bluuebunny/crossref_metadata_2025_split huggingface dataset:
Functional characterisation of the human cloned 5‐HT7 receptor (long form); antagonist profile of SB‐258719
Authors: Thomas David R. , Gittins Susan A. , Collin Lissa L. , Middlemiss Derek N. , Riley Graham , Hagan Jim , Gloger Israel , Ellis Catherine E. , Forbes Ian T. , Brown Anthony M. 
Published: January 2005

The functional profile of the long form of the human cloned 5‐HT7 receptor (designated h5‐HT7(a)) was investigated using a number of 5‐HT receptor agonists and antagonists and compared with its binding profile. Receptor function was measured using adenylyl cyclase activity in washed membranes from HEK293 cells stably expressing the recombinant h5‐HT7(a) receptor.
The receptor binding profile, determined by competition with [3H]‐5‐CT, was consistent with that previously reported for the h5‐HT7(a) receptor. The selective 5‐HT7 receptor antagonist SB‐258719 ((R)‐3,N‐Dimethyl‐N‐[1‐methyl‐3‐(4‐methylpiperidin‐1‐yl)propyl]benzene sulfonamide) displayed high affinity (pKi 7.5) for the receptor.
In the adenylyl cyclase functional assay, 5‐CT and 8‐OH‐DPAT were both full agonists compared to 5‐HT and the rank order of potency for agonists (5‐CT>5‐HT>8‐OH‐DPAT) was the same in functional and binding studies.
Risperidone, methiothepin, mesulergine, clozapine, olanzapine, ketanserin and SB‐258719 antagonised surmountably 5‐CT‐stimulated adenylyl cyclase activity. Schild analysis of the antagonism by SB‐258719 gave a pA2 of 7.2±0.2 and slope not significantly different from 1, consistent with competitive antagonism.
The same antagonists also inhibited basal adenylyl cyclase activity with a rank order of potency in agreement with those for antagonist potency and binding affinity. Both SB‐258719 and mesulergine displayed apparent partial inverse agonist profiles compared to the other antagonists tested. These inhibitory effects of antagonists appear to be 5‐HT7 receptor‐mediated and to reflect inverse agonism.
It is concluded that in this expression system, the h5‐HT7(a) receptor shows the expected binding and functional profile and displays constitutive activity, revealing inverse agonist activity for a range of antagonists.

British Journal of Pharmacology (1998) 124, 1300–1306; doi:10.1038/sj.bjp.0701946
Direct activation of endothelial NO pathway by Ba2+ in canine coronary artery
Authors: Yamazaki Jun , Sato Kazuo , Ohara Fumihiro , Nagao Taku 
Published: January 2005

We have reported that Ba2+ causes endothelium‐dependent relaxation of canine coronary arteries through NO synthesis in Ca2+‐free and depolarizing solution. To determine the cellular mechanisms by which the endothelium‐dependent relaxation occurs, we used fura‐2 fluorometry (F350 and F390; excitation wavelengths, 350 and 390 nm, respectively) and estimated the intracellular Ba2+ concentration in endothelial and vascular smooth muscle cells.
Ba2+ (10−3 m) increased the fura‐2 ratio (F350/F390) recorded from a combined preparation of smooth muscle and endothelium (0.445±0.073, n = 4) and contracted the arteries in the presence of 80 mm K+ (0.22±0.06 g, n = 4).
Diltiazem (3×10−6 m) blocks Ba2+ entry into vascular smooth muscle cells via l‐type Ca2+ channels. In this condition, Ba2+ increased the fura‐2 ratio in endothelial cells (0.141±0.014, n = 5) and relaxed the underlying smooth muscle (0.08±0.01 g, n = 5) by a mechanism which was sensitive to 10−4 m NG‐methyl‐l‐arginine (l‐NMMA).
Ba2+‐induced relaxation was not attenuated with repeated application and was elicited even after endothelium‐dependent relaxations in response to 10−6 m bradykinin were abolished due to tachyphylaxis. Neither 10−2 m caffeine nor 10−6 m thapsigargin had effect upon Ba2+‐induced relaxation.
To further rule out changes in intracellular Ca2+ as a mechanism of Ba2+‐induced relaxation, fura‐2 fluorescence was measured at the isosbestic wavelengths for Ca2+ (360 nm) and Ba2+ (370 nm) in endothelium‐intact arteries. Ba2+ altered F360, but not F370, suggesting little or no contribution of intracellular Ca2+ to the phenomenon of Ba2+‐induced relaxation.
These results suggest that the Ba2+‐induced relaxation is due to its direct activation of endothelial NO synthesis without mobilization of intracellular Ca2+.

British Journal of Pharmacology (1998) 124, 1149–1158; doi:10.1038/sj.bjp.0701948
Differences between proximal and distal portions of the male rabbit posterior urethra in the physiological role of muscarinic cholinergic receptors
Authors: Nagahama Katsushi , Tsujii Toshihiko , Morita Takashi , Azuma Hiroshi , Oshima Hiroyuki 
Published: January 2005

The aim of the present study was to elucidate functional differences between embryologically different portions of the posterior urethra of male rabbits in response to muscarinic acetylcholine receptor (mAChR) stimulation using in vitro isometric tension experiments and radioligand binding studies.
In the in vitro isometric tension experiments, carbachol, produced a dose‐dependent contraction of the proximal portion under the resting state, but did not change the basal tone of the distal portion. Contraction of the proximal portion by 10−5 m noradrenaline (NA) was dose‐dependently enhanced by carbachol either in the presence or absence of NG‐nitro‐l‐arginine (NOARG). In contrast, carbachol induced relaxation of the distal portion contracted by 10−5 m NA, which was reversed to dose‐dependent contraction in the presence of NOARG.
Both portions of the urethra had a similar number of [3H]‐quinuclidinyl benzilate ([3H]‐QNB) binding sites (195.3±74.1 fmols mg−1 protein for the proximal portion and 146.5±8.5 fmols mg−1 protein for the distal portion) with similar affinities (115.0±45.4 pM for the proximal portion and 79.9± 2.9 pM for the distal portion).
The concentration‐response curves to carbachol in both portions were shifted to the right in a parallel manner in the presence of pirenzepine (an M1 antagonist), 11‐[[2‐[(diethylamino)methyl]‐1‐piperidinyl] acetyl]‐5, 11‐dihydro‐6H‐pyrido‐2,3‐b)‐(1,4)‐benzodiazepin‐6‐one (AFDX‐116, an M2 antgonist) and 4‐diphenyl‐acetoxy‐n‐methyl‐piperidine (4‐DAMP, an M1/M3 antagonist). The pA2 values for pirenzepine, AFDX‐116 and 4‐DAMP were 7.5±0.1, 7.2±0.02 and 9.3±0.1 respectively for the contraction of the proximal portion, and 7.2±0.1, 7.1±0.2 and 9.1±0.2, respectively for the relaxation of the distal portion.
In conclusion mAChR subtypes distribute in a similar fashion throughout the length of the male rabbit posterior urethra with the discrepant responses to carbachol attributable to the differential involvement of the NO pathway in mAChR‐generated reactions.

British Journal of Pharmacology (1998) 124, 1175–1180; doi:10.1038/sj.bjp.0701952
Role of VIP1/PACAP receptors in postoperative ileus in rats
Authors: De Winter Benedicte Y. , Robberecht Patrick , Boeckxstaens Guy E. , De Man Joris G. , Moreels Tom G. , Herman Arnold G. , Pelckmans Paul A. 
Published: January 2005

Vasoactive intestinal polypeptide (VIP) is an inhibitory neurotransmitter in the enteric nervous system. We investigated the role of VIP1/PACAP receptors in postoperative ileus in rats.
Different degrees of inhibition of the gastrointestinal transit, measured by the migration of Evans blue, were achieved by skin incision, laparotomy or laparotomy plus mechanical stimulation of the gut.
The transit after skin incision or laparotomy was not altered by the VIP1/PACAP receptor antagonist Ac‐Hisl,D‐Phe2, K15, R16, VIP(3–7), GRF(8–27)‐NH2 nor by the VIP1/PACAP receptor agonist K15, R16, VIP(1–7), GRF(8–27)‐NH2 and the VIP2/PACAP receptor agonist RO 25‐1553 (5 μg kg−1).
However, the transit after laparotomy plus mechanical stimulation was significantly enhanced by the VIP1/PACAP receptor antagonist, whereas it was further inhibited by the VIP1/PACAP receptor agonist. The combination of the VIP1/PACAP receptor agonist and antagonist counteracted the effect of both drugs alone. The VIP2/PACAP receptor agonist did not alter the effect of the VIP1/PACAP receptor antagonist.
The combination of the VIP1/PACAP receptor antagonist plus the nitric oxide (NO) synthase inhibitor l‐nitroarginine had no effect on the transit after laparotomy plus mechanical stimulation, while the transit after skin incision was significantly decreased.
These findings suggest the involvement of VIP1/PACAP receptors, next to NO, in the pathogenesis of postoperative ileus. However, the combination of the VIP1/PACAP antagonist and the NO synthase inhibitor abolished the beneficial effect of each drug alone, suggesting the need for one of the inhibitory neurotransmitters to enable normal gastrointestinal transit.

British Journal of Pharmacology (1998) 124, 1181–1186; doi:10.1038/sj.bjp.0701954
MS‐551 and KCB‐328, two class III drugs aggravated adrenaline‐induced arrhythmias
Authors: Xue YiXue , Yamada Chikaomi , Nu Aye Nu , Hashimoto Keitaro 
Published: January 2005

We investigated the proarrhythmic effects of MS‐551 and KCB‐328, class III antiarrhythmic drugs using adrenaline‐induced arrhythmia models in halothane anaesthetized, closed‐chest dogs. In the control period, adrenaline, starting from a low dose of 0.25 to up to 1.0 μg/kg/50 s i.v., was injected to determine the arrhythmia inducing dose and the non‐inducing dose. After MS‐551 or KCB‐328 administration, the adrenaline injection was repeated and the interval between the injection and the occurrence of arrhythmia (latent interval), the changes in arrhythmic ratio (as calculated by dividing the number of ventricular premature contraction by the number of the total heart rate) and the severity of arrhythmia were observed.
MS‐551 infusion, 1 mg/kg/30 min, decreased the heart rate (HR) by 16% (P<0.01) and prolonged the QTc interval by 20% (P<0.01). During the 30 min of MS‐551 infusion, arrhythmias occurred in three out of seven dogs (torsades de pointes (TdP) type VT in one dog). After these arrhythmias disappeared, MS‐551 decreased the latent interval of the adrenaline arrhythmias produced by the inducing dose (30±2 s compared with 43±3 s of the control interval, P<0.05), increased the arrhythmic ratio (P<0.05) and induced arrhythmias by non‐inducing adrenaline doses (P<0.05).
Effect of a new class III drug KCB‐328 infusion, 0.3 mg/kg/30 min, was compared witih MS‐551 using the same model. KCB‐328 decreased the HR by 21% (P<0.01) and prolonged the QTc interval by 25% (P<0.01). During the 30 min of infusion, arrhythmias occurred in five out of seven dogs (TdP in two dogs). KCB‐328 also decreased the latent interval of the adrenaline arrhythmias produced by the inducing doses (31±3 s compared with 49±7 s of the control period, P<0.05), but did not significantly alter the arrhythmic ratio.
Adrenaline induced TdP only after MS‐551 or KCB‐328 was administered, i.e. after MS‐551, 1 mg/kg/30 min, 3/7 versus 0/7 in the control; KCB, 0.3 mg/kg/30 min, 3/7 versus 0/7 in the control.
To examine the direct arrhythmogenic effect of MS‐551 and whether an adrenergic mechanism plays some role on this arrhythmogenesis, a bolus injection of MS‐551, 3 mg/kg, was injected either without pre‐treatment or after pre‐treatment with propranolol 0.3 mg/kg. MS‐551 induced arrhythmias in five out of seven dogs (TdP in one dog). Also in the propranolol pre‐treated dogs, MS‐551 induced arrhythmias in five out of seven dogs (TdP in 1 dog).
In conclusion, these observations indicate that MS‐551 and KCB‐328 induced arrhythmias and intensified proarrhythmic effects of adrenaline, MS‐551 being stronger than KCB‐328 at the same QTc prolonging doses. The direct arrhythmogenic effect of MS‐551 was not influenced by β‐blocker treatment.

British Journal of Pharmacology (1998) 124, 1712–1718; doi:10.1038/sj.bjp.0701987
Evidence that tachykinins are the main NANC excitatory neurotransmitters in the guinea‐pig common bile duct
Authors: Patacchini Riccardo , De Giorgio Roberto , Barthó Lorand , Barbara Giovanni , Corinaldesi Roberto , Alberto Maggi Carlo 
Published: January 2005

Application of electrical field stimulation (EFS; trains of 10 Hz, 0.25 ms pulse width, supramaximal voltage for 60 s) to the guinea‐pig isolated common bile duct pretreated with atropine (1 μM), produced a slowly‐developing contraction (`on' response) followed by a quick phasic `off ' contraction (`off peak' response) and a tonic response (`off late' response), averaging 16±2, 73±3 and 20±4% of the maximal contraction to KCl (80 mM), n=20 each, respectively. Tetrodotoxin (1 μM; 15 min before) abolished the overall response to EFS (n=8).
Neither in vitro capsaicin pretreatment (10 μM for 15 min), nor guanethidine (3 μM, 60 min before) affected the excitatory response to EFS (n=5 each), showing that neither primary sensory neurons, nor sympathetic nerves were involved. Nω‐nitro‐L‐arginine (L‐NOARG, 100 μM, 60 min before) or naloxone (10 μM, 30 min before) significantly enhanced the `on' response (294±56 and 205±25% increase, respectively; n=6–8, P<0.01) to EFS. The combined administration of L‐NOARG and naloxone produced additive enhancing effects (655±90% increase of the `on' component, n=6, P<0.05).
The tachykinin NK2 receptor‐selective antagonist MEN 11420 (1 μM) almost abolished both the `on' and `off late' responses (P<0.01; n=5 each) to EFS, and reduced the `off‐peak' contraction by 55±8% (n=5, P<0.01). The subsequent administration of the tachykinin NK1 receptor‐selective antagonist GR 82334 (1 μM) and of the tachykinin NK3 receptor‐selective antagonist SR 142801 (30 nM), in the presence of MEN 11420 (1 μM), did not produce any further inhibition of the response to EFS (P>0.05; n=5 each). At 3 μM, GR 82334 significantly reduced (by 68±9%, P<0.05, n=6) the `on' response to EFS.
The contractile `off peak' response to EFS observed in the presence of both MEN 11420 and GR 82334 (3 μM each) was abolished (P<0.01; n=6) by the administration of the P2 purinoceptor antagonist pyridoxalphosphate‐6‐azophenyl‐2′,4′‐disulphonic acid (PPADS, 30 μM). PPADS (30 μM) selectively blocked (75±9 and 50±7% inhibition, n=4 each) the contractile responses produced by 100 and 300 μM ATP.
Tachykinin‐containing nerve fibres were detected by using immunohistochemical techniques in all parts of the bile duct, being distributed to the muscle layer and lamina propria of mucosa. In the terminal part of the duct (ampulla) some labelled ganglion cells were observed.
In conclusion, this study shows that in the guinea‐pig terminal biliary tract tachykinins, released from intrinsic neuronal elements, are the main NANC excitatory neurotransmitters, which act by stimulating tachykinin NK2 (and possibly NK1) receptors. ATP is also involved as excitatory neurotransmitter. Nitric oxide and opioids act as inhibitory mediators/modulators in this preparation.

British Journal of Pharmacology (1998) 124, 1703–1711; doi:10.1038/sj.bjp.0701999
Somatostatin displayed on filamentous phage as a receptor‐specific agonist
Authors: Rousch Mat , Lutgerink Jan T , Coote James , de Bruïne Adriaan , Arends Jan‐Willem , Hoogenboom Hennie R 
Published: January 2005

In search of methods to identify bio‐active ligands specific for G protein‐coupled receptors with seven transmembrane spanning regions, we have developed a filamentous phage‐based selection and functional screening method.
First, methods for panning peptide phage on cells were established, using the hormone somatostatin as a model. Somatostatin was displayed on the surface of filamentous phage by cloning into phage(mid) vectors and fusion to either pIII or pVIII viral coat proteins. Peptide displaying phage bound to a polyclonal anti‐somatostatin serum, and, more importantly, to several somatostatin receptor subtypes (Sst) expressed on transfected CHO‐K1 cells, in a pattern which was dependent on the used display method. Binding was competed with somatostatin, with an IC50 in the nanomolar range. The phage were specifically enriched by panning on cells, establishing conditions for cell selections of phage libraries.
Binding of somatostatin displaying phage to sst2 on a reporter cell line, in which binding of natural ligand reduces secretion of alkaline phosphatase (via a cyclic AMP responsive element sensitive promoter), proved that the phage particles act as receptor‐specific agonists. Less than 100 phage particles per cell were required for this activity, which is approximately 1000 fold less than soluble somatostatin, suggesting that phage binding interferes with normal receptor desensitization and/or recycling.
The combination of biopanning of phage libraries on cells with functional screening of phage particles for receptor triggering activity, may be used to select novel, bio‐active ligands from phage libraries of random peptides, antibody fragments, or libraries based on the natural receptor ligand.

British Journal of Pharmacology (1998) 125, 5–16; doi:10.1038/sj.bjp.0702011
Influence of aminoguanidine on parameters of liver injury and regeneration induced in rats by a necrogenic dose of thioacetamide
Authors: Díez‐Fernández Carmen , Sanz Nuria , Alvarez Alberto M , Zaragoza Asunción , Cascales María 
Published: January 2005

When aminoguanidine, a nucleophilic hydrazine compound, was administered to rats (50 mg kg−1 body wt) 30 min before a necrogenic dose of thioacetamide (500 mg kg−1 body wt), significant changes related to liver injury and hepatocellular regeneration were observed.
The extent of necrosis was noticeably less pronounced, as detected by the peak of serum aspartate aminotransferase activity. Depletion of hepatic glutathione (GSH) and the increase in malondialdehyde concentration as markers of oxidative stress, produced by thioacetamide metabolism, were significantly diminished. However, the activity of microsomal FAD monooxygenase, the system responsible for thioacetamide oxidation, did not show significant alterations. Antioxidant enzyme systems involved in the glutathione redox cycle, such as glutathione reductase and glutathione peroxidase activities, slightly decreased following aminoguanidine pretreatment.
Primary cultures of peritoneal macrophages from control rats, when incubated in the presence of serum collected following thioacetamide intoxication, showed a significant decrease in nitric oxide (NO) release at 24 h, that was more pronounced in the group pretreated with aminoguanidine. However, the sharp and progressive increase in macrophage NO release, when incubated in the presence of serum obtained at 48, 72 and 96 h, were increased by aminoguanidine‐pretreatment.
The cell population involved in DNA synthesis sharply increased in both groups at 48 h of intoxication, although the values at 0, 24, 72 and 96 h were markedly higher in the group pre‐treated with aminoguanidine. Polyploidy at 72 and 96 h of intoxication was delayed by the effect of aminoguanidine and a progressive increase in the hypodiploid hepatocyte population, which reached 16% of the total at 96 h, was observed.
These results indicate that a single dose of aminoguanidine before thioacetamide administration, markedly diminished the severity of the liver injury by decreasing oxidative stress and lipoperoxidation, but hepatocellular regeneration was apparently unaffected probably due to an enhanced mitogenic activity.

British Journal of Pharmacology (1998) 125, 102–108; doi:10.1038/sj.bjp.0702014
Rilmenidine reveals differences in the pharmacological characteristics of prejunctional α2‐adrenoceptors in the guinea‐pig, rat and pig
Authors: Ali A , Cheng H‐Y , Ting K N , Wilson V G 
Published: January 2005

The α2A and α2D‐adrenoceptor subtypes are thought to be species homologs most easily differentiated on the basis of the potency of antagonists. In the present study we have compared the effect of rilmenidine with two other selective α2‐adrenoceptor agonists, UK‐14304 (5‐bromo‐6‐ [2‐imidazolin‐2‐ylamino]‐quinoxaline) and clonidine, against electrically‐evoked contractions in five isolated preparations from the rat, guinea‐pig and pig, and, where possible, determined the receptor subtype involved.
UK‐14034, clonidine and rilmenidine produced concentration‐dependent inhibition of the electrically‐evoked contractions of the rat isolated vas deferens and tail artery and the guinea‐pig ileum. These inhibitory effects were reversed by the selective α2‐adrenoceptor antagonist, RX‐811058 (1 μM), except in the rat tail artery preparations where the remaining neurogenic response was inhibited; evidence for the involvement of ‘innervated’ α2‐adrenoceptors. Both clonidine and UK‐14304 produced concentration‐dependent inhibition of responses in the porcine isolated tail artery and urinary bladder but clonidine was markedly less efficacious in these preparations. In contrast, rilmenidine failed to inhibit the neurogenic contractions in either preparation.
Although rilmenidine failed to elicit a detectable response in either the porcine isolated tail artery or urinary bladder, it (10 μM and 30 μM, respectively) competitively antagonised the inhibitory effects of UK‐14304 with an estimated dissociation constant of (pKB) 5.82 and 5.93, respectively.
Prazosin (1 μM) failed to alter the effect of UK‐14304 against neurogenic contractions in the porcine isolated urinary bladder, while rauwolscine (pKB 8.87) was 10 fold more potent than phentolamine (pKB 7.56). On the other hand, phentolamine (pKB 8.42) was only marginally more potent than rauwolscine (pK 8.05) against clonidine‐induced inhibition of electrically‐evoked contractions of the guinea‐pig isolated ileum. This pharmacological evidence with antagonists supports the presence of α2D‐adrenoceptors in the rat and guinea‐pig and the α2A‐adrenoceptors in the pig.
We have demonstrated that rilmenidine, unlike clonidine and UK‐14304, is devoid of any agonist activity at prejunctional α2A‐adrenoceptors in the pig, but is an efficacious agonist at α2D‐adrenoceptors in the rat and guinea‐pig.

British Journal of Pharmacology (1998) 125, 127–135; doi:10.1038/sj.bjp.0702016
Kinin B2 receptor‐mediated contraction of tail arteries from normal or streptozotocin‐induced diabetic rats
Authors: Wang Zunzhe , Wu Lingyun , Wang Rui 
Published: January 2005

The vasoactive effects of bradykinin (BK) are mediated by different subtypes of kinin receptors, of which the expression varies among different tissues. In rat tail artery tissues, BK elicited a concentration‐dependent vasoconstriction (EC50, 25.9±2.4 nM; Emax, 0.39±0.01 g; n=16). This effect of BK was endothelium independent and indomethacin insensitive. The BK‐induced contraction of tail artery tissues, however, depended on both membrane potential‐sensitive extracellular Ca2+ entry and thapsigargin‐sensitive intracellular Ca2+ release.
Kinin B1 receptor antagonist or agonist did not affect the basal tension or the BK‐induced contraction of tail artery tissues in the absence or presence of endothelium (P>0.05). In contrast, the BK‐induced vasoconstriction was inhibited by kinin B2 receptor antagonists. Pretreatment of vascular tissues with Hoe 140 (1 nM) significantly changed EC50 of the BK‐induced vasoconstriction from 25.5±7.4 nM to 82.6±16.8 nM (n=8, P<0.01) and Emax from 0.43±0.03 g to 0.16±0.01 g (n=8, P<0.01).
In the tail artery tissues from streptozotocin‐induced diabetic rats, the BK‐elicited vasoconstriction was significantly reduced (EC50, 67.8±11 nM; Emax, 0.19±0.01 g) compared to their counterparts from normal rats. The decreased vasoconstrictive effects of BK on diabetic arteries were endothelium independent and indomethacin insensitive.
Our study demonstrated that the contraction of rat tail arteries induced by BK was mediated by B2 receptors located on vascular smooth muscles. The altered B2 receptor‐mediated vascular activity may play an important role in the vascular complications of diabetes.

British Journal of Pharmacology (1998) 125, 143–151; doi:10.1038/sj.bjp.0702017