bluuebunny/crossref_metadata_2025_split huggingface dataset:
The adrenergic, cholinergic and NANC nerve‐mediated contractions of the female rabbit bladder neck and proximal, medial and distal urethra
Authors: Deplanne Valérie , Palea Stéfano , Angel Itzchak 
Published: January 2005

The nerve‐mediated contraction of the female rabbit bladder neck and different portions of the urethra (proximal, medial and distal) was studied in vitro by electrical stimulation (50 V, 30 Hz, 0.05 ms width, trains of 5 s every 5 min) by use of a superfusion system.
The amplitude (Emax) and the duration (Dmax) of the stimulated contraction were studied in the four tissues. The Emax value was significantly higher in distal urethra (2.07±0.15 g) compared to the bladder neck (1.08±0.10 g), proximal urethra (0.73±0.07 g) and medial urethra (0.87±0.07 g). In contrast, the Dmax value appeared slightly but significantly lower (P<0.05) in distal urethra (68.5±2.3 s) than in bladder neck (76.7±6.0 s), proximal urethra (84.5±5.0 s) and medial urethra (81.3±3.5 s).
Cocaine (1 μM) significantly increased the basal Emax values in medial and distal urethra and the basal Dmax values in the four tissues.
Prazosin (1 μM) significantly reduced Emax value in proximal, medial and distal urethra and Dmax value in bladder neck and proximal urethra. Atropine (1 μM) also significantly reduced Emax values in bladder neck and proximal urethra and reduced Dmax value in bladder neck, but not in other tissues. Yohimbine (0.1 μM) was devoid of effect in the four tissues.
The association of prazosin (1 μM) and atropine (1 μM) did not modify the Emax and the Dmax values of the electrically‐induced contractions, except in proximal urethra and in bladder neck where an additive inhibitory effect (on Emax only) was observed compared to prazosin and atropine alone.
The residual contractile response after combined treatment with prazosin and atropine was significantly diminished by tetrodotoxin (TTX; 1 μM) but not completely abolished. These NANC contractions were insensitive to P2X‐purinoceptor desensitization by continuous tissue perfusion with α,β‐methylene ATP (30 μM).
These results demonstrate that bladder neck and proximal urethra are mainly innervated by the parasympathetic nervous system, whereas medial and distal urethras are to a greater extent under the control of the sympathetic innervation. The residual responses, insensitive to prazosin and atropine, may indicate a NANC innervation in the four tissues. However, the nature of the NANC neurotransmitter remains to be identified.

British Journal of Pharmacology (1998) 123, 1517–1524; doi:10.1038/sj.bjp.0701757
[3H]‐SCH 58261 labelling of functional A2A adenosine receptors in human neutrophil membranes
Authors: Varani Katia , Gessi Stefania , Dionisotti Silvio , Ongini Ennio , Andrea Borea Pier 
Published: January 2005

The present study describes the direct labelling of A2A adenosine receptors in human neutrophil membranes with the potent and selective antagonist radioligand, [3H]‐5‐amino‐7‐(2‐phenylethyl)‐2‐(2‐furyl)‐pyrazolo[4,3‐e]‐1,2,4 triazolo[1,5‐c]pyrimidine, ([3H]‐SCH 58261). In addition, both receptor affinity and potency of a number of adenosine receptor agonists and antagonists were determined in binding, adenylyl cyclase and superoxide anion production assays.
Saturation experiments revealed a single class of binding sites with Kd and Bmax values of 1.34 nM and 75 fmol mg−1 protein, respectively. Adenosine receptor ligands competed for the binding of 1 nM [3H]‐SCH 58261 to human neutrophil membranes, with a rank order of potency consistent with that typically found for interactions with the A2A adenosine receptors. In the adenylyl cyclase and in the superoxide anion production assays the same compounds exhibited a rank order of potency identical to that observed in binding experiments.
Thermodynamic data indicated that [3H]‐SCH 58261 binding to human neutrophils is entropy and enthalpy‐driven. This finding is in agreement with the thermodynamic behaviour of antagonists binding to rat striatal A2A adenosine receptors.
It was concluded that in human neutrophil membranes, [3H]‐SCH 58261 directly labels binding sites with pharmacological properties similar to those of A2A adenosine receptors of other tissues. The receptors labelled by [3H]‐SCH 58261 mediated the effects of adenosine and adenosine receptor agonists to stimulate cyclic AMP accumulation and inhibition of superoxide anion production in human neutrophils.

British Journal of Pharmacology (1998) 123, 1723–1731; doi:10.1038/sj.bjp.0701758
Effect of melatonin in the rat tail artery: role of K+ channels and endothelial factors
Authors: Geary Greg G. , Duckles Sue P. , Krause Diana N. 
Published: January 2005

The role of endothelial factors and potassium channels in the action of the pineal hormone melatonin to potentiate vasoconstrictor responses was investigated in the isolated perfused tail artery of the rat.
Melatonin (100 nM) potentiated contractile responses to both adrenergic nerve stimulation and α1‐adrenoceptor stimulation by phenylephrine. After removal of the endothelium, melatonin no longer caused potentiation.
The potentiating effect of melatonin was also lost when nitric oxide synthase was inhibited with L‐NAME (10 nM). Thus potentiating effects depend on the presence of nitric oxide released by the endothelium. However, melatonin did not affect relaxation responses to acetylcholine in endothelium‐intact arteries, nor did melatonin modulate relaxing responses to sodium nitroprusside in endothelium‐denuded arteries. While melatonin does not appear to modulate agonist‐induced release of nitric oxide nor its effect, melatonin may modulate nitric oxide production induced by flow and shear stress.
When the Ca2+‐activated K+ channel opener, NS 1619 (10 μM), was present, potentiating effects of melatonin were restored in endothelium‐denuded vessels. However, addition of the opener of ATP‐sensitive K+ channels, cromakalim (3 μM), did not have the same restorative effect. Furthermore, addition of a blocker of Ca2+‐activated K+ channels, tetraethylammonium (1 mM), significantly attenuated potentiating effects of melatonin. These findings support the hypothesis that melatonin inhibits the activity of large conductance Ca2+‐activated K+ channels to produce its potentiating effects.
Thus in the rat perfused tail artery, potentiation of constriction by melatonin depends on the activity of both endothelial factors and Ca2+‐activated K+ channels. Our findings suggest that melatonin inhibits endothelial K+ channels to decrease flow‐induced release of nitric oxide as well as block smooth muscle K+ channels to enhance vascular tone.

British Journal of Pharmacology (1998) 123, 1533–1540; doi:10.1038/sj.bjp.0701761
Effects of CGS 21680, a selective A2A adenosine receptor agonist, on cardiac output and vascular resistance in acute heart failure in the anaesthetized rat
Authors: Nekooeian Ali A. , Tabrizchi Reza 
Published: January 2005

The effects of CGS 21680, a selective A2A adenosine receptor agonist, on cardiac output, blood pressure, mean circulatory filling pressure (Pmcf), arterial and venous resistances, heart rate and left ventricular end‐diastolic pressure were assessed in rats with acute heart failure by means of coronary artery occlusion.
Animals (n=6 in each group) were divided into five groups: group I, sham‐operated vehicle‐treated (0.9% saline; 0.018 mL min−1); groups II‐V, subject to coronary artery occlusion and treated with vehicle (0.9% saline; 0.018 ml min−1) and CGS 21680 (0.1, 0.3 and 1.0 μg kg−1 min−1), respectively. Haemodynamic measurements were taken one hour after completion of surgery, ninety minutes after coronary artery occlusion (except in group I), and fifteen minutes after infusion of saline or CGS 21680.
Baseline haemodynamic measurements before occlusion were found not to differ significantly between the different groups of animals. However, after occlusion, cardiac output, rate of rise in left ventricular pressure (+dP/dt) and blood pressure were significantly reduced when compared to corresponding values in sham‐operated animals. In addition, occlusion of the coronary artery resulted in a significant elevation in venous resistance, Pmcf and left ventricular end‐diastolic pressure as compared to corresponding values in sham‐operated animals.
Infusion with CGS 21680 at the highest dose significantly reduced blood pressure, arterial resistance and left ventricular end‐diastolic pressure when compared to occluded vehicle‐treated animals (group II). Administration of CGS 21680 at the highest dose also significantly increased cardiac output (28%) and heart rate (10%) in comparison to occluded vehicle‐treated animals. In addition, the highest dose of CGS 21680 significantly reduced Pmcf (9%) and venous resistance (62%) in comparison to occluded vehicle‐treated animals. Administration of CGS 21680 did not significantly affect +dP/dt when compared to occluded vehicle‐treated animals.
The results from the present investigation indicate that occlusion of the coronary artery in rats results in a state of heart failure characterized by reduced arterial pressure and cardiac output, and increased venous resistance, Pmcf and left ventricular end‐diastolic pressure. Administration of CGS 21680 to animals with acute heart failure resulted in increased cardiac output which was due to reduced venous resistance, as well as increased heart rate.

British Journal of Pharmacology (1998) 123, 1666–1672; doi:10.1038/sj.bjp.0701764
Agonistic properties of alniditan, sumatriptan and dihydroergotamine on human 5‐HT1B and 5‐HT1D receptors expressed in various mammalian cell lines
Authors: Lesage Anne S. , Wouters Ria , Van Gompel Paul , Heylen Lieve , Vanhoenacker Peter , Haegeman Guy , Luyten Walter H. M. L. , Leysen Josée E. 
Published: January 2005

Alniditan, a novel migraine abortive agent, is a potent 5‐HT1B/5‐HT1D receptor agonist of nM affinity. We compared the agonistic properties of alniditan, sumatriptan and dihydroergotamine on the cloned human 5‐HT1B receptor expressed at 200 fmol mg−1 protein (Bmax) in non‐induced L929sA cells, at 740 fmol mg−1 protein in HEK 293 and at 2300 fmol mg−1 protein in mIFNβ‐induced L929sA cells, and on the human cloned 5‐HT1D receptor expressed in C6 glioma cells (Bmax 780 fmol mg−1 protein).
Sodium butyrate treatment increased the expression level of human (h)5‐HT1B receptors in HEK 293 cells and h5‐HT1D receptors in C6 glioma cells approximately 3 fold, the binding affinities of [3H]‐5‐HT and [3H]‐alniditan were unaffected.
Agonistic properties were evaluated based on inhibition of cyclic AMP accumulation in the cells after stimulation of adenylyl cyclase by forskolin or isoproterenol. Alniditan, sumatriptan and dihydroergotamine were full agonists at the h5‐HT1B receptor (IC50 values were 1.7, 20 and 2 nM, respectively in HEK 293 cells) and h5‐HT1D receptors (IC50 values of 1.3, 2.6 and 2.2 nM, respectively). At the h5‐HT1B receptor the agonist potency of the compounds slightly increased with higher receptor density. The opposite was seen for antagonists (ocaperidone, risperidone and ritanserin).
This comparative study demonstrated that alniditan was 10 times more potent than sumatriptan at the h5‐HT1B receptor, and twice as potent at the h5‐HT1D receptor. Dihydroergotamine was more potent an agonist at the h5‐HT1B receptor when expressed at high and low level in L929sA cells (but not in HEK 293 cells), and was less potent at the h5‐HT1D receptor.

British Journal of Pharmacology (1998) 123, 1655–1665; doi:10.1038/sj.bjp.0701766
Effect of the GABA uptake inhibitor tiagabine on sleep and EEG power spectra in the rat
Authors: Lancel Marike , Faulhaber Johannes , Deisz Rudolf A. 
Published: January 2005

The sleep profiles induced by agonists and agonistic modulators of γ‐aminobutyric acidA (GABAA) receptors differ markedly. With regard to GABAA agonists, the effects may be due to the fact that these agents are poor substrates for uptake and are therefore likely to activate GABAA receptors tonically. To investigate this possibility, we assessed the sleep effects of two doses (2 and 10 mg kg−1) of the GABA re‐uptake inhibitor tiagabine, administered intraperitoneally at light onset in 8 rats. Electroencephalogram (EEG) and electromyogram were recorded during the first 8 h after the injection.
Compared with vehicle, tiagabine had minimal effects on the temporal pattern of non‐rapid eye movement sleep (non‐REMS) and on the total time spent therein. However, tiagabine dose‐dependently elevated EEG activity during non‐REMs, most prominently in the lower frequencies (1–8 Hz) and least pronounced in the frequencies between 11 and 16 Hz. During the first 2 h after the injection, 10 mg kg−1 tiagabine elicited repetitive episodes of hypersynchronous EEG waves during wakefulness and slightly suppressed REMS. Except for these effects, tiagabine hardly influenced the time spent in and EEG activity during wakefulness and REMS.
The effects of tiagabine on state‐specific EEG activity were qualitatively very similar to those elicited by GABAA agonists. These findings support the hypothesis that the influence of GABAA agonists on EEG signals may be caused by tonic stimulation of GABAA receptors.

British Journal of Pharmacology (1998) 123, 1471–1477; doi:10.1038/sj.bjp.0701769
Evidence that ATP acts at two sites to evoke contraction in the rat isolated tail artery
Authors: McLaren G J , Burke K S , Buchanan K J , Sneddon P , Kennedy C 
Published: January 2005

The site(s) at which P2‐receptor agonists act to evoke contractions of the rat isolated tail artery was studied by use of P2‐receptor antagonists and the extracellular ATPase inhibitor 6‐N,N‐diethyl‐D‐β,γ‐dibromomethyleneATP (ARL 67156).
Suramin (1 μM–1 mM) and pyridoxalphosphate‐6‐azophenyl‐2′,4′‐disulphonic acid (PPADS) (0.3–300 μM) inhibited contractions evoked by equi‐effective concentrations of α,β‐methyleneATP (α,β‐meATP) (5 μM), 2‐methylthioATP (2‐meSATP) (100 μM) and adenosine 5′‐triphosphate (ATP) (1 mM) in a concentration‐dependent manner. Responses to α,β‐meATP and 2‐meSATP were abolished, but approximately one third of the peak response to ATP was resistant to suramin and PPADS.
Contractions evoked by uridine 5′‐triphosphate (UTP) (1 mM) were slightly inhibited by suramin (100 and 300 μM) and potentiated by PPADS (300 μM).
Desensitization of the P2X1‐receptor by α,β‐meATP abolished contractions evoked by 2‐meSATP (100 μM) and reduced those to ATP (1 mM) and UTP (1 mM) to 15±3% and 68±4% of control.
Responses to α,β‐meATP (5 μM) and 2‐meSATP (100 μM) were abolished when tissues were bathed in nominally calcium‐free solution, while the peak contractions to ATP (1 mM) and UTP (1 mM) were reduced to 24±6% and 61±13%, respectively, of their control response.
ARL 67156 (3–100 μM) potentiated contractions elicited by UTP (1 mM), but inhibited responses to α,β‐meATP (5 μM), 2‐meSATP (100 μM) and ATP (1 mM) in a concentration‐dependent manner.
These results suggest that two populations of P2‐receptors are present in the rat tail artery; ligand‐gated P2X1‐receptors and G‐protein‐coupled P2Y‐receptors.
Ribavirin uptake by human erythrocytes and the involvement of nitrobenzylthioinosine‐sensitive (es)‐nucleoside transporters
Authors: Jarvis Simon M. , Thorn James A. , Glue Paul 
Published: January 2005

The major toxicity associated with oral therapy with ribavirin is anaemia, which has been postulated to occur as a result of accumulation of ribavirin triphosphate interfering with erythrocyte respiration. The objective of this study was to determine the mechanism by which ribavirin enters into erythrocytes.
Entry into human erythrocytes was examined by measuring influx rates of [3H]‐ribavirin alone and with the inhibitor nitrobenzylthioinosine (NBMPR), and by investigating the inhibitory effects of nucleoside and nucleobase permeants on ribavirin transport, by use of inhibitor oil‐stop methods. Transport mechanisms were further characterized by assessment of substrates to cause countertransport of ribavirin in preloaded erythrocytes, and by measuring the effects of ribavirin on [3H]‐NBMPR binding to erythrocyte membranes.
Human erythrocytes had a saturable influx mechanism for ribavirin (Km at 22°C of 440±100 μM) which was inhibited by nanomolar concentrations of NBMPR (IC50 0.99±0.15 nM). Nucleosides also inhibited the influx of ribavirin (adenosine more effective than uridine) but the nucleobases hypoxanthine and adenine had no effect. In addition, uridine caused the countertransport of ribavirin in human erythrocytes. Entry of ribavirin into horse erythrocytes, a cell type that lacks the NBMPR‐sensitive (es) nucleoside transporter, proceeded slowly and via a pathway that was resistant to NBMPR inhibition. Ribavirin was a competitive inhibitor of adenosine influx (mean Ki 0.48±0.14 mM) and also inhibited NBMPR binding to erythrocyte membranes (mean Ki 2.2±0.39 mM).
These data indicate that ribavirin is a transported permeant for the es nucleoside transporter of human erythrocytes. There was no evidence for ribavirin entering cells via a nucleobase transporter.

British Journal of Pharmacology (1998) 123, 1587–1592; doi:10.1038/sj.bjp.0701775
Serine‐O‐sulphate transport by the human glutamate transporter, EAAT2
Authors: Vandenberg Robert J. , Mitrovic Ann D. , Johnston Graham A. R. 
Published: January 2005

Expression of the recombinant human excitatory amino aid transporters, EAAT1 and EAAT2, in Xenopus laevis oocytes allows electrogenic transport to be studied under voltage clamp conditions.
We have investigated the transport of the pharmacological substrate, L‐serine‐O‐sulphate transport by EAAT1 and EAAT2. The EC50 values for L‐serine‐O‐sulphate transport by EAAT2 showed a steep voltage‐dependence, increasing from 152±11 μM at −100 mV to 1930±160 μM at 0 mV. In contrast to EAAT2, EC50 values for L‐serine‐O‐sulphate transport by EAAT1 were relatively constant over the membrane potential range of −100 mV to 0 mV. The EC50 values for L‐glutamate and D‐aspartate transport, by EAAT2, were also relatively constant over this membrane potential range.
Chloride ions modulated the voltage‐dependent changes in EC50 values for transport by EAAT2. This effect was most apparent for L‐serine‐O‐sulphate transport, and to a lesser extent for L‐glutamate and not at all for D‐aspartate transport by EAAT2.
Extracellular sodium and proton concentrations also modulated the voltage‐dependence of L‐serine‐O‐sulphate EC50 values for EAAT2.
We speculate that these different properties of L‐serine‐O‐sulphate transport by EAAT2 compared to other substrates may be due to the much stronger acidity of the sulphate group of L‐serine‐O‐sulphate compared to carboxyl groups of L‐glutamate or D‐aspartate.
These results highlight some of the differences in the way different glutamate transporter subtypes transport substrates. This may be used to understand further the transport process and develop subtype selective inhibitors of glutamate transport.

British Journal of Pharmacology (1998) 123, 1593–1600; doi:10.1038/sj.bjp.0701776
Endothelium‐dependent relaxation and hyperpolarization in guinea‐pig coronary artery: role of epoxyeicosatrienoic acid
Authors: Eckman D M , Hopkins N , McBride C , Keef K D 
Published: January 2005

Acetylcholine (ACh) elicits an endothelium‐dependent relaxation and hyperpolarization in the absence of nitric oxide (NO) and prostaglandin synthesis in the guinea‐pig coronary artery (GPCA). This response has been attributed to a factor termed endothelial‐derived hyperpolarizing factor (EDHF). Recently it has been suggested that EDHF may be a cytochrome P450 product of arachidonic acid (AA) i.e., an epoxyeicosatrienoic acid (EET). The present study investigated whether this pathway could account for the response to ACh observed in the GPCA in the presence of 100 μM Nω‐nitro‐L‐arginine and 10 μM indomethacin.
ACh, AA and 11,12‐EET each produced concentration‐dependent relaxations in arteries contracted with the H1‐receptor agonist AEP (2,2‐aminoethylpyridine). The AA‐induced relaxation was significantly enhanced in the presence of the cyclo‐oxygenase/lipoxygenase inhibitor, eicosatetranynoic acid (30 μM).
The cytochrome P450 inhibitors proadifen (10 μM) and clotrimazole (10 μM) inhibited ACh, lemakalim (LEM) and AA‐induced relaxation, whereas 17‐octadecynoic acid (100 μM) and 7‐ethoxyresorufin (10 μM) were without effect on all three vasodilators. Proadifen and clotrimazole also inhibited ACh (1 μM) and LEM (1 μM)‐induced hyperpolarization.
The ability of various potassium channel blockers to inhibit relaxation responses elicited with ACh, AA and 11,12‐EET was also determined. Iberiotoxin (IBTX; 100 nM) was without effect on responses to ACh but significantly reduced responses to both AA and 11,12‐EET. In contrast, 4‐aminopyridine (4‐AP; 5 mM) significantly reduced response to ACh but not responses to AA and 11,12‐EET. Combined IBTX plus (4‐AP) inhibited the ACh‐induced relaxation to a greater extent than 4‐AP alone. Apamin (1 μM), glibenclamide (10 μM) and BaCl2 (50 μM) had no significant effect on responses to ACh, AA and 11,12‐EET.
IBTX (100 nM) significantly reduced both 11,12‐EET (33 μM) and AA (30 μM) hyperpolarization without affecting the ACh (1 μM)‐induced hyperpolarization. In contrast, 4‐AP significantly reduced the ACh‐induced hyperpolarization without affecting either AA or 11,12‐EET‐induced hyperpolarizations.
In summary, our results suggest that the coronary endothelium releases a factor upon application of AA which hyperpolarizes the smooth muscle. The similarity of pharmacology between AA and 11,12‐EET suggests that this factor is an EET. However, the disparity of pharmacology between responses to ACh versus responses to 11,12‐EET do not support the hypothesis that EETs represent the predominant factor which ACh releases from the endothelium that leads to NO‐ and prostaglandin‐independent hyperpolarization and relaxation in the GPCA.