bluuebunny/crossref_metadata_2025 huggingface dataset:
α‐Latrotoxin‐induced transmitter release in feline oesophageal smooth muscle: focus on nitric oxide and vasoactive intestinal peptide
Authors: Ny Lars , Waldeck Kristian , Carlemalm Eric , Andersson Karl‐Erik
Published: August 2006

The effects of α‐latrotoxin (αLTX) on muscle tone, resting membrane potential, cyclic nucleotide content, and ultrastructure were examined in feline oesophageal smooth muscle, including the lower oesophageal sphincter (LOS).

In circular smooth muscle strips from LOS developing active tone, αLTX (1 nm) induced a 94±3% (n=16) relaxation. Intermittent treatment with αLTX for 4 h abolished the response. Pretreatment with NG‐nitro‐l‐arginine (l‐NOARG; 0.1 mm) attenuated the relaxation.

In carbachol‐contracted circular smooth muscle strips from the LOS and oesophageal body (OB), αLTX induced a 95±5% (n=6) and 73±9% (n=8) relaxation, respectively. The relaxations were attenuated by l‐NOARG, and in LOS strips, the relaxation was abolished by the combination of l‐NOARG and vasoactive intestinal peptide (VIP)‐antiserum (1:25). At resting tension in circular smooth muscle strips from the OB, αLTX induced a scopolamine sensitive contraction in the presence of l‐NOARG.

In circular LOS and OB preparations, αLTX changed the resting membrane potential from −49±2 mV to −59±3 mV (n=4), and −62±2 mV to −71±3 mV (n=4), respectively.

The αLTX‐induced relaxation of LOS and OB muscle was associated with a 138% and 72% increase in cyclic GMP levels, respectively. No changes in cyclic AMP levels were observed.

Ultrastructural analysis of LOS and OB revealed a rich supply of nerve profiles containing small synaptic and large dense core vesicles. αLTX treatment resulted in a loss of both types of vesicle.

These results suggest that αLTX induces relaxation of oesophageal circular smooth muscle associated with NO‐generation and transmitter release from synaptic vesicles. Beside NO, VIP seems to be involved in the relaxant effects of αLTX on the LOS. In addition, αLTX may have contractile effects by release of acetylcholine.

British Journal of Pharmacology (1997) 120, 31–38; doi:10.1038/sj.bjp.0700882
Dose‐ and time‐dependence of l‐NAME neuroprotection in transient focal cerebral ischaemia in rats
Authors: Margaill Isabelle , Allix Monique , Boulu Roger G , Plotkine Michel
Published: August 2006

In this study the effect of the dose and administration time of NG‐nitro‐l‐arginine methyl ester (l‐NAME), an NO‐synthase inhibitor, in a model of transient focal cerebral ischaemia in rats was investigated.

Two injections of l‐NAME were given, of 1, 3 and 10 mg kg−1, 5 min and 3 h after the onset of ischaemia. None of the doses gave any striatal neuroprotection, but 1 and 3 mg kg−1l‐NAME reduced the infarcted volume in the cortex (by 26%, P<0.01 for 1 mg kg−1 and 21%, P<0.05 for 3 mg kg−1), whereas 10 mg kg−1 had no neuroprotective effect.

Single injections of l‐NAME 1 mg kg−1, given 5 min or 3 h after ischaemia onset, had similar neuroprotective effects on the cortical infarction as did the repeated injections.

l‐NAME 1 mg kg−1 given 3, 6 or 9 h after ischaemia induction reduced the cortical infarct volume by 19% (P<0.01) when given 3 h after ischaemia, by 21% (P<0.01) when given at 6 h, and by 16% (P<0.5) when given at 9 h, but had no neuroprotective activity when given 12 h after ischaemia.

Thus a low dose of l‐NAME is neuroprotective in a model of transient focal ischaemia, with a wide therapeutic window, much larger than that found for MK‐801.

British Journal of Pharmacology (1997) 120, 160–163; doi:10.1038/sj.bjp.0700889
Activation of ecto‐5′‐nucleotidase by protein kinase C and its role in ischaemic tolerance in the canine heart
Authors: Node Koichi , Kitakaze Masafumi , Minamino Tetsuo , Tada Michihiko , Inoue Michitoshi , Hori Masatsugu , Kamada Takenobu
Published: August 2006

Ischaemic preconditioning (IP) protects the myocardium against irreversible ischaemic injury by activating protein kinase C (PKC). The mechanism by which PKC protects the myocardium is unknown. We have shown that PKC increases the activity of ecto‐5′‐nucleotidase (ecto‐5′‐N) and thereby the production of adenosine in cardiomyocytes which may protect the myocardium against ischaemia‐reperfusion injury in vivo.

The objective of this study was to elucidate the possible role of PKC‐induced activation of ecto‐5′‐N in the cardioprotection associated with IP in the canine heart.

IP increased the activities of both ecto‐5′‐N and PKC, and minimized ischaemic damage (infarct size: 7.5±1.8 vs. 42.3±2.8%, P<0.01 vs. the control group). Treatment with the PKC activator (4β‐phorbol 12‐myristate‐13‐acetate) also reduced infarct size (13.5±2.9%, P<0.01 vs. the control group). 8‐Sulfophenyltheophylline (an antagonist of adenosine receptors) or α,β‐methyleneadenosine 5′‐diphosphate (an inhibitor of ecto‐5′‐N) eliminated the cardioprotective effect of the PKC activator (infarct size: 36.6±3.9 and 34.7±4.2%, respectively), suggesting that PMA limits infarct size by increasing the activity of ecto‐5′‐N and the adenosine level.

The PMA‐induced cardioprotection was blunted by GF109203X (an inhibitor of PKC, infarct size: 36.2±3.1%), but not by pretreatment with dexamethasone (infarct size, 14.2±2.6%).

We conclude that the PMA‐ and IP‐induced cardioprotection is attributable to phosphorylation and activation of ecto‐5′‐N.

British Journal of Pharmacology (1997) 120, 273–281; doi:10.1038/sj.bjp.0700890
Reperfusion injury in the endotoxin‐treated rat heart: reevaluation of the role of nitric oxide
Authors: Yang B C , Chen L Y , Saldeen T G P , Mehta J L
Published: August 2006

The role of nitric oxide (NO) in ischaemia‐reperfusion injury to the heart continues to be debated.

The role of NO released during endotoxemia on myocardial reperfusion injury was examined in rats given saline or lipopolysaccharide (LPS, 10 mg kg−1).

Aortic rings from LPS‐treated rats showed a markedly decreased contractile response to both noradrenaline (NA) and U46619, and a diminished relaxation response to acetylcholine, thrombin and aggregating platelets. Treatment of rat aortic rings from LPS‐treated rats with the NO synthesis inhibitor Nω‐nitro‐l‐arginine (l‐NOARG) reversed the diminished contractile response to NE and U46619.

Before ischaemia‐reperfusion, baseline force of cardiac contraction (FCC) and coronary perfusion pressure (CPP) were lower and coronary flow was higher in hearts from LPS‐treated rats (all P<0.05 vs. saline‐treated group). Treatment of hearts from LPS‐treated rats with l‐NOARG increased baseline FCC and CPP.

After ischaemia‐reperfusion, hearts from saline‐treated rats showed a 36±5% fall in FCC, a 38±6% rise in CPP and a 38±5% fall in coronary flow, whereas hearts from LPS‐treated rats revealed only a 16±9% fall in FCC, a 10±3% rise in CPP and a 20±4% fall in coronary flow (all P<0.05 vs. changes in saline‐treated group). Fewer hearts from LPS‐treated rats developed reperfusion arrhythmias (6% vs. 60% hearts from saline‐treated rats, P<0.02). Myocardial superoxide dismutase activity was higher in the LPS‐treated group (P<0.05).

NO synthesis, measured as formation of nitrite, was higher (P<0.05) in cardiac and aortic tissues from LPS‐treated rats. Prostacyclin (PGI2) release in coronary effluent was greater in LPS‐treated rat hearts (P<0.05 vs. saline‐treated rats).

Thus LPS‐treated hearts demonstrate a basal decrease in FCC and coronary vascular resistance. These hearts demonstrate a modest protection from reperfusion injury. Induction of NO synthesis, and possibly PGI2 release, may underlie cardioprotection from ischaemia‐reperfusion.

British Journal of Pharmacology (1997) 120, 305–311; doi:10.1038/sj.bjp.0700891
Effects of heptanol on electrical activity in the guinea‐pig vas deferens
Authors: Manchanda R. , Venkateswarlu K.
Published: August 2006

The effects of the putative intercellular uncoupling agent 1‐heptanol on electrical activity in the guinea‐pig vas deferens were studied by use of intracellular and extracellular recording techniques.

At concentrations of 0.5, 1 and 2 mM, heptanol rapidly, monotonically and reversibly attenuated intracellularly recorded excitatory junction potential (e.j.p.) amplitude without affecting its time course, while spontaneous excitatory junction potentials (s.e.j.ps) were left unaffected.

Heptanol did not affect either the extracellularly recorded evoked excitatory junction current (e.j.c), or the nerve terminal impulse that preceded it. These observations indicate that heptanol does not affect nerve impulse conduction, neurotransmitter release, or the postjunctional receptors involved in the production of the e.j.p.

E.j.ps appear to be suppressed by heptanol due to its intercellular uncoupling effects. Therefore, functional intercellular coupling may be necessary for the generation of the e.j.p. in smooth muscle.
In vivo receptor characterization of neuropeptide Y‐induced effects in consecutive vascular sections of cat skeletal muscle
Authors: Ekelund Ulf , Erlinge David
Published: August 2006

It has been suggested that the vasoconstrictor response to neuropeptide Y (NPY) is located in the microvessels and that it increases with reduced vessel diameter. The aim of the present study was to analyse quantitatively, on the cat gastrocnemius muscle preparation in vivo, the effects of NPY on total regional vascular resistance (RT) and its distribution to large‐bore arterial resistance vessels (>25 μm; Ra,prcx), small arterioles (<25 μm; Ra,micro) and the veins (Rv). Associated effects on capillary pressure (Pc,v) and fluid exchange were also studied.

Close‐arterially infused NPY (1‐32 μg kg−1 min−1) caused a dose‐dependent, slowly developing vasoconstriction in all three vascular sections, yet with a preferential action in the small arterioles. At 32 μg kg−1 min−1, NPY raised RT by 133 ± 22%, Ra,prox by 94 ± 15%, Ra,micro by 277 ± 104% and Rv by 81 ±11%. However, the veins (ED50 = 3.9 ± 1.2 μg kg−1 min−1) were more sensitive to NPY than both large‐bore arterial vessels (ED50 = 7.7 ± 1.6) and small arterioles (ED50 = 7.0 ± 1.4). NPY decreased Pc,v due to an increase in the pre‐to post‐capillary resistance ratio.

Close‐arterial infusions of Pro34NPY and peptide YY evoked vasoconstrictor responses which did not differ from the response to NPY. In contrast, the Y2‐preferring C‐terminal fragments: Ac‐[Leu28, Leu31]‐NPY(24–36) and NPY(13–36) were without effect in the muscle vascular bed. The selective NPY Y1 receptor antagonist BIBP3226 (100 μg kg−1 min−1, i.a.) abolished the vascular response to NPY.

The present findings indicate that the vasoconstrictor response to NPY in skeletal muscle is preferentially located in the small arterioles and mediated via the Y1 receptor and, further, that Y2 and Y3 receptors do not play a significant role in the vasoconstrictor response to NPY in cat skeletal muscle. BIBP3226 was found to be an effective NPY antagonist in vivo and to lack agonist activity.
Role of potassium channels and nitric oxide in the effects of iloprost and prostaglandin E1 on hypoxic vasoconstriction in the isolated perfused lung of the rat
Authors: Dumas Monique , Dumas Jean‐Paul , Rochette Luc , Advenier Charles , Giudicelli Jean‐François
Published: August 2006

The aims of this study were to compare in the rat isolated perfused lung preparation, the antagonist effects of iloprost, a stable analogue of prostacyclin, and prostaglandin E1 (PGE1) on the hypoxic pulmonary pressure response, and to investigate the possible involvement of KATP and KCa channels and of EDRF (NO) in these effects. In addition, iloprost and PGE1 effects were compared to those of adenosine and forskolin.

Isolated lungs from male Wistar rats (260–320 g) were ventilated with 21% O2 + 5% CO2 + 74% N2 (normoxia) or 5% CO2 + 95% N2 (hypoxia) and perfused with a salt solution supplemented with ficoll. Glibenclamide (1 μm), charybdotoxin (0.1 μm), NG‐nitro‐L‐arginine methyl ester (l‐NAME, 100 μm) were used to block KATP, KCa channels and NO synthesis, respectively.

Iloprost, PGE1, adenosine and forskolin caused relaxation during the hypoxic pressure response. The order of potency was: iloprost > PGE1 = forskolin > adenosine. EC50 values were 1.91 ± 0.52 10−9 M, 3.31 ± 0.58 10−7 M, 3.24 ± 0.78 10−7 M and 7.70 ± 1.68 10−5 M, respectively. Glibenclamide, charybdotoxin and L‐NAME inhibited partially the relaxant effects of iloprost and forskolin but not those of PGE1.

It is concluded that in the rat isolated lung preparation, iloprost and forskolin but not PGE1 dilate pulmonary vessels partly through KATP channels, KCa channels and nitric oxide release. Furthermore our results suggest that the role of cyclic AMP in these effects is not unequivocal.
Activation by high potassium of a novel voltage‐operated Ca2+ channel in rat spleen
Authors: Ko Feng‐Nien , Huang Shu‐Yi , Teng Che‐Ming
Published: August 2006

High potassium produced a concentration‐dependent contraction in rat isolated spleen.

The high potassium‐induced contraction of rat spleen was abolished in Ca2+‐free Krebs solution containing 1 mM EGTA, and the subsequent addition of 3 mM Ca2+ restored the high potassium‐induced contraction to the control level.

Nifedipine, verapamil, diltiazem, Cd2+, Ni2+, Co2+, R‐(+)‐Bay K 8644 and pimozide inhibited and relaxed high potassium‐induced contraction of rat spleen with IC50 and EC50 values much higher than those values in rat aorta.

In addition, high potassium‐stimulated contraction of rat spleen was insensitive to ω‐conotoxin GVIA, ω‐conotoxin MVIIC and ω‐agatoxin IVA.

The high potassium‐induced contraction of rat spleen was also unaffected by tetrodotoxin (TTX), prazosin, chloroethylclonidine (CEC), yohimbine, propranolol, atropine, diphenhydramine, cimetidine, ketanserin, 3‐tropanyl‐indole‐3‐carboxylate, saralasin, indomethacin, nordihydroguaiaretic acid, GR32191B, domperidone, naloxone, chlorpromazine, suramin, (±)‐2‐amino‐5‐phosphonopentanoic acid, 6,7‐dinitroquinoxaline‐2,3‐dione (DNQX), L‐659,877, L‐703,606, lorglumide, PD 135,158 N‐methyl‐D‐glucamine, benextramine, amiloride, dantrolene, TMB‐8, econazole, staurosporine and neomycin.

Forskolin and sodium nitroprusside relaxed high potassium‐induced contraction of rat spleen with EC50 values of 0.55 ± 0.04 and 20.0 ± 2.7 μm, respectively.

It is concluded that high potassium may activate a novel, pharmacologically uncharacterized voltage‐operated Ca2+ channel in rat spleen.
Inhibition by rapamycin of ornithine decarboxylase and epithelial cell proliferation in intestinal IEC‐6 cells in culture
Authors: Seidel E.R. , Ragan V.L.
Published: August 2006

Induction of the enzyme ornithine decarboxylase (ODC) appears to be controlled primarily at the level of ODC mRNA translation. The immunosuppressant drug, rapamycin, blocked the induction of ODC in response to serum by roughly 50% but was without effect on transport of putrescine into the intracellular space. The effect on ODC was specific for the intracellular signalling pathway leading to activation of p70S6k, as the immunosuppressant FK 506 was without effect on ODC activity.

Exposure of IEC‐6 duodenal epithelial cells to rapamycin inhibited cellular proliferation. The effect of rapamycin was cytostatic in that removal of the immunosuppressant from the medium resulted in renewed cell division. Conversely, addition of exogenous putrescine, the product of the ODC catalysed reaction, was unable to reverse the cytostatic effects of rapamycin.

At a concentration of 10 nM, rapamycin inhibited the induction of ODC by 50%, a level of inhibition which could not be enhanced by exposure cells to 1000 nM rapamycin. This observation suggests that other intracellular signalling pathways, in addition to the p70S6k cascade, might be involved in regulation of translation of ODC mRNA or that rapamycin does not completely inhibit p70S6k.
Anti‐insulin‐like growth factor‐I activity of a novel polysulphonated distamycin A derivative in human lung cancer cell lines
Authors: De Cupis Alessandra , Ciomei Marina , Pirani Paolo , Ferrera Alessandra , Ardizzoni Andrea , Favoni Roberto Enrico
Published: August 2006

The purpose of this study was to investigate the antiproliferative effect and the modulation of the mitogenic insulin‐like growth factor‐I (IGF‐I) system by FCE 26644 and FCE 27784, two polyanionic sulphonated distamycin A derivative compounds, on two human non‐small cell lung cancer (N‐SCLC) cell lines.

For cell growth studies the colorimetric MTT and the thymidine incorporation assays were performed; the presence of IGF‐I and IGF‐binding proteins in conditioned media was revealed by radioimmunoassay and Western ligand blot, respectively. Variations at the IGF‐I‐receptor level were tested by binding studies on cell monolayers.

A significant concentration‐and time‐dependent cytostatic activity of FCE 26644 (IC50∼200 μg ml−1 at 72 h) compared to its analogue FCE 27784 (IC50>8OO μg ml−1) was observed in both cell lines studied. The IGF‐I‐stimulated proliferation of the IGF‐I‐responsive A549 cell line was abolished by 24 h of FCE 26644 treatment whereas FCE 27784 was inactive. FCE 26644 increased (4 to 6 fold) the secretion of IGF‐I‐like material and reduced the IGF‐I binding (IC50>100 μg ml−1) in both A549 and Ca‐Lu‐1 cell lines. FCE 26644 (100 μg ml−1) did not affect the KD (∼0.5 nM) but reduced the Bmax and the number of receptor sites (50%).

Our findings demonstrate that the ability to down‐regulate the cell proliferation of N‐SCLC cell lines, shown by FCE 26644, depends at least partially, on interference with the ‘IGF‐I mitogenic system’.
Aminoguanidine‐effects on endoneurial vasoactive nitric oxide and on motor nerve conduction velocity in control and streptozotocin‐diabetic rats
Authors: Dewhurst M. , Omawari N. , Tomlinson D.R.
Published: August 2006

The effects of aminoguanidine (AG) treatment on reductions in motor nerve conduction velocity (MNCV) and sciatic nerve blood flow, indexed by laser Doppler flux (LDF), were investigated in rats with experimental diabetes (streptozotocin‐induced; 8–10 weeks duration). The contribution of endoneurial vasoactive nitric oxide to the LDF of these animals was also investigated by the direct micro‐injection of NG‐nitro‐L‐arginine methyl ester (l‐NAME; 1 nmol in 1 μ1), followed by L‐arginine (100 nmol in 1 μI), into the sciatic nerve endoneurium.

The MNCV (m s−1, mean ± 1 s.d.) of diabetic rats (38.2 ± 1.5) was lower (P<0.01) than that of age‐matched controls (47.2 ± 4.2). AG treatment (50 mg kg−1 day−1, i.p.) attenuated the diabetes‐induced deficits in MNCV (43.4±5.9; P<0.01), but had no effect in controls (48.8±3.8) or, if administered via drinking water (1 g 1−1), diabetics (37.4 ± 4.1).

L‐NAME markedly reduced the resting LDF (arbitrary units; mean ± s.e.mean) of controls (209 ± 13 to 120± 18; P<0.005), an effect reversed by subsequent L‐arginine (to 206±27). In diabetic rats the LDF reduction following L‐NAME was much smaller (111 ±11 to 84 ± 6; P<0.05), but the change with L‐arginine was significantly increased (to 145±12; P<0.001).

AG treatment increased the resting LDF of control (265 ± 34) and diabetic rats (133 ± 14 for daily injection and 119±13 for drinking water). The responses to L‐NAME and L‐arginine were not changed markedly by AG treatment. However, L‐arginine appeared to be less effective.

In conclusion, these data suggest that AG treatment may affect nitric oxide production in the vasa nervorum of peripheral nerves. However, the effects of AG‐treatment are not consistent with the prevention of a diabetes‐associated reduction in endoneurial nitric oxide production. The mechanisms by which AG attenuates nerve conduction slowing in streptozotocin‐diabetic rats therefore remain unclear.
Modulation of the firing activity of noradrenergic neurones in the rat locus coeruleus by the 5‐hydroxtryptamine system
Authors: Haddjeri Nasser , De Montigny Claude , Blier Pierre
Published: August 2006

The aim of the present study was to investigate the putative modulation of locus coeruleus (LC) noradrenergic (NA) neurones by the 5‐hydroxytryptaminergic (5‐HT) system by use of in vivo extracellular unitary recordings and microiontophoresis in anaesthetized rats. To this end, the potent and selective 5‐HT1A receptor antagonist WAY 100635 (N‐{2‐[4(2‐methoxyphenyl)‐1‐piperazinyl]ethyl}‐N‐(2‐pyridinyl)cyclohexanecarboxamide trihydroxychloride) was used.

In the dorsal hippocampus, both local (by microiontophoresis, 20 nA) and systemic (100 μg kg−1, i.v.) administration of WAY 100635 antagonized the suppressant effect of microiontophorectically‐applied 5‐HT on the firing activity of CA3 pyramidal neurones, indicating its antagonistic effect on postsynaptic 5‐HT1A receptors.

WAY 100635 and 5‐HT failed to modify the spontaneous firing activity of LC NA neurones when applied by microiontophoresis. However, the intravenous injection of WAY 100635 (100 μg kg−1) readily suppressed the spontaneous firing activity of LC NA neurones.

The lesion of 5‐HT neurones with the neurotoxin 5,7‐dihydroxytryptamine increased the spontaneous firing activity of LC NA neurones and abolished the suppressant effect of WAY 100635 on the firing activity of LC NA neurones.

In order to determine the nature of the 5‐HT receptor subtypes mediating the suppressant effect of WAY 100635 on NA neurone firing activity, several 5‐HT receptor antagonists were used. The selective 5‐HT3 receptor antagonist BRL 46470A (10 and 100 μg kg−1, i.v.), the 5‐HT1D receptor antagonist GR 127935 (100 μg kg−1, i.v.) and the 5‐HT1A/1B receptor antagonist (−)‐pindolol (15 mg kg−1, i.p.) did not prevent the suppressant effect of WAY 100635 on the firing activity of LC NA neurones. However, the suppressant effect of WAY 100635 was prevented by the non‐selective 5‐HT receptor antagonists spiperone (1 mg kg−1, i.v.) and metergoline (1 mg kg−1, i.v.), by the 5‐HT2 receptor antagonist ritanserin (500 μg kg−1, i.v.). It was also prevented by the 5‐HT1A receptor/α1D‐adrenoceptor antagonist BMY 7378 (1 mg kg−1, i.v.) and by the α1‐adrenoceptor antagonist prazosin (100 μg kg−1, i.v.).

These data support the notion that the 5‐HT system tonically modulates NA neurotransmission since the lesion of 5‐HT neurones enhanced the LC NA neurones firing activity and the suppressant effect of WAY 100635 on the firing activity of NA neurones was abolished by this lesion. However, the location of the 5‐HT1A receptors involved in this complex circuitry remains to be elucidated. It is concluded that the suppressant effect of WAY 100635 on the firing activity of LC NA neurones is due to an enhancement of the function of 5‐HT neurones via a presynaptic 5‐HT1A receptor. In contrast, the postsynaptic 5‐HT receptor mediating this effect of WAY 100635 on NA neurones appears to be of the 5‐HT2A subtype.

British Journal of Pharmacology (1997) 120, 865–875; doi:10.1038/sj.bjp.0700968
The involvement of a novel mechanism distinct from the thrombin receptor in the vasocontraction induced by trypsin
Authors: Komuro Taro , Miwa Soichi , Minowa Tetsuya , Okamoto Yasuo , Enoki Taijiro , Ninomiya Haruaki , Zhang Xiao‐Feng , Uemura Yoshihiko , Kikuchi Haruhiko , Masaki Tomoh
Published: August 2006

The vasocontracting effect of a serine protease trypsin and its mechanisms were investigated by monitoring the isometric tension in endothelium‐denuded rings of rabbit thoracic aortae and its effects on intracellular free Ca2+ concentrations ([Ca2+]i) in dispersed rabbit vascular smooth muscle cells with a Ca2+ indicator fura‐2. The actions of trypsin were compared with those of thrombin.

Both thrombin and trypsin reversibly contracted aortic rings without endothelium in a concentration‐dependent manner. The vasocontraction induced by trypsin was well correlated with the protease activity of trypsin actually added to the tissue baths containing the aortic rings and was completely blocked by soybean trypsin inhibitor and phenylmethylsulphonyl fluoride (PMSF), a serine protease inhibitor.

The trypsin‐induced contractions of the aortic rings were not the result of irreversible damage to vascular smooth muscle cells, since the contractile responses induced by noradrenaline or 30 mm KCl were unaffected by pretreatment with trypsin.

The contractions induced by either thrombin or trypsin were reduced to about 30% of control responses after removal of extracellular Ca2+, indicating that most of the contraction is dependent on extracellular Ca2+. By contrast, the contractions induced by either of the proteases were reduced by an antagonist of L‐type voltage‐operated Ca2+ channels, nifedipine, to about 70% of control responses, indicating that both nifedipine‐sensitive and ‐resistant Ca2+ channels are involved in these contractions.

In the aortic rings precontracted by a maximally effective concentration of thrombin, the second application of thrombin virtually failed to induce contractions but trypsin could still induce contractions amounting to 10% of control values by it's protease activity.

After the first application of a maximal concentration of thrombin, the second application of thrombin could not induce an increase in [Ca2+]i, but an application of trypsin could still induce an increase in [Ca2+]i in dispersed rabbit vascular smooth muscle cells.

These data suggest that in addition to activation of a thrombin receptor, trypsin can contract rabbit aortae by a proteinase‐activated receptor 2 or a novel mechanism.

British Journal of Pharmacology (1997) 120, 851–856; doi:10.1038/sj.bjp.0701003
Effect of binding protein surface charge on palmitate uptake by hepatocyte suspensions
Authors: Burczynski F. J. , Wang G. ‐Q. , Hnatowich M.
Published: August 2006

Studies were directed at determining whether hepatocytes, isolated from female Sprague‐Dawley rats, facilitate the uptake of protein‐bound long‐chain fatty acids. We postulated one form of facilitated uptake may occur through an ionic interaction between the protein‐ligand complex and the cell surface. These interactions are expected to supply additional ligand to the cell for uptake.

The clearance rate of [3H]‐palmitate in the presence of α1‐acid‐glycoprotein (pI=2.7), albumin (pI=4.9) and lysozyme (pI=11.0) was investigated. Palmitate uptake was determined in the presence of protein concentrations that resulted in similar unbound ligand fractions (=0.03). The experimental clearance rates were compared to the theoretical predictions based upon the diffusion‐reaction model.

By use of our experimentally determined equilibrium binding and dissociation rate constants for the various protein‐palmitate complexes, the diffusion‐reaction model predicted clearance rates were 4.9 μl s−1/106 cells, 4.8 μl s−1/106 cells and 5.5 μl s−1/106 cells for α1‐acid‐glycoprotein, albumin and lysozyme, respectively; whereas the measured hepatocyte palmitate clearance rates were 1.2±0.1 μl s−1/106 cells, 2.3±0.3 μl s−1/106 cells and 7.1±0.7 μl s−1/106, respectively.

Hepatocyte palmitate clearance was significantly faster (P<0.01) in the presence of lysozyme than albumin which was significantly faster than α1‐acid‐glycoprotein (P<0.01). The marked difference in clearance rates could not be explained by considering differences in solution viscosity.

Our results are consistent with the notion that ionic interactions between protein‐ligand complexes and the cell surface facilitate the ligand uptake by decreasing the diffusional distance of the unbound ligand and/or by facilitating the protein‐ligand dissociation rate.

British Journal of Pharmacology (1997) 120, 1215–1220; doi:10.1038/sj.bjp.0701030
Regulation of guanosine 3′:5′‐cyclic monophosphate in ovine tracheal epithelial cells
Authors: Range Simon P. , Holland Elaine D. , Basten Graham P. , Knox Alan J.
Published: August 2006

Guanosine 3′:5′‐cyclic monophosphate (cyclic GMP) is an important second messenger mediating the effects of nitric oxide (NO) and natriuretic peptides. Cyclic GMP pathways regulate several aspects of lung pathophysiology in a number of airway cells. The regulation of this system has not been extensively studied in pulmonary epithelial tissue.

We have studied the production of cyclic GMP by suspensions of ovine tracheal epithelial cells in response to activators of soluble guanylyl cyclase (sodium nitroprusside (SNP) and S‐nitroso‐N‐acetyl‐penicillamine (SNAP) and particulate guanylyl cyclase (atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), C‐type natriuretic peptide (CNP) and E. coli heat stable enterotoxin (STa)).

Both 10−710−3 m and 10−710−3 m SNAP generated a concentration‐dependent marked elevation in cyclic GMP production when incubated with 10−3 m 3‐isobutyl‐1‐methylxanthine (IBMX) (both greater than 25×baseline values with highest drug concentration).

The increase in production of cyclic GMP in response to 10−6 m SNP and 10−5 m SNAP was markedly inhibited by both 5×10−5 m haemoglobin (102% and 92% inhibition) and 5×10−5 m methylene blue (82% and 84% inhibition).

The increase in cyclic GMP in response to 10−3 m SNP was measured following co‐incubation with the phosphodiesterase inhibitors 10−710−3 m IBMX, 10−710−4 m milrinone and 10−710−4 m SKF 96231. Only 10−410−3 m IBMX significantly increased cyclic GMP levels.

Cyclic GMP production was also significantly elevated from baseline by 10−5 m ANP, 10−5 m BNP, 10−5 m CNP and 200 iu ml−1 of E. coli STa toxin in the presence of 10−3 m IBMX. Increases with these natriuretic peptides and STa toxin were smaller in magnitude (24 fold) than those seen with SNP and SNAP. CNP was the most potent of the natriuretic peptides studied suggesting type B membrane bound guanylate cyclase is the predominant form expressed.

These results suggest that ovine tracheal epithelial cells contain active guanylyl cyclases. The more marked response to SNP and SNAP than to natriuretic peptides suggests that soluble guanylyl cyclase predominates.

British Journal of Pharmacology (1997) 120, 1249–1254; doi:10.1038/sj.bjp.0701040
The effects of inhibitors of GABAergic transmission and stress on brain and plasma allopregnanolone concentrations
Authors: Barbaccia M. L. , Roscetti G. , Trabucchi M. , Purdy R. H. , Mostallino M. C. , Concas A. , Biggio G.
Published: August 2006

This study was undertaken to investigate the relationship between a reduction in brain GABAA receptor function and the cerebro‐cortical content of 3α‐hydroxy‐5α‐pregnan‐20 one (allopregnanolone, AP), a potent endogenous positive modulator of γ‐aminobutyric acid (GABA) action at GABAA receptors, with anticonflict and anticonvulsant effects in rodents.

An acute depletion of the cerebral content of GABA or an attenuation of GABAA receptor‐mediated transmission by systemic injections of isoniazid (375 mg kg−1, s.c.) or FG 7142 (15 mg kg−1, i.p.) induced a transient increase in the cerebro‐cortical and plasma concentrations of AP in handling‐habituated (not stressed) rats.

Two stress paradigms, handling in naive rats and mild foot shock in handling‐habituated rats, that reduce central GABAergic tone mimicked the effects of isoniazid and FG 7142 on cortical AP content; foot shock in handling‐habituated rats, but not handling in naive animals, also increased plasma AP. Isoniazid, FG 7142, and foot shock also each increased the concentrations of the AP precursors, pregnenolone and progesterone, in both brain and plasma of handling‐habituated rats, whereas handling in naive rats increased the concentrations of these steroids only in brain.

Pretreatment of handling‐habituated rats with the anxiolytic β‐carboline derivative abecarnil, a positive allosteric modulator of GABAA receptors, which per se failed to affect the AP concentration in brain or plasma, prevented the increase in brain and plasma AP induced by foot shock or isoniazid.

In adrenalectomized and castrated rats foot shock or isoniazid failed to increase AP both in brain cortex and plasma.

These observations indicate that inhibition of GABAergic transmission, induced by foot shock or pharmacological manipulations, results in an increase in the concentrations of AP in brain and plasma, possibly via a modulation of hypothalamic‐pituitary‐adrenal (HPA) axis.

Given that AP enhances GABAA receptor function with high efficacy and potency, an increase in brain AP concentration may be important in the fine tuning of the GABA‐mediated inhibitory transmission in the central nervous system.

British Journal of Pharmacology (1997) 120, 1582–1588; doi:10.1038/sj.bjp.0701046
Inhibitory effects of ω‐3 polyunsaturated fatty acids on receptor‐mediated non‐selective cation currents in rat A7r5 vascular smooth muscle cells
Authors: Asano Michiko , Nakajima Toshiaki , Iwasawa Kuniaki , Hazama Hisanori , Omata Masao , Soma Masaaki , Yamashita Kamejiro , Okuda Yukichi
Published: August 2006

The effects of ω‐3 polyunsaturated fatty acids on receptor‐mediated non‐selective cation current (Icat) and K+ current were investigated in aortic smooth muscle cells from foetal rat aorta (A7r5 cells). The whole‐cell voltage clamp technique was employed.

With a K+‐containing solution, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA, 30 μm) produced an outward current at a holding potential of −40 mV. This response was inhibited by tetraethylammonium (20 mm) or Cs+ in the patch pipette solution, and the reversal potential of the EPA‐induced current followed the K+ equilibrium potential in a near Nernstian manner.

Under conditions with a Cs+‐containing pipette solution, both vasopressin and endothelin‐1 (100 nm) induced a long‐lasting inward current at a holding potential of −60 mV. The reversal potential of these agonist‐induced currents was about +0 mV, and was not significantly altered by the replacement of the extracellular or intracellular Cl− concentration, suggesting that the induced current was a cation‐selective current (Icat).

La3+ and Cd2+ (1 mm) completely abolished these agonist‐induced Icat, but nifedipine (10 μm) failed to inhibit it significantly.

ω‐3 polyunsaturated fatty acids (3100 μm), EPA, DHA and docosapentaenoic acids (DPA), inhibited the agonist‐induced Icat in a concentration‐dependent manner. The potency of the inhibitory effect was EPA>DHA>DPA, and the half maximal inhibitory concentration (IC50) of EPA was about 7 μm.

Arachidonic and linoleic acids (10, 30 μm) showed a smaller inhibitory effect compared to ω‐3 fatty acids. Also, oleic and stearic acids (30 μm) did not show a significant inhibitory effect on Icat.

A similar inhibitory action of EPA was observed when Icat was activated by intracellularly applied GTPγS in the absence of agonists, suggesting that the site of action of ω‐3 fatty acids is not located on the receptor.

These results demonstrate that ω‐3 polyunsaturated fatty acids can activate a K+ current and also effectively inhibit receptor‐mediated non‐selective cation currents in rat A7r5 vascular smooth muscle cells. Thus, the data suggest that ω‐3 fatty acids may play an important role in the regulation of vascular tone.

British Journal of Pharmacology (1997) 120, 1367–1375; doi:10.1038/sj.bjp.0701047
Effect of partially modified retro‐inverso analogues derived from C‐reactive protein on the induction of nitric oxide synthesis in peritoneal macrophages
Authors: Arcoleo F. , Milano S. , D'Agostino P. , Misiano G. , Cappelletti S. , Gromo G. , Marcucci F. , Leoni F. , Cillari E.
Published: August 2006

The ability of three modified tetrapeptides, representing fragments of the C‐reactive protein (CRP) sequence and stabilized in the first peptide bond by retro‐inverso modification, to affect the secretion of nitric oxide (NO) was studied in macrophages of BALB/c mice.

These tetrapeptides, resembling the aminoacid sequence of tuftsin (CRP I, H‐gThr‐(R,S)mLys‐Pro‐Leu‐OH, ITF 1192; CRP II, H‐gGly‐(R, S)mLys‐Pro‐Arg‐OH, ITF 1127; CRP III, H‐gThr‐(R,S)mLys‐Pro‐Gln‐OH, ITF 1193), were able to induce NO synthesis by peritoneal macrophages in a dose‐dependent manner; the most stimulating dose was 1000 ng ml−1 for CRP II and 100 ng ml−1 for CRP I and CRP III. NO synthesis was not strictly dependent on lipopolysaccharide (LPS) activation.

The enhanced effect of retro‐inverso CRP‐related analogues on the expression of iNOS (inducible NO synthase) was confirmed by higher levels of iNOS activity in the cytosol and by the increase in iNOS protein, as evaluated by Western blot analysis, in macrophages stimulated by CPR compared with untreated ones.

The production of NO by retro‐inverso CRP‐peptide analogues was significantly inhibited by dexamethasone (20 μm), NG‐monomethyl‐l‐arginine (l‐NMMA) (500 μm) and pyrrolidine dithiocarbamate (PDTC) (100 μm).

Retro‐inverso CRP‐peptide analogues stimulated macrophages to produce high levels of interleukin‐1 (IL‐1) and tumour necrosis factor‐α (TNF‐α) in the presence of LPS.

Retro‐inverso CRP‐peptide analogues stimulated NO synthesis by the enhancement of endogenously produced IL‐1 and TNF‐α, as the treatment of peritoneal macrophages with LPS in the presence of neutralizing anti‐IL‐1 and anti‐TNF monoclonal antibodies (mAbs) reduced retro‐inverso analogue‐induced NO secretion. Data indicate a predominant role for IL‐1α in the induction of NO secretion by retro‐inverso analogues.

These results suggest that retro‐inverso CRP derived analogues act as costimulators of NO and cytokine synthesis in macrophages. The mechanisms by which they cause iNOS induction appear to be strongly dependent on the activation of nuclear factor‐κB (NF‐κB).

British Journal of Pharmacology (1997) 120, 1383–1389; doi:10.1038/sj.bjp.0701050
Prostaglandin E1 potentiation of the spontaneous phasic contraction of rat isolated portal vein by a cyclopiazonic acid‐sensitive mechanism
Authors: Miwa Takaaki , Endou Masayuki , Okumura Fukuichiro
Published: August 2006

The effect of prostaglandin E1 (PGE1) on the spontaneous phasic contraction of the rat isolated portal vein was studied.

The isolated portal vein exhibited spontaneous phasic contractions. Removal of Ca2+ from Krebs‐Ringer solution or application of nifedipine abolished the spontaneous contraction, indicating that the contraction depends exclusively on Ca2+ influx through L‐type Ca2+ channels. On the other hand, cyclopiazonic acid (CPA), a specific inhibitor of Ca2+‐ATPase of sarcoplasmic reticulum (SR) increased the amplitude of the contractions, suggesting that the SR regulates the spontaneous contractions negatively by sequestration of Ca2+ entering through L‐type Ca2+ channels and buffering the rise in cytosolic Ca2+.

PGE1 increased the amplitude of the spontaneous contraction in a concentration‐dependent manner without affecting the resting tension. The effect was completely abolished by nifedipine. Bay K 8644 and phenylephrine (PE) also increased the amplitude of the contraction in a concentration‐dependent manner. PGE1 at a concentration of 1 μm, Bay K 8644 at 100 nm and PE at 30 nm doubled the amplitude, respectively.

Pretreatment with 1 μm CPA abolished the effect of PGE1, but the effects of Bay K 8644 and PE were not inhibited by pretreatment with CPA. In contrast, 10 μm ryanodine attenuated the effect of PE without affecting the contractile effect of PGE1.

When the SR was depleted of Ca2+ by repeated applications of caffeine in a nominally Ca2+‐free Krebs‐Ringer solution, it took about 120 s to restore the spontaneous contraction after addition of Ca2+ into the solution. In CPA‐treated veins, the time taken to restore the contraction was shortened significantly. Pretreatment with 1 μm PGE1 shortened the time to the same extent as pretreatment with CPA did.

These results suggest that PGE1 increases the amplitude of the spontaneous phasic contraction by a different mechanism from those by which PE and Bay K 8644 increase it. Inhibition of Ca2+‐ATPase of the SR might be involved in the vasoactive effect of PGE1.

British Journal of Pharmacology (1997) 120, 1419–1426; doi:10.1038/sj.bjp.0701051
Stimulation of cyclic AMP‐dependent protein kinase in rat atria by (–;)‐CGP 12177 through an atypical β‐adrenoceptor
Authors: Kaumann Alberto J. , Lynham James A.
Published: August 2006

Mammalian hearts possess an atypical β‐adrenoceptor (non‐β1, non‐β2, non‐β3) through which (–)‐4‐(3‐t‐butylamino‐2‐hydroxypropoxy)benzimidazol‐2‐one ((–)‐CGP 12177) causes cardiostimulant effects. Here we showed that (–)‐CGP 12177 increased the activity of adenosine 3′ : 5′‐cyclic monophosphate (cyclic AMP)‐dependent protein kinase in the presence of 200 nm (–)‐propranolol in rat atria at a concentration (10 μm) that elicits maximum positive chronotropic and inotropic effects. The phosphodiesterase inhibitor 3‐isobutyl‐l‐methylxanthine (IBMX) potentiated the positive chronotropic and inotropic effects of (–)‐CGP 12177. We suggest that the atypical β‐adrenoceptor is coupled positively to the Gs protein‐adenylyl cyclase system.

British Journal of Pharmacology (1997) 120, 1187–1189; doi:10.1038/sj.bjp.0701053
Comparison of the reversed passive Arthus and local Shwartzman reactions of rabbit skin: effects of the long‐acting PAF antagonist UK‐74,505
Authors: Norman Keith E. , Williams Timothy J. , Rossi Adriano G.
Published: August 2006

By using the selective, potent and long acting platelet‐activating factor (PAF) antagonist, UK‐74,505, we investigated the role of PAF in a local Shwartzman reaction (LSR) and a reversed passive Arthus (RPA) reaction in rabbit skin. For comparison, we also studied the effect of the PAF antagonist on neutrophil aggregation in vitro and on acute inflammatory responses induced by intradermally (i.d.) injected lipopolysaccharide (LPS), PAF, bradykinin and zymosan‐activated plasma.

Neutrophil aggregation was assessed photometrically. Haemorrhage, oedema formation, platelet deposition and neutrophil accumulation were quantified in rabbit skin by measuring the accumulation of i.v. injected 51Cr‐labelled red blood cells (RBC), 125I‐labelled human serum albumin, 111In‐labelled platelets and 111In‐labelled neutrophils respectively.

UK‐74,505 inhibited in vitro neutrophil aggregation induced by PAF but not by leukotriene B4. When injected i.v. into rabbits UK‐74,505 suppressed oedema formation in response to i.d. PAF for up to 4 h but had no effect on oedema induced by bradykinin or zymosan‐activated plasma.

Oedema formation, but not neutrophil accumulation, produced during the RPA reaction was significantly inhibited by i.v. UK‐74,505. The PAF antagonist also suppressed 111In‐platelet but not 111In‐neutrophil accumulation in response to i.d. LPS. UK‐74,505 did not affect haemorrhage or oedema formation produced during the LPS‐mediated LSR.

The results demonstrate that PAF is an important mediator of oedema formation, but not neutrophil accumulation, in the immune‐complex mediated RPA reaction in rabbit skin. PAF also appears to be required for platelet, but not neutrophil, accumulation in response to locally injected LPS. Our studies do not suggest a role for PAF in the LPS‐mediated LSR.

British Journal of Pharmacology (1997) 120, 1286–1293; doi:10.1038/sj.bjp.0701057
Different cardiovascular profiles of three melanocortins in conscious rats; evidence for antagonism between γ2‐MSH and ACTH‐(1–24)
Authors: Van Bergen Patricia , Kleijne Jeroen A. , De Wildt Dick J. , Versteeg Dirk H. G.
Published: August 2006

We investigated the effects of [Nle4,d‐Phe7]α‐melanocyte‐stimulating hormone (NDP‐MSH), adrenocorticotropin‐(124) (ACTH‐(124)) and γ2‐MSH, three melanocortins with different agonist selectivity for the five cloned melanocortin receptors, on blood pressure and heart rate in conscious, freely moving rats following intravenous administration.

As was previously found by other investigators as well as by us, γ2‐MSH, a peptide suggested to be an agonist with selectivity for the melanocortin MC3 receptor, caused a dose‐dependent, short lasting pressor response in combination with a tachycardia. Despite the fact that NDP‐MSH is a potent agonist of various melanocortin receptor subtypes, among which the melanocortin MC3 receptor, it did not affect blood pressure or heart rate, when administered i.v. in doses of up to 1000 nmol kg−1.

ACTH‐(124) caused a dose‐dependent decrease in blood pressure in combination with a dose‐dependent increase in heart rate in a dose‐range from 15 to 500 nmol kg−1. The cardiovascular effects of ACTH‐(124) were independent of the presence of the adrenals.

Pretreatment with ACTH‐(124) caused a pronounced, dose‐dependent parallel shift to the right of the dose‐response curve for the pressor and tachycardiac effects of γ2‐MSH. The antagonistic effect of ACTH‐(124) was already apparent following a dose of this peptide as low as 10 nmol kg−1, which when given alone had no intrinsic hypotensive activity.

These results form further support for the notion that it is not via activation of one of the as yet cloned melanocortin receptors that γ‐MSH‐like peptides increase blood pressure and heart rate. The cardiovascular effects of ACTH‐(124) seem not to be mediated by the adrenal melanocortin MC2 receptors, for which ACTH‐(124) is a selective agonist, or by adrenal catecholamines.

There appears to be a functional antagonism between ACTH‐(124) and γ2‐MSH, two melanocortins derived from a common precursor, with respect to their effect on blood pressure and heart rate. Whether this antagonism plays a (patho)physiological role remains to be shown.

British Journal of Pharmacology (1997) 120, 1561–1567; doi:10.1038/sj.bjp.0701065
Effects of σ ligands on the nociceptin/orphanin FQ receptor co‐expressed with the G‐protein‐activated K+ channel in Xenopus oocytes
Authors: Kobayashi Toru , Ikeda Kazutaka , Togashi Shunji , Itoh Noboru , Kumanishi Toshiro
Published: August 2006

Taking advantage of the functional coupling of the nociceptin/orphanin FQ receptor with the G‐protein‐activated inwardly rectifying K+ (GIRK) channel, we investigated the effects of various σ ligands on the nociceptin/orphanin FQ receptor in Xenopus oocytes co‐injected with the cloned nociceptin/orphanin FQ receptor and GIRK1 mRNAs. Carbetapentane and rimcazole, which induced no current response at 100 μm, reversibly suppressed the inward K+ current responses induced by nociceptin in a concentration‐dependent manner, and the IC50 values (μm) for these compounds were 9.0 and 12.6, respectively. (±)‐N‐allylnormetazocine, (+)‐cyclazocine, (+)‐3‐(3‐hydroxyphenyl)‐N‐(1‐propyl)piperidine and 1,3‐di‐(2‐tolyl)guanidine, at 100 μm, had no effect on the receptor. These results suggest that carbetapentane and rimcazole act as antagonists at the nociceptin/orphanin FQ receptor and may be involved in pain regulation.

British Journal of Pharmacology (1997) 120, 986–987; doi:10.1038/sj.bjp.0701068
Potentiation by nitric oxide of the ATP‐sensitive K+ current induced by K+ channel openers in guinea‐pig ventricular cells
Authors: Shinbo Atsushi , Iijima Toshihiko
Published: August 2006

Modulation by nitric oxide (NO) of the ATP‐sensitive K+ channel (KATP) current (IK (ATP)) was investigated in single ventricular cells dissociated from guinea‐pig hearts. IK (ATP) was induced by 5‐amino‐N‐[2‐(2‐chlorophenyl)ethyl]‐N′‐cyano‐3‐pyridinecarboxamidine (KRN4884) and cromakalim.

In the whole‐cell patch clamp configuration, KRN4884 (0.13 μm) increased the outward current in a concentration‐dependent manner with an EC50 value of 0.48 μm. This current was completely antagonized by glibenclamide (1 μm).

IK (ATP) induced by either KRN4884 (0.3 μm) or cromakalim (10 μm) was significantly enhanced by the additional application of a NO donor (±)‐(E)‐ethyl‐2‐[(E)‐hydroxyimino]‐5‐nitro‐3‐hexeneamide (NOR3, 0.1 and 1 mm).

The potentiating effect was observed only when NOR3 solution was prepared just before experiments, when release of NO was considered to be on‐going. The effect was significantly eliminated in the presence of the NO scavenger oxyhaemoglobin (310 μm). Also, oxidative metabolites of NO, such as NO2− or NO3−, were without effect.

8‐Bromo‐guanosine‐3′ : 5′‐cyclic monophosphate (8‐Br‐cyclic GMP, 0.10.5 mm) significantly decreased IK (ATP) induced by KRN4884.

In cell‐attached patches, NOR3 (1 mm) potentiated the KRN4884‐induced IK (ATP) in a way similar to that seen in whole‐cell recordings. By contrast, NOR3 (1 mm) did not enhance the current in either inside‐out or outside‐out patches.

These results indicate that NO potentiates the action of K+ channel openers on the KATP through a mechanism which remains to be determined.

British Journal of Pharmacology (1997) 120, 1568–1574; doi:10.1038/sj.bjp.0701069