bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of the contraction to 5‐HT in the canine colon longitudinal muscle
Authors: Prins Nicolaas H. , Briejer Michel R. , Schuurkes Jan A.J. 
Published: August 2006

Although conscious dogs have often been used for colonic motility studies with 5‐hydroxytryptamine (5‐HT), the effects of 5‐HT on the isolated colon have not been thoroughly characterized yet. The current study was undertaken to characterize the response to 5‐HT of the canine isolated colon longitudinal muscle.
Longitudinal strips of canine midcolon deprived of (sub)mucosa were prepared for isotonic measurement. 5‐HT induced contractions from 3 nM onwards, which were not affected by selective inhibition of 5‐HT re‐uptake, monoamine oxidase or blockade of α‐adrenoceptors. Tetrodotoxin (0.3 μm) did not affect the responses to 5‐HT, suggesting that smooth muscle 5‐HT receptors are involved. The selective 5‐HT4 receptor antagonist SB 204070 (10 nM) slightly enhanced contractions to 5‐HT and therefore it was included in the organ bath solution in all further experiments. The 5‐HT1 and 5‐HT2 receptor antagonist methysergide (0.1 μm) depressed the curve to 5‐HT, but the selective 5‐HT3 receptor antagonist granisetron (0.3 μm) had no effect.
Besides 5‐HT, α‐methyl‐5‐HT (α‐Me‐5‐HT), 5‐methoxytryptamine (5‐MeOT), 2‐methyl‐5‐HT (2‐Me‐5‐HT) and 5‐carboxamidotryptamine (5‐CT) also induced contractions, with the following rank order of potency (pEC50 values in parentheses): 5‐HT (6.9) = α‐methyl‐5‐HT (6.9) >2‐Me‐5‐HT (5.8) = 5‐MeOT (5.7) = 5‐CT (5.6), indicative of 5‐HT2 receptor involvement. α‐Me‐5‐HT produced a bell‐shaped curve, which was not affected by α‐adrenoceptor blockade. 5‐HT, 5‐MeOT, 2‐Me‐5‐HT and 5‐CT produced a monophasic concentration‐response curve, consistent with an interaction with a single receptor site. 8‐Hydroxy‐2‐(di‐n‐propylamino) tetralin (8‐OH‐DPAT) and tryptamine only induced contractions at a concentration exceeding 1 μM.
The selective 5‐HT2B receptor antagonist SB 204741 (0.3 μM) did not affect the curve to 5‐HT. Ketanserin, cisapride and spiroxatrine behaved as competitive antagonists with p Kb values of, respectively, 8.4, 8.1 and 6.7. Spiroxatrine (1 μm) shifted the curve to 5‐MeOT rightward yielding an apparent pA2 of 7.1. Other antagonists at 5‐HT2A receptors also surmountably inhibited the contractions to 5‐HT (apparent pA2 value in parentheses): mesulergine (8.2), cinanserin (8.2), yohimbine (6.2) and mianserin (8.6). However, as well as a rightward shift, methiothepin (8.3), pizotifen (8.6) and spiperone (8.8) also caused a depression of the curve, indicative of ‘pseudo‐irreversible’ antagonism. Taken together, the above mentioned affinity estimates most closely corresponded to literature affinity values for 5‐HT2A receptors.
It was concluded that 5‐HT induces contractions of the canine midcolon longitudinal muscle primarily by stimulation of smooth muscle 5‐HT2A receptors. The presence of inhibitory 5‐HT4 receptors cannot be ruled out.
The effect of big endothelin‐1 in the proximal tubule of the rat kidney
Authors: Beara‐Lasić Lada , Knotek Mladen , Čejvan Kenan , Jakšić Ozren , Lasić Zoran , Skorić Boško , Brkljačić Vera , Banfić Hrvoje 
Published: August 2006

An obligatory step in the biosynthesis of endothelin‐1 (ET‐1) is the conversion of its inactive precursor, big ET‐1, into the mature form by the action of specific, phosphoramidon‐sensitive, endothelin converting enzyme(s) (ECE). Disparate effects of big ET‐1 and ET‐1 on renal tubule function suggest that big ET‐1 might directly influence renal tubule function. Therefore, the role of the enzymatic conversion of big ET‐1 into ET‐1 in eliciting the functional response (generation of 1,2‐diacylglycerol) to big ET‐1 was studied in the rat proximal tubules.
In renal cortical slices incubated with big ET‐1, pretreatment with phosphoramidon (an ECE inhibitor) reduced tissue immunoreactive ET‐1 to a level similar to that of cortical tissue not exposed to big ET‐1. This confirms the presence and effectiveness of ECE inhibition by phosphoramidon.
In freshly isolated proximal tubule cells, big ET‐1 stimulated the generation of 1,2‐diacylglycerol (DAG) in a time‐and dose‐dependent manner. Neither phosphoramidon nor chymostatin, a chymase inhibitor, influenced the generation of DAG evoked by big ET‐1.
Big ET‐1‐dependent synthesis of DAG was found in the brush‐border membrane. It was unaffected by BQ123, an ETA receptor antagonist, but was blocked by bosentan, an ETA B‐nonselective endothelin receptor antagonist.
These results suggest that the proximal tubule is a site for the direct effect of big ET‐1 in the rat kidney. The effect of big ET‐1 is confined to the brush‐border membrane of the proximal tubule, which may be the site of big ET‐1‐sensitive receptors.
Effects of extracellular nucleotides on single cells and populations of human osteoblasts: contribution of cell heterogeneity to relative potencies
Authors: Jane Dixon C , Bowler Wayne B , Walsh Catherine A , Gallagher James A 
Published: August 2006

Human osteoblasts responded to the application of extracellular nucleotides, acting at P2‐receptors, with increases in cytosolic free calcium concentration ([Ca2+]i).
In populations of human osteoblasts, adenosine 5′‐diphosphate (ADP) evoked a rise in [Ca2+]i with less than 40% of the amplitude of that induced by adenosine 5′‐triphosphate (ATP).
ATP and uridine 5′‐triphosphate (UTP) were applied to single human osteoblasts and induced [Ca2+]i rises of comparable amplitude in every cell tested.
However, from the results of single cell studies with ADP (and 2‐methylthioATP (2‐meSATP)) two groups of cells were delineated: one group responded to ADP (or 2‐meSATP) with a rise in [Ca2+]i indistinguishable from that evoked by ATP; whereas the second group failed completely to respond to ADP (or 2‐meSATP).
Therefore heterogeneity of receptor expression exists within this population of human osteoblasts. The limited distribution of the ADP‐responsive receptor underlies the small response to ADP, compared with ATP, recorded in populations of human osteoblasts. This heterogeneity may reflect differences in the differentiation status of individual cells.

British Journal of Pharmacology (1997) 120, 777–780; doi:10.1038/sj.bjp.0700961
Induction of cyclo‐oxygenase‐2 by cytokines in human cultured airway smooth muscle cells: novel inflammatory role of this cell type
Authors: Belvisi Maria G , Saunders Michael A , Haddad El‐Bdaoui , Hirst Stuart J , Yacoub Magdi H , Barnes Peter J , Mitchell Jane A 
Published: August 2006

Cyclo‐oxygenase (COX) is the enzyme that converts arachidonic acid to prostaglandin H2 (PGH2) which can then be further metabolized to prostanoids which modulate various airway functions. COX exists in at least two isoforms. COX‐1 is expressed constitutively, whereas COX‐2 is expressed in response to pro‐inflammatory stimuli. Prostanoids are produced under physiological and pathophysiological conditions by many cell types in the lung. However, the regulation of the different COX isoforms in human airway smooth muscle (HASM) cells has not yet been determined.
COX‐1 and COX‐2 protein were measured by Western blot analysis with specific antibodies for COX‐1 and COX‐2. COX‐2 mRNA levels were assessed by Northern blot analysis by use of a COX‐2 cDNA probe. COX activity was determined by measuring conversion of either endogenous or exogenous arachidonic acid to three metabolites, PGE2, thromboxane B2 or 6‐ketoPGF1α by radioimmunoassay.
Under control culture conditions HASM cells expressed COX‐1, but not COX‐2, protein. However, a mixture of cytokines (interleukin‐1β (IL‐1β), tumour necrosis factor α (TNFα) and interferon γ (IFNγ) each at 10 ng ml−1) induced COX‐2 mRNA expression, which was maximal at 12 h and inhibited by dexamethasone (1 μm; added 30 min before the cytokines). Furthermore, COX‐2 protein was detected 24 h after the cytokine treatment and the expression of this protein was also inhibited by dexamethasone (1 μm) and cyclohexamide (10 μg ml−1; added 30 min before the cytokines).
Untreated HASM cells released low or undetectable amounts of all COX metabolites measured over a 24 h period. Incubation of the cells with the cytokine mixture (IL‐1β, TNFα, IFNγ each at 10 ng ml−1 for 24 h) caused the accumulation of PGE2 and 6‐keto‐PGF1α.
In experiments where COX‐2 metabolized endogenous stores of arachidonic acid, treatment of HASM cells with IL‐1β in combination with TNFα caused a similar release of PGE2 to that when the three cytokines were given in combination.
In other experiments designed to measure COX‐2 activity directly, cells were treated with cytokines for 24 h before fresh culture medium was added containing exogenous arachidonic acid (30 μm for 15 min) after which PGE2 was measured. IL‐1β and TNFα increased COX‐2 activity and an additional small increase was produced by the three cytokines in combination.
These findings suggest that the increased expression of COX‐2 is intimately involved in the exaggerated release of prostanoids from HASM cells exposed to pro‐inflammatory cytokines. These data indicate a role for airway smooth muscle cells, in addition to their contractile function, as inflammatory cells involved in the production of mediators which may contribute to the inflammatory response seen in diseases such as asthma.

British Journal of Pharmacology (1997) 120, 910–916; doi:10.1038/sj.bjp.0700963
Inhibition of delayed rectifier K+ channels by phenytoin in rat neuroblastoma cells
Authors: Nobile Mario , Vercellino Paolo 
Published: August 2006

The action of the anticonvulsant drug phenytoin on K+ currents was investigated in neuroblastoma cells by whole‐cell voltage‐clamp recording.
Neuroblastoma cells expressed an outward K+ current with a voltage‐and time‐dependence which resembled the delayed‐rectifier K+ current found in other cells. When added to the standard external solution at concentrations ranging between 1 and 200 μM, phenytoin reduced the current (n = 65). Inhibition was concentration‐dependent with a half‐maximal inhibitory concentration of 30.9 + 0.8 μM.
The K+ current inhibition by phenytoin was voltage‐dependent with block by phenytoin being relieved by depolarization.
The times taken to reach steady‐state inhibition and complete recovery from inhibition were about 20 s. Neither the activation and inactivation rates of the K+ current nor the K+ channel availability were significantly altered by the blocking drug. A use‐dependent block was observed at phenytoin concentrations of 10, 25 and 50 μM.
These results suggest that phenytoin affects K+ currents and that this effect might lead to a reduction in neuronal excitability.
The effects of spiradoline (U‐62066E), a κ‐opioid receptor agonist, on neuroendocrine function in man
Authors: Ur Ehud , Wright D Mark , Bouloux Pierre M G , Grossman Ashley 
Published: August 2006

Opioid drugs act on specific receptors which are principally classified into μ, δ and κ subtypes. Spiradoline (U‐62066E) is a κ‐selective agent which has been shown to possess potent anti‐nociceptive effects but does not show cross tolerance with morphine.
We have assessed the neuroendocrine effects of spiradoline in healthy volunteers with two doses (1.6 and 4.0 μg kg−1, i.m.) of the compound. Six male non‐smokers aged 19–27 years were studied by use of a randomized, double‐blind three‐limb placebo‐controlled cross‐over design. Blood was taken from an in‐dwelling venous cannula basally and at 15 min intervals for 2 h for determination of serum cortisol, prolactin, growth hormone (GH) and catecholamines.
Psychological function was assessed by the Stanford Sleepiness Scale (SSS) and the Addiction Research Centre Inventory (ARCI) administered before the medication and at 35 min, 1 h 25 min and 2 h afterwards. Cardiovascular variables were recorded at 10 min intervals. Results were analysed by analysis of variance.
Spiradoline showed a significant (P<0.05) dose‐dependent increase in free water clearance, as predicted for a κ‐opioid agonist. It also caused a dose‐dependent stimulation of prolactin, (increment over baseline for higher dose 214%), GH (433%) and cortisol (215%) release (P<0.05). There were no significant drug‐related changes in plasma catecholamines, blood pressure, pulse or psychological variables.
We have therefore confirmed that κ‐opioids increase free‐water clearance and may participate in the stimulation of prolactin and GH release. In contrast to μ and δ‐opioid agonists, this novel κ‐agonist stimulates cortisol release in man.

British Journal of Pharmacology (1997) 120, 781–784; doi:10.1038/sj.bjp.0700971
Renal effects of intracerebroventricularly injected tachykinins in the conscious saline‐loaded rat: receptor characterization
Authors: Ding Yuan Yi , Couture Réjean 
Published: August 2006

The effects of intracerebroventricularly (i.c.v.) injected substance P (SP), neurokinin A (NKA) and [MePhe7]neurokinin B (NKB) were investigated on renal excretion of water, sodium and potassium in the conscious saline‐loaded rat. The central effects of [MePhe7]NKB were characterized with selective tachykinin antagonists for NK1 (RP 67580), NK2 (SR 48968) and NK3 (R 820) receptors.
Whereas SP or NKA (65 or 650 pmol) failed to modify the renal responses, [MePhe7]NKB (65–6500 pmol) produced dose‐dependent and long‐lasting (30–45 min) decreases in renal excretion of water (maximal reduction at 65 pmol: from 66.14±7.62 to 21.07±3.79 μl min−1), sodium (maximal reduction at 65 pmol: from 10.19±2.0 to 1.75±0.48 μmol min−1) and potassium (maximal reduction at 65 pmol: from 4.31±1.38 to 0.71±0.27 μmol min−1). While 650 pmol [MePhe7]NKB elevated urinary osmolality, neither 65 pmol nor 6.5 nmol [MePhe7]NKB altered this parameter.
Both the antidiuresis and antinatriuresis induced by [MePhe7]NKB (65 pmol) were significantly blocked by the prior i.c.v. injection of R 820 (1.3 nmol, 5 min earlier), although the potassium excretion was only partially reduced. However, R 820 did not affect the antidiuresis and antinatriuresis elicited by endothelin‐1 (1 pmol, i.c.v.). On its own, R 820 decreased renal potassium excretion with no effect on urinary osmolality and renal excretion of water and sodium. The i.c.v. co‐injection of RP 67580 and SR 48968 (6.5 nmol each, 5 min earlier) failed to modify the renal responses to [MePhe7]NKB in a similar study.
The central effects of [MePhe7]NKB (65 pmol) on renal excretion were blocked by the prior i.v. administration of a linear peptide vasopressin V2 receptor antagonist (50 μg kg−1, 5 min earlier).
These results suggest that the central NK3 receptor, probably located in the hypothalamus, is implicated in the renal control of water and electrolyte homeostasis through the release of vasopressin in the conscious saline‐loaded rat.

British Journal of Pharmacology (1997) 120, 785–796; doi:10.1038/sj.bjp.0700972
Inhibitory action of niflumic acid on noradrenaline‐ and 5‐hydroxytryptamine‐induced pressor responses in the isolated mesenteric vascular bed of the rat
Authors: Criddle D N , Soares de Moura R , Greenwood I A , Large W A 
Published: August 2006

The effects of niflumic acid, an inhibitor of calcium‐activated chloride currents, were compared with the actions of the calcium channel blocker nifedipine on noradrenaline‐ and 5‐hydroxytryptamine (5‐HT)‐induced pressor responses of the rat perfused isolated mesenteric vascular bed.
Bolus injections of noradrenaline (1 and 10 nmol) increased the perfusion pressure in a dose‐dependent manner. Nifedipine (1 μm) inhibited the increase in pressure produced by 1 nmol noradrenaline by 31±5%. Niflumic acid (10 and 30 μm) also inhibited the noradrenaline‐induced increase in perfusion pressure and 30 μm niflumic acid reduced the pressor response to 1 nmol noradrenaline by 34±6%.
The increases in perfusion elicited by 5‐HT (0.3 and 3 nmol) were reduced by niflumic acid (10 and 30 μm) in a concentration‐dependent manner and 30 μm niflumic acid inhibited responses to 0.3 and 3 nmol 5‐HT by, respectively, 49±8% and 50±7%. Nifedipine (1 μm) decreased the pressor response to 3 nmol 5‐HT by 44±9%.
In the presence of a combination of 30 μm niflumic acid and 1 μm nifedipine the inhibition of the pressor effects of noradrenaline (10 nmol) and 5‐HT (3 nmol) was not significantly greater than with niflumic acid (30 μm) alone. Thus the effects of niflumic acid and nifedipine were not additive.
In Ca‐free conditions the transient contractions induced by 5‐HT (3 nmol) were not reduced by 30 μm niflumic acid, suggesting that this agent does not inhibit calcium release from the intracellular store or the binding of 5‐HT to its receptor.
Niflumic acid 30 μm did not inhibit the pressor responses induced by KCl (20 and 60 μmol) which were markedly reduced by 1 μm nifedipine. In addition, 1 μm levcromakalim decreased pressor responses produced by 20 μmol KCl. These data suggest that niflumic acid does not block directly calcium channels or activate potassium channels.
It is concluded that niflumic acid selectively reduces a component of noradrenaline‐ and 5‐HT‐induced pressor responses by inhibiting a mechanism which leads to the opening of voltage‐gated calcium channels. Our data suggest that the Ca2+‐activated chloride conductance may play a pivotal role in the activation of voltage‐gated calcium channels in agonist‐induced constriction of resistance blood vessels.

British Journal of Pharmacology (1997) 120, 813–818; doi:10.1038/sj.bjp.0700981
Pharmacological characterization of an α1A‐adrenoceptor mediating contractile responses to noradrenaline in isolated caudal artery of rat
Authors: Lachnit Wilhelm G , Tran Antares M , Clarke David E , Ford Anthony P D W 
Published: August 2006

The α1‐adrenoceptor population mediating contraction of caudal artery of rat has been characterized by using quantitative receptor pharmacology.
Cumulative concentration‐effect (E/[A]) curves to noradrenaline (NA) yielded a p[A]50 of 5.56±0.05 (n=16). Prazosin caused concentration‐dependent, parallel, dextral shifts of E/[A] curves to NA yielding a pKb of 8.9 (Schild regression slope=1.0). RS‐17053 (N‐[2‐(2‐cyclopropyl methoxy phenoxy) ethyl]‐5‐chloro‐α,α‐dimethyl −1H‐indole‐ 3‐ethanamine hydrochloride; 10–100 nm), a selective α1A‐adrenoceptor antagonist, produced non‐parallel, biphasic, dextral shifts of E/[A] curves to NA, suggesting the involvement of more than one α1‐adrenoceptor subtype. Analysis of the high affinity component yielded an apparent pA2 value of 9.2±0.3.
A‐61603, a selective agonist at α1A adrenoceptors behaved as a full agonist relative to NA and yielded monophasic E/[A] curves with a p[A50] of 7.59±0.04 (n=15). Pretreatment of tissues with chloroethylclonidine (CEC; 100 μm for 20 min, followed by 40 min washout), which preferentially alkylates α1B‐ and α1D‐adrenoceptors, did not alter E/[A] curves to A‐61603. Prazosin (3–300 nm) caused concentration‐dependent, parallel, dextral shifts of E/[A] curves to A‐61603 yielding a pA2 estimate of 9.2±0.2.
Experiments with α1‐adrenoceptor antagonists of varying subtype selectivities (RS‐17053, SNAP 5089, tamsulosin, 5‐methylurapidil, BMY 7378, HV 723 and REC 15/2739) revealed parallel dextral shifts of E/[A] curves to A‐61603. Schild regression analyses yielded pA2 estimates of 9.2, 9.3, 11.2, 9.0, 6.3, 8.7 and 10.0 for RS‐17053, SNAP 5089, tamsulosin, 5‐methylurapidil, BMY 7378, HV 723 and REC 15/2739, respectively, although deviations from unit slope (possibly reflecting a secondary involvement of another α1‐adrenoceptor) hindered estimations of pKb for some antagonists. The antagonist affinity profile obtained reflects best that described for the α1A‐adrenoceptor.
In conclusion, caudal artery of rat contracts in response to NA via activation of at least two α1‐adrenoceptor subtypes. One of these subtypes displays the pharmacology of the α1A‐adrenoceptor, while the other remains to be defined. Use of the novel selective agonist, A‐61603, allows for limited pharmacological isolation of the α1A‐adrenoceptor permitting characterization of the properties of selective antagonists.

British Journal of Pharmacology (1997) 120, 819–826; doi:10.1038/sj.bjp.0700983
Vasoconstrictor responses via P2X‐receptors are selectively antagonized by NF023 in rabbit isolated aorta and saphenous artery
Authors: Ziyal Ragip , Ziganshin Airat U , Nickel Peter , Ardanuy Ursula , Mutschler Ernst , Lambrecht Günter , Burnstock Geoffrey 
Published: August 2006

The effects of NF023, the symmetrical 3′‐urea of 8‐(benzamido)naphthalene‐1,3,5‐trisulphonic acid), and its parent compound suramin were investigated on vasoconstrictor responses to α,β‐methylene ATP in rabbit isolated saphenous artery and vasodilator responses to ATP in noradrenaline‐precontracted rabbit isolated thoracic aorta.
In rabbit isolated saphenous artery, α,β‐methylene ATP‐induced vasoconstrictor responses via P2X‐receptors were concentration‐dependently and competitively antagonised by NF023 (30–300 μm; pA2=5.69±0.04). Suramin (100–1000 μm) also competitively blocked vasoconstrictor responses to α,β‐methylene ATP, albeit with lower potency (pA2=4.79±0.05). In contrast, NF023 (100 μm) did not significantly affect contractile responses to noradrenaline or histamine in the saphenous artery.
In noradrenaline‐precontracted rabbit isolated thoracic aorta preparations, ATP (3–3000 μm) concentration‐dependently induced relaxations via endothelium‐dependent or smooth muscle P2Y‐receptor subtypes. NF023 (30–300 μm) failed to block relaxant responses to ATP at endothelium‐dependent P2Y‐receptors, whereas suramin (100–1000 μm) did antagonise endothelium‐dependent vasodilator responses to ATP. Neither NF023 (100 μm) nor suramin (300 μm) influenced vasorelaxant responses to ATP via endothelium‐independent P2Y‐receptors.
In conclusion, this study outlines the selectivity of NF023 as an effective P2X‐receptor antagonist in rabbit isolated blood vessels without affecting endothelium‐dependent or endothelium‐independent P2Y‐receptor subtypes, adrenoceptors or histamine receptors.

British Journal of Pharmacology (1997) 120, 954–960; doi:10.1038/sj.bjp.0700984