bluuebunny/crossref_metadata_2025 huggingface dataset:
Involvement of CYP3A‐derived arachidonic acid metabolite(s) in responses to endothelium‐derived K+ channel opening substance in monkey lingual artery
Authors: Ayajiki Kazuhide , Okamura Tomio , Fujioka Hideyuki , Imaoka Susumu , Funae Yoshihiko , Toda Noboru
Published: January 2005

In monkey lingual artery strips partially contracted with prostaglandin F2α, acetylcholine‐induced, concentration‐related relaxations were abolished by removal of the endothelium. The response was not significantly influenced by indomethacin but attenuated by NG‐nitro‐L‐arginine (L‐NOARG); the effect of the nitric oxide (NO) synthase inhibitor was reversed by L‐arginine.

The response to acetylcholine resistant to L‐NOARG was suppressed in the strips exposed to high K+ media. Charybdotoxin partially inhibited the relaxation, and the remaining relaxation was abolished by additional treatment with apamin, whereas glibenclamide, iberiotoxin or apamin alone was without effect. Relaxations induced by sodium nitroprusside were not influenced by charybdotoxin.

The L‐NOARG‐resistant acetylcholine‐induced relaxation was inhibited by metyrapone, proadifen and 17‐octadecynoic acid, non‐selective cytochrome P450 mono‐oxygenase (CYP) inhibitors, and progesterone and ketoconazole, inhibitors selective to CYP3A. The inhibitors did not affect the nitroprusside‐induced relaxation. Selective inhibitors of other CYP isoforms, such as debrisoquine and lauric acid, did not reduce the response to acetylcholine.

Reaction mixture containing human liver microsome rich in CYPs, arachidonic acid and NADPH incubated at 37°C and filtrated relaxed endothelium‐denuded monkey lingual artery strips, used as bioassay tissues. This response was abolished in the strips exposed to high K+ media. The response was also suppressed by combined treatment of the assay tissue with charybdotoxin plus apamin, but was not affected by treatment with iberiotoxin. The reaction mixture co‐incubated with ketoconazole failed to relax the strips.

It is concluded that the monkey lingual arterial relaxation dependent on the endothelium is mediated by NO and also by a charybdotoxin plus apamin‐sensitive but iberiotoxin‐insensitive Ca2+‐activated K+ channel opening substance(s) that may be a CYP3A‐derived arachidonic acid metabolite(s).

British Journal of Pharmacology (1999) 128, 802–808; doi:10.1038/sj.bjp.0702843
Adrenergic and purinergic components in bisected vas deferens from spontaneously hypertensive rats
Authors: Guitart Mònica , Giraldo Jesús , Goñalons Eduard , Vila Elisabet , Badia Albert
Published: January 2005

Purinergic and adrenergic components of the contractile response to electrical field stimulation (EFS) have been investigated in epididymal and prostatic portions of Wystar Kyoto (WKY) and spontaneously hypertensive rat (SHR) vas deferens.

In both halves of SHR and WKY vas deferens, EFS (40 V, 0.5 ms for 30 s, 0.5–32 Hz) evoked frequency‐related contractions. The neurogenic responses were biphasic, consisting of a rapid non‐adrenergic response, dominant in the prostatic portion, followed by a slow tonic adrenergic component, dominant in the epididymal half.

Phasic and tonic components of the frequency‐response curves evoked by EFS were significantly higher in the epididymal but not in the prostatic portion of vas deferens from SHR compared to WKY rats.

The α1‐adrenoceptor antagonist prazosin (0.1 μM) was more effective against both components of the contractile response in the epididymal end of SHR than in WKY rats.

Inhibition by α,β‐methylene adenosine 5′‐triphosphate (α,β‐meATP 3 and 30 μM) was higher in both components of the contractile responses in WKY preparations than in SHR.

Combined α1‐adrenoceptor and P2x‐purinoceptor antagonism virtually abolished the EFS‐evoked contractile response in both strains. The degree of inhibition by prazosin (0.1 μM) after P2x‐purinoceptor blockade was higher in SHR than in WKY rats.

These results demonstrate a modification in the purinergic and noradrenergic contribution to neurogenic responses in SHR and WKY animals besides a co‐participation of ATP and noradrenaline in both contractile components of the response to EFS.

British Journal of Pharmacology (1999) 128, 873–880; doi:10.1038/sj.bjp.0702845
Influence of endothelins and sarafotoxin 6c and L‐NAME on renal vasoconstriction in the anaesthetized rat
Authors: Marshall Joanne L , Johns Edward J
Published: January 2005

An investigation was performed in pentobarbitone anaesthetized rats to compare the renal vasoconstrictor actions of endothelin‐1 (ET‐1), endothelin‐3 (ET‐3) and sarafotoxin 6c and their dependency on NO production.

Intra‐renal arterial infusion of ET‐1 and ET‐3, from 1–1000 ng had no effect on blood pressure, but reduced renal blood flow maximally by 82 and 81% with EC50 values of 510±18 and 1113±17 ng, respectively and correspondingly increased renal vascular resistance and decreased conductance.

Direct renal arterial administration of sarafotoxin 6c was without effect on blood pressure but caused a maximum reduction in renal blood flow of 56% at 300 ng and had an EC50 of 86±4 ng.

Administration of the selective ETA receptor antagonist FR139317 at 0.3 and 1.0 mg kg−1 had no effect on basal levels of blood pressure, renal vascular resistance or renal blood flow. The lower dose of FR139317 had no effect on the ET‐1 dose‐response curve for renal blood flow while at 1.0 mg kg−1, FR139317 reduced the EC50 to 363±32 ng (P<0.05).

Infusion of L‐NAME, 10 μg kg−1 min−1 increased blood pressure by approximately 15%, increased renal vascular resistance and decreased renal blood flow by some 40%. The EC50 values for renal blood flow were reduced to 358±68 ng (P<0.05) for ET‐1, 638±69 ng (P<0.05) for ET‐3 and 55±10 ng (P<0.01) for sarafotoxin 6c. The maximal reduction in renal blood flow induced by sarafotoxin 6c was raised (P<0.01) from 56% to approximately 100% and renal vascular resistance increased when NO production was blocked.

These results showed that the vasoconstrictor actions of ET‐1 and ET‐3 on resistance vessels controlling renal blood flow are mediated via ETB rather than ETA receptors. Moreover, both ET‐1 and ET‐3 dependent vasoconstrictions are slightly attenuated by concomitant NO production. By contrast, sarafotoxin 6c appears much more potent at the renal resistance vasculature and is much more powerfully modulated by NO.

British Journal of Pharmacology (1999) 128, 809–815; doi:10.1038/sj.bjp.0702846
Adrenocorticotropin reverses vascular dysfunction and protects against splanchnic artery occlusion shock
Authors: Squadrito Francesco , Guarini Salvatore , Altavilla Domenica , Squadrito Giovanni , Campo Giuseppe M , Arlotta Mariarita , Quartarone Cristina , Saitta Antonino , Cucinotta Domenico , Bazzani Carla , Cainazzo Maria M , Mioni Chiara , Bertolini Alfio , Caputi Achille P
Published: January 2005

Tumour necrosis factor (TNF‐α) is involved in the pathogenesis of splanchnic artery occlusion (SAO) shock. On the other hand, inhibition of TNF‐α is an important component of the mechanism of action of melanocortins in reversing haemorrhagic shock. We therefore investigated the effects of the melanocortin peptide ACTH‐(1–24) (adrenocorticotropin fragment 1–24) on the vascular failure induced by SAO shock.

SAO‐shocked rats had a decreased survival rate (0% at 4 h of reperfusion, while sham‐shocked rats survived for more than 4 h), enhanced serum TNF‐α concentrations (755±81 U ml−1), decreased mean arterial blood pressure, leukopenia, and increased ileal leukocyte accumulation, as revealed by means of myeloperoxidase activity (MPO=9.4±1 U g−1 tissue). Moreover, aortic rings from shocked rats showed a marked hyporeactivity to phenylephrine (PE, 1 nM–10 μM) (Emax and ED50 in shocked rats=7.16 mN mg−1 tissue and 120 nM, respectively; Emax and ED50 in sham‐shocked rats=16.31 mN mg−1 tissue and 100 nM, respectively), reduced responsiveness to acetylcholine (ACh, 10 nM‐10 μM) (Emax and ED50 in shocked rats=30% relaxation and 520 nM, respectively; Emax and ED50 in sham‐shocked rats=82% relaxation and 510 nM, respectively) and increased staining for intercellular adhesion molecule‐1 (ICAM‐1).

ACTH‐(1–24) [160 μg kg−1 intravenously (i.v.), 5 min after SAO] increased survival rate [SAO+ACTH‐(1–24)=80% at 4 h of reperfusion], reversed hypotension, reduced serum TNF‐α (55±13 U ml−1), ameliorated leukopenia, reduced ileal MPO (1.2±0.2 U g−1 tissue), restored the reactivity to PE, improved the responsiveness to ACh and blunted the enhanced immunostaining for ICAM‐1 in the aorta.

Adrenalectomy only in part–but not significantly–reduced the ACTH‐induced shock reversal, the survival rate of SAO+ACTH‐(1–24) adrenalectomized rats being 60% at 4 h of reperfusion; and methylprednisolone (80 mg−1 i.v., 5 min after SAO) had a non‐significant effect (10% survival) at 4 h of reperfusion.

The present data show that melanocortins are effective also in SAO shock, their effect being, at least in part, mediated by reduced production of TNF‐α. Furthermore, they demonstrate, for the first time, that this inhibition is responsible for the adrenocorticotropin‐induced reversal of vascular failure and leukocyte accumulation.

British Journal of Pharmacology (1999) 128, 816–822; doi:10.1038/sj.bjp.0702848
Type I and II metabotropic glutamate receptor agonists and antagonists evoke cardiovascular effects after intrathecal administration in conscious rats
Authors: Li Xiao C , Beart Philip M , Monn James A , Jones Nicole M , Widdop Robert E
Published: January 2005

In the present study, the role of metabotropic glutamate receptors (mGluRs) in central cardiovascular regulation in conscious rats was examined. To this end, agonists and antagonists for type I and II mGluRs were administered intrathecally, and the temporal changes in blood pressure and heart rate were recorded.

L‐glutamate (1 μmol) and the prototypical mGluR agonist (1S,3R)‐ACPD (0.1 and 0.3 μmol) both increased mean arterial pressure (MAP) and heart rate (HR), implicating functional mGluRs in the spinal cord. The type I mGluR agonist DHPG (0.01–0.1 μmol) evoked increases in MAP (max=25±5 mmHg) and HR (max=88±23 beats min−1). The duration of action, but not the maximum effects, were dose‐related and ranged from approximately 10 min to <90 min and 1 min to >90 min for MAP and HR, respectively.

The type I/II mGluR agonist CCG‐1 (0.1 and 0.3 μmol) caused smaller, variable increases in MAP and HR of intermediate duration (5–20 min), whereas the type II MGluR agonist APDC (0.1 and 1.0 μmol) caused marked, but transient (3–5 min), pressor and tachycardic responses. The highest doses of DHPG and CCG‐1, but not APDC, also evoked behavioural responses similar to a spontaneous nociceptive behavioural effect reported previously.

The type I and II mGluR antagonists (AIDA and LY307452, respectively) were also given approximately 5 min before the administration of the respective type I and II mGluR agonists (DHPG and APDC). Both compounds caused pressor and tachycardic responses, with the effect of AIDA, but not LY307452, returning to control levels before mGluR agonist administration. AIDA significantly attenuated the overall cardiovascular effects of DHPG, while LY307452 significantly attenuated the overall cardiovascular effects of APDC.

These results indicate that functional type I and II mGluRs exist in the spinal cord, and that their activation evokes prolonged cardiovascular effects.

British Journal of Pharmacology (1999) 128, 823–829; doi:10.1038/sj.bjp.0702850
Novel antimigraineur dotarizine releases Ca2+ from caffeine‐sensitive Ca2+ stores of chromaffin cells
Authors: Novalbos Jesús , Abad‐Santos Francisco , Zapater Pedro , Alvarez Javier , Alonso María Teresa , Montero Mayte , García Antonio G
Published: January 2005

The novel antimigraineur, dotarizine (30 μM), increased cytosolic Ca2+ concentration, [Ca2+]c, in fura‐2‐loaded bovine adrenal chromaffin cells. This increase was transient, reached a peak in about 2–5 min (0.53±0.07 μM; n=19) and then declined to basal levels over a further 5 min period.

This transient rise of [Ca2+]c was mimicked by 1 μM thapsigargin and by 30 μM cyclopiazonic acid (CPA), but not by 30 μM flunarizine. Both thapsigargin and CPA occluded the effects of dotarizine and vice versa.

All three compounds suppressed the transient [Ca2+]c rises induced by caffeine (10 mM, 10 s); blockade induced by thapsigargin was irreversible and that induced by CPA and dotarizine was reversible.

Of the three compounds, only dotarizine blocked reversibly the [Ca2+]c spikes induced by short pulses of high K+ (70 mM, 5 s), suggesting that dotarizine blocks voltage‐dependent Ca2+ channels but CPA and thapsigargin do not.

Dotarizine caused a gradual and reversible depletion of endoplasmic reticulum (ER) Ca2+ in chromaffin cells transfected with ER‐targeted aequorin. CPA had a similar effect.

These data show that dotarizine shares with thapsigargin and CPA the ability to deplete Ca2+ in the ER; this novel action of dotarizine could be relevant to its prophylactic effects in migraine. Unlike thapsigargin and CPA, however, dotarizine additionally and reversibly blocks Ca2+ entry through voltage‐dependent Ca2+ channels.

British Journal of Pharmacology (1999) 128, 621–626; doi:10.1038/sj.bjp.0702853
Novel strategies for the design of receptor‐selective vasopressin analogues: Aib‐substitution and retro‐inverso transformation
Authors: Howl John , Prochazka Zdenko , Wheatley Mark , Slaninová Jirina
Published: January 2005

We determined the pharmacological profile of novel backbone‐modified peptides designed as protease‐resistant, selective analogues of AVP. Binding affinities of peptides were determined at both V1A and V2 subtypes of vasopressin receptor (VPR). Biological potencies of selected peptides were tested in pressor and antidiuretic bioassays.

Substitution of the achiral α‐aminoisobutyric acid (Aib) at position 4 or 7 of AVP produced peptides that selectively bound the V2 VPR. Both [Aib4]AVP (140 IU mg−1) and [Aib7]AVP (36 IU mg−1) are selective antidiuretic agonists with little or no activity in uterotonic and pressor assays.

[Aib4] and [Aib7] derivatives of the linear V1A‐selective antagonist [PhaaDTyr(Et)2Arg6Tyr(NH2)9]AVP bound selectively and with high affinity (Kd 0.51 and 4.1 nM respectively) to the V1A VPR. Bioassays confirmed that these peptides were potent antivasopressor agents (pA2 8.10 and 8.36 respectively).

A total retro‐inverso strategy was used to prepare protease‐resistant mimetics of both AVP and linear V1A‐selective antagonists. Cyclic retro‐inverso mimetics of AVP did not bind either V1A or V2 VPRs. In contrast, rationally designed retro‐inverso mimetics of linear V1A‐selective antagonists selectively bound the V1A VPR.

Our findings indicate novel methods to improve the pharmacodynamic and pharmacokinetic parameters of neurohypophysial hormone analogues which could be equally applicable to other peptide‐receptor systems.

British Journal of Pharmacology (1999) 128, 647–652; doi:10.1038/sj.bjp.0702857
Acetylcholine‐induced relaxation of peripheral arteries isolated from mice lacking endothelial nitric oxide synthase
Authors: Waldron G J , Ding H , Lovren F , Kubes P , Triggle C R
Published: January 2005

Acetycholine‐mediated relaxations in phenylephrine‐contracted aortas, femoral and mesenteric resistance arteries were studied in vessels from endothelial nitric oxide synthase knock‐out (eNOS −/−) and the corresponding wild‐type strain (eNOS +/+) C57BL6/SV19 mice.

Aortas from eNOS (+/+) mice relaxed to acetylcholine in an endothelium‐dependent NG‐nitro‐L‐arginine (L‐NOARG) sensitive manner. Aortas from eNOS (−/−) mice did not relax to acetylcholine but demonstrated enhanced sensitivity to both authentic NO and sodium nitroprusside.

Relaxation to acetylcholine in femoral arteries was partially inhibited by L‐NOARG in vessels from eNOS (+/+) mice, but relaxation in eNOS (−/−) mice was insensitive to a combination of L‐NOARG and indomethacin and the guanylyl cyclase inhibitor 1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ). The L‐NOARG/ODQ/indomethacin‐insensitive relaxation to acetylcholine in femoral arteries was inhibited in the presence of elevated (30 mM) extracellular KCl.

In mesenteric resistance vessels from eNOS (+/+) mice, the acetylcholine‐mediated relaxation response was completely inhibited by a combination of indomethacin and L‐NOARG or by 30 mM KCl alone. In contrast, in mesenteric arteries from eNOS (−/−) mice, the acetylcholine‐relaxation response was insensitive to a combination of L‐NOARG and indomethacin, but was inhibited in the presence of 30 mM KCl.

These data indicate arteries from eNOS (−/−) mice demonstrate a supersensitivity to exogenous NO, and that acetylcholine‐induced vasorelaxation of femoral and mesenteric vessels from eNOS (−/−) mice is mediated by an endothelium‐derived factor that has properties of an EDHF but is neither NO nor prostacyclin. Furthermore, in mesenteric vessels, there is an upregulation of the role of EDHF in the absence of NO.

British Journal of Pharmacology (1999) 128, 653–658; doi:10.1038/sj.bjp.0702858
Deficiency in myocardial NO biosignalling after cardioplegic arrest: mechanisms and contribution to post‐storage mechanical dysfunction
Authors: Rach Craig , Gandhi Manoj , Docherty John , Finegan Barry A , Clanachan Alexander S
Published: January 2005

In order to understand mechanisms that limit the safe ischaemic time of donor hearts, this study evaluated NO/cyclic GMP biosignalling in the recovery of function after cardioplegia and hypothermic storage.

Hearts removed from anaesthetized rats were either perfused in working mode (Fresh) or arrested (St. Thomas' II cardioplegia) and stored at 3°C for 8 h (CPL) prior to working mode perfusion. LV work and indices of the production of NO (Ca2+‐dependent and Ca2+‐independent NOS), cyclic GMP (soluble guanylyl cyclase (sGC) and GTP) and superoxide (xanthine oxidase (XO) and xanthine dehydrogenase (XDH)) were measured.

Relative to Fresh hearts, CPL hearts were deficient in cyclic GMP and had poor function. Correction of cyclic GMP deficiency (SNP, 200 μM) improved LV work and LV compliance. SNP effects were prevented by inhibition of sGC (ODQ, 3 μM), and potentiated by inhibition of cyclic GMP‐dependent phosphodiesterase (zaprinast, 20 μM). SNP (200 μM) had no effect on function of Fresh hearts.

NOS activities (pH=7.2) were similar in CPL and Fresh hearts, but at end‐ischaemic pH (6.3), Ca2+‐dependent NOS activity was reduced. The sensitivity of sGC to SNP was greater, and activities of XO and XDH were higher, in CPL than in Fresh hearts.

The deficiency in NO biosignalling in CPL hearts may arise due to acidosis‐induced inhibition of NOS activity, reduced availability of GTP and/or enhanced inactivation of NO by superoxide. These findings provide rationales for novel strategies to prevent the deficiency in NO biosignalling and so improve the function of the transplanted heart.

British Journal of Pharmacology (1999) 128, 891–902; doi:10.1038/sj.bjp.0702863
Nicotinic acetylcholine receptor blocking effect of guanethidine in the rat gastric fundus
Authors: Blommaart P J E , Ferwerda G , Kodde A , Tytgat G N J , Boeckxstaens G E
Published: January 2005

Guanethidine is commonly used as a drug to investigate adrenergic neurotransmission and, in combination with atropine, to realize non‐adrenergic non‐cholinergic (NANC) conditions. Previous studies suggested a nicotinic acetylcholine receptor blocking effect of guanethidine. Therefore, we investigated the effect of increasing concentrations of guanethidine (0.1–100 μM) on nicotine‐induced relaxations of longitudinal muscle strips of rat gastric fundus.

In the presence of 1 μM atropine and 3 μM guanethidine, nicotine (30 μM) induces a fast and sustained relaxation which is partly inhibited by the nitric oxide synthase inhibitors Nω‐nitro‐L‐arginine (L‐NOARG) and Nω‐nitro‐L‐arginine methyl ester (L‐NAME) (both 30 and 100 μM). One μM tetrodotoxin (TTX) completely blocks this nicotine‐induced relaxation.

High concentrations of guanethidine (10 μM), but not adrenoceptor blockade by the α‐adrenoceptor antagonist phentolamine in combination with the β‐adrenoceptor antagonist nadolol (both 3 μM), inhibit the nicotine‐induced relaxation.

Guanethidine (0.1–100 μM) has no effect on relaxations induced by electrical field stimulation (EFS; 1–8 Hz), nitric oxide (NO; 0.01–1 μM), vasoactive intestinal polypeptide (VIP; 0.1–10 nM) or isoprenaline (1–10 nM).

We conclude that high concentrations of guanethidine (10 μM) block nicotine‐induced NANC relaxations of longitudinal muscle strips of the rat gastric fundus most likely at the level of the nicotinic acetylcholine receptor.

British Journal of Pharmacology (1999) 128, 903–908; doi:10.1038/sj.bjp.0702865
Distribution and regulation of cyclooxygenase‐2 in carrageenan‐induced inflammation
Authors: Nantel François , Denis Danielle , Gordon Robert , Northey Angela , Cirino Maria , Metters Kathleen M , Chan Chi Chung
Published: January 2005

We characterized the regulation of cyclooxygenase‐2 (COX‐2) at the mRNA, protein and mediator level in two rat models of acute inflammation, carrageenan‐induced paw ædema and mechanical hyperalgesia.

Carrageenan was injected in the hind paw of rat at low (paw ædema) and high doses (hyperalgesia). COX‐2 and prostaglandin E2 (PGE2) levels were measured by RT–PCR and immunological assays. We also determined the distribution of COX‐2 by immunohistochemistry.

The injection of carrageenan produced a significant and parallel induction of both COX‐2 and PGE2. This induction was significantly higher in hyperalgesia than in paw ædema. This was probably due to the 9 fold higher concentration of carrageenan used to provoke hyperalgesia.

Immunohistochemical examination showed COX‐2 immunoreactivity in the epidermis, skeletal muscle and inflammatory cells of rats experiencing hyperalgesia. In paw ædema however, only the epidermis showed positive COX‐2 immunoreactivity.

Pretreatment with indomethacin completely abolished the induction of COX‐2 in paw ædema but not in hyperalgesia.

These results suggest that multiple mechanisms regulate COX‐2 induction especially in the more severe model. In carrageenan‐induced paw ædema, prostanoid production have been linked through the expression of the COX‐2 gene which suggest the presence of a positive feedback loop mechanism.

British Journal of Pharmacology (1999) 128, 853–859; doi:10.1038/sj.bjp.0702866
The role of protease‐activated receptor‐2 (PAR2) in the modulation of beating of the mouse isolated ureter: lack of involvement of mast cells or sensory nerves
Authors: Moffatt J D , Cocks T M
Published: January 2005

The localization of protease‐activated receptor‐2 (PAR2) and the effects of PAR2 activators were investigated in the mouse isolated ureter in order to test the hypothesis that PAR2 activation may initiate neuropeptide release from sensory nerve fibres and hence contribute to inflammation.

PAR2 was localized by fluorescence immunohistochemistry to both the smooth muscle and epithelium of the ureter. Macrophage‐like cells in the adventitia of the ureter were also PAR2‐immunoreactive. PAR2‐immunoreactivity was not observed in mast cells or nerve fibres.

In circular muscle preparations of the ureter in which continuous rhythmic beating was induced by KCl (20 mM) and the thromboxane A2 mimetic U46619 (0.3 μM), trypsin (0.3 U ml−1) reduced beat frequency to 84.6±2.0% of control rates. The PAR2‐selective peptide agonist SLIGRL‐NH2 concentration‐dependently (0.1–3.0 μM) slowed beat frequency to a maximum of 72.7±2.0%.

Histamine (1–300 μM) was more efficacious than SLIGRL‐NH2 in inhibiting ureter beat frequency in a concentration‐dependent manner to a maximum (at 300 μM) of 7.9±2.5% of the control rate.

Pretreatment of preparations with capsaicin (10 μM for 30 min) markedly attenuated the inhibitory effect of histamine, but not that of SLIGRL‐NH2, indicating a role for sensory nerves in the inhibitory effect of histamine only.

The inhibitory effect of SLIGRL‐NH2 on ureter beat frequency was unaffected by the nitric oxide (NO) synthase inhibitor, L‐NOARG (100 μM) or the cyclo‐oxygenase inhibitor, indomethacin (3 μM).

In conclusion, PAR2 activation causes inhibition of beating in the mouse ureter that is not mediated by axon reflex release of inhibitory neuropeptides. This inhibitory effect of PAR2 appears to be mediated directly on smooth muscle cells, although the contribution of non‐NO, non‐prostanoid epithelium‐derived factors cannot be ruled out.

British Journal of Pharmacology (1999) 128, 860–864; doi:10.1038/sj.bjp.0702871
Autoregulation of nitric oxide‐soluble guanylate cyclase‐cyclic GMP signalling in mouse thoracic aorta
Authors: Hussain Monira B , Hobbs Adrian J , MacAllister Raymond J
Published: January 2005

The sensitivity of the soluble guanylate cyclase (sGC)‐cyclic guanosine‐3′,5′‐monophosphate (cyclic GMP) system to nitric oxide (NO) was investigated in mouse aorta from wild type (WT) and NO synthase (NOS) knockout (KO) animals.

The NO donor, spermine‐NONOate (SPER‐NO) was more potent in aortas from eNOS KO mice compared to WT (pEC50 7.30±0.06 and 6.56±0.04, respectively; n=6; P<0.05). In contrast, the non‐NO based sGC activator, YC‐1 was equipotent in vessels from eNOS WT and KO mice. The sensitivity of aortas from nNOS and iNOS KO animals to SPER‐NO was unchanged. Forskolin (an adenylate cyclase activator), was equipotent in vessels from eNOS WT and KO animals.

The cyclic GMP analogue, 8‐Br‐cGMP was equipotent in eNOS WT and KO mice (pEC50 4.38±0.04 and 4.40±0.05, respectively; n=5; P>0.05). Zaprinast (10−5 M) a phosphodiesterase type V (PDE V) inhibitor, had no effect on the response to SPER‐NO in vessels from eNOS WT or KO mice.

The NOS inhibitor NG‐nitro‐L‐arginine methyl ester (L‐NAME; 3×10−4 M) increased the potency of SPER‐NO in aortas from WT mice (pEC50 6.64±0.02 and 7.37±0.02 in the absence and presence of L‐NAME, respectively; n=4; P<0.05).

In summary, there is increased sensitivity of vessels from eNOS KO animals to NO. Cyclic AMP‐mediated dilatation is unchanged, consistent with a specific up‐regulation of sGC–cyclic GMP signalling. The functional activity of cyclic GMP‐dependent protein kinase (G‐kinase) and PDE V was also unchanged, suggesting that sGC is the site of up‐regulation. These alterations in the sensitivity of the sGC–cyclic GMP pathway might represent a mechanism for the dynamic regulation of NO bioactivity.

British Journal of Pharmacology (1999) 128, 1082–1088; doi:10.1038/sj.bjp.0702874
Investigation of the prejunctional α2‐adrenoceptor mediated actions of MDMA in rat atrium and vas deferens
Authors: Lavelle Aisling , Honner Valerie , Docherty J R
Published: January 2005

We have investigated the effects of methylenedioxymethamphetamine (MDMA, ‘ecstasy’) on peripheral noradrenergic neurotransmission in the rat.

In rat atrial slices pre‐incubated with [3H]‐noradrenaline and in the presence of desipramine (1 μM) to prevent effects of MDMA on basal outflow of tritium, MDMA (10 μM) significantly inhibited the release of tritium evoked by short trains of six pulses at 100 Hz every 10 s for 3 min. This effect did not occur in the presence of the α2‐adrenoceptor antagonist yohimbine (1 μM).

In epididymal portions of rat vas deferens in the presence of nifedipine (10 μM), MDMA produced a concentration‐dependent inhibition of single pulse nerve stimulation‐evoked contractions with a pD2 of 5.88±0.16 (n=4). Inhibitory effects of MDMA were antagonized by the α2‐adrenoceptor antagonist yohimbine (0.3 μM), but not by the 5‐hydroxytryptamine receptor antagonist cyanopindolol in a concentration (1 μM) which markedly antagonized the inhibitory actions of the 5‐HT‐1 receptor agonist 5‐carboxamidotryptamine.

In prostatic portions of rat vas deferens in the presence of cocaine (3 μM), MDMA produced a concentration‐dependent inhibition of single pulse nerve stimulation‐evoked contractions with a pD2 of 5.12±0.21 (n=4). In the absence of cocaine, only the highest concentration of MDMA (30 μM) produced an inhibition, but the α2‐adrenoceptor antagonist yohimbine (0.3 μM) converted the response to MDMA from inhibition to potentiation of the stimulation‐evoked contraction.

In radioligand binding studies, MDMA showed similar affinities for α2B, α2C and α2D‐adrenoceptor sites, with pKi values of 5.14±0.16, 5.11±0.05 and 5.31±0.14, respectively.

It is concluded that MDMA has significant α2‐adrenoceptor agonist actions.

British Journal of Pharmacology (1999) 128, 975–980; doi:10.1038/sj.bjp.0702875
Protein kinase C co‐expression and the effects of halothane on rat skeletal muscle sodium channels
Authors: Mounsey J Paul , Patel Manoj K , Mistry Dilaawar , John J Edward , Moorman J Randall
Published: January 2005

Voltage‐gated Na channels, which are potential targets for general anaesthetics, are substrates for PKC, which phosphorylates a conserved site in the channel inactivation gate. We investigated the idea that PKC modulates the effect of volatile anaesthetics on Na channels via phosphorylation of this inactivation gate site.

Na currents through rat skeletal muscle Na channel α‐subunits expressed in Xenopus oocytes were measured by two‐microelectrode voltage clamp in the presence of the volatile anaesthetic agent halothane (2‐bromo‐2‐chloro‐1,1,1‐trifluroethane). PKC activity was modulated by co‐expression of a constitutively active PKC α‐isozyme.

Halothane (0.4 mM) had no effect on Na currents. With co‐expression of PKC, however, halothane dose‐dependently enhanced the rate of Na current decay and caused a small, but statistically significant reduction in Na current amplitude.

The enhancement of Na current decay was absent in a Na channel mutant in which the inactivation gate phosphorylation site was disabled. Effects of halothane on amplitude were independent of this mutation.

Co‐expression of a PKC α‐isozyme permits an effect of halothane to hasten current decay and reduce current amplitude, at least in part through interaction with the inactivation gate phosphorylation site. We speculate that the interaction between halothane and Na channels is direct, and facilitated by PKC activity and by phosphorylation of a site in the channel inactivation gate.

British Journal of Pharmacology (1999) 128, 989–998; doi:10.1038/sj.bjp.0702877
The anticonvulsant BW534U87 depresses epileptiform activity in rat hippocampal slices by an adenosine‐dependent mechanism and through inhibition of voltage‐gated Na+ channels
Authors: Dupere Joe R B , Dale Tim J , Starkey Sarah J , Xie Xinmin
Published: January 2005

The cellular and molecular actions of BW534U87 were studied using intracellular and extracellular recordings from the CA1 region of rat hippocampal slices and whole‐cell voltage‐clamp recordings of recombinant human brain type IIA Na+ channels expressed in Chinese hamster ovary (CHO) cells.

Normal excitatory and inhibitory postsynaptic potentials evoked in hippocampal slices were unaffected by BW534U87 or the adenosine deaminase inhibitor EHNA. However, epileptiform activity was depressed by BW534U87 (50 μM) and this inhibition was reversed by the adenosine receptor antagonist 8‐phenyl theophylline (8‐PT, 30 μM). EHNA (10 μM) mimicked the effects of BW534U87. Furthermore, BW534U87 enhanced the inhibitory effects of exogenous adenosine on evoked synaptic potentials. BW534U87 (50 μM) also voltage‐ and use‐dependently inhibited action potentials elicited by current injection, independent of the adenosine system, since it was not affected by 8‐PT.

In CHO cells expressing the recombinant human brain Na+ channel, BW534U87 produced a concentration‐ and voltage‐dependent inhibition of Na+ currents with a half‐maximal inhibitory concentration of 10 μM at a Vh of −60 mV. Use‐dependent inhibition was evident at high‐frequencies (20×20 ms pulse train at 10 Hz).

In conclusion, BW534U87 blocks hippocampal epileptiform activity by a dual mechanism. The first action is similar to that produced by EHNA and is dependent on endogenous adenosine probably by inhibition of adenosine deaminase. Secondly, BW534U87 directly inhibits voltage‐gated Na+ channels in a voltage‐ and frequency‐dependent manner. Both actions of BW534U87 are activity‐dependent and may synergistically contribute to its overall anticonvulsant effects in animal models of epilepsy.

British Journal of Pharmacology (1999) 128, 1011–1020; doi:10.1038/sj.bjp.0702881
Chronic and acute effects of thiazolidinediones BM13.1258 and BM15.2054 on rat skeletal muscle glucose metabolism
Authors: Fürnsinn C , Brunmair B , Meyer M , Neschen S , Furtmüller R , Roden M , Kühnle H F , Nowotny P , Schneider B , Waldhäusl W
Published: January 2005

New thiazolidinediones BM13.1258 and BM15.2054 were studied with regard to their PPARγ‐agonistic activities and to their acute and chronic effects on glucose metabolism in soleus muscle strips from lean and genetically obese rats.

Both BM13.1258 and BM15.2054 revealed to be potent PPARγ‐activators in transient transfection assays in vitro.

In insulin‐resistant obese rats, but not in lean rats, 10 days of oral treatment with either compound increased the stimulatory effect of insulin on muscle glycogen synthesis to a similar extent (insulin‐induced increment in μmol glucose incorporated into glycogen g−1 h−1: control, +1.19±0.28; BM13.1258, +2.50±0.20; BM15.2054, +2.55±0.46; P<0.05 vs control each).

In parallel to insulin sensitization, mean glucose oxidation increased insulin‐independently in response to BM13.1258 (to 191 and 183% of control in the absence and presence of insulin, respectively; P<0.01 each), which was hardly seen in response to BM15.2054 (to 137 and 124% of control, respectively; ns).

Comparable effects on PPARγ activation and on amelioration of insulin resistance by BM13.1258 and BM15.2054 were therefore opposed by different effects on glucose oxidation.

In contrast to chronic oral treatment, acute exposure of muscles to BM13.1258 or BM15.2054 in vitro elicited a distinct catabolic response of glucose metabolism in specimens from both lean and obese rats.

The results provide evidence that BM13.1258 and BM15.2054 can affect muscle glucose metabolism via more than one mechanism of action.

Further efforts are required to clarify, to what extent other mechanisms besides insulin sensitization via the activation of PPARγ are involved in the antidiabetic actions of thiazolidinediones.

British Journal of Pharmacology (1999) 128, 1141–1148; doi:10.1038/sj.bjp.0702886
Effects of rupatadine, a new dual antagonist of histamine and platelet‐activating factor receptors, on human cardiac Kv1.5 channels
Authors: Caballero Ricardo , Valenzuela Carmen , Longobardo Mónica , Tamargo Juan , Delpón Eva
Published: January 2005

The effects of rupatadine, a new dual antagonist of both histamine H1 and platelet‐activating factor receptors, were studied on human cloned hKv1.5 channels expressed in Ltk− cells using the whole‐cell patch‐clamp technique.

Rupatadine produced a use‐ and concentration‐dependent block of hKv1.5 channels (KD=2.4±0.7 μM) and slowed the deactivation of the tail currents, thus inducing the ‘crossover’ phenomenon.

Rupatadine‐induced block was voltage‐dependent increasing in the voltage range for channel opening suggesting an open channel interaction. At potentials positive to +10 mV the blockade decreased with a shallow voltage‐dependence. Moreover, rupatadine also modified the voltage‐dependence of hKv1.5 channel activation, which exhibited two components, the midpoint of the steeper component averaging −25.2±2.7 mV.

When the intracellular K+ concentration ([K+]i) was lowered to 25% the voltage‐dependent unblock observed at positive potentials was suppressed and the activation curve in the presence of rupatadine did not exhibit two components even when the midpoint of the activation curve was shifted to more negative potentials (−30.3±1.3 mV).

On channels mutated on the residue R485 (R485Y) which is located on the external entryway of the pore the rupatadine‐induced block did not decrease at potentials positive to +10 mV. In contrast, on V512M channels rupatadine reproduced all the features of the blockade observed on wild type channels.

All these results suggest that rupatadine blocks hKv1.5 channels binding to an external and to an internal binding site but only at concentrations much higher than therapeutic plasma levels in man. Efflux of K+ promotes the unbinding from the external site. Furthermore, rupatadine binds to an internal site and dramatically modifies the voltage‐dependence of channel opening.

British Journal of Pharmacology (1999) 128, 1071–1081; doi:10.1038/sj.bjp.0702890
Changes in EEG spectral power in the prefrontal cortex of conscious rats elicited by drugs interacting with dopaminergic and noradrenergic transmission
Authors: Sebban C , Zhang X Q , Tesolin‐Decros B , Millan M J , Spedding M
Published: January 2005

The electroencephalographic (EEG) effects of drugs interacting with dopaminergic and noradrenergic systems were studied in conscious rats. Power spectra (0–30 Hz) were recorded from electrodes implanted bilaterally in the prefrontal cortex. Drug effects on EEG power were calculated as the spectral power following drug administration divided by the spectral power after vehicle administration.

Dopaminergic agonists at low doses, (apomorphine 0.01 mg kg−1 s.c., quinpirole 0.01 mg kg−1 i.p.) and dopaminergic antagonists (haloperidol 1 mg kg−1 i.p., raclopride 2.5 mg kg−1 s.c.), which decrease dopaminergic transmission, induced an increase of EEG power. Conversely, dopaminergic agonists at higher doses (apomorphine 0.5 mg kg−1 s.c., quinpirole 0.5 mg kg−1 i.p.) which increase activation of postsynaptic D2 and D3 receptors, induced a decrease of EEG power.

The α1‐adrenoceptor antagonists (phenoxybenzamine 0.64 mg kg−1 s.c., prazosin 0.32 mg kg−1 s.c.) and the α2‐adrenoceptor agonists (UK 14304 0.05 mg kg−1 s.c., clonidine 0.025 mg kg−1 i.p.), which decrease noradrenergic transmission, induced an increase of EEG power. Conversely, the α1‐adrenoceptor agonist, cirazoline (0.05 mg kg−1 s.c.), the adrenergic agent modafinil (250, 350 mg kg−1 i.p.) and α2‐adrenoceptor antagonists (RX 821002 0.01 mg kg−1 s.c., yohimbine 0.5 mg kg−1 i.p.), which increase noradrenergic transmission, induced a decrease of EEG power. The effects of prazosin (0.64 mg kg−1 s.c.) were dose‐dependently antagonized by co‐administration with modafinil and cirazoline, but not by apomorphine.

In conclusion, pharmacological modulation of dopaminergic and noradrenergic transmission may result in consistent EEG changes: decreased dopaminergic or noradrenergic activity induces an increase of EEG spectral power; while increased dopaminergic or noradrenergic activity decreases EEG spectral power.

British Journal of Pharmacology (1999) 128, 1045–1054; doi:10.1038/sj.bjp.0702894
Effects of glibenclamide on glycylsarcosine transport by the rat peptide transporters PEPT1 and PEPT2
Authors: Sawada Kyoko , Terada Tomohiro , Saito Hideyuki , Hashimoto Yukiya , Inui Ken‐ichi
Published: January 2005

Glibenclamide is a widely used sulphonylurea for the treatment of non‐insulin‐dependant diabetes mellitus (NIDDM). This agent has been reported to inhibit the activities of various ion channels and transporters. In the present study, we examined the effects of glibenclamide on the function of the H+/peptide cotransporters PEPT1 and PEPT2 by using stable transfectants.

Uptake of [14C]‐glycylsarcosine, a typical substrate for peptide transporters, by PEPT1‐ or PEPT2‐expressing transfectant was inhibited by glibenclamide as well as other sulphonylureas including tolbutamide. 3 Kinetic analysis revealed that the inhibition by glibenclamide was noncompetitive. Dixon plot analyses showed that the Ki values of this agent were 25 and 7.8 μM for PEPT1 and PEPT2, respectively.

Glibenclamide did not inhibit Na+‐coupled alanine and α‐methyl‐D‐glucoside transport, suggesting that the inhibitory effects of glibenclamide on peptide transporters were not due to nonspecific interactions.

There was little uptake of [3H]‐glibenclamide by PEPT‐expressing transfectants as compared to mock‐transfected cells, suggesting that glibenclamide was not a substrate for these peptide transporters.

In summary, glibenclamide inhibited the [14C]‐glycylsarcosine transport by PEPT1 and PEPT2 in a noncompetitive fashion, although glibenclamide per se was not transported through these transporters. These findings would provide important information for clinical, physiological and biochemical aspects of peptide transporters.

British Journal of Pharmacology (1999) 128, 1159–1164; doi:10.1038/sj.bjp.0702895
Early increases in renal kallikrein secretion on administration of potassium or ATP‐sensitive potassium channel blockers in rats
Authors: Fujita Tomoe , Hayashi Izumi , Kumagai Yuji , Inamura Naoya , Majima Masataka
Published: January 2005

This study aimed to examine whether administration of potassium or ATP‐sensitive potassium channel (KATP channel) blockers caused early increases in renal kallikrein (KK) secretion. To clarify this mechanism, the effect on renal KK secretion of a KATP channel blocker was compared with the effect resulting from use of an osmotic diuretic or volume load. Furthermore, the effect on potassium‐induced increases in renal KK secretion by an additional treatment using a KATP channel blocker was examined. Lastly, the effect of a KATP channel blocker on renal KK secretion was also examined in superfused slices of kidney cortex.

Intravenous infusion of potassium augmented renal KK secretion within 30 min while urine volume increased gradually in both the potassium loading and control groups.

Administration of the KATP channel blocker, 4‐morpholinecarboximidine‐N‐1‐adamantyl‐N′‐cyclohexylhydrochloride (PNU‐37883A) or glibenclamide, caused a dose‐dependent increase in renal KK secretion.

The concentration of KK in urine was higher in the PNU‐37883A group as compared to the osmotic‐diuretic or volume‐load group.

PNU‐37883A had no additive effect on the potassium‐induced increase in renal KK secretion.

Renal KK secretion increased in slices of kidney cortex incubated with PNU‐37883A within 10 min of superfusion.

In conclusion, administration of both potassium and KATP channel blockers induced early increases in renal KK secretion in the absence of the washout phenomenon. Potassium loading may have increased renal KK secretion through the same mechanism as the KATP channel blocker.

British Journal of Pharmacology (1999) 128, 1275–1283; doi:10.1038/sj.bjp.0702899
Increased hindrance on the chiral carbon atom of mexiletine enhances the block of rat skeletal muscle Na+ channels in a model of myotonia induced by ATX
Authors: Desaphy Jean‐François , Camerino Diana Conte , Franchini Carlo , Lentini Giovanni , Tortorella Vincenzo , De Luca Annamaria
Published: January 2005

The antiarrhythmic drug mexiletine (Mex) is also used against myotonia. Searching for a more efficient drug, a new compound (Me5) was synthesized substituting the methyl group on the chiral carbon atom of Mex by an isopropyl group. Effects of Me5 on Na+ channels were compared to those of Mex in rat skeletal muscle fibres using the cell‐attached patch clamp method.

Me5 (10 μM) reduced the maximal sodium current (INa) by 29.7±4.4 % (n=6) at a frequency of stimulation of 0.3 Hz and 65.7±4.4 % (n=6) at 1 Hz. At same concentration (10 μM), Mex was incapable of producing any effect (n=3). Me5 also shifted the steady‐state inactivation curves by −7.9±0.9 mV (n=6) at 0.3 Hz and −12.2±1.0 mV (n=6) at 1 Hz.

In the presence of sea anemone toxin II (ATX; 5 μM), INa decayed more slowly and no longer to zero, providing a model of sodium channel myotonia. The effects of Me5 on peak INa were similar whatever ATX was present or not. Interestingly, Me5 did not modify the INa decay time constant nor the steady‐state INa to peak INa ratio.

Analysis of ATX‐induced late Na+ channel activity shows that Me5 did not affect mean open times and single‐channel conductance, thus excluding open channel block property.

These results indicate that increasing hindrance on the chiral atom of Mex increases drug potency on wild‐type and ATX‐induced noninactivating INa and that Me5 might improve the prophylaxis of myotonia.

British Journal of Pharmacology (1999) 128, 1165–1174; doi:10.1038/sj.bjp.0702901
The sulphonylurea glibenclamide inhibits voltage dependent potassium currents in human atrial and ventricular myocytes
Authors: Schaffer Peter , Pelzmann Brigitte , Bernhart Eva , Lang Petra , Mächler Heinrich , Rigler Bruno , Koidl Bernd
Published: January 2005

It was the aim of our study to investigate the effects of the sulphonylurea glibenclamide on voltage dependent potassium currents in human atrial myocytes.

The drug blocked a fraction of the quasi steady state current (ramp response) which was activated positive to −20 mV, was sensitive to 4‐aminopyridine (500 μM) and was different from the ATP dependent potassium current IK(ATP).

Glibenclamide dose dependently inhibited both, the peak as well as the late current elicited by step depolarization positive to −20 mV. The IC50 for reduction in charge area of total outward current was 76 μM.

The double‐exponential inactivation time‐course of the total outward current was accelerated in the presence of glibenclamide with a τfast of 12.7±1.5 ms and a τslow of 213±25 ms in control and 5.8±1.9 ms (P<0.001) and 101±20 ms (P<0.05) under glibenclamide (100 μM).

Our data suggest, that both repolarizing currents in human atrial myocytes, the transient outward current (Ito1) and the ultrarapid delayed rectifier current (IKur) were inhibited by glibenclamide.

In human ventricular myocytes glibenclamide inhibited Ito1 without affecting the late current.

Our data suggest that glibenclamide inhibits human voltage dependent cardiac potassium currents at concentrations above 10 μM.

British Journal of Pharmacology (1999) 128, 1175–1180; doi:10.1038/sj.bjp.0702904
Pharmacological characterization of the human P2Y11 receptor
Authors: Communi Didier , Robaye Bernard , Boeynaems Jean‐Marie
Published: January 2005

The human P2Y11 receptor is coupled to both the phosphoinositide and the cyclic AMP pathways. A pharmacological characterization of the recombinant human P2Y11 receptor has been conducted following stable expression in two different cell lines: the 1321N1 astrocytoma cells for inositol trisphosphate measurements and the CHO‐K1 cells for cyclic AMP assays. The rank order of potency of a series of nucleotides was almost identical for the two pathways: ATPγS∼BzATP>dATP>ATP>ADPβS>2MeSATP.

ADPβS, AMPαS and A3P5PS behaved as partial agonists of the human P2Y11 receptor. At high concentrations, these three nucleotides were able to partially inhibit the ATP response.

Suramin was a more potent antagonist than reactive blue 2, whereas pyridoxal‐phosphate‐6‐azophenyl‐2′,4′‐disulphonic acid was completely inactive. The P2Y11 receptor proved to be sensitive to suramin in a competitive way with an apparent Ki value of 0.82±0.07 μM.

The ATP derivative AR‐C67085 (2‐propylthio‐β, γ‐dichloromethylene‐D‐ATP), a potent inhibitor of ADP‐induced platelet aggregation, was the most potent agonist of the P2Y11 receptor, among the various nucleotides tested.

The pharmacological profile of the recombinant human P2Y11 receptor is closely similar to that of the cyclic AMP‐coupled P2 receptor recently described in HL‐60 cells, suggesting that it is the same receptor.

British Journal of Pharmacology (1999) 128, 1199–1206; doi:10.1038/sj.bjp.0702909