated by roxatidine and its structural analogues A (2‐hydroxy‐N‐(3‐[m‐(1‐piperidinylmethyl)phenoxy]‐propyl)acetamide) and B (N‐(3‐[m‐(1‐piperidinylmethyl)phenoxy]‐propyl)acetamide). This effect was seen in mucosal cultures of the corpus, but not antrum, region.
Structural analogues, in which the length of the flexible chain between the benzene ring and the amide structure differs from that of roxatidine, failed to activate mucin synthesis. No significant change in mucus synthesis occurred with the addition of analogues in which the piperidine ring attached to the benzene ring via a methylene bridge was changed.
Specific [125I]‐APT binding to the histamine H2 receptor of guinea pig brain membranes was inhibited by roxatidine and all structural analogues used in this study, except F (N‐(3‐[m‐(N, N‐dimethyl‐aminomethyl)phenoxy]‐propyl)acetamide).
Ranitidine at 10−4 M did not suppress the roxatidine‐induced increase in [3H]glucosamine incorporation into mucin.
Roxatidine‐induced stimulation of [3H]glucosamine incorporation into mucin was completely blocked by the addition of either NG‐nitro‐L‐arginine (10−5 M) or 2‐(4‐carboxyphenyl)‐4,4,5,5,‐tetramethylimidazoline‐1‐oxyl‐3‐oxide sodium salt (10−5 M). The inhibitory action of NG‐nitro‐L‐arginine was totally reversed by L‐arginine (5×10−3 M).
These results suggest that the cardinal chemical features of roxatidine for the activation of mucin biosynthesis in the corpus region of the rat stomach are the appropriate length of the flexible chain between the amide structure and the aromatic ring system bearing the methylpiperidinyl group at the meta position. The activity of roxatidine and its analogues to stimulate mucin synthesis is not related to their histamine H2 receptor antagonistic activity. Roxatidine‐induced activation of mucin biosynthesis in the corpus tissue is mediated by nitric oxide.

British Journal of Pharmacology (1997) 122, 1230–1236; doi:10.1038/sj.bjp.0701488
Effects of dexamethasone and phorbol ester on P2 receptor‐coupled Ca2+ signalling and lipocortin 1 presentation in U937 cells
Authors: Willmott Nicholas J. , Choudhury Qam , Flowers Roderick J. 
Published: January 2005

Cell surface bound lipocortin 1 (LC1) is a putative mediator of the antiproliferative and anti‐inflammatory effects of glucocorticoids. This study assessed the hypothesis that the glucocorticoid, dexamethasone‐phosphate (dex‐p), might exert the above effects via an LC1‐mediated downregulation of receptor‐coupled Ca2+ signalling, using P2‐receptor mediated intracellular Ca2+ accumulation in U937 cells as an appropriate model.
Addition of ATP (1–100 μM) to cells resulted in a transient increase in cytosolic Ca2+ ([Ca2+]i). Prior treatment of cells with dex‐p (3–24 h) increased the magnitude of this Ca2+ transient at high, but not low concentrations of ATP, and increased thapsigargin (Tg)‐induced Ca2+ influx, indicating that store‐operated Ca2+ influx was potentiated in these cells. For cells treated with dex‐p for 24 h, cell surface levels of LC1 were significantly reduced by 63%.
Differentiation of cells with 1 nM phorbol ester (PMA) for 24 h resulted in a 2.4 fold increase in the cell surface level of LC1 and inhibition of the ATP‐induced Ca2+ response. However, the Tg‐induced Ca2+ response was unaffected by long‐term PMA treatment, and incubating cells with LC1 did not alter Tg‐induced Ca2+ mobilization and influx, or the ATP‐mediated Ca2+ response.
Data from this study suggest that: (1) dex‐p does not inhibit P2‐receptor‐coupled Ca2+ signalling in this cell line, (2) the observed modulation of the ATP‐induced increase in [Ca2+]i by dex‐p and PMA, and store‐operated Ca2+ influx by dex‐p, is not linked to an increase in the cell surface level of LC1, and (3) differentiation of U937 cells with PMA downregulates the ATP‐induced Ca2+ response, but does not affect the thapsigargin‐sensitive Ca2+ pool or store‐operated Ca2+ influx of these cells.

British Journal of Pharmacology (1997) 122, 1055–1060; doi:10.1038/sj.bjp.0701490
Nitrergic modulation of cholinergic responses in the opossum lower oesophageal sphincter
Authors: Cellek Selim , Moncada Salvador 
Published: January 2005

Electrical field stimulation (EFS) of the superfused lower oesophageal sphincter from opossum (Monodelphis domestica) elicited biphasic responses. The first phase (relaxation) was strictly dependent on the duration of the EFS. The second phase (contraction) started following termination of the EFS (15 Hz). EFS at frequencies above 15 Hz led only to contraction, which started immediately upon initiation of the stimulation.
In the presence of NG‐nitro‐L‐arginine (L‐NOARG; 0.1–300 μM), the relaxation phase was abolished and the contractile response started with the initiation of EFS (at all frequencies) and was greater in magnitude. The contractile response to EFS was completely blocked with scopolamine (10 μM).
Exogenous acetylcholine (1–100 μM) elicited concentration‐dependent contractions of the sphincter in the presence of botulinum toxin. These contractions were abolished when EFS was applied during administration of acetylcholine. This inhibitory effect of EFS was completely reversed when the tissue was treated with L‐NOARG (100 μM).
These results suggest that the cholinergic response in the opossum lower oesophageal sphincter is under nitrergic control.

British Journal of Pharmacology (1997) 122, 1043–1046; doi:10.1038/sj.bjp.0701497
Intravascular and interstitial degradation of bradykinin in isolated perfused rat heart
Authors: Dendorfer Andreas , Wolfrum Sebastian , Wellhöner Peter , Korsman Katja , Dominiak Peter 
Published: January 2005

Bradykinin (BK) has been shown to exert cardioprotective effects which are potentiated by inhibitors of angiotensin I‐converting enzyme (ACE). In order to clarify the significance of ACE within the whole spectrum of myocardial kininases we investigated BK degradation in the isolated rat heart.
Tritiated BK (3H‐BK) or unlabelled BK was either repeatedly perfused through the heart, or applied as an intracoronary bolus allowing determination of its elution kinetics. BK metabolites were analysed by HPLC. Kininases were identified by ramiprilat, phosphoramidon, diprotin A and 2‐mercaptoethanol or apstatin as specific inhibitors of ACE, neutral endopeptidase 24.11 (NEP), dipeptidylaminopeptidase IV and aminopeptidase P (APP), respectively.
In sequential perfusion passages, 3H‐BK concentrations in the perfusate decreased by 39% during each passage. Ramiprilat reduced the rate of 3H‐BK breakdown by 54% and nearly abolished [1‐5]‐BK generation. The ramiprilat‐resistant kininase activity was for the most part inhibited by the selective APP inhibitor apstatin (IC50 0.9 μM). BK cleavage by APP yielded the intermediate product [2‐9]‐BK, which was rapidly metabolized to [4‐9]‐BK by dipeptidylaminopeptidase IV.
After bolus injection of 3H‐BK, 10% of the applied radioactivity were protractedly eluted, indicating the distribution of this fraction into the myocardial interstitium. In samples of such interstitial perfusate fractions, 3H‐BK was extensively (by 92%) degraded, essentially by ACE and APP. The ramiprilat‐ and mercaptoethanol‐resistant fraction of interstitial kininase activity amounted to 14%, about half of which could be attributed to NEP. Only the product of NEP, [1–7]‐BK, was continuously generated during the presence of 3H‐BK in the interstitium.
ACE and APP are located at the endothelium and represent the predominant kininases of rat myocardium. Both enzymes form a metabolic barrier for the extravasated fraction of BK. Thus, only interstitial, but not intravascular concentrations of BK are increased by kininase inhibitors to the extent that a significant potentiation of BK effects could be explained. NEP contributes less than 5% to the total kininase activity, but is the only enzyme which is exclusively present in the interstitial space.

British Journal of Pharmacology (1997) 122, 1179–1187; doi:10.1038/sj.bjp.0701501