bluuebunny/crossref_metadata_2025_split huggingface dataset:
RS 39604: a potent, selective and orally active 5‐HT4 receptor antagonist
Authors: Hegde S.S. , Bonhaus D.W. , Johnson L.G. , Leung E. , Clark R.D. , Eglen R.M. 
Published: July 2012

Selective antagonism of 5‐HT4 receptors may provide therapeutic benefit in certain disorders of the myocardium, alimentary and lower urinary tract. We now report on RS 39604, a novel and selective 5‐HT4 receptor antagonist and compare its pharmacological properties with those of SB 204070.
In guinea‐pig striatal membranes, both RS 39604 and SB 204070 inhibited specific binding of [3H]‐GR 113808 in a concentration‐dependent manner yielding p Ki estimates of 9.1 and 10.9, respectively. RS 39604 displayed a low affinity (pKi <6.5) for 5‐HT1A, 5‐HT2C, 5‐HT3, α1c, D1? D2, M1 M2, AT1 B1 and opioid u receptors and moderate affinity for σ1 (pK1 = 6.8) and σ2 (pK1 = 7.8) sites.
In the rat isolated oesophagus, precontracted with carbachol, RS 39604 (30–300 nM) behaved as a competitive antagonist towards 5‐HT‐induced relaxation (pA2 = 9.3; Schild slope =1.0). We and others have shown previously that SB 204070 behaves as an unsurmountable antagonist in this preparation (pA2‐10.5). In the guinea‐pig isolated ileal mucosa, RS 39604 (30 nM) antagonized 5‐MeOT‐induced increase in short‐circuit current (pA2 = 9.1).
In anaesthetized vagotomized micropigs, RS 39604, administered by the i.v. or intraduodenal (i.duod.) route, produced dose‐dependent inhibition of 5‐HT‐induced tachycardia (ID50 = 4.7 μg kg−1, i.v. and 254.5 ug kg−1, i.duod). At maximal doses of 30 μg kg−1, i.v. and 6 mg kg−1, i.duod., the inhibitory effects of RS 39604 lasted for more than 6 h. In this preparation, SB 204070 was as potent as RS 39604 by the i.v. route but was inactive by the intraduodenal route at doses up to 3 mg kg−1.
In conscious mice, RS 39604, administered by the i.p. or p.o. route, produced dose‐dependent inhibition of 5‐hydroxytryptophan (5‐HTP)‐induced diarrhoea (ID50 = 81.3 ug kg−1, i.p. and 1.1 mg kg−1, p.o.). In this assay, SB 204070 was inactive by the oral route at doses up to 30 mg kg−1.
In anaesthetized guinea‐pigs, RS 39604 antagonized the contractile effect of 5‐HT in the proximal colon by producing parallel, dextral displacement of the dose‐response curve to 5‐HT. The mean dose‐ratios to 5‐HT at 0.1 mg kg−1, i.v., 1 mg kg−1, i.v. and 10 mg kg−1, i.duod. were 4.6, 30.7 and 10.8, respectively. SB 204070 behaved as an unsurmountable antagonist in this assay.
In a model of visceral pain in conscious rats, RS 39604 (0.01‐1 mg kg−1, i.v.) did not affect colorectal distension‐induced increases in arterial pressure whereas morphine (1 mg kg−1, i.v.) produced significant inhibition of the response, implying that 5‐HT4 receptors are not involved in nociception in this model.
The data suggest that RS 39604 is a high affinity and selective 5‐HT4 receptor antagonist that is orally active and long‐lasting in vivo. It is concluded that RS 39604 may be the preferable probe to use for investigating the physiological and pathophysiological role of 5‐HT4 receptors in vivo.
Blockade by sigma site ligands of N‐methyl‐D‐aspartate‐evoked responses in rat and mouse cultured hippocampal pyramidal neurones
Authors: Fletcher Elizabeth J. , Church John , Abdel‐Hamid Khaled , MacDonald John F. 
Published: July 2012

The effects of a range of structurally‐dissimilar compounds which possess affinity for σ binding sites were examined on the responses of cultured hippocampal pyramidal neurones to the excitatory amino acid analogues N‐methyl‐D‐aspartate (NMDA), kainate and (RS)‐α‐ammo‐3‐hydroxy‐5‐methylisoxazole‐4‐propionic acid (AMPA).
In mouse hippocampal neurones under whole‐cell voltage‐clamp, the compounds tested reversibly attenuated NMDA‐, but not kainate‐ or AMPA‐, evoked currents with a rank order potency (IC50 values in μm): ifenprodil (0.8)>(+)‐N‐allylnormetazocine (1.1)>dextromethorphan (1.8) = haloperidol (1.9)>(+)‐pentazocine (7.2)>1S, 2R‐(−)−cis‐N‐methyl‐N‐[2‐(3, 4‐dichlorophenyl) ethyl]‐2‐(1‐pyrrolidinyl)cyclohexylamine (17) = rimcazole (18)>1,3‐di(2‐tolyl)guanidine (37)>opipramol (96)>caramiphen (110)=carbetapentane (112)> >(+)‐3‐(3‐hydroxyphenyl)‐N‐(1‐propyl)piperidine (485).
The attenuation of NMDA‐evoked responses was not mediated through interactions with the agonist, glycine (except haloperidol) or polyamine (except ifenprodil) binding sites on the NMDA receptor‐channel complex but, in the light of the voltage‐ and, in some cases, use‐dependent nature of their antagonism, an interaction with the ion channel appears to be a likely mechanism of action for many of the compounds.
Micromolar concentrations of selected σ site ligands also reduced NMDA‐evoked rises in intracellular free calcium concentration in Fura‐2‐loaded cultured hippocampal neurones of the rat with the same rank order potency as observed in the electrophysiological studies.
The data indicate that, at micromolar concentrations, the σ site ligands tested act as NMDA receptor antagonists, an action which does not appear to be mediated by high‐affinity σ binding site(s). The functional effects of micromolar concentrations of σ site ligands cannot, therefore, be attributed exclusively to interactions with high‐affinity σ binding sites.
Characterization of metabotropic glutamate receptor‐stimulated phosphoinositide hydrolysis in rat cultured cerebellar granule cells
Authors: Toms N.J. , Jane D.E. , Tse H‐W. , Roberts P.J. 
Published: July 2012

The pharmacology of excitatory amino acid (EAA)‐stimulated phosphoinositide (PI) hydrolysis, monitored via [3H]‐inositol monophosphate accumulation, was investigated in primary cultures of rat cerebellar granule cells.
EAA‐stimulated PI hydrolysis peaked after 4–5 days in vitro and subsequently declined.
The agonist order of potency was found to be (EC50): L‐quisqualic acid (Quis) (2 μm)»L‐glutamate (50 μm)>(1S,3R)‐11‐aminocyclopentane‐1,3‐dicarboxylic acid ((1S,3R)‐ACPD) (102 μm). L‐Glutamate (Emax = 873% of basal activity) elicited the largest stimulation of PI hydrolysis, whereas Quis (Emax = 603%) and (1S,3R)‐ACPD (Emax = 306%) produced somewhat lower stimulations.
Several phenylglycine derivatives were found to be active in inhibiting 2 μm Quis‐stimulated PI hydrolysis, in order of potency (IC50): (S)‐4‐carboxy‐3‐hydroxyphenylglycine (41 μm) ≤ (S)‐4‐carboxyphenylglycine (51 μm)»(+)‐α‐methyl‐4‐carboxyphenylglycine (243 μm).
Cultured cerebellar granule cells of the rat appear to have Group I mGluR pharmacology similar to that reported for cloned mGluRl and provide an ideal system for investigating novel mGluRl ligands in a native environment.
Enhancement of the haemodynamic effects of NG‐monomethyl‐l‐arginine by transforming growth factor‐β1 in conscious, normal, but not endotoxaemic, rats
Authors: Gardiner S.M. , Kemp P.A. , March J.E. , Bennett T. 
Published: July 2012

Male, Long Evans rats (350–450 g) were chronically instrumented for the measurement of regional haemodynamics, and the effects of TGF‐β1 (25 μg kg−1 i.v. bolus) were assessed during infusion of saline (n=9) or lipopolysaccharide (LPS, 150 μg kg−1 h−1; n= 12). In the same animals, responses to NG‐monomethyl‐l‐arginine (l‐NMMA 10 mg kg−1 bolus; 10 mg kg−1 h−1 infusion) were determined 18 h after administration of TGF‐β1. In a separate experiment, the effects of the endothelin antagonist, SB 209670 (10 μg kg−1 min−1) on responses to TGF‐β1 and to l‐NMMA subsequently, were determined.
In the absence of LPS, TGF‐β1 had slow‐onset bradycardic and pressor effects accompanied by mesenteric and hindquarters, but not renal, vasoconstriction. Eighteen hours after TGF‐β1, these effects had gone, but the bradycardic, pressor, and mesenteric vasoconstrictor responses to l‐NMMA were enhanced. The haemodynamic changes following TGF‐β1 and the augmentation of the subsequent responses to l‐NMMA, were inhibited by SB 209670. These results are consistent with TGF‐β1 stimulating the synthesis and release of endothelin, and an involvement of the latter in responses to l‐NMMA.
The pressor effects of TGF‐β1 were similar in LPS‐infused and saline‐infused animals, but in the former group the mesenteric vasoconstriction was enhanced and the hindquarters vasoconstriction diminished. Since, in the absence of TGF‐β1, LPS‐infused animals showed a developing hindquarters vasodilatation and mesenteric vasoconstriction, it is feasible that, in the presence of TGF‐β1 and LPS together, the haemodynamic profile represented an amalgam of the individual effects of the two interventions, rather than a specific effect of TGF‐β1 on the haemodynamic sequelae of endotoxaemia.
In the presence of LPS, haemodynamic responses to l‐NMMA were suppressed, and TGF‐β1 generally did not affect this suppression. A possible explanation of this observation is that LPS increased circulating endothelin levels, and thus resulted in desensitization to the effects of endothelin released following administration of l‐NMMA.
The ineffectiveness of the NO‐cyclic GMP signaling pathway in the atrial myocardium
Authors: Nawrath Hermann , Bäumner Dörte , Rupp Johanna , Oelert Hellmut 
Published: July 2012

This study was performed to determine whether nitric oxide (NO) has direct effects on force of contraction (Fc) in atrial myocardium from rats, rabbits, guinea‐pigs, frogs, and man.
Glyceryl trinitrate, isosorbide dinitrate, 3‐morpholino‐sydnonimine hydrochloride (SIN‐1), and S‐nitroso‐N‐acetylpenicillamine (SNAP) did not signficantly reduce Fc in the various preparations investigated, either given alone or after stimulation of α‐ or β‐adrenoceptors.
SNAP did not change the time course of contractions in rat, guinea‐pig and human preparations.
8‐Bromo‐guanosine‐3′:5′‐cyclic monophosphate (8‐Br‐cyclic GMP) produced a negative inotropic effect in rat, guinea‐pig and human atrial preparations and shortened time to peak tension and relaxation time in human preparations.
High K+ (85 mmol 1−1‐induced contracture in rat heart muscle was reduced by 8‐Br‐cyclic GMP but not by SIN‐1.
N‐monomethyl‐L‐arginine (l‐NMMA), an inhibitor of NO synthase, failed to influence muscarinic effects on Fc or frequency from rat and guinea‐pig hearts.
We conclude that NO, under the experimental conditions described here, has no direct effects on the heart, although cyclic GMP may be involved in the regulation of myocardial contraction.
The involvement of ATP‐sensitive potassium channels and adenosine in the regulation of coronary flow in the isolated perfused rat heart
Authors: Randall Michael D. 
Published: July 2012

The roles of adenosine 5′‐triphosphate (ATP)‐sensitive potassium channels (KATP) and endogenous adenosine in the regulation of coronary flow have been assessed in the isolated, buffer‐perfused heart of the rat.
In the presence of glibenclamide 10 μm there was a significant (P< 0.001) reduction in coronary flow from a baseline value of 8.78 ± 0.76 ml min−1 g_1 to 3.89 ± 0.59 ml min−1 g−1. This change was accompanied by a significant (P<0.01) reduction in cardiac mechanical performance as shown by the decrease in the pressure‐rate product from 21,487 ± 2,577 mmHg min−1 to 6,950 ± 1,104 mmHg min−1.
The non‐selective adenosine antagonist 8‐phenyltheophylline (10 μm) also caused a significant (P<0.001) reduction in coronary flow from a basal value of 10.4 ± 0.6 ml min−1 g_1 to 6.32 ± 0.60 ml min−1 g_1. The subsequent addition of glibenclamide, in the presence of 8‐phenyltheo‐phylline, brought about a further significant (p<0.001) reduction in coronary flow to 3.05 ± 0.55 ml min−1 g_1 and this value was similar to that in the presence of glibenclamide alone.
In hearts perfused under constant flow conditions, exogenous adenosine caused dose‐related reductions in coronary perfusion pressure described by a maximum reduction in pressure of 30.7 ± 3.9 mmHg and an ED50 of 977 ± 813 pmol. Addition of glibenclamide caused a significant (P<0.01) increase in coronary perfusion pressure of 44.7 ± 7.2 mmHg and a significant (P<0.05) rightward shift of the dose‐response curve for the depressor effects of adenosine (ED50= 13.5 ± 3.8 nmol), with a depression (P<0.05) of the maximum (16.3 ± 2.4 mmHg).
In conclusion, both KAtp and endogenous adenosine make major contributions towards coronary vascular tone and the regulation of coronary flow in the rat isolated heart. Furthermore, in the coronary vasculature a significant proportion of the vasodilator action of adenosine is mediated through the activation of KAtp
Improved survival and reversal of endothelial dysfunction by the 21‐aminosteroid, U‐74389G in splanchnic ischaemia‐reperfusion injury in the rat
Authors: Squadrito Franceso , Altavilla Domenica , Ammendolia Letteria , Squadrito Giovanni , Campo Giuseppe M. , Sperandeo Agostino , Canale Patrizia , Ioculano Mariapatrizia , Saitta Antonino , Caputi Achille P. 
Published: July 2012

Anaesthetized rats subjected to total occlusion of the superior mesenteric artery and the coeliac trunk for 45 min developed a severe shock state (splanchnic artery occlusion, SAO shock) resulting in death within 70–90 min after release of the occlusion. Sham‐operated animals were used as controls.
Survival rate, survival time, serum tumour necrosis factor (TNF‐α), white blood cell (WBC) count, mean arterial blood pressure (MAP), plasma malonylaldehyde (MAL), myeloperoxidase activity (MPO) and the responsiveness to acetylcholine (ACh 10 nM‐10 μM) of aortic rings were investigated.
SAO shocked rats had a decreased survival rate and survival time (74 ± 10 min, while sham‐shocked rats survived more than 4 h), reduced mean arterial blood pressure, increased serum levels of TNF‐α (267 ± 13 u ml−1) and plasma levels of MAL (57 ± 7 nmol ml−1), enhanced MPO activity in the ileum (0.23 ± 0.04 u × 10−3 g−1 tissue) and in the lung (2.2 ± 0.8 u × 10−3 g−1 tissue), leukopenia and reduced responsiveness to ACh of aortic rings.
The 21‐aminosteroid U‐74389G (30 mg kg−1, i.v.) increased survival (survival time = 232 ± 15 min), lowered the serum levels of TNF‐α and the plasma levels of MAL, reduced leukopenia and MPO activity both in the ileum (0.021 ± 0.004 u × 10−3 g−1 tissue) and in the lung (0.23 ± 0.03 u × 10−3 g−1 tissue), improved MAP and restored the responsiveness to ACh of aortic rings.
Our data suggest that U‐74389G is a potent lipid peroxidation inhibitor and that it has antishock and endothelial protective actions.
Effect of diabetes and elevated glucose on nitric oxide‐mediated neurotransmission in rat anococcygeus muscle
Authors: Way Kerrie J. , Reid Julianne J. 
Published: July 2012

Nitric oxide (NO)‐mediated neurotransmission is impaired in anococcygeus muscle from 8‐week streptozotocin‐induced diabetic rats. This study investigated the effects of insulin treatment, and the duration of diabetes on this impairment. In addition, the effect of in vitro exposure to elevated glucose has been investigated on NO‐mediated relaxations, in muscles from untreated rats.
Relaxant responses to field stimulation (0.5‐5 Hz, 10 s train), sodium nitroprusside (SNP; 5 and 10 nM) and NO (1 and 3 μM) were significantly impaired in anococcygeus muscles from 8‐week diabetic rats, compared to responses from control rats. Insulin treatment (5 u Lente day−1, s.c.) of diabetic rats prevented the development of this impairment.
Consistent with findings in 8‐week diabetic rats, relaxations induced by field stimulation, SNP and NO were attenuated in tissues from 2‐week and 4‐week diabetic rats compared to corresponding control responses, whereas relaxations to papaverine (3 and 10 μM) were not reduced. In contrast, diabetes of 3‐days duration did not affect relaxations to field stimulation, SNP or NO.
Incubation of anococcygeus muscles from untreated rats in medium containing elevated glucose (44.1 mM) for 6 h, significantly impaired relaxations to field stimulation compared to responses obtained after normal glucose (11.1 mM) incubation. Relaxations to SNP and to NO were not affected by 6h exposure to elevated glucose. Similarly, incubation in hyperosmolar solutions containing mannose or sucrose for 6 h, impaired relaxations to field stimulation, but not to SNP or NO.
The results indicate that the diabetes‐induced impairment of NO‐mediated neurotransmission in the rat anococcygeus muscle develops between 3 days and 2 weeks after the induction of diabetes with streptozotocin. Prevention of the impairment by insulin treatment suggests that it is specific for the diabetic state. In addition, the impairment may be related to hyperglycaemia and the consequent rise in osmolarity, since in vitro exposure to high glucose as well as to other hyperosmolar media impaired NO‐mediated relaxations to field stimulation.
Central versus peripheral site of action of the tachykinin NK1‐antagonist RP 67580 in inhibiting chemonociception
Authors: Holzer‐Petsche Ulrike , Rordorf‐Nikolić Tamara 
Published: July 2012

Many studies indicate an involvement of substance P in the transmission of nociceptive stimuli, without, however, presenting any conclusive evidence as to its exact site and mode of action. The present experiments tested the involvement of substance P in the mediation of chemical nociception using the non‐peptidic specific tachykinin NK1 ‐receptor antagonist, RP 67580 (2‐[1‐imino‐2‐(2‐methoxyphenyl‐ethyl]‐7, 7diphenyl‐4‐perhydroisoindolone (3aR, 7aR)).
Mean arterial pressure (MAP) and intragastric pressure (IGP) were measured in anaesthetized rats. The reflex changes of these parameters in response to i.p. or s.c. injections of hydrochloric acid or capsaicin were taken to indicate nociception.
Intravenous administration of RP 67580 up to 5 mg kg−1 had little influence on the reflex changes in MAP or IGP in response to hydrochloric acid or capsaicin. In contrast, the sensitization of rats to i.p. capsaicin by preinjection of prostaglandin E2 was significantly reduced by 1 mg kg−1 RP 67580.
Intrathecal injection of 5 μg RP 67580 inhibited the reflex changes of MAP and IGP in response to i.p. or s.c. capsaicin whereas the inactive enantiomer RP 68651 was ineffective.
The results indicate that spinal NK1 ‐receptors are involved in the acute transmission of chemically induced pain, while such receptors in the periphery take part in the sensitization by prostaglandin E2. The rather minor ability of i.v. RP 67580 to inhibit the acute nociceptive reflex is attributed to an insufficient penetration of the blood‐brain‐barrier.
Factors involved in the relaxation of female pig urethra evoked by electrical field stimulation
Authors: Werkström Viktoria , Persson Katarina , Ny Lars , Bridgewater Melissa , Brading Alison F. , Andersson Karl‐Erik 
Published: July 2012

Non‐adrenergic, non‐cholinergic (NANC) relaxations induced by electrical field stimulation (EFS) were studied in pig isolated urethra. The mechanism for relaxation was characterized by measurement of cyclic nucleotides and by study of involvement of different subsets of voltage‐operated calcium channels (VOCCs).
EFS evoked frequency‐dependent and tetrodotoxin‐sensitive relaxations in the presence of propranolol (1 JIM), phentolamine (1 μM) and scopolamine (1 μIM). At low frequencies (<:12Hz), relaxations were rapid, whereas at high (> 12 Hz) frequencies distinct biphasic relaxations were evoked. The latter consisted of a rapidly developing first phase followed by a more long‐lasting second phase.
Treatment with the NO‐synthesis inhibitor NG‐nitro‐L‐arginine (L‐NOARG; 0.3 mM) inhibited relaxations at low frequencies of stimulation. At high frequencies (>12 Hz) only the first relaxation phase was affected.
Measurement of cyclic nucleotides in preparations subjected to continuous nerve‐stimulation, revealed an increase in guanosine 3′:5′‐cyclic monophosphate (cyclic GMP) levels from 1.3 ± 0.3 to 3.0±0.4 pmol mg−1 protein (P<0.01). In the presence of L‐NOARG, there was a significant decrease in cyclic GMP content to control. However, there was no increase in cyclic GMP content in response to EFS. Levels of cyclic AMP remained unchanged following EFS.
Treatment with the N‐type VOCC‐inhibitor, ω‐conotoxin GVIA (0.1 μMs) reduced NO‐dependent relaxations, the effect being most pronounced at low frequencies (1‐4 Hz) of stimulation. The NO‐independent second phase of the relaxation, studied in the presence of L‐NOARG (0.3 mM) at 16–30 Hz, was however markedly reduced or abolished by ω‐conotoxin GVIA. ω‐Conotoxin MVIIC (1 μM) or ω‐agatoxin IVA (30 nM) had no effect on electrically evoked relaxations.
These results suggest that NANC‐nerve derived urethral relaxation in the pig consists of two apparently independent components. One is mediated by NO and associated with an increase in cyclic GMP content. The other mediator is unknown and produces relaxations not associated with changes in levels of cyclic nucleotides. The release of this mediator seems to involve the N‐type VOCC, since the relaxation was markedly reduced or abolished by ω‐conotoxin GVIA.
pH‐dependent transport of procainamide in cultured renal epithelial monolayers of OK cells: consistent with nonionic diffusion
Authors: Dudley Adam J. , Brown Colin D.A. 
Published: July 2012

Previous studies suggest that procainamide is a substrate for organic cation/proton antiport. In order to study the coupling between procainamide flux and proton flux in greater detail we investigated the effects of extracellular procainamide addition upon intracellular pH in cultured monolayers of renal OK cells. Intracellular pH was monitored by use of BCECF as a probe.
Apical addition of procainamide (10 mM) caused a significant alkalinisation of intracellular pH. Basolateral addition of procainamide was equally effective in raising intracellular pH. A similar alkalinisation was found in two other renal cell Unes: MDCK strain 1 and LLCPK1.
In contrast, both tetraethylammonium and N‐methylnicotinamide, archetypal substrates for organic cation/proton antiport were without effect upon intracellular pH.
At physiological pH values, procainamide exists as a neutral weak base (B) and its conjugate weak acid (BH+). To test which species of procainamide was responsible for the alkalinisation, experiments in which [B] was kept constant whilst [BH+] was varied from 1.15 mM to 7.25 mM were performed. The results suggested that the neutral weak base (B) was the permeant species.
Procainamide efflux from procainamide‐loaded cell monolayers resulted in a significant acidification of intracellular pH. As with procainamide uptake, this result could be ascribed to the movement of neutral weak base.
These effects of procainamide upon intracellular pH are consistent with nonionic diffusion of procainamide rather than an interaction of procainamide with the organic cation/proton antiporter. In addition, the results suggest that organic cation/proton antiport is not highly expressed in OK cells.