bluuebunny/crossref_metadata_2025_split huggingface dataset:
Antagonistic properties of McNeil‐A‐343 at 5‐HT4 and 5‐HT3 receptors
Authors: Sagrada A. , Schiavi G.B. , Cereda E. , Ladinsky H. 
Published: July 2012

This study describes the in vitro interaction of the muscarinic ligand McNeil‐A‐343 with two 5‐hydroxytryptamine (5‐HT) receptor subtypes, the 5‐HT4 and 5‐HT3 receptors, using functional as well as radioligand binding studies.
In the rat oesophageal muscularis mucosae, precontracted with carbachol, McNeil‐A‐343 was a competitive antagonist (pA2 6.2) of the 5‐HT4 receptor which mediates the relaxation induced by 5‐HT. The compound per se relaxed the oesophagus at high concentration only (≥ 10 μm), an effect unchanged by desensitization of the 5‐HT4 receptor with 10 μm 5‐methoxytryptamine. In the same preparation in the absence of tone, McNeil‐A‐343 displaced the carbachol concentration‐response curve to the right, yielding an apparent affinity (pA2) of 4.9 for muscarinic receptors.
In the rat isolated superior cervical ganglion preparation, after blockade of muscarinic and nicotinic receptors, McNeil‐A‐343 caused a concentration‐dependent depolarization that was unaffected by 100 nm ondansetron. The concentration‐fast depolarization curve to 5‐HT, mediated by the 5‐HT3 receptor, was displaced to the right by McNeil‐A‐343, which showed an apparent affinity (pA2) of 4.8 for the 5‐HT3 subtype.
In binding studies, McNeil‐A‐343 recognized a single population of 5‐HT4 receptors in pig caudate nucleus, with a pAi of 5.9. The binding affinity of McNeil‐A‐343 for 5‐HT3 receptors in NG 108‐15 cells was approximately four times lower (pK1 5.3). Binding affinities (pK1) for muscarinic receptor subtypes in rat tissues were 5.3 (Mb cortex), 5.2 (M2, heart) and 4.9 (M3, submandibular glands), respectively.
McNeil‐A‐343 is an antagonist at 5‐HT4 and 5‐HT3 receptors; the interaction of the compound with these receptor subtypes (notably the 5‐HT4) occurs in a range of concentrations which generally overlaps that relevant to the interaction with muscarinic receptors.
Pharmacological evidence of distinct oci‐adrenoceptor subtypes mediating the contraction of human prostatic urethra and peripheral artery
Authors: Hatano Akihiko , Takahashi Hitoshi , Tamaki Makoto , Komeyama Takeshi , Koizumi Takako , Takeda Masayuki 
Published: July 2012

The α1‐adrenoceptor subtypes mediating contractions of the smooth muscle in human prostatic urethra and branches of internal iliac artery were characterized in isometric contraction experiments.
Phenylephrine produced concentration‐dependent contractions in both the urethra and artery. These responses were competitively inhibited by prazosin, WB4101 and 5‐methyl‐urapidil, and the slopes of Schild plots for all these antagonists were close to unity.
The pA2 values for prazosin were not significantly different between the urethra (9.42 ± 0.11; mean ± s.d.) and artery (9.50 ± 0.27), while the pA2 values for WB4101 and 5‐methyl‐urapidil in the human prostatic urethra (8.94 ± 0.19 and 8.42 ± 0.14, respectively) were significantly greater than in the branches of human internal iliac artery (7.94 ± 0.21 and 7.43 ± 0.22, respectively; P < 0.01).
Pretreatment with chlorethylclonidine (CEC) at concentrations ranging from 0.1 μm to 100 μm attenuated the maximum contraction to phenylephrine in a concentration‐dependent manner in both the urethra and artery. However, the urethra was significantly less affected by CEC than the artery. The pD'2 values (negative logarithm of the molar concentration of antagonist which reduced the maximum contraction to one half) in the urethra and artery were 4.35 ± 0.27 and 5.20 ± 0.37, respectively (P < 0.01).
The present results indicate that there are distinct populations of α1‐adrenoceptor subtypes in the human prostatic urethra and branches of the internal iliac artery. The α1‐adrenoceptors responsible for the contraction of the human internal iliac artery branches are predominantly α1B‐subtype, whereas those in the human prostatic urethra are considered to be not α1B, but α1C or possibly α1A or α1A/D‐subtype.
The anticonvulsant and behavioural profile of L‐687,414, a partial agonist acting at the glycine modulatory site on the N‐methyl‐D‐aspartate (NMDA) receptor complex
Authors: Tricklebank M.D. , Bristow L.J. , Hutson P.H. , Leeson P.D. , Rowley M. , Saywell K. , Singh L. , Tattersall F.D. , Thorn L. , Williams B.J. 
Published: July 2012

The anticonvulsant and behavioural effects of the glycine/NMDA receptor partial agonist, L‐687,414 (R(+)‐cis‐β‐methyl‐3‐amino‐1‐hydroxypyrrolid‐2‐one) have been investigated in rodents.
L‐687,414 dose‐dependently antagonized seizures induced by N‐methyl‐D, L‐aspartic acid (NMDLA, ED50 = 19.7 mg kg−1), pentylenetetrazol (PTZ, ED50 = 13.0 mg kg−1) and electroshock (ED50 = 26.1 mg kg−1) when given intravenously 15min before test, in male Swiss Webster mice but was most potent against audiogenic seizures induced by a 120 dB bell in DBA/2 mice (ED50 = 5.1 mg kg−1, i.p., 30min before test).
L‐687,414 also induced impairments of performance in a rotarod test in both Swiss Webster and DBA/2 mice and the ratio [rotarod MED:anticonvulsant ED50] varied between 0.9 and 5, depending on the convulsant used.
Similar behaviours to those seen after administration of the non‐competitive NMDA receptor antagonist, MK‐801 (head weaving, body rolling, hyperlocomotion) were seen in the mouse after giving L‐687,414, although the peak effect occurred at a dose (100 mg kg−1) which was 5–20 times the anticonvulsant ED50S, depending on the convulsant used. Unlike MK‐801, however, doses of L‐687,414 that were behaviourally stimulant did not increase dopamine turnover in the nucleus accumbens.
Consistent with the interaction of L‐687,414 with the glycine/NMDA receptor, the anticonvulsant, ataxic and motor stimulant effects of the compound were significantly attenuated by the glycine/NMDA receptor agonist, D‐serine (10–100 μg per mouse, i.c.v.).
The results show that L‐687,414 is a potent, orally active anticonvulsant with a more benign pharmacological profile than antagonists acting at the ion channel of the NMDA receptor complex. The compound is a useful tool with which to probe the functional role of the glycine co‐agonist site in vivo.
Failure of CGS15943A to block the hypotensive action of agonists acting at the adenosine A3 receptor
Authors: Patel M. , Sheehan M.J. , Strong P. 
Published: July 2012

Adenosine receptor agonists were evaluated for their activity at the putative adenosine A3 receptor which mediates a ‘xanthine‐resistant’ hypotensive response in the anaesthetized rat. The compounds tested were: the A1/A3 receptor agonist, N‐[2‐(4‐aminophenyl)ethyl]adenosine (APNEA), the nonselective adenosine receptor agonist, 5′‐N‐ethylcarboxamidoadenosine (NECA), the adenosine A1 receptor‐selective agonists, N‐[(lS,trarts)‐2‐hydroxycyclopentyl]adenosine (GR79236) and N6‐cyclopentyl adenosine (CPA), the A2a receptor‐selective agonists, 2‐[[2‐[4‐(2‐carboxyethyl) phenyl] ethyl] amino]‐N‐ethylcarboxamidoadenosine (CGS21680) and 2‐phenylaminoadenosine (CV1808), and the moderately A2b selective agonist, N‐[(2‐methylphenyl)methyl]adenosine (metrifudil).
In confirmation of literature findings, APNEA (1–1000 nmol kg−1) induced hypotension and bradycardia; the hypotension was not blocked by pretreatment with the xanthine antagonist, 8‐P‐sulphophenyltheophylline (8‐sPT; 40 mg kg−1, i.v.), whereas the bradycardia was attenuated. The non‐xanthine antagonist, 9‐fluoro‐2‐(2‐furyl)‐5,6‐dihydro [1,2,4]triazolo{1,5‐c}‐quinazin‐5‐imine (CGS15943A; 3 mg kg−1 i.v.), also attenuated the bradycardia without affecting the hypotension.
The adenosine A1 receptor‐selective agonists, GR79236 and CPA, both produced dose‐dependent falls in blood pressure and heart rate which were antagonized by 8‐sPT (40 mg kg−1) and CGS15943A (3 mg kg−1).
The adenosine A2a receptor‐selective agonists, CGS21680 and CV1808, produced only a hypotensive response which was antagonized by 8‐sPT (40 mg kg−1) and to a much greater extent by CGS15943A (3 mg kg−1), consistent with the response being mediated solely by A2a receptors.
The modestly A2b receptor‐selective agonist, metrifudil, produced a dose‐dependent fall in blood pressure and at higher doses a fall in heart rate. The hypotension induced by metrifudil was not antagonized by either 8‐sPT (40 mg kg−1) or CGS15943A (3 mg kg−1) even though the bradycardia was abolished, suggesting that this agonist activates the putative A3 receptor.
The non‐selective adenosine receptor agonist, NECA, produced a hypotension and bradycardia that was attenuated by 8‐sPT (40 mg kg−1), confirming previous work. The non‐xanthine antagonist, CGS15943A (3 mg kg−1), also attenuated the hypotension and bradycardia. The bradycardia was blocked to a much greater extent, suggesting that NECA may therefore induce hypotension partly by activating the putative A3 receptor.
In conclusion, we have confirmed that the putative A3 receptor mediating hypotension in the anaesthetized rat is not blocked by 8‐sPT, and further shown that it is not blocked by CGS15943A. The A2a agonists CGS21680 and CV1808 showed no discernible activity at the A3 receptor, whereas APNEA, NECA, CPA and metrifudil appear to activate this receptor. The adenosine A1 receptor agonist, GR79236, shows considerable selectivity for the A1 receptor but may activate the A3 receptor at high doses.
Identification of renal natriuretic peptide receptor subpopulations by use of the non‐peptide antagonist, HS‐142‐1
Authors: Rutherford Richard A.D. , Matsuda Yuzuru , Wilkins Martin R. , Polak Julia M. , Wharton John 
Published: July 2012

The renal actions of natriuretic peptides are dictated by the distribution of guanylyl cyclase‐linked (NPRA and NPRB) and non‐guanylyl cyclase‐linked (NPRC) receptors. Natriuretic peptide receptors have previously been distinguished on the basis of their differential affinity for peptide fragments and analogues; however, most of the available ligands are not fully selective. We have used the specific guanylyl cyclase‐linked receptor antagonist, HS‐142‐1, to investigate the differential distribution of natriuretic peptide receptor subtypes in the human, bovine and rat kidney.
Specific, high affinity 3‐([125I]‐iodotyrosyl)‐rat‐ANP‐(1‐28)([125I]‐rANP1‐28) binding sites were identified in all three species, localized to glomeruli, inner medulla, intrarenal arteries and regions in the outer medulla corresponding to vasa recta bundles. Binding sites were also identified in the smooth muscle lining of the hilar region in the bovine and rat kidney.
In the rat, [125I]‐rANP1‐28 binding was inhibited by unlabelled peptide sequences with a rank order of potency (rANP1‐28 > pCNPl‐22 > C‐ANP4‐23). The glomeruli exhibited a heterogeneous population of binding sites, C‐ANP4‐23 and pCNP1‐22 producing a significantly better fit to a two component inhibition curve compared to the single component curve for rANP1‐28.
Competitive inhibition experiments with the receptor selective ligands, C‐ANP4‐23 and HS‐142‐1, suggested that, like the rat, human and bovine glomeruli possessed a heterogeneous population of binding sites, whilst those in the inner medulla and intrarenal arteries of all three species represented a homogeneous population. Rat glomeruli exhibited a high proportion (> 80%) of the NPRc receptor subtype whereas in human and bovine glomeruli this receptor represented less than 20% of the total population, the majority of binding sites being HS‐142‐1‐sensitive.
C‐ANP4‐23 exhibited a significantly higher inhibitory potency for binding sites in rat glomeruli compared to those in human and bovine kidney whilst HS‐142‐1 was significantly more potent in the rat and bovine kidney compared to man. No evidence was found to suggest the presence of a renal NPRB receptor subtype.
The relative density, affinity and proportion of natriuretic receptor subtypes in the kidney exhibit significant species differences. HS‐142‐1 may be a valuable tool in further elucidating the localization and function of these receptors, but heterogeneity between species should be considered when selecting experimental models.
Long‐lasting inhibitory activity of the hetrazepinic BN 50730 on exudation and cellular alterations evoked by PAF and LPS
Authors: Pires Ana L.A. , e. Silva Patricia M.R. , Pasquale Claudia , Castro‐Faria‐Neto Hugo C. , Bozza Patricia T. , Cordeiro Renato S.B. , Rae Giles A. , Braquet Pierre , Lagente Vincent , Martins Marco A. 
Published: July 2012

Inhibitory effects of the hetrazepinic derivative BN 50730 on the rat pleural inflammatory response, triggered by PAF or lipopolysaccharides (LPS), were examined. The type of pharmacological blockade exerted by this antagonist in in vitro assays of eosinophil chemotaxis and platelet aggregation were also investigated.
Intrathoracic injection of PAF (1 μg per cavity) caused a 4 fold increase in the extravasated protein within 15min and led to a marked eosinophil accumulation 24 h post‐challenge. BN 50730 (0.5–10 μg per cavity) inhibited exudation by PAF dose‐dependently without modifying the response induced by histamine, bradykinin or 5‐hydroxytryptamine (5‐HT).
The kinetics of the inhibitory effect on exudation revealed that the actions of WEB 2086 and BN 52021 (10 μg per cavity) were over within 2 and 4h respectively, whereas BN 50730 (10 μg per cavity) retained 80% of its inhibitory activity for 4 days.
Oral treatment with BN 50730 (10–20 mg kg−1, 1 h beforehand) suppressed the leucocyte accumulation and late eosinophilia observed 6 and 24 h after PAF respectively, but did not modify the eosinophilia induced by leukotriene B4 (LTB4) or bradykinin. BN 50730 also failed to reduce the eosinophil accumulation induced by LPS but drastically inhibited the neutrophil influx.
The pre‐incubation of rat peritoneal eosinophils for 10 min with BN 50730 (30nM‐1 μm) dose‐dependently inhibited the chemotaxis induced by PAF (0.1 μm) in vitro. The IC50 values for BN 52021, WEB 2086 and BN 50730 in this system were 5, 5 and 0.05 μm respectively.
In separate assays, rat peritoneal eosinophils and rabbit washed platelets were preincubated with BN 50730 or WEB 2086 (1 μm) then subjected to a series of at least two consecutive washings in order to remove the antagonist from the receptor environment. Under such conditions, only the cells pretreated with WEB 2086 recovered the sensitivity to the lipid.
We conclude that BN 50730 is a potent, specific and long‐acting PAF antagonist and its effect seems to result from a high affinity and non‐competitive interaction of the drug with the PAF receptor.
Effect of cyclopiazonic acid, an inhibitor of sarcoplasmic reticulum Ca2+‐ATPase, on the frequency‐dependence of the contraction‐relaxation cycle of the guinea‐pig isolated atrium
Authors: Yard Nicola J. , Chiesi Michele , Ball Howard A. 
Published: July 2012

The relevance of a functional sarcoplasmic reticulum (SR) membrane system to the contraction‐relaxation cycle and to the force‐frequency relationship of guinea‐pig atrial tissue was investigated. Cyclopiazonic acid (CPA) was used to inhibit selectively the activity of the SR Ca2+‐ATPase. IQo values of 0.2 μm or 1.0 μm were measured in guinea‐pig isolated SR membranes in the absence or presence of millimolar ATP, respectively. CPA (0.3–30 μm) did not inhibit the activity of the sarcolemmal Na+‐Ca2+‐exchanger as measured in isolated cardiac cell membrane preparations.
In guinea‐pig isolated left atrium paced at 2.5 Hz (30°C), CPA (1–100 μm) produced a concentration‐dependent reduction in developed tension and a fall in the maximum rate of tension increase (+ dT/dtmax) and decrease (‐dT/dtmax). The twitch duration was markedly increased due to a prolongation of the time to peak tension, and in particular, the relaxation phase.
The contraction‐relaxation cycle of the left atrium showed a marked dependence on the frequency of stimulation. The developed tension and +dT/dtmax showed a progressive increase from 0.5 Hz, reaching peak values at a stimulation rate of 1.5‐2.5 Hz, the positive staircase phenomenon. Higher frequencies of stimulation caused a fall in these parameters. Resting tension was unaffected. The time‐course of the contraction‐relaxation cycle was also frequency‐dependent, with both time to peak tension and relaxation time showing a progressive fall from 2.0–3.5 Hz.
The addition of CPA (30 μm) caused marked alterations in the frequency‐dependence of the contraction‐relaxation cycle. The frequency‐dependence of developed tension, + dT/dtmax, was shifted downwards, particularly at higher frequencies, and the frequency at which peak values of + dT/dtmax and — dT/dtmax were reached was shifted leftwards. The resting tension of the tissues in the presence of 30 μm CPA was increased markedly at frequencies greater than 2 Hz. The time‐course of the contraction‐relaxation cycle was markedly prolonged between 1.0 and 3.5 Hz, due to an effect on both time to peak tension and relaxation time.
In conclusion, these results show that CPA is a highly selective inhibitor of the cardiac SR Ca2+‐ATPase, without effect on the sarcolemmal Na+‐Ca2+‐exchanger, and suggest that a functional SR Ca2+‐ATPase is necessary for the normal contraction‐relaxation cycle of guinea‐pig cardiac tissue. Additionally, the results suggest an increasing dependence of tension development on SR Ca2+‐ATPase with increasing frequency, which may reflect either a frequency‐dependent activation of this enzyme or the diminished contribution of the Na+‐Ca2+ exchanger. These results also provide novel support for the mechanism of the depressed force‐frequency relation found in cardiac tissue of heart failure patients, in which there is a reduced expression of Ca2+‐ATPase.
FPL 66096: a novel, highly potent and selective antagonist at human platelet P2T‐purinoceptors
Authors: Humphries R.G. , Tomlinson W. , Ingall A.H. , Cage P.A. , Leff P. 
Published: July 2012

ADP‐dependent platelet aggregation is mediated by the P2T‐purinoceptor and is specifically inhibited by ATP, which is a competitive P2T‐purinoceptor antagonist. However, ATP functions as an agonist at other P2‐purinoceptor subtypes in other tissues and is, therefore, non‐selective. This paper describes the effects of the novel ATP analogue, FPL 66096 (2‐propylthio‐D‐β,γ‐difluoromethylene ATP), on ADP‐induced and ADP‐independent aggregation of human washed platelets and in standard preparations containing P2X‐ (rabbit ear artery) and P2Y‐purinoceptors (guinea‐pig aorta).
In suspensions of human washed platelets, FPL 66096 (1‐100nM) produced concentration‐dependent rightward displacement of concentration‐effect (E/[A]) curves obtained for ADP‐induced platelet aggregation. Logistic fitting of E/[A] data indicated that the effect of FPL 66096 was consistent with simple competition with a pKB value of 8.66. FPL 66096 (10–1000 nm) had no effect on aggregation produced by the thromboxane A2‐mimetic, U46619 (0.1–10 μm) when the response to this agent was rendered ADP‐independent by inclusion of the non‐selective P2‐purinoceptor antagonist, suramin (100 μ).
The antiaggregatory potency of FPL 66096 was not influenced by increasing the incubation time from 2 to 15min nor by inclusion of the P1‐purinoceptor antagonist 8‐sulphophenyltheophylline at a concentration (300 μm) that produced a 68 fold rightward displacement of the anti‐aggregatory E/[A] curve for the P1‐purinoceptor agonist, 5′‐N‐ethylcarboxamidoadenosine (0.1–1000 μm).
FLP 66096 behaved as a weak (pA50 3.68) but full P2x‐purinoceptor agonist in preparations of the rabbit isolated ear artery and as a weak, competitive antagonist (apparent pKB 4.71) at P2Y‐purinoceptors in the guinea‐pig isolated aorta, indicating a selectivity of at least 9000 fold for the P2T‐subtype. In the latter preparation, non‐specific relaxations were produced by concentrations of FPL 66096 ≥ 10 μm.
These results indicate that FPL 66096 is a P2T‐purinoceptor antagonist of unprecedented potency and selectivity and that its effects are consistent with simple competition at the P2T‐purinoceptor. Therefore, FPL 66096 represents a novel pharmacological tool in the classification of P2‐purinoceptors and in the elucidation of the mechanisms involved in activation of platelets by ADP.
Blockade of noradrenaline‐induced constrictions by yohimbine and prazosin differs between consecutive segments of cutaneous arteries in guinea‐pig ears
Authors: Morris J.L. 
Published: July 2012

The study has examined the receptors mediating constriction produced by brief local application of noradrenaline (NA) to cutaneous arteries and arterioles in the ear vasculature of anaesthetized guinea‐pigs. The innervation of the corresponding vascular segments has been examined immunohis‐tochemically at the conclusion of the pharmacological experiments.
Small arteries of branch order 4 (4°, 40–110 μm internal diameter) ‐were more sensitive to the vasoconstrictor action of NA than were more proximal arteries of branch order 3 (3°, 60–150 μm internal diameter), or more distal arteries and arterioles of branch orders 5 to 7 (5°‐7°, 18‐ 85 μm internal diameter). This higher sensitivity of 4° arteries was maintained after blockade of neuronal uptake with desipramine (1 μm), and after blockade of β‐adrenoceptors with propranolol (1 μm).
NA‐induced vasoconstrictions of distal arterioles (5°‐7°) were abolished or greatly reduced by yohimbine (1 μm). The blockade by yohimbine decreased progressively with increasing vessel diameter of proximal arteries, while the blockade by prazosin (1 μm) increased progressively in arteries >40 μm diameter.
In 3° and 4° arteries, a substantial component (approximately 50%) of NA‐induced vasoconstrictions remained after combined treatment with yohimbine and prazosin, in the presence or absence of desipramine. These constrictions were not further reduced by benextramine (1–10 μm), but were abolished by dihydroergotamine (1–10 μm). Constrictions induced by ATP (0.1‐1 μm) were not affected by dihydroergotamine.
5‐Hydroxytryptamine (3–100 μm) had a variable effect on 3° and 4° arteries including: concentration‐dependent constrictions (n = 3); small constrictions at some concentrations, and dilatations or no change in diameter at other concentrations (n = 6); concentration‐dependent dilatations only (n = 3). The 5‐HT2 receptor antagonist, ketanserin (0.1‐0.3 μm), did not affect NA‐induced constrictions.
In 16 arterial segments ranging from 3° arteries to 6° arterioles, there was a significant correlation between the presence of neuropeptide Y‐immunoreactive (NPY‐IR) sympathetic axons and the degree of blockade of NA‐induced constrictions by yohimbine, prazosin and dihydroergotamine.
These results demonstrate marked differences in the postsynaptic adrenoceptors mediating vasoconstriction to a bolus of NA applied briefly to the adventitial surface of different segments of the cutaneous vasculature of the guinea‐pig ear. Furthermore, the presence or absence of adrenoceptors sensitive to blockade by yohimbine or prazosin is related to the proportion of sympathetic axons innervating each vascular segment which contain NPY‐IR.
Dissociation of castor oil‐induced diarrhoea and intestinal mucosal injury in rat: effect of NG‐nitro‐L‐arginine methyl ester
Authors: Capasso Francesco , Mascolo Nicola , Izzo Angelo A. , Gaginella Timothy S. 
Published: July 2012

Castor oil (2 ml orally) produced diarrhoea in rats 1–7 h after challenge, which was associated with gross damage to the duodenal and jejunal mucosa.
The injury was accompanied by release of acid phosphatase into the gut lumen, indicating cellular injury.
Intraperitoneal injection of the nitric oxide (NO) synthase inhibitor NG ‐nitro‐L‐arginine methyl ester (1‐NAME, 2.5–50 mg kg−1 twice), prevented the diarrhoea. The dose of 1‐NAME (50mg kg−1) completely blocked the diarrhoea but increased the release of acid phosphatase and worsened the gross damage.
The NO donating compound, isosorbide‐5‐mononitrate (IMN, 150 mg kg−1 twice) reversed the effects of 1‐NAME (50 mg kg1) on castor oil‐induced diarrhoea, gross damage and acid phosphatase release.
The apparent dissociation of the diarrhoeal and intestinal mucosal damaging effects of castor oil suggest that NO has a protective effect on the rat duodenal and jejunal mucosa, but that NO mediates, in part, the diarrhoea effect of this laxative.