bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pharmacology of a non‐selective ETA and ETB receptor antagonist, TAK‐044 and the inhibition of myocardial infarct size in rats
Authors: Watanabe Toshifumi , Awane Yumiko , Ikeda Shota , Fujiwara Shuji , Kubo Kazuki , Kikuchi Takashi , Kusumoto Keiji , Wakimasu Mitsuhiro , Fujino Masahiko 
Published: July 2012

The aims of the present study were to characterize the pharmacological profile of a new endothelin (ET) receptor antagonist, TAK‐044 and to consider whether it limits the extension of myocardial infarct size in rats.
Binding of [125I]‐ET‐1 to ET receptors on rabbit ventricular and cerebellar membrane fractions was inhibited by TAK‐044 with IC50 values of 3.8 nm and 130 nm, respectively.
It inhibited ET‐1, ET‐2 and ET‐3‐induced vasoconstriction of porcine isolated coronary arteries in a competitive (ET‐1, ET‐2) and a non‐competitive (ET‐3) manner.
In the rat in vivo, the ET‐1‐induced blood pressure changes including transient hypotension followed by sustained hypertension, were inhibited by TAK‐044 (0.1–10 mg kg−1, i.v.) in a dose‐dependent manner.
Acute myocardial infarction induced by 1 h coronary occlusion followed by 24 h reperfusion in rats caused an infarct size of 60 ± 2% (n = 12) of the area‐at‐risk by weight.
Intravenous injection of TAK‐044 10 min before coronary occlusion reduced the infarct size in a dose‐dependent manner: 32% and 54% reductions at 1 and 3 mg kg−1, respectively.
TAK‐044 administered 10 min before or 1 h after reperfusion (1 mg kg−1, i.v.) showed similar inhibitory effects: 34% and 23% reductions, respectively.
We conclude that TAK‐044 is an ETA/ETB receptor antagonist which shows strong inhibitory effects on the extension of myocardial infarct size after coronary artery occlusion‐reperfusion in rats.
The effect of morphine on formalin‐evoked behaviour and spinal release of excitatory amino acids and prostaglandin E2 using microdialysis in conscious rats
Authors: Malmberg Annika B. , Yaksh Tony L. 
Published: July 2012

In the present study, the object was to examine the effects of morphine on spinal release in vivo of excitatory amino acids (EAA), prostaglandin E2 (PGE2), and a marker for nitric oxide (NO) synthesis, citrulline (Cit), evoked by a protracted noxious stimulus produced by the injection of formalin into the paw. Spinal release was monitored in conscious rats using a microdialysis probe implanted into the subarachnoid space with the active site placed at the level of the lumbar enlargement. In split dialysate samples, EAAs were measured by high performance liquid chromatography (h.p.l.c.) and PGE2 was determined by radioimmunoassay.
Resting concentrations in nmol ml−1 for the amino acids (mean ± s.e.mean, n = 21) were: 4.8 ± 0.4 for glutamate (Glu), 0.8 ± 0.1 for aspartate (Asp), 8.8 ± 0.8 for taurine (Tau), 24 ± 3 for glycine (Gly), 19 ± 3 for serine (Ser), 5.2 ± 0.8 for asparagine (Asn), 64 ± 4 for glutamine (Gln) and 5.2 ± 0.4 for Cit. Mean basal release for PGE2 was 12 ± 1 pmol ml−1.
Subcutaneous (s.c.) injection of 5% formalin evoked a biphasic flinching behaviour (phase 1: 0–9 min and phase 2: 10–60 min) of the injected paw. Corresponding to phase 1 behaviour, there was a significant increase (50–100%) in spinal levels of Glu, Asp, Tau, Gly, Cit and PGE2, but not Ser, Asn and Gln. A significant (P<0.01) second phase increase in release was observed only for Cit and PGE2. However, Glu and Asp levels were increased by approximately 45%.
Injection of morphine sulphate (3 mg kg−1, s.c.) had no effect on resting release, but produced a significant suppression of the formalin‐evoked behaviour and release of Glu, Asp, Tau, Gly, Cit and PGE2. The effect of morphine was reversed by pretreatment with 1 mg kg−1 naloxone. Naloxone by itself did not change the release or behaviour of the formalin test.
This study demonstrates that both spinal EAA and PGE2 release patterns correlate with behavioural nociceptive responses in the formalin test and that morphine suppresses the formalin‐evoked behaviours and spinal release. The reversal by naloxone of the morphine effect indicates mediation via an opioid receptor.
Copper chelation‐induced reduction of the biological activity of S‐nitrosothiols
Authors: Gordge M.P. , Meyer D.J. , Hothersall J. , Neild G.H. , Payne N.N. , Noronha‐Dutra A. 
Published: July 2012

The effect of copper on the activity of the S‐nitrosothiol compounds S‐nitrosocysteine (cysNO) and S‐nitrosoglutathione (GSNO) was investigated, using the specific copper chelator bathocuproine sul‐phonate (BCS), and human washed platelets as target cells.
Chelation of trace copper with BCS (10 μm) in washed platelet suspensions reduced the inhibition of thrombin‐induced platelet aggregation by GSNO; however, BCS had no significant effect on the anti‐aggregatory action of cysNO. BCS inhibited cyclic GMP generation in response to both cysNO and GSNO.
The effect of BCS was rapid (within 30 s), and could be abolished by increasing the platelet concentration to 500 times 109 1−1.
In BCS‐treated platelet suspensions, the addition of Cu2+ ions (0.37–2.37 μm) led to a restoration of both guanylate cyclase activation and platelet aggregation inhibition by GSNO.
The anti‐aggregatory activity of GSNO was reduced in a concentration‐dependent manner by the copper (I)‐specific chelators BCS and neocuproine, and to a smaller extent by desferal. No effect was observed with the copper (II) specific chelator, cuprizone, the iron‐specific chelator, bathophenanthroline sulphonate, or the broader‐specificity copper chelator, d‐penicillamine.
In both BCS‐treated and ‐untreated platelet suspensions, cys NO was more potent than GSNO as a stimulator of guanylate cyclase. In BCS‐treated platelet suspensions there was no significant difference between the anti‐aggregatory potency of cysNO and GSNO; however, in untreated suspensions, GSNO was significantly more potent than cysNO. Thus, when copper was available, GSNO produced a greater inhibition of aggregation than cysNO, despite being a less potent activator of guanylate cyclase.
The breakdown of cysNO and GSNO was measured spectrophotometrically by decrease in absor‐bance at 334 nm. In Tyrode buffer, cysNO (10 μm) broke down at a rate of 3.3 μm min−1. BCS (10 μm) reduced this to 0.5 μm min−1. GSNO, however, was stable, showing no fall in absorbance over a period of 7 min even in the absence of BCS.
We conclude that copper is required for the activity of both cysNO and GSNO, although its influence on anti‐aggregatory activity is only evident with GSNO. The stimulatory effect of copper is unlikely to be explained solely by catalysis of S‐nitrosothiol breakdown. The enhancement by copper of th anti‐aggregatory activity of GSNO, relative to cysNO, suggests that copper may be required for biological activity of GSNO which is independent of guanylate cyclase stimulation.
Differential effects of OPC‐18790, amrinone and dobutamine on cardiac function and energy metabolism in the guinea‐pig isolated ischaemic heart
Authors: Itoh Shuji , Mori Toyoki , Tominaga Michiaki , Ishikawa Makoto , Koga Keiko , Yabuuchi Youichi 
Published: July 2012

The effects of OPC‐18790, a novel positive inotropic agent, on cardiac function and myocardial energy metabolism in the guinea‐pig isolated heart with ischaemia were studied by 31P‐magnetic resonance spectroscopy (MRS) and compared with those of amrinone and dobutamine.
Cardiac ischaemia was induced by intracoronary infusion of 15 μm microspheres to reduce coronary perfusion flow (CPF) by 50%. Microsphere embolisation caused a 40% decrease in left ventricular systolic pressure (LVSP), cardiac contractility measured by peak of ventricular pressure development (LVdP/dt) and slightly reduced heart rate. There was also a decrease in ATP and creatine phosphate (PCr) by 20%, an increase in inorganic phosphate (Pi) by 25% and an acidic shift of intracellular pH in the ischaemic heart.
In the ischaemic heart, OPC‐18790, amrinone and dobutamine were applied at concentrations which increased LVdP/dt by about 60%. These compounds increased LVP by 15% to 30% and increased CPF by about 10%. Amrinone and dobutamine but not OPC‐18790 increased heart rate. When these drugs produced the haemodynamic changes described above, amrinone and dobutamine reduced ATP and PCr, increased Pi and produced further intracellular acidosis, whereas, OPC‐18790 did not change these parameters.
Cardiac pacing at 285 beats min−1 produced decreases in LVP, LVdP/dt and CPF by about 30%, 20%, 5%, respectively and an increase in Pi, decreases in PCr and ATP, and intracellular acidosis.
These results suggest that degradation of high energy phosphate compounds closely relates to increase in heart rate in the ischaemic heart. Positive inotropic agents without chronotropic action seem to be beneficial in support of the ischaemic heart.
Characterization of [3H]‐imidazenil binding to rat brain membranes
Authors: Lipartiti Maria , Arban Roberto , Fadda Emanuela , Zanotti Adriano , Giusti Pietro 
Published: July 2012

1 The binding of [3H]‐imidazenil, an imidazobenzodiazepine carboxamide, to rat cerebellar membranes was characterized at different temperatures.2 Specific binding was linear with tissue concentrations and reached maximum after 90, 30 and 5 min incubation at 0, 21 and 37°, respectively. The binding was of high affinity, specific and saturable; non linear regression and Scatchard analysis of the data was compatible with the presence of a single population of receptor sites with Bmax of 0.74 ± 0.020, 0.90 ± 0.011 and 1.0 ± 0.036 pmol mg−1 protein at 0, 21 and 27°, respectively. Binding affinity decreased with increasing temperature: Kd were 0.29 ± 0.051 nM (0°), 1.0 ± 0.080 nM (21°) and 2.4 ± 0.38 nM (37°).3 At all tested temperatures, [3H]‐imidazenil binding was reversible and the Kd calculated from the dissociation and association rate constants approximated the equilibrium Kd.4 In the presence of γ‐aminobutyric acid (GABA), Kd increased 4 fold at 0°, whereas Bmax increased, albeit slightly, at all temperatures.5 Benzodiazepines (BZDs), imidazopyridines and methyl‐β‐carboline‐3‐carboxylate (βCCM) were effective inhibitors of [3H]‐imidazenil binding. Conversely, GABAA antagonists, barbiturates, picrotoxin and peripheral BZD receptor ligands were devoid of any activity.6 Comparing [3H]‐imidazenil to [3H]‐flumazenil binding in various brain areas, similar densities of recognition sites as well as like regional differences in the distribution of binding sites for both radioligands were observed (cortex=striatum>cerebellum>spinal cord).7 The present results indicate that [3H]‐imidazenil specifically binds to the BZD sites of GABAA receptors. Furthermore, the effects of GABA and temperature differentiate imidazenil from classical BZDs. It is suggested that the characteristics of imidazenil binding may be relevant to the in vivo pharmacology of the drug.
Participation of NMDA and non‐NMDA excitatory amino acid receptors in the mediation of spinal reflex potentials in rats: an in vivo study
Authors: Farkas S. , Ono H. 
Published: July 2012

1 The effect of various intravenously administered excitatory amino acid (EAA) antagonists on the dorsal root stimulation‐evoked, short latency (up to 10 ms) spinal root reflex potentials of chloralose‐urethane anaesthetized C1 spinal rats was studied, in order to gain information on the involvement of non‐NMDA (AMPA/kainate; AMPA = α‐amino‐3‐hydroxy‐5‐methyl‐isoxazole‐4‐propionate) and NMDA (N‐methyl‐d‐aspartate) receptors in their mediation. The competitive non‐NMDA antagonist, 2,3‐dihydroxy‐6‐nitro‐7‐sulphamoyl‐benzo(F)quinoxaline (NBQX; 1–32 mg kg−1), the non‐competitive non‐NMDA antagonist, 1‐(amino)phenyl‐4‐methyl‐7,8‐methylendioxy‐5H‐2,3‐benzodiazepine (GYKI 52466; 0.5–8 mg kg−1), the competitive NMDA antagonist 3‐((±)‐2‐carboxypiperazin‐4‐yl)‐propyl‐1‐phosphonic acid (CPP, 2‐8mg kg−1) and two non‐competitive NMDA antagonists: MK‐801 (0.5–2 mg kg−1) and ketamine (2–32 mg kg−1) were used as pharmacological tools.2 Validating the applied pharmacological tools regarding selectivity at the applied doses, their effects were tested on direct (electrical) as well as on synaptic excitability of motoneurones evoked by intraspinal stimulation. Furthermore, their effect was investigated on the responses elicited by microion‐tophoretic application of EAA agonists (AMPA, kainate and NMDA) into the motoneurone pool, where the extracellular field potential evoked by antidromic stimulation of the ventral root was recorded to detect the effects of EAA agonists.3 NBQX and GYKI 52466 were able to abolish completely the mono‐, di‐ and polysynaptic ventral root reflexes (MSR, DSR, PSR) and the synaptic excitability of motoneurones, while hardly influencing direct excitability of motoneurones. They markedly attenuated AMPA and kainate responses whilst having little or no effect on NMDA responses.4 Apparently ‘supramaximal’ doses of CPP and MK‐801 slightly inhibited MSR (by about 10%) moderately reduced DSR and PSR (by about 20–30%) and did not influence excitability of motoneurones. They selectively blocked responses to NMDA.5 Ketamine dose‐dependently inhibited MSR, DSR and PSR. Nevertheless, diminution of none of the responses exceeded 50%. It reduced both direct and synaptic excitability of motoneurones, thus displaying a local anaesthetic‐like effect, which may contribute to its reflex inhibitory action. It depressed responses to NMDA whilst having negligible effects on responses to AMPA and kainate.6 We conclude that non‐NMDA receptors play a substantial role in the mediation of MSR, DSR and PSR, while NMDA receptors contribute little to this. Neither MSR nor PSR is mediated exclusively by non‐NMDA or NMDA receptors, respectively.7 The drugs investigated in this study, with the exception of ketamine, proved to be useful tools for elucidation of the involvement of EAA receptors in various processes in vivo
Acute withdrawal after bremazocine and the interaction between μ‐ and κ‐opioid receptors in isolated gut tissues
Authors: Valeri P. , Morrone L.A. , Romanelli L. , Amico M.C. 
Published: July 2012

1 This study was undertaken to investigate whether, after a brief exposure of guinea‐pig isolated ileum and rabbit jejunum to bremazocine, a κ‐opioid agonist also possessing antagonist activity at μ‐opioid receptors, the addition of opioid antagonists produced withdrawal contractures. Our aim was to verify in these tissues the existence of an interaction between the μ‐ and κ‐opioid systems.2 In guinea‐pig ileum preparations previously exposed for 5 min to bremazocine at 5.7 times 10−7 m and 5.7 times 10−8 m, naloxone (5 times 10−7 m) elicited no response whereas in tissues exposed to a lower bremazocine concentration (5.7 times 10−9 m), naloxone (5 times 10−7 m) and the selective κ‐opioid antagonist, nor‐binaltorphimine (3.4 times 10−8 m) both produced a strong contracture.3 Bremazocine (5.7 times 10−7 m) administered to guinea‐pig isolated ileum, previously exposed for 5 min to morphine (10−7 m), induced a withdrawal contracture. In contrast, lower bremazocine concentrations (1.4 and 7.1 times 10−8 m) did not elicit a withdrawal contracture.4 Naloxone (5 times 10−7 m), added to the bath after a 5 min exposure of guinea‐pig ileum to morphine (10−7 m), elicited the characteristic withdrawal contracture. Bremazocine (1.4–7.1 times 10−8 m) added 1 min before naloxone (5 times 10−7 m) inhibited the naloxone withdrawal contracture in a dose‐related way whereas naloxone 5 times 10−8 m added 1 min before naloxone 5 times 10−7m, did not affect the withdrawal response.5 In the rabbit jejunum, bremazocine (1.4–7.1 times 10−8 m) caused a decrease in amplitude in the spontaneous tissue activity. In tissues exposed to these bremazocine concentrations, naloxone (5 times 10−7 m) elicited a marked contracture. A similar contracture occurred when nor‐binaltorphimine (3.4 times 10−8 m) was added in place of naloxone. These effects were dose‐related to the bremazocine concentration. The specific κ‐agonist, U‐50,488H (5 times 10−8 m), elicited the same effects as bremazocine.6 These findings show that stimulation of κ‐opioid receptors induces a state of dependence that is not prevented by blocking the μ‐opioid system. The observation that low bremazocine concentrations inhibit the morphine‐induced withdrawal contractures, indicates an interaction between the μ‐ and κ‐opioid system in guinea‐pig isolated ileum, similar to that observed in the whole animal.
An electrophysiological investigation of the properties of a murine recombinant 5‐HT3 receptor stably expressed in HEK 293 cells
Authors: Gill Catherine H. , Peters John A. , Lambert Jeremy J. 
Published: July 2012

1 The pharmacological and biophysical properties of a recombinant 5‐HT3 receptor have been studied by use of patch‐clamp techniques applied to HEK 293 cells stably transfected with the murine 5‐HT3 R‐A cDNA.2 At a holding potential of −60 mV, 77% of cells investigated responded to ionophoretically applied 5‐HT with an inward current. Such currents were unaffected by methysergide (1 μm), or ketanserin (1 μm), but were antagonized in a concentration‐dependent and reversible manner by the selective 5‐HT3 receptor antagonist, ondansetron (IC50 = 440 pm) and the non‐selective antagonists (+)‐tubocurarine (IC50 = 1.8 nm) and metoclopramide (IC50 50 nm).3 The 5‐HT‐induced current reversed in sign (E5‐HT) at approximately – 2 mV and exhibited inward rectification. The influence of extra‐ and intracellular ion substitutions upon E5‐HT indicates the 5‐HT‐evoked current to be mainly mediated by a mixed monovalent cation conductance.4 Calcium and magnesium (0.1–10 nm) produced a concentration‐dependent, voltage‐independent, inhibition of the 5‐HT‐induced response. Zinc (0.3–300 μm) exerted a biphasic effect with low concentrations enhancing, and high concentrations depressing, the 5‐HT‐evoked current.5 Fluctuation analysis of inward currents evoked by a low (1 μm) concentration of 5‐HT suggests the current to be mediated by the opening of channels with a conductance of 420 fS.6 The pharmacological and biophysical properties of the 5‐HT3 R‐A are similar to those previously described for 5‐HT3 receptors native to murine neuroblastoma cell lines, with the exception that the function of the recombinant receptor was enhanced by low concentrations of zinc. This observation suggests that the properties of the native receptor are not completely represented by the 5‐HT3 R‐A subunit alone.
Potentiation by endothelin‐1 of 5‐hydroxytryptamine responses in aortae from streptozotocin‐diabetic rats: a role for thromboxane A2
Authors: James Gail M. , Hodgson Wayne C. 
Published: July 2012

1 We have previously reported maximum responses to 5‐hydroxytryptamine (5‐HT) are diminished in endothelium‐intact and ‐denuded aortae from rats with streptozotocin‐induced diabetes of 2‐weeks duration.2 In the present study, the thromboxane A2/prostaglandin H2 (TP) receptor antagonist GR32191B (1 μm) significantly reduced maximum responses to 5‐HT in endothelium‐intact aortae from both control and diabetic rats. In the presence of GR32191B, maximum responses to 5‐HT, in endothelium‐intact aortae from diabetic rats, were still significantly reduced compared to those obtained in aortae from controls.3 GR32191B (1 μm) had no significant effect on maximum responses to 5‐HT in endothelium‐denuded aortae from either control or diabetic rats.4 Interaction between 5‐HT (0.1 μm‐0.1 mm) and threshold concentrations of endothelin‐1 (ET‐1) or the thromboxane (Tx)A2‐mimetic, U46619, were examined in endothelium‐intact and ‐denuded aortae from control and 2‐week streptozotocin‐diabetic rats.5 Maximum responses to 5‐HT in the presence of a threshold concentration of ET‐1 (3 nm), in endothelium‐intact aortae from diabetic rats, were not significantly different from those of control rats.6 Maximum responses to 5‐HT in the combined presence of ET‐1 (3 nm) and GR32191B (1 μm), in endothelium‐intact aortae from diabetic rats, were significantly reduced compared to those obtained in aortae from controls.7 Maximum responses to 5‐HT in the presence of ET‐1 (3 nm) in endothelium‐denuded aortae from diabetic rats were significantly reduced compared to those from controls.8 Maximum responses to 5‐HT in the presence of a threshold concentration of U46619 (20 or 30 nm), in endothelium‐intact aortae from diabetic rats, were not significantly different from responses of controls.9 Maximum responses to 5‐HT in the presence of a threshold (5–20 nm) concentration of U46619, in endothelium‐denuded aortae from diabetic rats, were not significantly different from responses of controls.10 The results of the present study indicate that endothelial‐derived TxA2 contributes to the contractile response to 5‐HT in aortae from control and diabetic rats. Endothelial‐derived TxA2 also appears to play a role in the potentiation of 5‐HT responses by ET‐1 in aortae from diabetic rats.
Enhancement of cyclic AMP accumulation mediated by 5‐HT after chronic amitriptyline treatment in NG 108‐15 cells
Authors: Shimizu Masami , Nishida Akira , Fukuda Hiroyuki , Saito Hiroshi , Yamawaki Shigeto 
Published: July 2012

1 The effects of chronic in vitro administration of amitriptyline, a tricyclic antidepressant, on 5‐hydroxytryptamine (5‐HT) receptor‐mediated adenylyl cyclase activity was studied in the neuroblastoma x glioma hybrid cell line, NG 108‐15.2 Treatment of NG 108–15 cells with 8 μm amitriptyline for 3 days increased forskolin‐stimulated (0.1 μm) adenosine 3′:5′‐cyclic monophosphate (cyclic AMP) accumulation. Addition of 5‐HT (0.1–100 μm) increased forskolin‐stimulated cyclic AMP accumulation in amitriptyline‐treated cells in a concentration‐dependent manner. However, 5‐HT did not affect forskolin‐stimulated cyclic AMP accumulation in untreated cells.3 The 5‐HT4 receptor agonist, 5‐methoxytryptamine, significantly enhanced forskolin‐stimulated cyclic AMP accumulation in amitriptyline‐treated cells. In contrast, amitriptyline treatment failed to modify 8‐hydroxy‐2‐(di‐n‐propylamine) tetralin‐induced inhibition of forskolin‐stimulated cyclic AMP accumulation.4 Pretreatment of cells with pertussis toxin did not affect the 5‐HT‐induced enhancement of cyclic AMP accumulation.5 The 5‐HT‐induced enhancement of cyclic AMP accumulation in amitriptyline‐treated cells was attenuated by the 5‐HT4 receptor antagonists, GR 113808 and ICS 205–930, with relatively low potency. However, spiperone, SCH 23390, and pindolol were completely ineffective against this 5‐HT‐induced enhancement.6 Chronic treatment with amitriptyline did not modify the cyclic AMP production stimulated by prostaglandin E1 or cholera toxin. This treatment also had no effect on GTPγS‐, NaF‐, and Mn2+‐stimulated cyclic AMP accumulation in isolated cell membranes.7 Chronic treatment with the 5‐HT receptor antagonists, pindolol or ICS 205–930, did not inhibit the 5‐HT‐induced enhancement of cyclic AMP accumulation.8 Chronic treatment with other antidepressant drugs, imipramine, mianserin or paroxetine, elicited the 5‐HT‐induced enhancement of cyclic AMP accumulation.9 Taken together, these results suggest that chronic amitriptyline treatment of NG 108–15 cells causes 5‐HT to enhance forskolin‐stimulated cyclic AMP accumulation by enhancing 5‐HT receptor‐mediated stimulation of adenylyl cyclase and not by reducing 5‐HT‐mediated inhibition of adenylyl cyclase. The 5‐HT‐induced enhancement of cyclic AMP accumulation in amitriptyline‐treated cells may result from changes at the level of the 5‐HT receptor rather than at the level of Gs proteins or adenylyl cyclase. It is unlikely that this enhancement of cyclic AMP accumulation is caused by long‐term antagonism of the 5‐HT receptor by amitriptyline.