bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct block of native and cloned (Kir2.1) inward rectifier K+ channels by chloroethylclonidine
Authors: Barrett‐Jolley R , Dart C , Standen N B 
Published: January 2005

We have investigated the inhibition of inwardly rectifying potassium channels by the α‐adrenergic agonist/antagonist chloroethylclonidine (CEC). We used two preparations; two‐electrode voltage‐clamp of rat isolated flexor digitorum brevis muscle and whole‐cell patch‐clamp of cell lines transfected with Kir2.1 (IRK1).
In skeletal muscle and at a membrane potential of −50 mV, chloroethylclonidine (CEC), an agonist at α2‐adrenergic receptors and an antagonist at α1x‐receptors, was found to inhibit the inward rectifier current with a Ki of 30 μM.
The inhibition of skeletal muscle inward rectifier current by CEC was not mimicked by clonidine, adrenaline or noradrenaline and was not sensitive to high concentrations of α1‐(prazosin) or α2‐(rauwolscine) antagonists.
The degree of current inhibition by CEC was found to vary with the membrane potential (approximately 70% block at −50 mV c.f. ∼10% block at −190 mV). The kinetics of this voltage dependence were further investigated using recombinant inward rectifier K+ channels (Kir2.1) expressed in the MEL cell line. Using a two pulse protocol, we calculated the time constant for block to be ∼8 s at 0 mV, and the rate of unblock was described by the relationship τ=exp((Vm+149)/22) s.
This block was effective when CEC was applied to either the inside or the outside of patch clamped cells, but ineffective when a polyamine binding site (aspartate 172) was mutated to asparagine.
The data suggest that the clonidine‐like imidazoline compound, CEC, inhibits inward rectifier K+ channels independently of α‐receptors by directly blocking the channel pore, possibly at an intracellular polyamine binding site.

British Journal of Pharmacology (1999) 128, 760–766; doi:10.1038/sj.bjp.0702819
Differential effects of bepridil on functional properties of troponin C in slow and fast skeletal muscles
Authors: Kischel P , Stevens L , Mounier Y 
Published: January 2005

Bepridil (BPD) is a pharmacological compound able to bind to the Ca2+ sensor protein troponin C (TnC), which triggers skeletal muscle contraction upon Ca2+‐binding. BPD can thereby modulate the Ca2+‐affinity of this protein.
The Ca2+‐sensitizing action of bepridil was investigated on slow and fast isoforms of TnC from skinned slow and fast skeletal muscle fibres, activated by either Ca2+ or Sr2+ ions.
Bepridil did not modify the Ca2+ maximal tension of slow and fast fibres, suggesting that binding of the drug to TnC did not induce a change in the number of cross‐bridges involved in maximal tension.
Sr2+ ions induced lower maximal tension than Ca2+ ions. However, in fast fibres, these lower Sr2+ maximal tensions could be reinforced by bepridil, suggesting an effect of bepridil on the function of site I of fast TnC.
Under submaximal tension, bepridil induced an increase in Ca2+ affinity of TnC in both slow and fast fibres. However, slow fibres were more drug reactive than fast fibres, and the increase in tension appeared to be modulated by the Ca2+ concentration.
Thus, bepridil exerted a differential effect on slow and fast fibres. Moreover, the results suggest that bepridil was more effective when activation conditions were unfavourable.

British Journal of Pharmacology (1999) 128, 767–773; doi:10.1038/sj.bjp.0702820
Evidence for a role for central 5‐HT2B as well as 5‐HT2A receptors in cardiovascular regulation in anaesthetized rats
Authors: Knowles Ian D , Ramage Andrew G 
Published: January 2005

The effects of injections i.c.v. of quipazine, (2 μmol kg−1) and 1‐(2,5‐di‐methoxy‐4‐iodophenyl)‐2‐aminopropane (DOI; 2 μmol kg−1) on renal sympathetic and phrenic nerve activity, mean arterial blood pressure (MAP) and heart rate were investigated in α‐chloralose anaesthetized rats pretreated with a peripherally acting 5‐HT2 receptor antagonist.
Quipazine or DOI caused a rise in MAP which was associated with a tachycardia and renal sympathoinhibition in rats pretreated (i.c.v.) with the antagonist vehicle 10% PEG. These effects of quipazine were completely blocked by pretreatment with cinanserin (a 5‐HT2 receptor antagonist) and attenuated by spiperone (a 5‐HT2A receptor antagonist). However, pretreatment with SB200646A (a 5‐HT2B/2C receptor antagonist) only blocked the sympathoinhibition, while pretreatment with SB204741 (a 5‐HT2B receptor antagonist) reversed the sympathoinhibition to excitation as it also did for DOI. Quipazine also caused renal sympathoexcitation in the presence (i.v.) of a vasopressin V1 receptor antagonist.
Injection (i.v.) of the V1 receptor antagonist at the peak pressor response evoked by quipazine alone and in the presence of SB204741 caused an immediate fall in MAP. For quipazine alone the renal sympathoinhibition was slowly reversed to an excitation, while the renal sympathoexcitation observed in the presence of SB204741 was potentiated. In both, the quipazine‐evoked tachycardia was unaffected.
The data indicate that cardiovascular responses caused by i.c.v. quipazine and DOI are primarily due to activation of central 5‐HT2A receptors, which causes the release of vasopressin and a tachycardia. This released vasopressin appears to suppress a 5‐HT2A receptor‐evoked central increase in sympathetic outflow, which involves the activation of central 5‐HT2B receptors indirectly by the released vasopressin.

British Journal of Pharmacology (1999) 128, 530–542; doi:10.1038/sj.bjp.0702822
Beneficial effects of Mn(III)tetrakis (4‐benzoic acid) porphyrin (MnTBAP), a superoxide dismutase mimetic, in zymosan‐induced shock
Authors: Cuzzocrea Salvatore , Costantino Giuseppina , Mazzon Emanuela , De Sarro Angela , Caputi Achille P 
Published: January 2005

The therapeutic efficacy of Mn(III)tetrakis (4‐benzoic acid) porphyrin (MnTBAP), a novel superoxide dismutase mimetic which scavenges peroxynitrite, was investigated in rats subjected to shock induced by peritoneal injection of zymosan.
Our data show that MnTBAP (given at 1, 3 and 10 mg kg−1 intraperitoneally, 1 and 6 h after zymosan injection) significantly reduce in dose dependent manner the development of peritonitis (peritoneal exudation, high nitrate/nitrite and peroxynitrite plasma levels, leukocyte infiltration and histological examination).
Furthermore, our data suggest that there is a reduction in the lung, small intestine and liver myeloperoxidase (MPO) activity and lipid peroxidation activity from MnTBAP‐treated rats.
MnTBAP also reduced the appearance of nitrotyrosine immunoreactivity in the inflamed tissues.
Furthermore, a significant reduction of suppression of mitochondrial respiration, DNA strand breakage and reduction of cellular levels of NAD+ was observed in ex vivo macrophages harvested from the peritoneal cavity of zymosan‐treated rat.
In vivo treatment with MnTBAP significantly reduced in a dose‐dependent manner peroxynitrite formation and prevented the appearance of DNA damage, the decrease in mitochondrial respiration and the loss of cellular levels of NAD+.
In conclusion our results showed that MnTBAP was effective in preventing the development of zymosan‐induced shock.

British Journal of Pharmacology (1999) 128, 1241–1251; doi:10.1038/sj.bjp.0702826
Regulation of induction of nitric oxide synthase and the inhibitory actions of dexamethasone in the human intestinal epithelial cell line, Caco‐2: influence of cell differentiation
Authors: Cavicchi M , Whittle B J R 
Published: January 2005

The inducible isoform of nitric oxide synthase (iNOS) may be involved in the pathogenesis of inflammatory bowel disease. Using the human intestinal epithelial cell line, Caco‐2, iNOS expression, regulation and sensitivity to the glucocorticoid, dexamethasone after cytokine exposure and its relationship to the degree of differentiation has been studied.
NOS activity, assessed by NO2− and NO3− release, was time‐dependently increased after exposure to interferon γ alone or in combination with interleukin‐1β and tumour necrosis factor α.
Cytokine‐induced iNOS activity was increased with days in culture over 20 days and number of passages, suggesting iNOS up‐regulation during enterocyte‐like differentiation. This activity was inhibited by the selective iNOS inhibitor 1400 W (0.1–100 μM). In addition, iNOS protein induction was confirmed by Western blot.
Actinomycin D (5 μg ml−1) inhibited cytokine‐induced iNOS activity, protein expression and mRNA level. Pyrrolidine dithiocarbamate (PDTC: 10–200 μM) and 3,4 dichloroisocoumarin (0.1–100 μM) reduced cytokine‐induced iNOS activity and protein expression at both day 10 and 15 after confluence. PDTC also decreased iNOS mRNA levels, suggesting NF‐κB involvement in its transcription at these times.
The tyrphostins A25 and B42 reduced cytokine‐induced iNOS activity at both day 10 and 15 after confluence, indicating the JAK‐2 kinase is also involved at these times. The tyrphostins also reduced the iNOS protein expression.
Dexamethasone (0.1–10 μM, for 24 h) reduced cytokine‐induced iNOS activity at day 15 and 20 after cell confluence, but not at day 5 or 10.
Dexamethasone (5 μM) decreased cytokine‐induced iNOS protein expression at day 10 as well as at day 15 after confluence.
These findings indicate that iNOS induction and its inhibition by dexamethasone in this human intestinal epithelial cell line is dependent on the degree of differentiation.

British Journal of Pharmacology (1999) 128, 705–715; doi:10.1038/sj.bjp.0702827
Structural determinants of the partial agonist‐inverse agonist properties of 6′‐azidohex‐2′‐yne‐Δ8‐tetrahydrocannabinol at cannabinoid receptors
Authors: Ross Ruth A , Gibson T Michael , Stevenson Lesley A , Saha Bijali , Crocker Peter , Razdan Raj K , Pertwee Roger G 
Published: January 2005

We have extended previous investigations of four analogues of Δ8‐tetrahydrocannabinol (Δ8‐THC): 6′‐azidohex‐2′‐yne‐Δ8‐THC (O‐1184), 6′‐azidohex‐cis‐2′‐ene‐Δ8‐THC (O‐1238) and octyl‐2′‐yne‐Δ8‐THC (O‐584) and its 1‐deoxy‐analogue (O‐1315).
O‐1184, O‐1238 and O‐584 displaced [3H]‐CP55940 from specific binding sites on Chinese hamster ovary (CHO) cell membranes expressing CB1 or CB2 cannabinoid receptors, with pKi values of 8.28 to 8.45 (CB1) and 8.03 to 8.13 (CB2). The pKi values of O‐1315 were significantly less, 7.63 (CB1) and 7.01 (CB2).
All the analogues inhibited forskolin‐stimulated cyclic AMP production by CB1‐transfected CHO cells (pEC50=9.16 to 9.72). Only O‐1238 behaved as a full agonist in this cell line.
In mouse vasa deferentia, O‐1238 inhibited electrically‐evoked contractions (pEC50=10.18 and Emax=70.5%). Corresponding values for O‐1184 were 9.08 and 21.1% respectively. At 1 nM, O‐1184 produced surmountable antagonism of the cannabinoid receptor agonist, CP55940. However, at 0.1 nM, O‐1184 did not attenuate CP55940‐induced inhibition of cyclic AMP production by CB1‐transfected CHO cells.
In CB2‐transfected CHO cells, cyclic AMP production was inhibited by CP55940 (pEC50=8.59), enhanced by O‐1184 and O‐584 (pEC50=8.20 and 6.86 respectively) and not significantly affected by O‐1238 or O‐1315.
At 100 nM, O‐1184 and O‐1238 produced surmountable antagonism of CP55940 in CB2 cells, decreasing the pEC50 of CP55940 from 8.61 to 7.42 (O‐1184) or from 8.54 to 7.44 (O‐1238).
These data support the hypothesis that increasing the degree of unsaturation of the aliphatic side‐chain of Δ8‐THC analogues has little effect on CB1 or CB2 receptor affinity but can reduce CB1 receptor efficacy and reverse the direction of responses elicited at CB2 receptors.

British Journal of Pharmacology (1999) 128, 735–743; doi:10.1038/sj.bjp.0702836
5‐hydroxytryptamine receptors mediating contraction in human small muscular pulmonary arteries: importance of the 5‐HT1B receptor
Authors: Morecroft Ian , Heeley Robert P , Prentice Howard M , Kirk Alan , MacLean Margaret R 
Published: January 2005

The 5‐hydroxytryptamine (5‐HT) receptors mediating vasoconstriction in isolated human small muscular pulmonary arteries (SMPAs) were determined using techniques of wire myography and reverse transcription‐polymerase chain reaction (RT–PCR).
The agonists 5‐HT, 5‐carboxamidotryptamine (5‐CT, unselective for 5‐HT1 receptors) and sumatriptan (selective for 5‐HT1B/D receptors) all caused contraction and were equipotent (pEC50s: 7.0±0.2, 7.1±0.3 and 6.7±0.1, respectively) suggesting the presence of a 5‐HT1 receptor.
Ketanserin (5‐HT2A‐selective antagonist, 0.1 μM) inhibited 5‐HT‐induced contractions only at non‐physiological/pathological concentrations of 5‐HT (>0.1 μM) whilst GR55562 (5‐HT1B/1D‐selective antagonist, 1 μM) inhibited 5‐HT‐induced contractions at all concentrations of 5‐HT (estimated pKB=7.7±0.2). SB‐224289 (5‐HT1B‐selective antagonist, 0.2 μM) inhibited sumatriptan‐induced contractions (estimated pKB=8.4±0.1) whilst these were unaffected by the 5‐HT1D‐selective antagonist BRL15572 (0.5 μM) suggesting that the 5‐HT1B receptor mediates vasoconstriction in this vessel.
RT–PCR confirmed the presence of substantial amounts of mRNA for the 5‐HT2A and 5‐HT1B receptor subtypes in these arteries whilst only trace amounts of 5‐HT1D receptor message were evident.
These findings suggest that a heterogeneous population of 5‐HT2A and 5‐HT1B receptors co‐exist in human small muscular pulmonary arteries but that the 5‐HT1B receptor mediates 5‐HT‐induced vasoconstriction at physiological and pathophysiological concentrations of 5‐HT. These results have important implications for the treatment of pulmonary hypertension in which the 5‐HT1B receptor may provide a novel and potentially important therapeutic target.

British Journal of Pharmacology (1999) 128, 730–734; doi:10.1038/sj.bjp.0702841
Cannabinoid CB1 receptors fail to cause relaxation, but couple via Gi/Go to the inhibition of adenylyl cyclase in carotid artery smooth muscle
Authors: Holland Michael , Challiss R A John , Standen Nicholas B , Boyle John P 
Published: January 2005

The aim of the current study was to characterize which cannabinoid receptors, if any, are present on rat carotid artery smooth muscle. Additionally, the effects of cannabinoids on carotid artery tone, on cyclic AMP accumulation and on forskolin‐induced relaxation were examined in the same tissue.
Stimulation of carotid arteries with forskolin (10 μM) significantly increased cyclic AMP accumulation, an effect that was inhibited in a concentration‐dependent manner by the cannabinoid receptor agonist, methanandamide.
Similar inhibition was seen with the CB1 agonist HU‐210 but this inhibition was not mimicked by the CB2 agonist, WIN 55,2212‐2.
The inhibitory effect of methanandamide on cyclic AMP accumulation was prevented by incubation of the arteries with pertussis toxin and was significantly reduced by LY320135, a selective CB1 antagonist, but not by SR 144528, a CB2‐selective antagonist.
Methanandamide failed to relax carotid arteries pre‐contracted with phenylephrine, but inhibited forskolin‐induced relaxation of these arteries. This functional inhibition of relaxation by methanandamide was inhibited by CB1‐selective (LY320135 and SR 141716A), but not a CB2‐selective antagonist (SR 144528).
These data demonstrate the presence of functional G protein‐linked cannabinoid receptors of the CB1 subtype in the rat carotid artery, but show that these receptors inhibit cyclic AMP accumulation rather than cause relaxation.

British Journal of Pharmacology (1999) 128, 597–604; doi:10.1038/sj.bjp.0702842
Response‐selective C5a agonists: differential effects on neutropenia and hypotension in the rat
Authors: Short Anna J , Paczkowski Natalii J , Vogen Shawn M , Sanderson Sam D , Taylor Stephen M 
Published: January 2005

Some in vivo activities of two complement C5a agonist analogues have been evaluated by measuring changes in blood pressure and neutropenia in the rat and comparing the results with their receptor affinities in peritoneal macrophages and polymorphonuclear leucocytes (PMNs). In vitro C5a receptor (C5aR) binding experiments showed that YSFKPMPLaR and YSFKD(NMeNle)PlaR had similar affinities for the macrophage C5aR (IC50 0.2, 0.1 μM respectively). In PMNs, the affinity of YSFKPMPLaR (IC50 0.1 μM) was similar to that in macrophages, whereas the affinity of YSFKD(NMeNle)PLaR for the PMN C5aR was >100 μM. Given i.v., YSFKD(NMeNle)PLaR had similar activity to YSFKPMPLaR on blood pressure but did not cause neutropenia. These results demonstrate selectivity of a new C5a agonist in vitro, which is paralleled in vivo. The results suggest the possibility of developing selective agonists of C5a for in vivo use in humans. British Journal of Pharmacology (1999) 128, 511–514; doi:10.1038/sj.bjp.0702847
Receptor density as a factor governing the efficacy of the dopamine D4 receptor ligands, L‐745,870 and U‐101958 at human recombinant D4.4 receptors expressed in CHO cells
Authors: Gazi L , Bobirnac I , Danzeisen M , Schüpbach E , Langenegger D , Sommer B , Hoyer D , Tricklebank M , Schoeffter P 
Published: January 2005

The relationships between the density of dopamine D4.4 receptors and the agonist efficacies of L‐745,870 (3‐(4‐[4‐chlorophhenyl]piperazin‐1‐yl)‐methyl‐1H‐pyrrolo [2,3‐b]pyridine) and U‐101958 ((1‐benzyl‐piperidin‐4‐yl)‐(3‐isopropoxy‐pyridin‐2‐yl)‐methyl‐amine) were investigated in Chinese hamster ovary (CHO) cells, after treatment with the gene expression enhancer, sodium butyrate.
In CHO cells expressing D4.4 receptors (CHO/D4 cells), dopamine inhibited forskolin‐stimulated cyclic AMP accumulation (Emax 56±1% inhibition, pEC50 7.4±0.1, n=10). U‐101958 behaved as a partial agonist (39±7% the efficacy of dopamine, pEC50 8.1±0.3, n=4), whereas L‐745,870 had no detectable agonist effect.
Receptor density, as estimated by [3H]‐spiperone saturation binding was 240±30 fmol mg−1 protein (n=8) in CHO/D4 cell homogenates. It reached 560±150 (n=6), 1000±190 (n=4) and 840±120 (n=4) fmol mg−1 protein after treatment with sodium butyrate (5 mM) for 6, 18 and 48 h, respectively.
The increase in receptor density was associated with a gradual enhancement of the agonist effects (increased Emax and pEC50 values) of dopamine. The efficacy of U‐101958 (relative to dopamine) doubled and L‐745,870 was turned into a partial agonist (efficacy 49% relative to dopamine, pEC50 8.6±0.2, n=6, after 48 h treatment with sodium butyrate). These agonist effects of U‐101958 and L‐745,870 could be antagonized by spiperone (0.1 μM) but not by raclopride (10 μM).
The results show that U‐101958 and L‐745,870 are partial agonists at human dopamine D4.4 receptors expressed in CHO cells. Their efficacy is governed by receptor density. Agonist effects of these two compounds in vivo cannot be excluded under circumstances of increased receptor levels.

British Journal of Pharmacology (1999) 128, 613–620; doi:10.1038/sj.bjp.0702849
Preweanling naltrindole administration differentially affects clonidine induced antinociception and plasma adrenaline levels in male and female neonatal rats
Authors: Alberti Israel , Fernández Beatriz , Alguacil Luis Fernando , Aguilar Antonio , Caamaño Manuel , Romero Eva M , Viveros M Paz 
Published: January 2005

The influence of a chronic treatment with the δ‐selective opioid antagonist naltrindole (1 mg kg−1) during the preweanling period (daily injections from birth to postnatal day 19), on the antinociceptive and sympatholytic effects of the α2‐adrenergic agonist clonidine in male and female rats of 20 and 25 days of age was investigated.
Nociception was assessed using the tail immersion test (water at 50°C) and plasma levels of adrenaline were measured by high‐performance liquid chromatography.
The dose of clonidine (1.5 mg kg−1) and the time point at which nociceptive responses were recorded (30 min after the administration of the drug) were chosen on the basis of dose‐response (0.5, 1, 1.5 and 2 mg kg−1) and time‐response (5, 10, 15, 30 and 60 min) curves which were previously carried out in naive control neonatal rats.
In females, the functional blockade of the δ‐receptor by neonatal naltrindole treatment did not modify the sympatholytic effect of clonidine but prevented clonidine induced antinociception. Conversely, in males naltrindole treatment allowed the appearance of clonidine antinociception and the sympatholytic effect of clonidine.
The results indicate that the δ‐receptor is involved in the modulation of antinociceptive and sympatholytic responses to clonidine in neonatal rats and suggest the existence of sex differences in the interactions between δ‐opioid and α2‐adrenergic receptors.

British Journal of Pharmacology (1999) 128, 953–960; doi:10.1038/sj.bjp.0702852
Acetylcholine‐induced arteriolar dilation is reduced in streptozotocin‐induced diabetic rats with motor nerve dysfunction
Authors: Terata K , Coppey L J , Davidson E P , Dunlap J A , Gutterman D D , Yorek M A 
Published: January 2005

Diabetes mellitus produces marked abnormalities in motor nerve conduction, but the mechanism is not clear. In the present study we hypothesized that in the streptozotocin (STZ)‐induced diabetic rat impaired vasodilator function is associated with reduced endoneural blood flow (EBF) which may contribute to nerve dysfunction.
We examined whether diabetes‐induced reductions in sciatic nerve conduction velocity and EBF were associated with impaired endothelium‐dependent dilation in adjacent arterioles. We measured motor nerve conduction velocity (MNCV) in the sciatic nerve using a non‐invasive procedure, and sciatic nerve nutritive blood flow using microelectrode polarography and hydrogen clearance. In vitro videomicroscopy was used to quantify arteriolar diameter responses to dilator agonists in arterioles overlying the sciatic nerve.
MNCV and EBF in 4‐week‐STZ‐induced diabetic rats were decreased by 22% and 49% respectively. Arterioles were constricted with U46619 and dilation to acetylcholine (ACh), aprikalim, or sodium nitroprusside (SNP) examined. All agonists elicited dose‐dependent dilation in control and diabetic rats, although ACh‐induced dilation was significantly reduced in diabetic rats. Treating vessels from normal or diabetic rats with indomethacin (INDO) alone did not significantly affect ACh‐induced relaxation. However, ACh‐induced vasodilation was significantly reduced by treatment with KCl or Nω‐nitro‐L‐arginine (LNNA) alone. Combining LNNA and KCl further reduced ACh‐induced dilation in these vessels.
Diabetes causes vasodilator dysfunction in a microvascular bed that provides circulation to the sciatic nerve. These studies imply that ACh‐induced dilation in these vessels is mediated by multiple mechanisms that may include the endothelial‐dependent production of nitric oxide and endothelial‐derived hyperpolarizing factor. This impaired vascular response is associated with neural dysfunction.

British Journal of Pharmacology (1999) 128, 837–843; doi:10.1038/sj.bjp.0702856