bluuebunny/crossref_metadata_2025 huggingface dataset:
On the inhibition of voltage activated calcium currents in rat cortical neurones by the neuroprotective agent 619C89
Authors: Stefani A , Hainsworth A. H. , Spadoni F , Bernardi G
Published: January 2005

The lamotrigine analogue 619C89, utilised to reduce postischaemic and posttraumatic neuronal injury, has been shown to inhibit sodium channels and cloned N‐type calcium channels. To verify whether this neuroprotective agent also blocked native calcium channels, we have tested its action in cortical pyramidal neurones, acutely isolated from the adult rat brain.

619C89 inhibited more than 90% of the high voltage‐activated calcium currents recorded in the whole‐cell configuration. The response was relatively slow in onset (30–60 s), recovered incompletely (96%), but showed no consistent desensitization.

This inhibitory effect was not selective for any calcium channel subtype, being largely unaffected by ω‐conotoxin‐GVIA, ω‐agatoxin‐IVA, ω‐conotoxin‐MVIIC and dihydropyridine antagonists.

Saturating responses to 619C89 were detected for concentrations 50 μM. Dose‐response curves revealed that 619C89 have an approximately 8 μM binding site.

The effect of 619C89 was dependent on the divalent concentrations in that its potency was reduced on increase of the charge carrier up to 20 mM barium. Since the lamotrigine analogue shifted to the right the dose‐dependence of the cadmium block, the 619C89‐mediated inhibition of calcium currents seemed to rely on a direct interaction with the channel pore. Functional implications are discussed.

British Journal of Pharmacology (1998) 125, 1058–1064; doi:10.1038/sj.bjp.0702134
Pharmacological characterization of endothelin‐induced contraction in the guinea‐pig oesophageal muscularis mucosae
Authors: Uchida Kohsuke , Yuzuki Rika , Kamikawa Yuichiro
Published: January 2005

In the oesophageal muscularis mucosae, we examined the effects of endothelin‐1 (ET‐1), endothelin‐2 (ET‐2), endothelin‐3 (ET‐3) and sarafotoxin S6c (SX6c) as agonists, and FR139317, BQ‐123 and RES‐701‐1 as endothelin receptor antagonists.

All of the endothelins produced tonic contractions which were frequently superimposed on rhythmic motility in a concentration‐dependent manner. The order of potency (−log EC50) was ET‐1 (8.61)=SX6c (8.65)>ET‐2 (8.40)>ET‐3 (8.18).

FR139317 (1–3 μM) and BQ‐123 (1 μM) caused parallel rightward shifts of the concentration‐response curve to ET‐1, but at higher concentrations caused no further shift. RES‐701‐1 (3 μM) caused a rightward shift of the concentration‐response curve to ET‐1, while RES‐701‐1 (10 μM) had no additional effect. RES‐701‐1 (0.1–1 μM) concentration‐dependently caused a rightward shift of the concentration‐response curve to SX6c. The contraction to ET‐1 (10 nM) in preparations desensitized to the actions of SX6c was greatly inhibited by pretreatment with FR139317 (10 μM).

Modulation of the Ca2+ concentration in the Krebs solution caused the concentration‐response curve to ET‐1 or SX6c to shift to the right and downward as external Ca2+ concentrations decreased. Verapamil (30 μM) abolished rhythmic motility induced by ET‐1 or SX6c. Ni2+ (0.1 mM) weakly inhibited ET‐1‐ or SX6c‐induced tonic contraction. SK&F 96365 (60 μM) completely inhibited ET‐1‐induced contractions.

We conclude that there are two types of ET‐receptors, excitatory ETA‐ and ETB‐receptors in the oesophageal muscularis mucosae. These receptors mediate tonic contractions predominantly by opening receptor‐operated Ca2+ channels (ROCs) and partly by opening T‐type Ca2+ channels, and mediate rhythmic motility by opening L‐type Ca2+ channels.

British Journal of Pharmacology (1998) 125, 849–857; doi:10.1038/sj.bjp.0702140
Excitatory motor and electrical effects produced by tachykinins in the human and guinea‐pig isolated ureter and guinea‐pig renal pelvis
Authors: Patacchini Riccardo , Santicioli Paolo , Zagorodnyuk Vladimir , Lazzeri Massimo , Turini Damiano , Alberto Maggi Carlo
Published: January 2005

In isolated tissue experiments, neurokinin A (NKA) produced concentration‐dependent contraction of human and guinea‐pig ureter (pD2=6.7 and 7.2, respectively); an effect greatly reduced (>80% inhibition) by the tachykinin NK2 receptor‐selective antagonist MEN 11420 (0.1 μM). The tachykinin NK1 and NK3 receptor agonists septide and senktide, respectively, were ineffective.

Electrical field stimulation (EFS) of the guinea‐pig isolated renal pelvis produced an inotropic response blocked by MEN 11420 (0.01–1 μM). In the same preparation MEN 11420 (0.1 μM) blocked (apparent pKB=8.2) the potentiation of spontaneous motor activity produced by the NK2 receptor‐selective agonist [βAla8]NKA(4–10).

In sucrose‐gap experiments, EFS evoked action potentials (APs) accompanied by phasic contractions of human and guinea‐pig ureter, which were unaffected by tetrodotoxin or MEN 11420 (3 μM), but were blocked by nifedipine (1–10 μM). NKA (1–3 μM) produced a slow membrane depolarization with superimposed APs and a tonic contraction with superimposed phasic contractions. NKA prolonged the duration of EFS‐evoked APs and potentiated the accompanying contractions. MEN 11420 completely prevented the responses to NKA in both the human and guinea‐pig ureter.

Nifedipine (1–10 μM) suppressed the NKA‐evoked APs and phasic contractions in both human and guinea‐pig ureter, and slightly reduced the membrane depolarization induced by NKA. A tonic‐type contraction of the human ureter in response to NKA persisted in the presence of nifedipine.

In conclusion, tachykinins produce smooth muscle excitation in both human and guinea‐pig ureter by stimulating receptors of the NK2 type only. NK2 receptor activation depolarizes the membrane to trigger the firing of APs from latent pacemakers.

British Journal of Pharmacology (1998) 125, 987–996; doi:10.1038/sj.bjp.0702147
Dual pathway for angiotensin II formation in human internal mammary arteries
Authors: Voors Adriaan A. , Pinto Yigal M. , Buikema Hendrik , Urata Hidenori , Oosterga Margreeth , Rooks Gerrit , Grandjean Jan G. , Ganten D , Van Gilst Wiek H.
Published: January 2005

Angiotensin converting enzyme (ACE) is thought to be the main enzyme to convert antiotensin I to the vasoactive angiotensin II. Recently, in the human heart, it was found that the majority of angiotensin II formation was due to another enzyme, identified as human heart chymase. In the human vasculature however, the predominance of either ACE or non‐ACE conversion of angiotensin I remains unclear.

To study the effects of ACE‐ and chymase‐inhibition on angiotensin II formation in human arteries, segments of internal mammary arteries were obtained from 37 patients who underwent coronary bypass surgery.

Organ bath experiments showed that 100 μM captopril inhibited slightly the response to angiotensin I (pD2 from 7.09±0.11–6.79±0.10, P<0.001), while 100 μM captopril nearly abolished the response to [pro10] angiotensin I, a selective substrate for ACE, and the maximum contraction was reduced from 83±19%–23±17% of the control response (P=0.01). A significant decrease of the pD2 of angiotensin I similar to captopril was observed in the presence of 50 μM chymostatin (pD2 from 7.36±0.13–6.99±0.15, P<0.039), without influencing the maximum response. In the presence of both inhibitors, effects were much more pronounced than either inhibitor alone, and a 300 times higher dose was needed to yield a significant contraction response to angiotensin I.

These results indicate the presence of an ACE and a non‐ACE angiontensin II forming pathway in human internal mammary arteries.

British Journal of Pharmacology (1998) 125, 1028–1032; doi:10.1038/sj.bjp.0702150
Use‐dependent block of Ih in mouse dorsal root ganglion neurons by sinus node inhibitors
Authors: Raes A , Van de Vijver G , Goethals M , van Bogaert P P
Published: January 2005

The sinus node inhibitors UL–FS 49 and DK–AH 269 reduce heart rate by slowing diastolic depolarization rate in the sino‐atrial (SA) node, which might originate from the use‐dependent blockade of a hyperpolarization‐activated current If. A hyperpolarization‐activated current Ih, which is present in many types of neurons, is similar to If. We studied the effects of these drugs on Ih in cultured mouse dorsal root ganglion (DRG) neurons.

With the whole‐cell patch‐clamp technique use‐dependent block of Ih was observed. The steady‐state block following a voltage‐clamp pulse train (1‐s steps from −38 to −108 mV applied at 0.5 Hz) was dependent on drug concentration and showed an apparent Kd of 0.1 and 0.79 μM with DK–AH 269 and UL–FS 49 respectively.

The rate of block increased linearly with drug concentration. The rate of recovery from block was, however, much slower compared to cardiac tissue.

There was no significant effect of UL–FS 49 on the activation curve.

At high concentrations of UL–FS 49 a clear association of the drug with the open channel was observed.

When the cell was stimulated at a frequency of 3 Hz, a distinct hyperpolarization was observed in the presence of extracellular Cs+ or when Ih was blocked with UL–FS 49, but not in the absence of Cs+ and UL–FS 49.

These results indicate that Ih protects the cell against hyperpolarizations and subsequent inexcitability. The action of the drugs on the hyperpolarization‐activated current in cardiac and neuronal tissue show some similarities; however, some pronounced differences indicate that different subtypes of the channel might exist.

British Journal of Pharmacology (1998) 125, 741–750; doi:10.1038/sj.bjp.0702153
Endothelium‐dependent and ‐independent responses to protease‐activated receptor‐2 (PAR‐2) activation in mouse isolated renal arteries
Authors: Moffatt J D , Cocks T M
Published: January 2005

Protease‐activated receptors (PARs) are receptors which require proteolytic cleavage to be self‐activated by newly exposed N‐terminal ‘tethered ligands’, and hence serve as sensors for protelytic enzymes. While both the thrombin receptor (PAR‐1) and PAR‐2 (activated by tryptic enzymes) have been shown to mediate endothelium‐dependent vasorelaxation, only PAR‐1 has been shown to cause direct vascular smooth muscle contraction. In this study, we report that trypsin and the PAR‐2 selective peptide ligand SLIGRL‐NH2 not only caused endothelium‐dependent relaxation of mouse renal arteries but also direct smooth muscle contraction if endothelial nitric oxide synthase was inhibited or if the endothelium was removed.

British Journal of Pharmacology (1998) 125, 591–594; doi:10.1038/sj.bjp.0702157
Examination of somatostatin involvement in the inhibitory action of GIP, GLP‐1, amylin and adrenomedullin on gastric acid release using a new SRIF antagonist analogue
Authors: Rossowski Wojciech J. , Cheng Beng‐L , Jiang Ning‐Y , Coy David H.
Published: January 2005

The effect of a new type 2 selective somatostatin (SRIF) receptor antagonist (DC‐41‐33) on somatostatin‐induced inhibition of pentagastrin‐stimulated gastric acid secretion in conscious, chronic gastric fistula equipped rats was studied.

Infused intravenously, DC‐41‐33 dose‐dependently inhibits SRIF‐induced inhibition of pentagastrin‐stimulated gastric acid secretion with an IC50 of 31.6±1.2 nmol kg−1 versus 10 nmol kg−1 SRIF and blocks the inhibitory effects of SRIF when simultaneously co‐infused. Its effectiveness provides additional evidence that SRIF‐inhibition of gastric acid release is a SRIF type 2 receptor‐mediated process.

DC‐41‐33 is able to completely reverse the inhibitory effect of glucose‐dependent insulinotropic polypeptides, GIP and GIP‐(1–30)NH2, and glucagon‐like polypeptide, GLP‐1(7‐36)NH2, on pentagastrin‐stimulated gastric acid secretion thus confirming that they exert these effects through stimulation of endogenous SRIF release.

DC‐41‐33 only partially blocks potent amylin and adrenomedullin‐induced inhibition of gastric acid secretion, therefore suggesting that somatostatin may not function as a primary mediator in the action of these peptides.

Our results indicate that DC‐41‐33, is a potent in vivo inhibitor of exogenous and endogenous SRIF in rats. It represents a new class of SRIF analogues which should eventually provide excellent tools for further evaluating the many physiological roles of SRIF and its five receptor subtypes.

British Journal of Pharmacology (1998) 125, 1081–1087; doi:10.1038/sj.bjp.0702160
The 5‐HT4 receptor antagonist ML10375 inhibits the constitutive activity of human 5‐HT4(c) receptor
Authors: Blondel Olivier , Gastineau Monique , Langlois Michel , Fischmeister Rodolphe
Published: January 2005

Transient expression in COS‐7 cells of the recombinant human 5‐hydroxytryptamine (5‐HT) h5‐HT4(c) receptor isoform led to constitutive activity of the receptor. The 5‐HT4 receptor antagonist 2‐(cis‐3,5‐dimethylpiperidino)ethyl 4‐amino‐5‐chloro‐2‐methoxybenzoate (ML10375) at 1 μM completely abolished the 5‐HT (1 μM)‐mediated increase in adenylyl cyclase activity in COS‐7 cells expressing the h5‐HT4(c) receptor. Moreover, ML10375 also reduced basal cAMP levels in cells over‐expressing the receptor, even in the absence of agonist. The inhibitory effect of ML10375 on basal adenylyl cyclase activity was not modified by pre‐treatment of the cells with pertussis toxin, indicating that ML10375 acts through inactivation of spontaneously active h5‐HT4(c) receptors rather than through a Gi/Go regulatory pathway. We conclude that ML10375 acts as an inverse agonist on the h5‐HT4(c) receptor.

British Journal of Pharmacology (1998) 125, 595–597; doi:10.1038/sj.bjp.0702163
Differential role of vasoactive prostanoids in porcine and human isolated pulmonary arteries in response to endothelium‐dependent relaxants
Authors: Lawrence R N , Clelland C , Beggs D , Salama F D , Dunn W R , Wilson V G
Published: January 2005

The pig is increasingly being used in medical research, both as a model of the human cardiovascular system, and as a possible source of organs for xenotransplantation. However, little is known about the comparative functions of the vascular endothelium between porcine and human arteries. We have therefore compared the effects of two endothelium‐dependent vasorelaxants, acetylcholine (ACh) and the Ca2+‐ATPase inhibitor, cyclopiazonic acid (CPA) on the porcine and human isolated pulmonary artery using isometric tension recording.

ACh and CPA produced endothelium‐dependent relaxations of both the human and porcine pulmonary arteries.

In the porcine pulmonary artery, the cyclo‐oxygenase inhibitor, flurbiprofen had no effect on relaxations to ACh (Emax: control 67.8±8.8% versus 72.4±9.5% (n = 11)) or CPA (Emax: control 79.6±5.0% versus 94.0±10.6% (n = 7)). The nitric oxide synthase inhibitor, l‐NAME converted relaxations to both ACh and CPA into contractile responses (maximum response: ACh 30.0±11.1% (n = 10); CPA 80.4±26.2% (n = 8) of U46619‐induced tone). These contractile responses in the presence of l‐NAME were abolished by flurbiprofen.

In the human pulmonary artery, l‐NAME and flurbiprofen partly attenuated relaxations to ACh (Emax: control: 45.1±12.1%; flurbiprofen: 33.4±13.5%; l‐NAME: 10.1±7.2%) and CPA (Emax: control: 78.1±5.5%; flurbiprofen: 69.6±7.2%; l‐NAME 37.9±10.7% of U46619‐induced tone). These responses were abolished by the combination of both inhibitors.

We have demonstrated that while the release of nitric oxide is important in responses to endothelium‐dependent vasorelaxants in both human and porcine pulmonary arteries, in the human arteries, there is an important role for vasorelaxant prostanoids whilst in the porcine arteries, vasoconstrictor prostanoids are released.

British Journal of Pharmacology (1998) 125, 1128–1137; doi:10.1038/sj.bjp.0702168
Functional response of the rat kidney to inhibition of nitric oxide synthesis: role of cytochrome P450‐derived arachidonate metabolites
Authors: Oyekan Adebayo O. , McGiff J. C.
Published: January 2005

We tested the hypothesis that nitric oxide (NO) exerts a tonic inhibitory influence on cytochrome P450 (CYP450)‐dependent metabolism of arachidonic acid (AA).

Nω‐nitro‐L‐Arginine methyl ester (L‐NAME), an inhibitor of nitric oxide synthase (NOS), increased mean blood pressure (MBP), from 91±6 to 137±5 mmHg, renal vascular resistance (RVR), from 9.9±0.6 to 27.4±2.5 mmHg ml−1 min−1, and reduced renal blood flow (RBF), from 9.8±0.7 to 6.5±0.6 ml min−1) and GFR from 1.2±0.2 to 0.6±0.2 ml 100 g−1 min−1) accompanied by diuresis (UV, 1.7±0.3 to 4.3±0.8 μl 100 g−1 min−1), and natriuresis (UNaV, 0.36±0.04 to 1.25±0.032 μmol 100 g−1 min−1).

12, 12 dibromododec‐enoic acid (DBDD), an inhibitor of ω hydroxylase, blunted L‐NAME‐induced changes in MBP, RVR, UV and UNaV by 63±8, 70±5, 45±8 and 42±9%, respectively, and fully reversed the reduction in GFR by L‐NAME. Clotrimazole, an inhibitor of the epoxygenase pathway of CYP450‐dependent AA metabolism, was without effect.

BMS182874 (5‐dimethylamino)‐N‐(3,4‐dimethyl‐5‐isoxazolyl)‐1‐naphthalenesulfonamide), an endothelin (ET)A receptor antagonist, also blunted the increases in MBP and RVR and the diuresis/natriuresis elicited by L‐NAME without affecting GFR.

Indomethacin blunted L‐NAME‐induced increases in RVR, UV and UNaV. BMS180291 (1S‐(1α,2α,3α.4α)]‐2‐[[3‐[4‐[(pentylamino)carbonyl]‐2‐oxazolyl] ‐ 7 ‐ oxabicyclo[2.2.1]hept ‐ 2 ‐yl]methyl]benzenepropanoic acid), an endoperoxide receptor antagonist, attenuated the pressor and renal haemodynamic but not the renal tubular effects of L‐NAME.

In conclusion, the renal functional effects of the CYP450‐derived mediator(s) expressed after inhibition of NOS with L‐NAME were prevented by inhibiting either CYP450 ω hydroxylase or cyclo‐oxygenase or by antagonizing either ETA or endoperoxide receptors. 20‐hydroxyeicosatetraenoic acid (20‐HETE) fulfils the salient properties of this mediator.

British Journal of Pharmacology (1998) 125, 1065–1073; doi:10.1038/sj.bjp.0702171
Inhibition of the rapid component of the delayed‐rectifier K+ current by therapeutic concentrations of the antispasmodic agent terodiline
Authors: Jones Stephen E , Ogura Toshitsugu , Shuba Lesya M , McDonald Terence F
Published: January 2005

Prolongation of the QT interval and malignant ventricular arrhythmia have been observed in patients administered terodiline for urinary incontinence. Since this adverse reaction might be caused by inhibition of delayed‐rectifier K+ current (IK), we investigated whether clinically relevant (10 μm) concentrations of the drug modify IK in guinea‐pig ventricular myocytes.

Myocytes superfused with normal Tyrode's solution were pulsed from −40 mV to more positive test potentials (V) for 0.2–1 s to elicit tail IK on repolarization and measure tail IK‐V relationships. IKr was distinguished from IKs by its sensitivity to the selective blocker E4031.

Inhibition of IKr by 5 μm E4031 was completely occluded by pretreatment with 3 μm terodiline. In addition, action potential lengthening by E4031 in guinea‐pig papillary muscles (29±3%) was abolished (3±2%) (P < 0.001) by terodiline pretreatment.

Inhibition of IKr by terodiline appeared to be voltage‐independent, and the parameters of the Hill equation describing the inhibition were IC50=0.7 μm and nH=1.6. High concentrations of the drug also affect IKs; in experiments with K+‐free Tyrode's, 10 μm terodiline inhibited tail IKs by 27±3% (n = 5) (P < 0.001).

These data suggest that QT lengthening at therapeutic concentrations of the drug (≈amp;1.5 μm) is primarily due to inhibition of IKr. Inhibition of other K+ currents such as IKs is likely to be important at higher concentrations.

British Journal of Pharmacology (1998) 125, 1138–1143; doi:10.1038/sj.bjp.0702173
Impaired function of alpha‐2 adrenoceptors in smooth muscle of mesenteric arteries from spontaneously hypertensive rats
Authors: Feres Teresa , Borges Antonio Carlos R , Silva Eneida G , Paiva Antonio C M , Paiva Therezinha B
Published: January 2005

The α2‐adrenoceptor function in mesenteric arteries of spontaneously hypertensive rats (SHR) was investigated by comparing membrane potential changes in response to adrenergic agonists in preparations from female SHR, Wistar‐Kyoto (WKY) and normotensive Wistar rats (NWR).

Resting membrane potential was found to be less negative in mesenteric arteries from SHR than in those from NWR and WKY. Apamin induced a decrease in the membrane potential of mesenteric artery rings without endothelium from NWR and WKY, but had no effects in those from SHR. Both UK 14,304 and adrenaline, in the presence of prazosin, induced a hyperpolarization that was significantly lower in de‐endothelialized mesenteric rings from SHR than in those from NWR and WKY. In mesenteric rings with endothelium, however, similar hyperpolarization was observed in the three strains.

In NWR mesenteric rings with endothelium the hyperpolarization induced by activation of α2‐adrenoceptors was abolished by apamin, whereas in intact SHR mesenteric rings this hyperpolarization was slightly reduced by apamin and more efficiently reduced by Nω‐nitro‐l‐arginine.

It is concluded that the activity of potassium channels coupled to α2‐adrenoceptors is altered in the smooth muscle cells of SHR mesenteric arteries, contributing to their less negative membrane potential. On the other hand, the endothelial α2‐receptors are functioning in mesenteric vessels from SHR and their stimulation induces a hyperpolarization mainly through the release of nitric oxide.

British Journal of Pharmacology (1998) 125, 1144–1149; doi:10.1038/sj.bjp.0702177
The mechanism by which aminoglycoside antibiotics cause vasodilation of canine cerebral arteries
Authors: Gergawy Mourad , Vollrath Bozena , Cook David
Published: January 2005

The effects of aminoglycoside antibiotics were examined in canine cerebral arteries and in cultured cerebrovascular smooth muscle cells stimulated with oxyhemoglobin (OxyHb), a blood constituent which has been implicated in the pathogenesis of cerebrovascular spasm.

In cerebral arterial rings precontracted with OxyHb (10 μm), the aminoglycosides caused a concentration‐dependent decrease in isometric tension. The EC50s for the relaxation were 0.46±0.1 mm (n = 6), 0.53±0.08 mm (n = 12), 1.6±0.3 mm (n = 7) and 3.9±0.5 mm (n = 5) for neomycin, gentamicin, streptomycin and kanamycin, respectively. This order of potency corresponds approximately to the number of positive charges in the molecules.

The aminoglycosides also inhibited the contractions to prostaglandin F2α (1 μm) and depolarizing concentrations of potassium chloride (60 mm). The order of potency was neomycin>gentamicin>streptomycin>kanamycin.

The relaxation was maintained in vascular preparations denuded of endothelium.

Neomycin (5 mm) abolished the Ca2+‐independent contraction to PGF2α.

In Fura‐2‐loaded cerebrovascular smooth muscle cells, OxyHb (1 μm) significantly enhanced the concentration of intracellular calcium ([Ca2+]i) by 330%. The administration of neomycin, gentamicin, kanamycin and streptomycin in concentrations corresponding to the EC50 from contractility studies, reduced the effects of OxyHb on [Ca2+]i by about 50% to 221±35 nm (n = 7), 270±31 nm (n = 7), 229±33 nm (n = 6) and 240±6 nm (n = 5), respectively.

These results suggests that the effects of the aminoglycosides on the OxyHb‐induced contraction and the long‐term increase in [Ca2+]i, may arise from several effects, including inhibition of PLC, protection of calcium extrusion mechanisms, and interference with the process of [Ca2+]i accumulation.

British Journal of Pharmacology (1998) 125, 1150–1157; doi:10.1038/sj.bjp.0702180
Comparison of two soluble guanylyl cyclase inhibitors, methylene blue and ODQ, on sodium nitroprusside‐induced relaxation in guinea‐pig trachea
Authors: Hwang Tsong‐Long , Wu Chin‐Chung , Teng Che‐Ming
Published: January 2005

To clarify further the role of cyclic GMP in mediating the relaxant response in guinea‐pig trachea induced by sodium nitroprusside (SNP), the effects of soluble guanylyl cyclase inhibitors, methylene blue and 1H‐[1,2,4]oxadiazolo[4,3,‐a]quinoxalin‐1‐one (ODQ) on SNP‐induced muscle relaxation and cyclic GMP accumulation were determined.

SNP (0.3–100 μm) evoked a concentration‐dependent relaxation of guinea‐pig isolated tracheas precontracted with 0.3 μm carbachol. Preincubation of the preparations with methylene blue (10, 30 and 100 μm) resulted in a slight but concentration‐dependent prevention of the relaxant response to SNP. In contrast, the relaxation to SNP was extensively prevented by 3 μm ODQ and almost abolished by 10 μm ODQ.

SNP (30 μm) induced a significant elevation of cyclic GMP accumulation (from 1.34±0.14 to 5.39±0.28 pmol mg−1 protein, n = 5; P < 0.001), which was partially attenuated by 100 μm methylene blue (3.11±0.51 pmol mg−1 protein, n = 5; P < 0.05), whereas completely abolished by 10 μm ODQ (1.31±0.28 pmol mg−1 protein, n = 5; P < 0.001).

Methylene blue, but not ODQ and Nω‐nitro‐l‐arginine methyl ester (l‐NAME), caused a concentration‐dependent contraction in the tracheal preparation. The tension produced by 100 μm methylene blue was 41.8±4.3% (0.3 μm carbachol as 100%; n=12). Moreover, the non‐selective muscarinic receptor antagonist atropine and the M3‐selective antagonist 4‐diphenylacetoxy‐N‐methylpiperidine methiodine greatly inhibited the contractile effect evoked by methylene blue (100 μm).

In conclusion, this study provides substantial evidence that SNP‐induced muscle relaxation in guinea‐pig trachea is completely via a cyclic GMP‐dependent mechanism. Furthermore, ODQ, but not methylene blue, will likely become an important tool in differentiating between cyclic GMP‐dependent and ‐independent effects of nitric oxide.

British Journal of Pharmacology (1998) 125, 1158–1163; doi:10.1038/sj.bjp.0702181
The central action of the 5‐HT2 receptor agonist 1‐(2,5‐dimethoxy‐4‐iodophenyl)‐2‐aminopropane (DOI) on cardiac inotropy and vascular resistance in the anaesthetized cat
Authors: Ramage Andrew G , de Burgh Daly M
Published: January 2005

Experiments were carried out to determine the effects of the application of the selective 5‐HT2 receptor agonist DOI intravenously (in the presence of the peripherally acting 5‐HT2 receptor antagonist, BW501C67, 1 mg kg−1, i.v.) or to the ‘glycine sensitive area’ of the ventral surface (30 μg each side) on the left ventricular inotropic (left ventricular dP/dt max) and vascularly isolated hindlimb responses in anaesthetized cats. For the ventral surface experiments, NMDA (10 μg each side) was applied to act as a positive control. In all experiments heart rate and mean arterial blood pressure were held constant to exclude any secondary effects caused by changes in these variables.

DOI (n = 6) i.v or on the ventral surface had no effect on left ventricular dP/dt max but caused a significant increase in hindlimb perfusion pressure of 40±9 and 50±14 mmHg, respectively. Respiration was unaffected. NMDA (n = 6), applied to the ventral surface, caused significant increases in both left ventricular dP/dt max and hindlimb perfusion pressure of 1950±349 mmHg s−1 and 69±17 mmHg respectively, with no associated change in left ventricular end‐diastolic pressure. The amplitude of respiratory movements increased.

It is concluded that activation of 5‐HT2 receptors at the level of the rostral ventrolateral medulla (RVLM) excites sympathetic premotor neurons and/or their antecedents controlling hindlimb vascular resistance but not those controlling the inotropic effects on the left ventricle.

British Journal of Pharmacology (1998) 125, 1172–1179; doi:10.1038/sj.bjp.0702183
Kinetics of leukocyte‐induced changes in endothelial barrier function
Authors: Gautam N , Hedqvist P , Lindbom L
Published: January 2005

Extravasation of polymorphonuclear leukocytes (PMN) and associated plasma leakage are key events in the inflammatory process. The kinetics of PMN‐induced changes in endothelial barrier function were studied by means of confluent monolayers of bovine aorta or human umbilical vein endothelial cells (EC), cultured on permeable membranes and mounted in a two‐compartment diffusion chamber. The model permitted continuous measurement of transendothelial electrical resistance (TEER), and analysis of protein efflux and PMN migration across the EC monolayer.

Transendothelial chemotactic stimulation (fMLP or LTB4) of PMN resting on EC in the upper compartment induced a prompt decline in TEER, followed by an increase in protein flux and transmigration of PMN. Adding the chemoattractant together with PMN in the upper compartment provoked adhesion of PMN, fall in TEER and increase in protein permeability, but no transmigration of PMN, whereas inhibition of PMN adhesion to EC by pretreatment with anti‐CD18 mAb prevented all responses to chemotactic stimulation.

Chemoattractant‐induced adhesion of PMN to the EC monolayer induced a rapid rise in EC cytosolic free Ca2+, similar to that obtained by direct stimulation of EC with histamine, indicating an active response of EC to PMN activation and adhesion.

In summary, continuous recording of transendothelial electrical resistance in the in vitro model described permits rapid and sensitive analysis of leukocyte activation‐induced effects on EC barrier function. The kinetics and specificity of the EC and PMN responses to chemoattractant stimulation suggest that activated PMN, via adhesion‐dependent events, have a direct effect on EC junctional integrity independent of whether transmigration occurs or not.

British Journal of Pharmacology (1998) 125, 1109–1114; doi:10.1038/sj.bjp.0702186
The antihypertensive profile of the angiotensin AT1 receptor antagonist, GR138950, and the influence of potential homeostatic compensatory mechanisms in renal hypertensive rats
Authors: Anderson Ian K , Drew Geoffrey M
Published: January 2005

The cardiovascular profile of the angiotensin AT1 receptor antagonist, GR138950, and the influence of potential compensatory homeostatic mechanisms on this profile, were investigated in renal artery ligated hypertensive (RALH) rats.

GR138950 caused a marked reduction in blood pressure associated with immediate tachycardia in conscious RALH rats. The antihypertensive action of GR138950 appeared biphasic; an immediate fall in blood pressure, which plateaued within 1 h, and which was followed by a further slow decline that reached maximum between 5–7 h after administration.

The tachycardia caused by GR138950 was attenuated by atenolol and was abolished by combined pretreatment with atenolol and atropine methyl nitrate. However, the antihypertensive profile of GR138950 was unchanged by these pretreatments.

The resting blood pressure and the antihypertensive effect of GR138950, in RALH rats, were unaffected by the vasopressin V1 receptor antagonist, [β‐mercapto‐β,β‐cyclopentamethylene propionyl1‐O‐Me‐Tyr2,Arg8]‐vasopressin. Thus, vasopressinergic mechanisms are not involved in either maintaining blood pressure in RALH rats, or in compensating for the fall in blood pressure caused by GR138950.

In anaesthetized RALH rats, GR138950 caused a marked fall in blood pressure that was accompanied by an increase in heart rate along with sustained increases in renal and splanchnic sympathetic nerve activity.

In summary, the biphasic fall in blood pressure evoked by GR138950 in RALH rats can not be explained on the basis of changes in autonomic control of the heart, alteration of vasopressin‐mediated vasoconstrictor mechanisms or overall suppression of central sympathetic outflow. Rather, increased vasoconstrictor tone might serve to oppose the initial fall in blood pressure.

British Journal of Pharmacology (1998) 125, 1236–1246; doi:10.1038/sj.bjp.0702187
Characterization of a prostanoid EP3‐receptor in guinea‐pig aorta: partial agonist action of the non‐prostanoid ONO‐AP‐324
Authors: Jones Robert L , Qian Yue‐ming , Chan Kam‐ming , Yim Anthony P C
Published: January 2005

Contraction of guinea‐pig isolated aorta induced by the prostaglandin E analogue sulprostone (1–400 nm) has a lower maximum response (40%) than that of phenylephrine or U‐46619 (TP‐receptor agonist). A prostanoid EP3‐receptor subtype is involved based on agonist potency ranking: equi‐effective molar ratios (EMR) are sulprostone (EC50∼23 nm) 1.0, SC‐46275 0.11, misoprostol 2.2, gemeprost 3.3, PGE2 5.4, 17‐phenyl PGE2 6.0, GR‐63799 8.9. GR‐63799, which contains a bulky ester group, is relatively more potent on neuronal EP3 preparations than on the aorta.

ONO‐AP‐324, a relative of the non‐prostanoid prostacyclin mimetic series, behaves as an EP3 partial agonist on the aorta, inhibiting sulprostone responses but acting synergistically (in a similar manner to sulprostone) with phenylephrine; it may be a useful pharmacological tool for studying EP3‐receptors.

Sulprostone contractions are markedly suppressed in zero‐Ca2+ bathing fluid containing either 2 mm EDTA or 50 μm EGTA, and by Cd2+ (500 μm), but are usually unaffected by nifedipine (0.3 μm) and verapamil (4.44 μm). Influx of Ca2+, but not through L‐type Ca2+‐channels, appears to be the major contractile mechanism.

The guinea‐pig aorta is a valuable addition to the vascular EP3 preparations available and may increase our knowledge of the mechanisms whereby Gi‐coupled receptors mediate vasoconstriction (c.f. 5‐HT1B/D‐ and α2‐receptors). The possibility of certain EP3 agonists distinguishing EP3‐receptor isoforms is discussed.

British Journal of Pharmacology (1998) 125, 1288–1296; doi:10.1038/sj.bjp.0702189
In vitro functional evidence of neuronal cannabinoid CB1 receptors in human ileum
Authors: Croci Tiziano , Manara Luciano , Aureggi Giulio , Guagnini Fabio , Rinaldi‐Carmona Murielle , Maffrand Jean‐Pierre , Le Fur Gérard , Mukenge Sylvain , Ferla Gianfranco
Published: January 2005

We investigated the effect of the cannabinoid agonist (+)WIN‐55212‐2 on human ileum longitudinal smooth muscle preparations, either electrically stimulated or contracted by carbachol. Electrical field stimulation mostly activated cholinergic neurons, since atropine and tetrodotoxin (TTX), alone or co‐incubated, reduced twitch responses to a similar degree (85%). (+)WIN‐55212‐2 concentration‐dependently inhibited twitch responses (IC50 73 nm), but had no additive effect with atropine or TTX. The cannabinoid CB1 receptor antagonist SR 141716 (pA2 8.2), but not the CB2 receptor antagonist, SR 144528, competitively antagonized twitch inhibition by (+)WIN‐55212‐2. Atropine but not (+)WIN‐55212‐2 or TTX prevented carbachol‐induced tonic contraction.  These results provide functional evidence of the existence of prejunctional cannabinoid CB1‐receptors in the human ileum longitudinal smooth muscle. Agonist activation of these receptors prevents responses to electrical field stimulation, presumably by inhibiting acetylcholine release. SR 141716 is a potent and competitive antagonist of cannabinoid CB1 receptors naturally expressed in the human gut.

British Journal of Pharmacology (1998) 125, 1393–1395; doi:10.1038/sj.bjp.0702190
Role of cyclo‐oxygenase‐2 induction in interleukin‐1β induced attenuation of cultured human airway smooth muscle cell cyclic AMP generation in response to isoprenaline
Authors: Pang Linhua , Holland Elaine , Knox Alan J
Published: January 2005

Airway smooth muscle (ASM) in human asthma shows reduced relaxation and cyclic AMP generation in response to β‐adrenoceptor agonists. IL‐β attenuates cyclic AMP generation but the underlying mechanism is unclear. We have reported that IL‐1β induces cyclo‐oxygenase‐2 (COX‐2) in human ASM cells and results in a marked increase in prostanoid generation with PGE2 and PGI2 as the major products.

We investigated the role of COX‐2 induction and prostanoid release (measured as PGE2) in IL‐1β induced attenuation of cyclic AMP generation in response to the β‐adrenoceptor agonist isoprenaline (ISO).

Pre‐treatment of human ASM cells with IL‐1β significantly attenuated cyclic AMP generation in response to high concentrations of ISO (1.0–10.0 μm) in a time‐ and concentration‐dependent manner. The effect was accompanied by a high concentration of PGE2 release. The non‐selective COX inhibitor indomethacin (Ind), the selective COX‐2 inhibitor NS‐398, the protein synthesis inhibitors cycloheximide (CHX) and actinomycin D and the steroid dexamethasone (Dex) all abolished the PGE2 release and prevented the attenuated cyclic AMP generation.

COX substrate arachidonic acid time‐ and concentration‐dependently mimicked IL‐1β induced attenuation and the effect was prevented by the non‐selective COX inhibitors Ind and flurbiprofen, but not by NS‐398, CHX and Dex.

In contrast to IL‐1β, TNFα and IFNγ, which are ineffective in inducing COX‐2 and releasing PGE2 from human ASM cells, did not affect the cyclic AMP formation.

Our study demonstrates that COX‐2 induction and the consequent release of prostanoids plays a crucial role in IL‐1β induced attenuation of human ASM cell cyclic AMP response to ISO.

British Journal of Pharmacology (1998) 125, 1320–1328; doi:10.1038/sj.bjp.0702193
Expression of cyclooxygenase‐2 in foetal rat hepatocytes stimulated with lipopolysaccharide and pro‐inflammatory cytokines
Authors: Martín‐Sanz Paloma , Callejas Nuria A , Casado Marta , Díaz‐Guerra María J M , Boscá Lisardo
Published: January 2005

Cyclooxygenase‐2 (COX‐2) is involved in the biosynthesis of prostanoids in the course of inflammatory reactions. This isoenzyme is regulated at the transcription level and many cells express COX‐2 upon challenge with lipopolysaccharide (LPS) or pro‐inflammatory cytokines.

Since hepatocytes respond to LPS and pro‐inflammatory stimuli, we investigated the expression of COX‐2 in foetal and adult hepatocytes upon challenge with these substances.

COX‐2 was expressed in foetal hepatocytes incubated with LPS, tumour necrosis factor‐α and interleukin‐1β. This response rapidly decreased after birth and was absent in hepatocytes from animals aged 2 days or more and treated under identical conditions. The expression of COX‐2 was determined at the mRNA, protein and enzyme activity levels using Northern and Western blot, and following the synthesis of prostaglandin E2, respectively. The use of NS 398, a specific pharmacological inhibitor of COX‐2, confirmed the expression of this isoenzyme in activated foetal hepatocytes.

Synergism in COX‐2 expression was observed between LPS, tumour necrosis factor‐α and interleukin‐1β. Interleukin‐6 and permeant analogues of cyclic AMP failed to induce COX‐2 or to synergize with LPS. Also, transforming growth factor‐β inhibited the LPS‐ and pro‐inflammatory cytokines‐dependent expression of COX‐2.

These results indicate that foetal hepatocytes are competent to express COX‐2 upon challenge with pro‐inflammatory stimuli, a process lost completely in hepatocytes isolated from animals aged 2 days.

British Journal of Pharmacology (1998) 125, 1313–1319; doi:10.1038/sj.bjp.0702196
Stimulation of airway sensory nerves by cyclosporin A and FK506 in guinea‐pig isolated bronchus
Authors: Harrison S. , Reddy S. , Page C. P. , Spina D.
Published: January 2005

We have investigated the contractile property of cyclosporin A and FK506 in guinea‐pig isolated bronchus.

Cyclosporin A (10 μm) failed to significantly attenuate the excitatory non‐adrenergic non‐cholinergic (eNANC) and cholinergic contractile response (per cent methacholine Emax) induced by electrical field stimulation (EFS). In contrast, eNANC responses were significantly attenuated by both the neurokinin (NK)‐1 and (NK)‐2 receptor antagonists, N‐acetyl‐l‐tryptophan 3,5‐bis (trifluoromethyl)‐benzyl and SR48968, respectively.

Cyclosporin A and FK506 caused a concentration‐dependent contraction in guinea‐pig isolated bronchus, which was significantly attenuated by NK‐1 and NK‐2 receptor antagonists. The capsaicin receptor antagonist, capsazepine (10 μm) significantly reduced the contractile response to cyclosporin A and capsaicin, but not to FK506.

The N‐type calcium channel blocker, ω‐Conotoxin (ωCTX: 10 nm), significantly reduced the contractile response to FK506 and the eNANC response following EFS. In contrast, ω‐CTX failed to significantly reduce the contractile potency to capsaicin or cyclosporin A.

In bronchial preparations desensitized by repeated application of capsaicin (1 μm), the contractile responses to both cyclosporin A (100 μm) and FK506 (100 μm), were significantly reduced. In contrast, the contractile responses to substance P and neurokinin A (10 μm) were not altered. Furthermore, repeated application of cyclosporin A (100 μm) significantly inhibited the contractile response to capsaicin (1 μm).

The findings from this study would indicate that cyclosporin A and FK506 mediate contraction of guinea‐pig isolated bronchus secondary to the release of neuropeptides from airway sensory nerves. However, the release of sensory neuropeptides appears to be mediated via different mechanisms for cyclosporin A and FK506, the former by stimulation of the vanilloid receptor and the latter via opening of N‐type calcium channels.

British Journal of Pharmacology (1998) 125, 1405–1412; doi:10.1038/sj.bjp.0702198
Functional cross‐talk between endothelial muscarinic and α2‐adrenergic receptors in rabbit cerebral arteries
Authors: Thorin Eric
Published: January 2005

Interactions between two classes of receptors have been observed in several cell lines and preparations. The aim of this work was to assess the impact of simultaneous stimulation of endothelial muscarinic and α2‐adrenergic receptors (α2‐AR) on vascular reactivity.

Rabbit middle cerebral arteries were isolated and changes in isometric tension were recorded in the presence of indomethacin.

Inhibition of nitric oxide (NO) synthase with Nω‐nitro‐l‐arginine (l‐NOARG, 100 μmol l−1) revealed α‐AR‐dependent contractions. Pre‐addition of acetylcholine (ACH, 1 μmol l−1) augmented oxymetazoline (OXY, 10 μmol l−1, α2‐AR agonist)‐, but decreased phenylephrine (PE, 10 μmol l−1, α1‐AR agonist)‐induced contraction (P < 0.05). The effects of ACH were endothelium‐dependent.

Vessels were precontracted with 40 mmol l−1 KCl‐physiological salt solution (PSS) in the absence of l‐NOARG, or PE or OXY in the presence of l‐NOARG. In the presence of high external K+ or PE, ACH induced a potent relaxation (P < 0.05). In the presence of OXY, however, ACH mediated contraction (P < 0.05).

After pertussis toxin (PTX, inactivator of Gαi/o proteins) pre‐treatment, α2‐AR‐dependent contractions were abolished. Forty mmol l−1 KCl‐PSS induced contraction was not altered by PTX whereas ACH‐induced relaxation was augmented (P < 0.05).

To investigate if endothelin‐1 (ET‐1) intervened in the endothelium‐dependent contractile response to ACH in the presence of OXY‐dependent tone, vessels were incubated in the presence of BQ123 (1 μmol l−1), an ETA receptor antagonist. OXY‐mediated tone was not affected by BQ123; however, ACH‐induced contraction was reversed to a relaxation (P < 0.05).

These data indicate that activation of endothelial α2‐AR triggers an endothelium‐dependent, ET‐1 mediated, contraction to ACH. This suggests that activation of α2‐AR affects muscarinic receptor/G protein coupling leading to an opposite biological effect.

British Journal of Pharmacology (1998) 125, 1188–1193; doi:10.1038/sj.bjp.0702199
Developmental changes in endothelium‐dependent vasodilation and the influence of superoxide anions in perinatal rabbit pulmonary arteries
Authors: Morecroft Ian , MacLean Margaret R
Published: January 2005

ACh‐induced vasodilation was investigated in pulmonary arteries from 8 and 2 day pre‐term foetal, neonatal (0–12 h and 4 day old) and adult rabbits. The effects of superoxide anion generation [with hypoxanthine (HX, 0.1 mm)/xanthine oxidase (XO, 15 mu ml−1)], endogenous superoxide dismutase (SOD) inhibition [with the Cu‐Zn SOD inhibitor triethylenetetramine (TETA, 1 mm)], endogenous superoxide anion scavenging [by superoxide dismutase (SOD, 50 u ml−1)] and inhibition of endothelial nitric oxide synthase (eNOS) [with, Nω‐nitro‐l‐arginine methylester (l‐NAME, 0.1 mm)], on basal and ACh‐induced NO activity were studied by examining phenylephrine‐induced contraction and ACh‐induced vasodilation respectively.

l‐NAME and endothelium removal abolished all ACh‐induced vasodilation and 1 μm sodium nitroprusside fully dilated all vessels. ACh‐induced vasodilation was absent in the 8 day pre‐term foetus and 0–12 h neonate but present at all other ages. l‐NAME itself contracted 2 day pre‐term foetal vessels. At 0–12 h, SOD, but not the phosphodiesterase 5 inhibitor zaprinast (1 μm), uncovered ACh‐induced vasodilation. At this age SOD reduced phenylephrine‐induced contraction which was not influenced by TETA, l‐NAME or HX/XO, and l‐NAME itself did not cause contraction. This suggests both ACh‐induced and basal NO activity are compromise in these vessels by endogenous superoxide anion production and deficiencies in endogenous SOD activity.

In 4 day vessels, but not adult vessels, l‐NAME, TETA and HX/XO augmented contractions to phenylephrine, and l‐NAME itself induced vasoconstriction, suggesting that basal NO and SOD activities were present by 4 days but were not evident in the adult. ACh‐induced NO activity, and the influence of endogenous SOD on this, were present in the adult (and 4 day) vessels as superoxide generation with HX/XO significantly reduced ACh‐induced vasodilation and this effect was inhibited by SOD and augmented by TETA.

Increased oxygen tensions >500 mmHg attenuated ACh‐induced vasodilation in the foetal but not neonatal rabbits. Raising the oxygen tension from ∼20 to ∼120 mmHg revealed ACh‐induced vasodilation in the 8 day pre‐term vessels.

In summary, superoxide anion accumulation combined with deficiencies in SOD activity may transiently compromise basal and ACh‐induced NO activity at birth. Experimental oxygen tensions markedly influence ACh‐induced vasodilation in foetal rabbit pulmonary arteries.

British Journal of Pharmacology (1998) 125, 1585–1593; doi:10.1038/sj.bjp.0702217
Modulation of inhibitory post‐synaptic currents (IPSCs) in mouse cerebellar Purkinje and basket cells by snake and scorpion toxin K+ channel blockers
Authors: Southan Andrew P , Robertson Brian
Published: January 2005

Using an in vitro mouse cerebellar slice preparation and whole‐cell electrophysiological recording techniques we have characterized Purkinje and basket cell inhibitory post‐synaptic currents (IPSCs), and examined the effects of a number of selective peptidergic K+ channel blockers.

Spontaneous IPSC amplitude ranged from ∼10 pA up to ∼3 nA for both cell types [mean values: Purkinje cells −122.8±20.0 pA (n=24 cells); basket cells −154.8±15.9 pA (n=26 cells)]. Frequency varied from ∼3 up to ∼40 Hz, [mean values: basket cells 14.9±1.7 Hz (n=26 cells); Purkinje cells 17.9±2.2 Hz (n=24 cells)]. 5 μm bicuculline eliminated virtually all spontaneous currents.

IPSC rise times were fast (∼0.6 ms) and the decay phase was best fit with the sum of two exponential functions (τ1 and τ2: ∼4 ms and ∼20 ms, n = 40; for both cell types).

The snake toxins alpha‐dendrotoxin (α‐DTX) and toxin K greatly enhanced IPSC frequency and amplitude in both cell types; the closely related homologues toxin I and gamma‐dendrotoxin (γ‐DTX) produced only marginal enhancements (all at 200 nm).

Two scorpion toxins, margatoxin (MgTX) and agitoxin‐2 (AgTX‐2) had only minor effects on IPSC frequency or amplitude (both at 10 nm).

Low concentrations of tetraethylammonium (TEA; 200 μm) had no overall effect on cerebellar IPSCs, whilst higher concentrations (10 mm) increased both the frequency and amplitude.

The results suggest that native K+ channels, containing Kv1.1 and Kv1.2 channel subunits, play an influential role in controlling GABAergic inhibitory transmission from cerebellar basket cells.

British Journal of Pharmacology (1998) 125, 1375–1381; doi:10.1038/sj.bjp.0702218