bluuebunny/crossref_metadata_2025 huggingface dataset:
Protective effects of Cyclosporin‐A in splanchnic artery occlusion shock
Authors: Squadrito Francesco , Altavilla Domenica , Squadrito Giovanni , Ferlito Marcella , Deodato Barbara , Arlotta Mariarita , Minutoli Letteria , Campo Giuseppe M , Bova Antonio , Quartarone Cristina , Urna Giuseppe , Sardella Aurora , Saitta Antonino , Caputi Achille P
Published: January 2005

Cyclosporin A (CsA) is an immunosuppressant drug that inhibits nitric oxide (NO) synthase induction in vascular smooth muscle cells. Splanchnic artery occlusion (SAO) shock is a lethal type of shock characterized by a marked vascular dysfunction in which the L‐arginine/nitric oxide pathway plays an important role. We investigated whether CsA exerts protective effects in SAO shock by interfering with the L‐arginine/nitric oxide pathway.

Male anaesthetized rats (n=156) were subjected to clamping of the splanchnic arteries for 45 min. This surgical procedure resulted in an irreversible state of shock (SAO shock). Sham operated animals were used as controls. SAO shocked rats had a decreased survival (86±6 min, while sham shocked rats survived more than 240 min), marked hypotension, increased serum levels of TNF‐α, enhanced plasma nitrite/nitrate concentrations (75±7.1 μM; sham shocked rats=1.6±0.5 μM) and enhanced inducible NO synthase (iNOS) protein induction and activity in the aorta. Moreover aortic rings from shocked rats showed a marked hyporeactivity to phenylephrine (PE, 1 nM–10 μM).

CsA (0.25, 0.5 and 1 mg kg−1, 5 min after reperfusion) increased survival rate (SAO+CsA=236±9 min following the highest dose), reverted the marked hypotension, reduced plasma nitrite/nitrate concentration (11±5.2 μM following the highest dose), restored to control values the hyporeactivity to PE, and blunted iNOS protein induction and activity in aortic rings.

The present data indicate that in an experimental rat model CsA may have antishock properties related to inhibition of L‐arginine/nitric oxide pathway.

British Journal of Pharmacology (2000) 130, 339–344; doi:10.1038/sj.bjp.0703310
Heat stress‐induced protection of endothelial function against ischaemic injury is abolished by ATP‐sensitive potassium channel blockade in the isolated rat heart
Authors: Joyeux Marie , Bouchard Jean‐François , Lamontagne Daniel , Godin‐Ribuot Diane , Ribuot Christophe
Published: January 2005

The protection conferred by heat stress (HS) against myocardial ischaemia‐reperfusion injury, in terms of mechanical function preservation and infarct size reduction, is well documented and mechanisms underlying these effects have been extensively explored. However, the effect of HS on coronary circulation is less known. The aim of this study was thus to investigate the role of ATP‐sensitive potassium (KATP) channels in the protection against ischaemic injury afforded by HS to the coronary endothelial function.

Twenty‐four hours after whole body hyperthermia (42°C for 15 min, H groups) or sham anaesthesia (Sham groups), isolated perfused rat hearts were subjected to a 15 min stabilization period followed by a 30 min infusion of either 0.3 μM glibenclamide (Gli, a KATP channel blocker) or its vehicle (V). Hearts were then exposed to a low‐flow ischaemia (30 min)‐reperfusion (20 min) (I/R) or normally perfused (50 min), after which coronaries were precontracted with 0.1 μM U‐46619. Finally, the response to the endothelium‐dependent vasodilator, 5‐hydroxytryptamine (5‐HT, 10 μM) was compared to that of the endothelium‐independent vasodilator, sodium nitroprusside (SNP, 3 μM).

In hearts from Sham‐V and Sham‐Gli groups, I/R selectively diminished 5‐HT‐induced vasodilatation without affecting the vasodilatation to SNP. In V‐treated groups, prior HS preserved the vasodilatation produced by 5‐HT. This HS‐induced protection was abolished by Gli treatment.

In conclusion, these results suggest that KATP channel activation contributes to the preservation of coronary endothelial function conferred by heat stress against ischaemic insult.

British Journal of Pharmacology (2000) 130, 345–350; doi:10.1038/sj.bjp.0703312
Contractile responses to human urotensin‐II in rat and human pulmonary arteries: effect of endothelial factors and chronic hypoxia in the rat
Authors: MacLean M R , Alexander D , Stirrat A , Gallagher M , Douglas S A , Ohlstein E H , Morecroft I , Polland K
Published: January 2005

Responses to human urotensin‐II (hU‐II) were investigated in human and rat pulmonary arteries. Rat pulmonary arteries: hU‐II was a potent vasoconstrictor of main pulmonary arteries (2–3 mm i.d.) (pEC50, 8.55±0.08, n=21) and was ∼4 fold more potent than endothelin‐1 [ET‐1] (P<0.01), although its Emax was considerably less (∼2.5 fold, P<0.001). The potency of hU‐II increased 2.5 fold with endothelium removal (P<0.05) and after raising vascular tone with ET‐1 (P<0.01). Emax was enhanced ∼1.5 fold in the presence of Nω‐nitro‐L‐arginine methylester (L‐NAME, 100 μM, P<0.01) and ∼2 fold in vessels from pulmonary hypertensive rats exposed to 2 weeks chronic hypoxia (P<0.05). hU‐II did not constrict smaller pulmonary arteries. Human pulmonary arteries (∼250 μm i.d.): in the presence of L‐NAME, 3 out of 10 vessels contracted to hU‐II and this contraction was highly variable. hU‐II is, therefore, a potent vasoconstrictor of rat main pulmonary arteries and this response is increased by endothelial factors, vascular tone and onset of pulmonary hypertension. Inhibition of nitric oxide synthase uncovers contractile responses to hU‐II in human pulmonary arteries.

British Journal of Pharmacology (2000) 130, 201–204; doi:10.1038/sj.bjp.0703314
Non‐competitive antagonism of amylin on CGRP1‐receptors in rat coronary small arteries
Authors: Sheykhzade Majid , Nyborg Niels C Berg
Published: January 2005

We examined the interaction between rat‐amylin and relaxations induced by rat‐αCGRP and isoprenaline in rat isolated coronary small arteries.

Amylin, 0.1–100 nM, had a concentration dependent non‐competitive antagonistic effect on rat‐αCGRP‐induced responses with an EC50 of approximately 1 nM. Amylin did not affect the relaxations induced by isoprenaline at a concentration of 10 nM.

The apparent equilibrium dissociation constant, KA, for CGRP1‐receptors in the rat coronary small arteries was approximately 2 nM. Analysis of the relationship between receptor occupancy and response to rat‐αCGRP indicates that the receptor reserve is small.

Our results show that amylin in low concentrations acts as a selective non‐competitive inhibitor at CGRP1‐receptors in rat isolated coronary small arteries.

British Journal of Pharmacology (2000) 130, 386–390; doi:10.1038/sj.bjp.0703316
Interaction of hypoxanthine/xanthine oxidase with nitrergic relaxation in the porcine gastric fundus
Authors: Colpaert E E , Lefebvre R A
Published: January 2005

The influence of hypoxanthine (HX)/xanthine oxidase (XO) on short‐term [electrical field stimulation (EFS; 4 Hz) for 10 s and 3 min; bolus of exogenous NO (10−5 M)] and long‐term [EFS (4 Hz) and continuous NO‐infusion for 20 min] nitrergic relaxations was investigated in circular muscle strips of the pig gastric fundus.

HX (3×10−4 M) / XO (64 mu ml−1) did not affect EFS for 10 s and 3 min; the short‐lasting relaxation in response to a bolus of exogenous NO (10−5 M) was changed into a biphasic relaxation with a small and short first phase followed by a larger and prolonged second phase. Cu/Zn superoxide dismutase (Cu/Zn SOD; 1000 u ml−1) and uricase (100 mu ml−1) respectively enhanced the amplitude of the first phase and diminished the amplitude of the second phase. Ascorbate (5×10−4 M) and bilirubin (2×10−4 M) prevented the prolonged component.

Exposure to HX/XO during long‐term EFS elicited a complete, stable reversal of relaxation starting after a delay. During continuous NO‐infusion, HX/XO induced an immediate, complete but transient reversal.

The antioxidants bilirubin, ascorbate, α‐tocopherol, urate, glutathione and Cu/Zn SOD, the hydrogen peroxide degrading enzyme catalase, the hydroxyl radical scavengers dimethylsulphoxide and mannitol, and the cofactor flavin adenine dinucleotide did not influence the reversal induced by HX/XO during either EFS or NO‐infusion. The cell‐permeable manganese SOD mimetic EUK‐8 modified the stable reversal during long‐term EFS into a transient one.

The results suggest that a nitrated uric acid derivative is responsible for the prolonged second phase in the relaxation to a bolus of exogenous NO in the presence of HX/XO. The exact underlying mechanism of the reversal induced by HX/XO during sustained relaxation remains unclear.

British Journal of Pharmacology (2000) 130, 359–366; doi:10.1038/sj.bjp.0703317
Acute blood pressure effects of YC‐1‐induced activation of soluble guanylyl cyclase in normotensive and hypertensive rats
Authors: Rothermund Lars , Friebe Andreas , Paul Martin , Koesling Doris , Kreutz Reinhold
Published: January 2005

We used YC‐1 as a pharmacological tool to investigate the short‐term blood pressure effects of NO‐independent activation of sGC in normotensive and hypertensive rats. Four groups of normotensive Wistar‐Kyoto rats were treated by i.v. injection with vehicle (V), YC‐1 (YC‐1), sodium nitroprusside (SNP), or YC‐1 and SNP (YC‐1+SNP). Hypertension was induced in four additional groups of WKY rats by 3 weeks of oral treatment with L‐NAME. These animals were investigated with the same protocol as the normotensive animals: L‐NAME/V, L‐NAME/YC‐1, L‐NAME/SNP, L‐NAME/YC‐1+SNP. YC‐1 lowered mean arterial blood pressure (MAP) in normotensive and hypertensive animals similarly to SNP alone (P<0.05, respectively). The combination of YC‐1 with SNP caused a strong decrease of MAP in both the hypertensive and normotensive animals (P<0.05, respectively). SNP with YC‐1 also induced a pronounced cyclic GMP increase in the aorta. This study shows for the first time the blood pressure lowering potential of bimodal targeting of the NO‐sGC‐system.

British Journal of Pharmacology (2000) 130, 205–208; doi:10.1038/sj.bjp.0703320
Modulation of 5‐hydroxytryptamine efflux from rat cortical synaptosomes by opioids and nociceptin
Authors: Sbrenna S , Marti M , Morari M , Calo' G , Guerrini R , Beani L , Bianchi C
Published: January 2005

The modulation of [3H]‐5‐hydroxytryptamine ([3H]‐5‐HT) efflux from superfused rat cortical synaptosomes by delta, kappa, mu and ORL1 opioid receptor agonists and antagonists was studied.

Spontaneous [3H]‐5‐HT efflux was reduced (20% inhibition) by either 0.5 μM tetrodotoxin or Ca2+‐omission. Ten mM K+‐evoked [3H]‐5‐HT overflow was largely Ca2+‐dependent (90%) and tetrodotoxin‐sensitive (50%).

The delta receptor agonist, deltorphin‐I, failed to modulate the K+‐evoked neurotransmitter efflux up to 0.3 μM. The kappa and the mu receptor agonists, U‐50,488 and endomorphin‐1, inhibited K+‐evoked [3H]‐5‐HT overflow (EC50=112 and 7 nM, respectively; Emax=28 and 29% inhibition, respectively) in a norBinaltorphimine‐ (0.3 μM) and naloxone‐ (1 μM) sensitive manner, respectively. None of these agonists significantly affected spontaneous [3H]‐5‐HT efflux.

The ORL1 receptor agonist nociceptin inhibited both spontaneous (EC50=67 nM) and K+‐evoked (EC50=13 nM; Emax=52% inhibition) [3H]‐5‐HT efflux. The effect of NC was insensitive to naloxone (up to 10 μM), but was antagonized by [Nphe1]nociceptin(1‐13)NH2 (a novel selective ORL1 receptor antagonist; pA2=6.7) and by naloxone benzoylhydrazone (pA2=6.3). The ORL1 ligand [Phe1ψ(CH2‐NH)Gly2]nociceptin(1‐13)NH2 also inhibited K+ stimulated [3H]‐5‐HT overflow (EC50=64 nM; Emax=31% inhibition), but its effect was partially antagonized by 10 μM naloxone.

It is concluded that the ORL1 receptor is the most important presynaptic modulator of neocortical 5‐HT release within the opioid receptor family. This suggests that the ORL1/nociceptin system may have a powerful role in the control of cerebral 5‐HT‐mediated biological functions.

British Journal of Pharmacology (2000) 130, 425–433; doi:10.1038/sj.bjp.0703321
A2A adenosine receptor mediated potassium channel activation in rat epididymal smooth muscle
Authors: Haynes John M
Published: January 2005

The effects of A2 adenosine receptor agonists upon phenylephrine‐stimulated contractility in preparations of rat epididymis were investigated.

Preparations responded to phenylephrine (3 μM) with submaximal contractions. Adenosine and the stable agonists 5′‐N‐ethylcarboxamido‐adenosine (NECA) and 2‐p‐(2‐carboxyethyl) phenethylamino‐N‐ethylcarboxamide adenosine (CGS 21680) inhibited phenylephrine‐induced contractions (potency order, NECA>CGS 21680>adenosine). The A2A receptor‐selective antagonist, 4‐(2‐[7‐amino‐2‐(2‐furyl)[1,2,4]‐triazolo‐[2,3‐a][1,3,5]triazin‐5‐ylamino]ethyl)phenol (ZM 241385, 30 μM) blocked the response to NECA.

The A2A adenosine receptor‐mediated inhibitory responses to NECA were reduced by the KATP channel blocker, glibenclamide (3 μM) and abolished by charybdotoxin (100 nM).

The diterpene forskolin elicited a concentration‐dependent inhibition of phenylephrine (3 μM)‐stimulated contractility (by 62±8% of control at 100 μM). Charybdotoxin (100 nM), but not glibenclamide (3 μM) blocked the forskolin (10 μM) inhibition of phenylephrine‐stimulated contractility.

NECA elicited concentration‐dependent increases in both cyclic AMP and cyclic GMP accumulation which were antagonized by ZM 241385 (30 nM).

The protein kinase G activator, APT‐cyclic GMP (8‐(‐Aminophenylthio) guanosine‐3′,5′‐cyclic monophosphate) and the protein kinase A activator (Sp)‐8‐bromoadenosine‐3′,5′‐cyclic monophosphorothioate (Sp‐8‐Br‐cyclic AMPs), inhibited phenylephrine (3 μM) induced contractions of rat epididymis. Glibenclamide (3 μM), but not charybdotoxin (100 nM), inhibited ATP‐cyclic GMP responses. Charybdotoxin (100 nM), but not glibenclamide (3 μM) reduced the effect of Sp‐8‐Br‐cyclic AMPs.

This study shows that the A2A adenosine receptor inhibition of epididymal contractility may be mediated through the activation of charybdotoxin‐ and glibenclamide‐sensitive potassium channels and may involve the activation of both protein kinases A and G.

British Journal of Pharmacology (2000) 130, 685–691; doi:10.1038/sj.bjp.0703323
Differential effects of UTP and ATP on ion transport in porcine tracheal epithelium
Authors: Inglis S K , Olver R E , Wilson S M
Published: January 2005

Isolated segments of porcine tracheal epithelium were mounted in Ussing chambers, current required to maintain transepithelial potential difference at 0 mV (short circuit current, ISC) was monitored and effects of nucleotides upon ISC were studied.

Mucosal UTP (100 μM) evoked a transient rise in ISC that was followed by a sustained fall below basal ISC maintained for 30 min. Mucosal ATP (100 μM) also stimulated a transient rise in ISC but in contrast to UTP did not inhibit basal ISC. Submucosal UTP and ATP both transiently increased ISC.

UTP‐prestimulated epithelia were refractory to ATP but prestimulation with ATP did not abolish the response to UTP. The epithelia thus appear to express two populations of apical receptors allowing nucleotides to modulate ISC.

The UTP‐induced rise was reduced by pretreatment with either bumetanide (100 μM), diphenylamin‐2‐carboxylic acid (DPC, 1 mM), or Cl− and HCO3−‐free solution whilst the fall was abolished by amiloride pretreatment.

Thapsigargin (0.3 μM) abolished the UTP‐induced increase in ISC but not the subsequent decrease. Staurosporine (0.1 μM) inhibited basal ISC and blocked UTP‐induced inhibition of ISC. Inhibitors of either protein kinase C (PKC) (D‐erythro sphingosine) or PKA (H89) had no effect.

This study suggests that UTP stimulates Cl− secretion and inhibits basal Na+ absorption. ATP has a similar stimulatory effect, which may be mediated by activation of P2Y2 receptors and an increase in [Ca2+]in, but no inhibitory effect, which is likely mediated by activation of a pyrimidine receptor and possible inhibition of a protein kinase other than PKC or PKA.

British Journal of Pharmacology (2000) 130, 367–374; doi:10.1038/sj.bjp.0703324
Thyrotropin regulates adenosine A1 receptor expression in rat thyroid FRTL‐5 cells
Authors: Vainio Minna , Fredholm Bertil B , Törnquist Kid
Published: January 2005

The effect of thyrotropin (TSH), on adenosine A1 receptor expression in thyroid FRTL‐5 cells was examined by [3H]‐1,3‐dipropyl‐,8‐cyclopentyl xanthine ([3H]‐DPCPX) binding on cells in suspension and on membrane preparation, and by in situ mRNA labelling.

The estimated KD for intact cells was 0.19 nM and about 47,000 binding sites per cell were found in cells constantly grown in the presence of TSH.

Three days deprivation of TSH decreased the number of [3H]‐DPCPX binding sites without any significant effect of KD. Reintroduction of TSH to the cells returned the higher level of A1 receptors both in suspension binding studies on whole cells and on membrane preparations.

In situ hybridization revealed that TSH evoked an increase in the number of cells densely labelled with a probe against A1 receptor mRNA.

The potency of the A1 receptor agonist N6‐cyclohexyladenosine (CHA) as an inhibitor of cyclic AMP formation induced by forskolin was increased in TSH‐treated cells, with a shift in the IC50 from 2.05 nM in TSH‐deprived cells to 0.14 nM in TSH‐treated cells.

Since the activation of A1 receptors inhibits TSH‐mediated cyclic AMP signalling, our results suggest a regulatory feedback mechanism between signalling via adenosine A1 receptors and TSH receptors.

British Journal of Pharmacology (2000) 130, 471–477; doi:10.1038/sj.bjp.0703325
The mechanism of cryoinjury: In vitro studies on human internal mammary arteries
Authors: Müller‐Schweinitzer Else , Brett Wolfgang , Zerkowski Hans‐Reinhard , Haefeli Walter E
Published: January 2005

The mechanism of cryoinjury was investigated in human internal mammary arteries (IMA) by monitoring contractile responses to ET‐1 and KCl.

For cryopreservation segments of IMA were equilibrated for 20 min with the cryomedium (RPMI 1640 culture medium containing 1.8 M DMSO and 0.1 M sucrose), frozen at a mean cooling rate of 1.3°C min−1 to −70°C and stored in liquid nitrogen. Before use, samples were thawed slowly and the cryomedium removed by dilution.

Compared to unfrozen controls, ET‐1 stimulated frozen/thawed IMA with similar efficacy but at 3 fold lower concentrations (P<0.001). Addition of ET‐1 (100 nM) induced maximal contraction of unfrozen IMA within 10 min, declining thereafter to 25% after 90 min. In frozen/thawed IMA the ET‐1‐induced contraction was sustained but could be reversed if protein kinase C was blocked by staurosporine (100 nM). Responses to ET‐1 of cryostored IMA were 5 fold more susceptible to blockade by nifedipine than those of controls.

After cryostorage the efficacy of KCl was diminished to 40% (P<0.05) and the KCl curve was shifted to the left (2 fold, P<0.001). In both unfrozen and cryostored IMA the KCl (60 mM) effect was sustained and equally susceptible to nifedipine.

It is suggested that the smooth muscle cell of IMA is receptive to physical forces which occur during cryopreservation. These forces modify transmembrane signal transduction and intracellular pathways, that are common to pharmacological agonists thereby changing vascular responses to several contractile agonists after thawing.

British Journal of Pharmacology (2000) 130, 636–640; doi:10.1038/sj.bjp.0703326
Effects of peroxisome proliferator‐activated receptor‐α and ‐γ agonist, JTT‐501, on diabetic complications in Zucker diabetic fatty rats
Authors: Shibata Tsutomu , Takeuchi Satomi , Yokota Seiko , Kakimoto Kochi , Yonemori Fumihiko , Wakitani Korekiyo
Published: January 2005

This study has investigated the effects of JTT‐501, a peroxisome proliferator‐activated receptor (PPAR)‐α and PPAR‐γ agonist, on the pathogenesis of diabetic complications in the Zucker diabetic fatty (ZDF) rats, a model of type 2 diabetes. Comparison is made with troglitazone, a PPAR‐γ agonist.

The ZDF rats exhibited hyperglycaemia and hyperlipidaemia, and developed diabetic complications such as cataract, nephropathy, and neuropathy. Treatment with JTT‐501 from the prediabetic stage controlled glycaemia and lipidaemia, and prevented the development of diabetic complications. Troglitazone was less effective in controlling serum cholesterol and neuropathy.

ZDF rats developed diabetic osteopenia with reduced bone turnover, and this was prevented by JTT‐501 and troglitazone, possibly mediated by increased bone turnover and bone formation.

Since JTT‐501 controlled glycaemia and lipidaemia in ZDF rats and prevented several diabetic complications, it is suggested that treatment with JTT‐501, which activates both PPAR‐α and PPAR‐γ, could provide a valuable therapeutic approach against diabetic complications in type 2 diabetes.

British Journal of Pharmacology (2000) 130, 495–504; doi:10.1038/sj.bjp.0703328
Effects of halothane on the membrane potential in skeletal muscle of the frog
Authors: Sauviat Martin‐Pierre , Frizelle Henry P , Descorps‐Declère Adrien , Mazoit Jean‐Xavier
Published: January 2005

Halothane has many effects on the resting membrane potential (Vm) of excitable cells and exerts numerous effects on skeletal muscle one of which is the enhancement of Ca2+ release by the sarcoplasmic reticulum (SR) resulting in a sustained contracture. The aim of this study was to analyse the effects of clinical doses of halothane on Vm, recorded using intracellular microelectrodes on cleaned and non stimulated sartorius muscle which was freshly isolated from the leg of the frog Rana esculenta.

We assessed the mechanism of effects of superfused halothane on Vm by the administration of selective antagonists of membrane bound Na+, K+ and Cl− channels and by inhibition of SR Ca2+ release.

Halothane (3%) induced an early and transient depolarization (4.5 mV within 7 min) and a delayed and sustained hyperpolarization (about 11 mV within 15 min) of Vm.

The halothane‐induced transient depolarization was sensitive to ryanodine (10 μM) and to 4‐acetamido‐4′‐isothiocyanatostilbene 2,2′ disulphonic acid (SITS, 1 mM).

The hyperpolarization of Vm induced by halothane (0.1–3%) was dose‐dependent and reversible. It was insensitive to SITS (1 mM), tetrodotoxin (0.6 μM), and tetraethylammonium (10 mM) but was blocked and/or prevented by ryanodine (10 μM), charybdotoxin (CTX, 1 μM), and glibenclamide (10 nM).

Our observations revealed that the effects of halothane on Vm may be related to the increase in intracellular Ca2+ concentration produced by the ryanodine‐sensitive Ca2+ release from the SR induced by the anaesthetic. The depolarization may be attributed to the activation of Ca2+‐dependent Cl− (blocked by SITS) channels and the hyperpolarization to the activation of large conductance Ca2+‐dependent K+ channels, blocked by CTX, and to the opening of ATP‐sensitive K+ channels, inhibited by glibenclamide.

British Journal of Pharmacology (2000) 130, 619–624; doi:10.1038/sj.bjp.0703330
EDHF, NO and a prostanoid: hyperpolarization‐dependent and ‐independent relaxation in guinea‐pig arteries
Authors: Tare Marianne , Parkington Helena C , Coleman H A
Published: January 2005

The contribution of endothelium‐derived hyperpolarizing factor (EDHF), nitric oxide (NO) and a prostanoid (PG) to endothelium‐dependent hyperpolarization and relaxation were assessed in coronary and mammary arteries of guinea‐pigs by integration of the responses evoked during discrete applications of acetylcholine (ACh). The results of this integration approach were compared with those using traditional peak analysis methods.

Nω‐nitro‐L‐arginine methyl ester (L‐NAME, 100 μM) and indomethacin (1 μM), alone or in combination, were without effect on peak hyperpolarizations or relaxations while they markedly reduced the integrated responses in both arteries.

Integrated responses attributed to NO and PG were larger than those attributed to EDHF in the coronary artery (at 2 μM ACh, hyperpolarization (mV s): NO, 4200±91; PG, 5046±157; EDHF, 1532±94; relaxation (mN s mm−1): NO, 2488±122; PG, 2234±96; EDHF, 802±54). Integrated responses attributed to NO, PG and EDHF were similar in the mammary artery (at 2 μM ACh, hyperpolarization: NO, 347±69; PG, 217±49; EDHF, 310±63; relaxation: NO, 462±94; PG, 456±144; EDHF, 458±40).

Gilbenclamide (1 μM) all but abolished the hyperpolarization attributable to NO and PG but not EDHF in both arteries allowing assessment of the role of the hyperpolarization in relaxation. Gilbenclamide was without effect on the integrated relaxation due to NO but significantly reduced the relaxation associated with PG in the two arteries.

In conclusion, integration of the responses enabled a more complete assessment of the contribution of EDHF, NO and PG to endothelium‐dependent responses, which were strikingly different in the two arteries. There is commonality in the role of hyperpolarization in relaxation in both arteries: EDHF‐dependent relaxation is strongly dependent on hyperpolarization; hyperpolarization plays an important role in PG relaxation, whereas it has a small facilitatory role in NO‐dependent relaxation.

British Journal of Pharmacology (2000) 130, 605–618; doi:10.1038/sj.bjp.0703332
Properties and pharmacological modification of ATP‐sensitive K+ channels in cat tracheal myocytes
Authors: Teramoto Noriyoshi , Nakashima Tadasu , Ito Yushi
Published: January 2005

The effects of levcromakalim and nucleoside diphosphates (NDPs) on both membrane currents and unitary currents in cat trachea myocytes were investigated by use of patch‐clamp techniques.

In conventional whole‐cell configuration, levcromakalim produced a concentration‐dependent K+ current which was suppressed by additional application of 5 μM glibenclamide at −70 mV. When 3 mM ATP was added in the pipette solution, the peak amplitude of the levcromakalim‐induced current was much smaller than that in the absence of ATP.

When 3 mM uridine 5′‐diphosphate (UDP) was included in the pipette solution, much higher concentrations of glibenclamide (50 μM) were required to suppress the 100 μM levcromakalim‐induced membrane current in comparison with those in the absence of UDP.

In the cell‐attached patches, levcromakalim activated a 40 pS K+ channel which was inhibited by additional application of glibenclamide in symmetrical 140 mM K+ conditions.

UDP (0.1 mM) was capable of reactivating the channel in inside‐out patches in which the glibenclamide‐sensitive K+ channel had run down, in the presence of levcromakalim. The K+ channel reactivated by UDP was suppressed by additional application of either intracellular 3 mM ATP or 100 μM glibenclamide.

These results demonstrate that smooth muscle cells in the cat trachea possess ATP‐sensitive 40 pS K+ channels which are blocked by glibenclamide (i.e. KATP) and can be activated by levcromakalim and that intracellular UDP causes a significant shift of the glibenclamide‐sensitivity of these channels.

British Journal of Pharmacology (2000) 130, 625–635; doi:10.1038/sj.bjp.0703333
Effects of a quaternary bupivacaine derivative on delayed rectifier K+ currents
Authors: Longobardo M , González T , Navarro‐Polanco R , Caballero R , Delpón E , Tamargo J , Snyders D J , Tamkun M M , Valenzuela C
Published: January 2005

Block of hKv1.5 channels by R‐bupivacaine has been attributed to the interaction of the charged form of the drug with an intracellular receptor. However, bupivacaine is present as a mixture of neutral and charged forms both extra‐ and intracellularly.

We have studied the effects produced by the R(+) enantiomer of a quaternary bupivacaine derivative, N‐methyl‐bupivacaine, (RB+1C) on hKv1.5 channels stably expressed in Ltk− cells using the whole‐cell configuration of the patch‐clamp technique.

When applied from the intracellular side of the membrane, RB+1C induced a time‐ and voltage‐dependent block similar to that induced by R‐bupivacaine. External application of 50 μM RB+1C reduced the current at +60 mV by 24±2% (n=10), but this block displayed neither time‐ nor voltage‐dependence.

External RB+1C partially relieved block induced by R‐bupivacaine (61±2% vs 56±3%, n=4, P<0.05), but it did not relieve block induced by internal RB+1C. In addition, it did not induce use‐dependent block, but when applied in combination with internal RB+1C a use‐dependent block that increased with pulse duration was observed.

These results indicate that RB+1C induces different effects on hKv1.5 channels when applied from the intra or the extracellular side of the membrane, suggesting that the actions of bupivacaine are the resulting of those induced on the external and the internal side of hKv1.5 channels.

British Journal of Pharmacology (2000) 130, 391–401; doi:10.1038/sj.bjp.0703334
Activation and block of recombinant GABAA receptors by pentobarbitone: a single‐channel study
Authors: Akk Gustav , Steinbach Joe Henry
Published: January 2005

Recombinant GABAA receptors (α1β2γ2L) were transiently expressed in HEK 293 cells. We have investigated activation and block of these receptors by pentobarbitone (PB) using cell‐attached single‐channel patch clamp.

Clusters of single‐channel activity elicited by 500 μM PB were analysed to estimate rate constants for agonist binding and channel gating. The minimal model able to describe the kinetic data involved two sequential binding steps, followed by channel opening. The estimated channel opening rate constant is ∼1500 s−1, and the estimated equilibrium dissociation constants for the binding steps involved in activation are ∼2 mM.

Our results show a dose‐dependent block of receptors at millimolar concentrations of PB that results in reduced open interval durations. The reduction in mean open time is linearly proportional to PB concentration, indicating that block can be produced by binding of a single PB molecule.

Addition of millimolar concentrations of PB in the presence of GABA also produces a reduction of open channel lifetime in addition to a progressive increase in the closed interval durations within a cluster. The data suggest that the receptor contains two or more blocking sites while occupancy of only one of the sites is sufficient for channel block.

Neither the blocking rate constant nor return rate from the blocked state(s) is affected by pH (ionization status of the PB molecule) demonstrating that both neutral and anionic forms of PB cause channel block.

British Journal of Pharmacology (2000) 130, 249–258; doi:10.1038/sj.bjp.0703335
Octopamine receptors in the honey bee and locust nervous system: pharmacological similarities between homologous receptors of distantly related species
Authors: Degen Joern , Gewecke Michael , Roeder Thomas
Published: January 2005

Honey bees are perhaps the most versatile models to study the cellular and pharmacological basis underlying behaviours ranging from learning and memory to sociobiology. For both aspects octopamine (OA) is known to play a vital role.

The neuronal octopamine receptor of the honey bee shares pharmacological similarities with the neuronal octopamine receptor of the locust. Both, agonists and antagonists known to have high affinities for the locust neuronal octopamine receptor have also high affinities for the bee neuronal octopamine receptor.

The distribution of receptors is more or less congruent between locusts and bees. Optic lobes and especially the mushroom bodies are areas of greatest octopamine receptor expression in both species, which mirrors the physiological significance of octopamine in the insect nervous system.

The neuronal octopamine receptor of insects served as a model to study the pharmacological similarity of homologous receptors from distantly related species, because bees and locusts are separated by at least 330 million years of evolution.

British Journal of Pharmacology (2000) 130, 587–594; doi:10.1038/sj.bjp.0703338
Long‐lasting cholecystokinin2 receptor blockade after a single subcutaneous injection of YF476 or YM022
Authors: Kitano Masayuki , Norlén Per , Ding Xi‐Qin , Nakamura Sanae , Håkanson Rolf
Published: January 2005

Histamine‐forming ECL cells in the rat stomach operate under the control of gastrin. They represent a convenient target for studying cholecystokinin‐B/gastrin (CCK2) receptor antagonists in vivo.

We examined the effectiveness and duration of action of two CCK2 antagonists, YM022 and YF476, with respect to their effect on ECL‐cell histidine decarboxylase (HDC) activity in the rat.

Oral administration of subcutaneous deposition of YF476 or YM022 reduced the HDC activity. The maximum/near‐maximum dose for both drugs and for both modes of administration was 300 μmol kg−1 (effects measured 24 h after dose). At this dose and time the serum concentration of YF476 was 20–40 nmol l−1. The dose 300 μmol kg−1 was used in all subsequent studies.

A single subcutaneous injection of YF476 inhibited the HDC activity for 8 weeks. The circulating concentration of YF476 remained high for the same period of time (15 nmol l−1). Subcutaneous YM022 suppressed the HDC activity for 4 weeks. A single oral dose of YF476 or YM022 inhibited the HDC activity for 2–3 days.

Chronic gastric fistula rats were used to study the effect of subcutaneous YF476 on gastrin‐stimulated acid secretion. A single injection of YF476 prevented gastrin from causing an acid response for at least 4 weeks (the longest time studied).

We conclude that a single subcutaneous injection of 300 μmol kg−1 YF476 causes blockade of CCK2 receptors in the stomach of the rat for 8 weeks thus providing a convenient method for studies of the consequences of long‐term CCK2 receptor inhibition.

British Journal of Pharmacology (2000) 130, 699–705; doi:10.1038/sj.bjp.0703342
Substance P mediates inflammatory oedema in acute pancreatitis via activation of the neurokinin‐1 receptor in rats and mice
Authors: Grady Eileen F , Yoshimi Shandra K , Maa John , Valeroso Dahlia , Vartanian Robert K , Rahim Shamila , Kim Edward H , Gerard Craig , Gerard Norma , Bunnett Nigel W , Kirkwood Kimberly S
Published: January 2005

Pancreatic oedema occurs early in the development of acute pancreatitis, and the overall extent of fluid loss correlates with disease severity. The tachykinin substance P (SP) is released from sensory nerves, binds to the neurokinin‐1 receptor (NK1‐R) on endothelial cells and induces plasma extravasation, oedema, and neutrophil infiltration, a process termed neurogenic inflammation. We sought to determine the importance of neurogenic mechanisms in acute pancreatitis.

Pancreatic plasma extravasation was measured using the intravascular tracers Evans blue and Monastral blue after administration of specific NK1‐R agonists/antagonists in rats and NK1‐R(+/+)/(−/−) mice. The effects of NK1‐R genetic deletion/antagonism on pancreatic plasma extravasation, amylase, myeloperoxidase (MPO), and histology in cerulein‐induced pancreatitis were characterized.

In rats, both SP and the NK1‐R selective agonist [Sar9 Met(O2)11]SP stimulated pancreatic plasma extravasation, and this response was blocked by the NK1‐R antagonist CP 96,345. Selective agonists of the NK‐2 or NK‐3 receptors had no effect.

In rats, cerulein stimulated pancreatic plasma extravasation and serum amylase. These responses were blocked by the NK1‐R antagonist CP 96,345.

In wildtype mice, SP induced plasma extravasation while SP had no effect in NK1‐R knockout mice.

In NK1‐R knockout mice, the effects of cerulein on pancreatic plasma extravasation and hyperamylasemia were reduced by 60%, and pancreatic MPO by 75%, as compared to wildtype animals.

Neurogenic mechanisms of inflammation are important in the development of inflammatory oedema in acute interstitial pancreatitis.

British Journal of Pharmacology (2000) 130, 505–512; doi:10.1038/sj.bjp.0703343
Accelerated resequestration of cytosolic calcium and suppression of the pro‐inflammatory activities of human neutrophils by CGS 21680 in vitro
Authors: Anderson R , Visser S S , Ramafi G , Theron A J
Published: January 2005

We have investigated the effects of the adenosine A2A receptor agonist CGS 21680 (0.01–1 μM) on reactive oxidant production by, and elastase release from FMLP‐activated human neutrophils, as well as on cytosolic Ca2+ fluxes and intracellular concentrations of cyclic AMP.

Oxidant production, elastase release and cyclic AMP were assayed using lucigenin‐enhanced chemiluminescence, colourimetric and radioimmunoassay procedures respectively, while cytosolic Ca2+ fluxes were measured by fura‐2 spectrofluorimetry in combination with radiometric procedures which distinguish between net efflux and influx of the cation.

Treatment of neutrophils with CGS 21680 did not affect the FMLP‐activated release of Ca2+ from intracellular stores, but resulted in dose‐related acceleration of the rate of decline in fura‐2 fluorescence, as well as decreases in both efflux and store‐operated influx of Ca2+, compatible with enhancement of resequestration of the cation by the endo‐membrane Ca2+‐ATPase. These effects on neutrophil Ca2+ handling were associated with increased intracellular cyclic AMP and with inhibition of oxidant production and release of elastase.

In contrast, treatment of neutrophils with the selective A2A receptor antagonist, ZM 241385 (2.5 μM), prevented the transient increase in cyclic AMP in FMLP‐activated neutrophils which was associated with delayed sequestration of incoming Ca2+ during store‐operated influx.

The CGS 21680‐mediated reduction of Ca2+ efflux from FMLP‐activated neutrophils was also antagonized by pretreatment of the cells with ZM 241385 (2.5 μM), as well as by thapsigargin (1 μM), an inhibitor of the endo‐membrane Ca2+‐ATPase. ZM 241385 also neutralized the cyclic AMP‐elevating and anti‐inflammatory interactions of CGS 21680 with neutrophils.

We conclude that A2A receptors regulate the pro‐inflammatory activities of human neutrophils by promoting cyclic AMP‐dependent sequestration of cytosolic Ca2+.

British Journal of Pharmacology (2000) 130, 717–724; doi:10.1038/sj.bjp.0703344
Retinoid‐mediated inhibition of interleukin‐12 production in mouse macrophages suppresses Th1 cytokine profile in CD4+ T cells
Authors: Kang B Y , Chung S W , Kim S H , Kang S N , Choe Y K , Kim T S
Published: January 2005

Interleukin‐12 (IL‐12) plays a central role in the immune system by driving the immune response towards T helper 1 (Th1) type responses characterized by high IFN‐γ and low IL‐4 production. In this study we investigated whether retinoid‐mediated inhibition of interleukin‐12 production in mouse macrophages could regulate cytokine profile of antigen (Ag)‐primed CD4+ Th cells.

Pretreatment with retinoids (9‐cis‐RA, all‐trans‐RA, TTNPB) significantly inhibited IL‐12 production by mouse macrophages stimulated with lipopolysaccharide (LPS) or heated‐killed Listeria monocytogenes (HKL). Retinoid‐pretreated macrophages reduced their ability to induce IFN‐γ and increased the ability to induce IL‐4 in Ag‐primed CD4+ T cells.

Addition of recombinant IL‐12 to cultures of retinoid‐pretreated macrophages and CD4+ T cells restored IFN‐γ production in CD4+ T cells.

The in vivo administration of 9‐cis‐RA resulted in the inhibition of IL‐12 production by macrophages stimulated in vitro with either LPS or HKL, leading to the inhibition of Th1 cytokine profile (decreased IFN‐γ and increased IL‐4 production) in CD4+ T cells.

These findings may explain some known effects of retinoids including the inhibition of encephalitogenicity, and point to a possible therapeutic use of retinoids in the Th1‐mediated immune diseases such as autoimmune diseases.

British Journal of Pharmacology (2000) 130, 581–586; doi:10.1038/sj.bjp.0703345
Somatostatin potentiates NMDA receptor function via activation of InsP3 receptors and PKC leading to removal of the Mg2+ block without depolarization
Authors: Pittaluga Anna , Bonfanti Andrea , Raiteri Maurizio
Published: January 2005

N‐methyl‐D‐aspartate (NMDA) receptors exist on noradrenergic axon terminals and mediate enhancement of noradrenaline (NA) release. We here investigated modulation by somatostatin (SRIF, somatotropin release inhibiting factor) of the NMDA‐induced release of NA using superfused hippocampal synaptosomes.

The NMDA response was increased by SRIF‐28 and SRIF‐14, but not SRIF‐28(1–14), whereas the release of [3H]‐NA elicited by α‐amino‐3‐hydroxy‐5‐methylisoxazide‐4‐propionic acid (AMPA) was unaffected. SRIF‐14 did not mimic glycine at the NMDA receptor but activated SRIF receptors sited on noradrenergic terminals.

The SRIF‐14 effect was blocked by pertussis toxin but mimicked by mastoparan, a G‐protein activator. BIM‐23056, but not Cyanamid 154806, antagonized the SRIF‐14 effect. This effect was mimicked by L362855, a partial agonist at the sst5 subtype, but not by the new selective sst1–sst4 receptor agonists L797591, L779976, L796778 and L803087.

Protein kinase C (PKC) inhibitors (H7, staurosporine, GF 209103X, cheleritrine and sphingosine) prevented the SRIF‐14 effect, while phorbol 12‐myristate 13‐acetate enhanced the NMDA response.

SRIF‐14 permitted NMDA receptor activation in the presence of 1.2 mM Mg2+ ions, both in hippocampal synaptosomes and slices. Blockade of inositol‐1,4,5‐trisphosphate (InsP3) receptors with heparin abolished the effect of SRIF‐14.

It is concluded that SRIF receptors, possibly of the sst5 subtype, can exert a permissive role on NMDA receptors colocalized on hippocampal noradrenergic terminals: activation of sst5 receptors is coupled to pertussis toxin‐sensitive G proteins enhancing phosphoinositide metabolism with activation of InsP3 receptors and PKC; NMDA receptor subunits might be phosphorylated with consequent removal of the Mg2+ block in absence of depolarization.

British Journal of Pharmacology (2000) 130, 557–566; doi:10.1038/sj.bjp.0703346
Endogenous nitric oxide decreases hippocampal levels of serotonin and dopamine in vivo
Authors: Wegener Gregers , Volke Vallo , Rosenberg Raben
Published: January 2005

Nitric oxide (NO) modulates the levels of various neurotransmitters in the CNS. Here we determined whether the specific nitric oxide synthase (NOS) inhibitor 7‐nitroindazole (7‐NI), the non‐selective inhibitor of guanylate cyclase (GC) and NOS, methylene blue (MB), the NO‐precursor L‐arginine (L‐Arg), and the selective soluble GC inhibitor 1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ) affect extracellular levels of serotonin (5‐HT), dopamine (DA), 5‐hydroxyindoleacetic acid (5‐HIAA), and homovanillic acid (HVA) in the rat ventral hippocampus by using microdialysis in freely moving animals.

Local perfusion of 7‐NI (1 mM) and MB (1 mM) significantly increased extracellular level of 5‐HT, whereas DA was increased by 7‐NI only. Systemic administration of 7‐NI (50 mg kg−1) and MB (30 mg kg−1) increased the extracellular levels of 5‐HT and DA. Extracellular levels of 5‐HIAA was not influenced by local or systemic MB or 7‐NI. In contrast, extracellular level of HVA was decreased by systemic MB and retrodialyzed MB, but was not influenced by 7‐NI.

Retrodialysis of L‐Arg (2 mM) decreased the levels of 5‐HT, DA, 5‐HIAA and HVA in the hippocampus. Systemic administration of L‐Arg (250 mg kg−1) decreased the level of 5‐HT, but failed to influence DA, 5‐HIAA and HVA.

Local perfusion of ODQ (400 μM) did not affect 5‐HT overflow in the hippocampus.

We conclude that NOS inhibitors increased extracellular levels of 5‐HT and DA in the rat ventral hippocampus after local or systemic administration, whereas the NO precursor L‐Arg had the opposite effect. Thus, endogenous NO may exert a negative control over the levels of 5‐HT and DA in the hippocampus. However, this effect is probably not mediated by cyclic GMP.

British Journal of Pharmacology (2000) 130, 575–580; doi:10.1038/sj.bjp.0703349
High affinity interaction of mibefradil with voltage‐gated calcium and sodium channels
Authors: Eller Philipp , Berjukov Stanislav , Wanner Siegmund , Huber Irene , Hering Steffen , Knaus Hans‐Günther , Toth Geza , Kimball S David , Striessnig Jörg
Published: January 2005

Mibefradil is a novel Ca2+ antagonist which blocks both high‐voltage activated and low voltage‐activated Ca2+ channels. Although L‐type Ca2+ channel block was demonstrated in functional experiments its molecular interaction with the channel has not yet been studied. We therefore investigated the binding of [3H]‐mibefradil and a series of mibefradil analogues to L‐type Ca2+ channels in different tissues.

[3H]‐Mibefradil labelled a single class of high affinity sites on skeletal muscle L‐type Ca2+ channels (KD of 2.5±0.4 nM, Bmax=56.4±2.3 pmol mg−1 of protein).

Mibefradil (and a series of analogues) partially inhibited (+)‐[3H]‐isradipine binding to skeletal muscle membranes but stimulated binding to brain L‐type Ca2+ channels and α1C‐subunits expressed in tsA201 cells indicating a tissue‐specific, non‐competitive interaction between the dihydropyridine and mibefradil binding domain.

[3H]‐Mibefradil also labelled a heterogenous population of high affinity sites in rabbit brain which was inhibited by a series of nonspecific Ca2+ and Na+‐channel blockers.

Mibefradil and its analogue RO40‐6040 had high affinity for neuronal voltage‐gated Na+‐channels as confirmed in binding (apparent Ki values of 17 and 1.0 nM, respectively) and functional experiments (40% use‐dependent inhibition of Na+‐channel current by 1 μM mibefradil in GH3 cells).

Our data demonstrate that mibefradil binds to voltage‐gated L‐type Ca2+ channels with very high affinity and is also a potent blocker of voltage‐gated neuronal Na+‐channels. More lipophilic mibefradil analogues may possess neuroprotective properties like other nonselective Ca2+‐/Na+‐channel blockers.

British Journal of Pharmacology (2000) 130, 669–677; doi:10.1038/sj.bjp.0703352
Gadolinium inhibits Na+‐Ca2+ exchanger current in guinea‐pig isolated ventricular myocytes
Authors: Zhang Y H , Hancox J C
Published: January 2005

The trivalent cation, gadolinium (Gd3+) is commonly used to inhibit stretch‐activated channels. In this report, we show that Gd3+ also inhibits ionic current (INaCa), carried by the Na+‐Ca2+ exchanger protein. Under selective recording conditions, Gd3+ inhibited both outward and inward INaCa from guinea‐pig isolated ventricular myocytes in a dose‐dependent manner, with half‐maximal inhibition concentrations (IC50) of 30.0±4.0 μM at +60 mV (Hill‐coefficient, h=1.04±0.13) and 20.0±2.7 μM at −100 mV (h=1.13±0.16), respectively (P>0.05, n=5–9). Thus, inhibition was not voltage‐dependent. The time from Gd3+ application to steady‐state effect was slow compared to the divalent blocker Ni2+. The slow time course appeared to reflect gradual Gd3+ accumulation at its binding site on the exchanger, rather than a use‐dependent blocking mechanism. This study indicates that for experiments in which Gd3+ is used, its inhibitory effect on INaCa should be taken into account.

British Journal of Pharmacology (2000) 130, 485–488; doi:10.1038/sj.bjp.0703353
Xestospongin C, a selective and membrane‐permeable inhibitor of IP3 receptor, attenuates the positive inotropic effect of α‐adrenergic stimulation in guinea‐pig papillary muscle
Authors: Miyamoto Shigeki , Izumi Masanori , Hori Masatoshi , Kobayashi Motomasa , Ozaki Hiroshi , Karaki Hideaki
Published: January 2005

We evaluated the role of the inositol 1,4,5‐triphosphate (IP3) receptor‐mediated Ca2+ release on the positive inotropic effects of α‐adrenergic stimulation using a novel, potent, selective membrane‐permeable blocker of IP3 receptor, xestospongin C.

Guinea‐pig papillary muscle permeabilized with saponin exhibited spontaneous oscillatory contractions in solution buffered with pCa2+ 6.5 by a low concentration of EGTA. The oscillatory activity was increased by adding 100 μM IP3 and abolished by 1 μM ryanodine or 30 μM cyclopiazonic acid. Xestospongin C (3 μM) inhibited the IP3‐induced increase in the oscillatory contractions without affecting basal oscillations.

In intact papillary muscle, xestospongin C (3 μM) inhibited the positive inotropic effects of phenylephrine, resulting in a rightward and downward shift of the concentration‐response curve for phenylephrine. On the contrary, xestospongin C did not affect the concentration‐response curve for phenylephrine obtained in the presence of ryanodine (1 μM).

On the other hand, xestospongin C affected neither basal contractions nor the positive inotropic effects of a high extracellular Ca2+ concentration (3.2 mM) or that of isoprenaline (1 and 10 nM).

These results suggest that the IP3‐mediated increase in Ca2+ release is involved in the positive inotropic effects of α‐adrenergic stimulation in the guinea‐pig cardiac muscle.

British Journal of Pharmacology (2000) 130, 650–654; doi:10.1038/sj.bjp.0703358