bluuebunny/crossref_metadata_2025 huggingface dataset:
Further investigation of endothelium‐derived hyperpolarizing factor (EDHF) in rat hepatic artery: studies using 1‐EBIO and ouabain
Authors: Edwards G , Gardener M J , Félétou M , Brady G , Vanhoutte P M , Weston A H
Published: January 2005

The characteristics of endothelium‐dependent hyperpolarization in rat hepatic artery have been further investigated in the presence of inhibitors of cyclo‐oxygenase and nitric oxide synthase.

Using sharp micro‐electrodes, the smooth muscle hyperpolarization induced by acetylcholine, KCl or 1‐ethyl‐2‐benzimidazolinone (1‐EBIO) in intact hepatic arteries was abolished by 30 μM barium plus 500 nM ouabain.

In vessels without endothelium, the smooth muscle hyperpolarization induced by KCl was not reduced by 30 μM barium alone. However, in the presence of barium the effects of KCl were partially inhibited by 100 nM ouabain and essentially abolished by 500 nM ouabain.

Using sharp micro‐electrodes, the hyperpolarization of both the smooth muscle and the endothelium induced by 1‐EBIO or by acetylcholine was unaffected by 100 nM iberiotoxin. However, in the presence of 100 nM charybdotoxin, the effects of 1‐EBIO were abolished whereas those of acetylcholine were only partially reduced. The hyperpolarization induced by levcromakalim was unaffected by either charybdotoxin or iberiotoxin.

Under whole‐cell patch‐clamp recording conditions, 1‐EBIO induced a voltage‐insensitive, charybdotoxin‐sensitive K+ current in cultured endothelial cells but was without effect on K+ currents in smooth muscle cells isolated from hepatic arteries.

It is concluded that the endothelium‐dependent hyperpolarization of smooth muscle induced by either acetylcholine or by 1‐EBIO in rat hepatic artery is initially associated with the opening of endothelial calcium‐sensitive K+‐channels insensitive to iberiotoxin. The resulting accumulation of K+ in the myoendothelial space activates an isoform of Na+/K+‐ATPase which is sensitive to low concentrations of ouabain.

British Journal of Pharmacology (1999) 128, 1064–1070; doi:10.1038/sj.bjp.0702916
Histamine H1‐receptor‐mediated modulation of the delayed rectifier K+ current in guinea‐pig atrial cells: opposite effects on IKs and IKr
Authors: Matsumoto Yasunori , Ogura Takehiko , Uemura Hiroko , Saito Toshihiro , Masuda Yoshiaki , Nakaya Haruaki
Published: January 2005

Histamine receptor‐mediated modulation of the rapid and slow components of the delayed rectifier K+ current (IK) was investigated in enzymatically‐dissociated atrial cells of guinea‐pigs using the whole cell configuration of the patch clamp technique.

Histamine at a concentration of 10 μM enhanced IK recorded during strong depolarization to potentials ranging from +20 to +40 mV and inhibited IK recorded during mild depolarization to potentials ranging from −20 to −10 mV. The increase of IK was more prominent with longer depolarizing pulses, whereas the inhibition of IK was more marked with shorter depolarizing pulses, suggesting that histamine enhances IKs (the slow component of IK) and inhibits IKr (the rapid component of IK).

The histamine‐induced enhancement of IKs and inhibition of IKr were abolished by 3 μM chlorpheniramine but not by 10 μM cimetidine, suggesting that these opposite effects of histamine on IKr and IKs are mediated by H1‐receptors.

In the presence of 5 μM E‐4031, an IKr blocker, histamine hardly affected IK during mild depolarization although it enhanced IK during strong depolarization in a concentration‐dependent manner. Histamine increased IKs with EC50 value of 0.7 μM. In the presence of 300 μM indapamide, an IKs blocker, histamine hardly affected IKs but inhibited IKr in a concentration‐dependent manner. Histamine decreased IKr with IC50 value of 0.3 μM.

Pretreatment with 100 nM calphostin C or 30 nM staurosporine, protein kinase C inhibitors, abolished the histamine‐induced enhancement of IKs, but failed to affect the histamine‐induced inhibition of IKr.

We conclude that in guinea‐pig atrial cells H1‐receptor stimulation enhances IKs and inhibits IKr through different intracellular mechanisms.

British Journal of Pharmacology (1999) 128, 1545–1553; doi:10.1038/sj.bjp.0702918
The anticonvulsant effects of the enantiomers of losigamone
Authors: Jones Francis A , Davies John A
Published: January 2005

Losigamone is a novel anticonvulsant undergoing phase III clinical trials in patients with partial and secondary generalized seizures. This study investigated the effects of the S(+)‐ and R(−)‐ enantiomers of losigamone on endogenous amino acid release from BALB/c mouse cortical slices, spontaneous depolarizations in the cortical wedge preparation of the DBA/2 mouse and audiogenic seizures in DBA/2 mice.

S(+)‐losigamone (100 and 200 μM) significantly reduced both potassium‐ and veratridine‐elicited release of glutamate and aspartate from cortical slices. R(−)‐losigamone had no effect on release at concentrations up to 400 μM.

Cortical wedges exhibit spontaneous depolarizations when perfused with magnesium‐free artificial cerebrospinal fluid. S(+)‐losigamone significantly reduced these depolarizations at 50–200 μM whilst R(−)‐losigamone had a significant effect at 200–800 μM.

DBA/2 mice are susceptible to audiogenic seizures and S(+)‐losigamone dose‐dependently (5, 10 and 20 mg kg−1, i.p.) significantly inhibited clonic/tonic convulsions with 91% of the mice protected at 20 mg kg−1. There was no protection at 20 mg kg−1 with R(−)‐losigamone.

These results, from both in vitro and in vivo experiments, confirm that the pharmacological activity profiles of the two losigamone enantiomers are not identical and suggest further that excitatory amino acid‐mediated processes are involved in the mode of action of S(+)‐losigamone whereas R(−)‐losigamone does not possess such properties. For the treatment of neurological conditions involving exaggerated excitatory amino acid function the use of S(+)‐losigamone might therefore be more effective clinically than losigamone or its R(−)‐enantiomer.

British Journal of Pharmacology (1999) 128, 1223–1228; doi:10.1038/sj.bjp.0702919
Functional and electrophysiological effects of a novel imidazoline‐based KATP channel blocker, IMID‐4F
Authors: McPherson Grant A , Bell Karen L , Favaloro Joanne L , Kubo Masahiro , Standen Nicholas B
Published: January 2005

The functional and electrophysiological effects of IMID‐4F (2‐[N‐(2,6‐dichlorophenyl)‐N‐(4‐flurorobenzyl)amino]imidazoline), a fluoro‐benzyl derivative of clonidine, on vascular KATP channels were investigated. In pig coronary artery, IMID‐4F inhibited the vasorelaxation response to the KATP channel opener levcromakalim with a pKB value of approximately 7.1. IMID‐4F (30 μM) did not affect the vasorelaxation response to sodium nitroprusside (SNP).

In rat mesenteric artery smooth muscle cells IMID‐4F (1–10 μM) caused a concentration‐dependent depolarization of membrane potential. IMID‐4F (10 μM) abolished the hyperpolarizing effects of levcromakalim (10 μM).

In patch clamp experiments using rat mesenteric artery smooth muscle cells, KATP channel currents induced by levcromakalim (10 μM) were inhibited by IMID‐4F (0.3–3 μM) in a concentration‐dependent manner. The calculated IC50 for IMID‐4F inhibiting KATP channel current was approximately 0.8 μM.

Radioligand binding studies using bovine aortic smooth muscle cell membranes showed that IMID‐4F (30 μM) did not displace binding to the KATP channel opener [3H]‐P1075. However, both levcromakalim (10 μM) and glibenclamide (10 μM) caused significant displacement of [3H]‐P1075.

These studies show that the imidazoline compound IMID‐4F is one of the most potent antagonists of arterial KATP channels identified. Vasorelaxation, hyperpolarization and K+ currents through KATP channels were all inhibited by IMID‐4F at micromolar concentrations. Radioligand binding studies indicate that IMID‐4F does not bind to the same site as levcromakalim or as glibenclamide. Considering other evidence, it is likely that IMID‐4F acts by interacting directly with the pore of the KIR channel, rather than through the sulphonylurea subunit of the KATP channel complex.

British Journal of Pharmacology (1999) 128, 1636–1642; doi:10.1038/sj.bjp.0702925
Antiplatelet effect of the anaesthetic drug propofol: influence of red blood cells and leucocytes
Authors: De La Cruz J P , Páez M V , Carmona J A , Sánchez De La Cuesta F
Published: January 2005

The present study was designed to investigate the mechanism of the antiplatelet action of the anaesthetic propofol in vitro.

Human whole blood was incubated with different concentrations of propofol and its solvent Intralipid®. We determined, platelet aggregometry in whole blood, platelet‐enriched plasma (PRP), PRP plus red blood cells (RBC), and PRP plus leucocytes (LC); platelet production of thromboxane B2 (TxB2), ATP release by platelet dense granules, adenosine uptake by RBC, intraplatelet levels of cyclic adenosine monophosphate (cyclic AMP) and cyclic guanosine monophosphate (cyclic GMP), and LC production of nitric oxide (NO).

Propofol‐induced inhibition of platelet aggregation was greater in whole blood (IC50 80–136 μM) than in PRP (IC50>600 μM), except when aggregation was induced by arachidonic acid, in which case the antiaggregatory effect of the anaesthetic was similar in both media (IC50 72–85 μM). Inhibition of platelet aggregation correlated significantly with inhibition of TxB2 synthesis (r2=0.83). Propofol also inhibited granular ATP release; this effect was greatest in whole blood.

The presence of RBC or LC increased the antiaggregatory effect of propofol, mainly when collagen was used as aggregating agent. Intralipid inhibited the uptake of adenosine by RBC, however this effect probably does not contribute significantly to its antiaggregatory effect.

The anaesthetic potentiated the NO‐cyclic GMP pathway, mainly by increasing the synthesis of NO by LC. Intralipid had no effect on the NO‐cyclic GMP pathway in the LC‐platelet interaction.

Propofol inhibited platelet aggregation in human whole blood, possibly through the sum of the effects of Intralipid on the platelet‐RBC interaction and the increased synthesis of NO by LC in the platelet‐LC interaction.

British Journal of Pharmacology (1999) 128, 1538–1544; doi:10.1038/sj.bjp.0702927
Evidence that somatostatin sst2 receptors mediate striatal dopamine release
Authors: Hathway G J , Humphrey P P A , Kendrick K M
Published: January 2005

Somatostatin (SRIF) is a cyclic tetradecapeptide present in medium‐sized aspiny interneurones in the rat striatum. We have previously shown that exogenous SRIF potently stimulates striatal dopamine (DA) release via a glutamate‐dependent mechanism. We now report the ability of the selective sst2 receptor agonist, BIM‐23027, to mimic this effect of SRIF.

In vivo microdialysis studies were performed in anaesthetized male Wistar rats. In most experiments, compounds were administered by retrodialysis into the striatum for 15 min periods, 90 min and 225 min after sampling commenced, with levels of neurotransmitters being measured by HPLC with electrochemical and fluorescence detection.

BIM‐23027 (50 and 100 nM) stimulated DA release with extracellular levels increasing by up to 18 fold.

Prior retrodialysis of BIM‐23027 (50 nM) abolished the effects of subsequent administration of SRIF (100 nM).

The agonist effects of both BIM‐23027 and SRIF were abolished by the selective sst2 receptor antagonist, L‐Tyr8‐CYN‐154806 (100 nM).

The AMPA/kainate receptor antagonist, DNQX (100 μM), abolished the agonist effects of BIM‐23027 as previously shown for SRIF.

This study provides evidence that the sst2 receptor mediates the potent dopamine‐releasing actions observed with SRIF in the rat striatum. Dopamine release evoked by both peptides appears to be mediated indirectly via a glutamatergic pathway. Other subtype‐specific somatostatin receptor ligands were unable to elicit any effects and therefore we conclude that no other somatostatin receptor types are involved in mediating the dopamine‐releasing actions of SRIF in the striatum.

British Journal of Pharmacology (1999) 128, 1346–1352; doi:10.1038/sj.bjp.0702934
Platelet‐activating factor increases mucosal permeability in rat intestine via tyrosine phosphorylation of E‐cadherin
Authors: Tan Xiao‐Di , Chang Hong , Qu Xiao‐Wu , Caplan Michael , Gonzalez‐Crussi Frank , Hsueh Wei
Published: January 2005

Platelet‐activating factor (PAF), an inflammatory mediator, plays an important role in mediating intestinal injury. However, it remains unclear whether PAF has a function in the intestine. The production of PAF by normal intestine and by unstimulated intestinal epithelial cell lines suggests that PAF may have a regulatory function in the normal bowel.

In this study we investigated the role of PAF in modulating intestinal mucosal permeability in rats. Lumen‐to‐blood transit of FD‐4 (dextran 4400), (an index of intestinal permeability), was assessed in sham‐operated rats and rats injected with PAF (1.25 μg kg−1, i.v., a dose insufficient to induce intestinal injury).

PAF‐induced villus cytoskeletal changes were examined by staining the intestine for F‐actin. The effect of PAF on tyrosine phosphorylation of the junctional protein E‐cadherin was examined by immunoprecipitation. Some rats were pretreated with AG1288 (a tyrosine kinase inhibitor) before PAF injection, and mucosal permeability change was assessed.

To investigate the role of endogenous PAF upon mucosal permeability, we studied the effect of PAF antagonists on (intraluminal) glucose‐induced increase in mucosal permeability.

We found that low dose PAF: (a) alters the cytoskeletal structure of intestinal epithelium, (b) causes the influx of FD4 from intestinal lumen to systemic circulation, (c) induces tyrosine phosphorylation of E‐cadherin and cadherin‐associated proteins. Glucose‐induced mucosal permeability increase is abolished by using two structurally different PAF antagonists.

These results suggest that endogenous PAF modulates macromolecular movement across the intestinal mucosal barrier, probably via tyrosine phosphorylation of E‐cadherin and cytoskeletal alteration of enterocytes.

British Journal of Pharmacology (2000) 129, 1522–1529; doi:10.1038/sj.bjp.0702939
Oxidative stress as a mechanism for quinolinic acid‐induced hippocampal damage: protection by melatonin and deprenyl
Authors: Behan W M H , McDonald M , Darlington L G , Stone T W
Published: January 2005

There are differences between the excitotoxic actions of quinolinic acid and N‐methyl‐D‐aspartate (NMDA) which suggest that quinolinic acid may act by mechanisms additional to the activation of NMDA receptors. The present study was designed to examine the effect of a potent antioxidant, melatonin, and the potential neuroprotectant, deprenyl, as inhibitors of quinolinic acid‐induced brain damage. Injections were made into the hippocampus of anaesthetized rats, which were allowed to recover before the brains were taken for histology and the counting of surviving neurones.

Quinolinic acid (120 nmols) induced damage to the pyramidal cell layer, which was prevented by the co‐administration of melatonin (5 nmols locally plus 2×20 mg kg−1 i.p.). This protective effect was not prevented by the melatonin receptor blocker luzindole. Neuronal damage produced by NMDA (120 nmols) was not prevented by melatonin.

Quinolinic acid increased the formation of lipid peroxidation products from hippocampal tissue and this effect was prevented by melatonin.

Deprenyl also prevented quinolinic acid‐induced damage at a dose of 50 nmols but not 10 nmols plus 2×1.0 mg kg−1 i.p. The non‐selective monoamine oxidase inhibitor nialamide (10 and 50 nmols plus 2×25 mg kg−1) did not afford protection.

The results suggest that quinolinic acid‐induced neuronal damage can be prevented by a receptor‐independent action of melatonin and deprenyl, agents which can act as a potent free radical scavenger and can increase the activity of endogenous antioxidant enzymes respectively. This suggests that free radical formation contributes significantly to quinolinic acid‐induced damage in vivo.

British Journal of Pharmacology (1999) 128, 1754–1760; doi:10.1038/sj.bjp.0702940
Effect of vasoactive intestinal peptide (VIP)‐related peptides on cholinergic neurogenic and direct mucus secretion in ferret trachea in vitro
Authors: Liu Yu‐Chih , Khawaja Aamir M , Rogers Duncan F
Published: January 2005

We investigated whether vasoactive intestinal peptide (VIP) and its related peptides, pituitary adenylate cyclase activating peptide (PACAP) and secretin, regulate cholinergic neural mucus secretion in ferret trachea in vitro, using 35SO4 as a mucus marker. We also studied the interaction between VIP and secretin on cholinergic mucus output.

VIP (1 and 10 μM) increased secretion, whereas neither PACAP1–27, PACAP1–38 nor secretin (up to 10 μM) increased mucus output. In contrast, VIP, PACAP1–27 and PACAP1–38 concentration‐dependently inhibited cholinergic neural secretion, with an order of potency of VIP>PACAP 1–38>PACAP1–27. Neither PACAP1–27 nor PACAP1–38 altered the secretion induced by acetylcholine (ACh).

Secretin increased cholinergic neural secretion with a maximal increase of 190% at 1 μM. This potentiation was blocked by VIP or atropine. Similarly, secretin (1 μM) potentiated VIP (1 μM)‐induced mucus output by 160%. Secretin did not alter exogenous ACh‐induced secretion. VIP vs secretin competition curves suggested these two peptides were competing reversibly for the same receptor.

We conclude that, in ferret trachea in vitro, VIP and PACAPs inhibit cholinergic neural secretion via pre‐junctional modulation of cholinergic neurotransmission. VIP and secretin compete for the same receptor, possibly a VIP1 receptor, at which secretin may be a receptor antagonist.

British Journal of Pharmacology (1999) 128, 1353–1359; doi:10.1038/sj.bjp.0702942
Effect of nitro‐L‐arginine on electrical and mechanical responses to acetylcholine in the superior mesenteric artery from stroke‐prone hypertensive rat
Authors: Ghisdal Philippe , Godfraind Théophile , Morel Nicole
Published: January 2005

High salt diet is known to aggravate the vascular pathology in spontaneously hypertensive stroke‐prone rats (SHR‐SP). The aim of the present study was to assess the involvement of endothelial dysfunction in this effect. Contractile tension and membrane potential were simultaneously recorded in superior mesenteric artery rings of untreated and NaCl‐loaded (1% NaCl in the drinking water) SHR‐SP and normotensive Wistar Kyoto rats (WKY).

In unstimulated artery, hyperpolarization evoked by acetylcholine was not different in WKY and in NaCl‐loaded WKY; it was reduced in SHR‐SP and further reduced in NaCl‐loaded SHR‐SP. Hyperpolarization was unaffected by Nω‐nitro‐L‐arginine (L‐NA) but was abolished in high‐KCl solution.

In noradrenaline‐stimulated artery, ACh‐evoked hyperpolarization and relaxation were not different in WKY and in SHR‐SP. NaCl‐treatment did not affect the responses to ACh in WKY but decreased maximum relaxation in SHR‐SP from 93±2% to 72±7% of the contraction. In WKY, in NaCl‐loaded WKY and in SHR‐SP, L‐NA similarly shifted the concentration‐relaxation curve to ACh to the right and depressed its maximum but L‐NA did not affect the hyperpolarization to ACh. In NaCl‐loaded SHR‐SP, L‐NA blunted the effects of ACh on membrane potential and on contraction.

The NO donor SNAP abolished the depolarization and the contraction evoked by noradrenaline with the same potency in WKY and in untreated SHR‐SP but was more potent in NaCl‐loaded SHR‐SP.

In KCl‐contracted arteries the relaxations to ACh were not different in WKY and SHR‐SP but NaCl‐loaded SHR‐SP were more sensitive to ACh.

The results showed that NaCl‐rich diet markedly reduced the L‐NA‐resistant responses to ACh and increased the sensitivity to NO in SHR‐SP.

British Journal of Pharmacology (1999) 128, 1513–1523; doi:10.1038/sj.bjp.0702947
Evidence for the involvement of spinal endogenous ATP and P2X receptors in nociceptive responses caused by formalin and capsaicin in mice
Authors: Tsuda Makoto , Ueno Shinya , Inoue Kazuhide
Published: January 2005

The aim of the present study is to characterize the role of spinal endogenous ATP and P2X receptors in the generation of neurogenic and inflammatory pain. We examined the effects of intrathecal treatment with P2X receptor antagonists on the formalin‐ and capsaicin‐induced nociceptive behaviours in mice.

Intrathecal pretreatment with the general P2 receptor antagonist, pyridoxal‐phosphate‐6‐azophenyl‐2′,4′‐disulphonic acid (PPADS), significantly suppressed both the first and second phases of the formalin‐induced nociceptive behaviour. The second phase of the nociceptive response was also suppressed by intrathecal treatment with PPADS after the first phase. Furthermore, pretreatment with the selective antagonist for the P2X1, P2X3 and P2X2+3 receptors, 2′,3′‐O‐(2,4,6‐trinitrophenyl)adenosine 5′‐triphosphate (TNP‐ATP), significantly reduced the first phase, but not the second phase. The second phase was also not suppressed by intrathecal TNP‐ATP after the first phase.

Capsaicin‐induced nociceptive behaviour that has been shown to be a model for neurogenic pain, was also significantly suppressed by intrathecal pretreatment with PPADS or TNP‐ATP.

Nociceptive behaviour in the first phase of the formalin test and in the capsaicin test were significantly inhibited by intrathecal pretreatment with α,β‐methylene ATP (α,βmeATP: 5 μg mouse−1) 15 min prior to injection of formalin or capsaicin. This treatment has been previously shown to desensitize spinal P2X3 receptor subtypes in vivo.

These findings suggest that spinal endogenous ATP may play a role in (1) the formalin‐ and capsaicin‐induced neurogenic pain via the PPADS‐ and TNP‐ATP‐sensitive P2X receptors which are also desensitized by α,βmeATP (perhaps the P2X3 receptor subtype) and (2) formalin‐induced inflammatory pain via PPADS‐sensitive, TNP‐ATP‐ and α,βmeATP‐insensitive P2X (and/or P2Y) receptors.

British Journal of Pharmacology (1999) 128, 1497–1504; doi:10.1038/sj.bjp.0702960
Characterization of excitatory prostanoid receptors in the human umbilical artery in vitro
Authors: Boersma J I , Janzen K M , Oliveira L , Crankshaw D J
Published: January 2005

5‐HT and the prostanoid TP receptor agonists, U46619 and I‐BOP, constricted the human umbilical artery with pEC50 values of 7.3±0.2, 6.7±0.1, and 7.3±0.2, respectively. The selective TP receptor antagonist, GR32191 (0.1 μM), shifted the concentration‐effect curves to U46619 and I‐BOP to the right, but had no effect on the response to 5‐HT.

The natural prostaglandins, PGF2α and PGE2, caused concentration‐dependent contraction with pEC50 values of 5.2±0.2 and 4.9±0.2, respectively. PGD2 was a partial agonist with a pEC50 of 5.24±0.03. GR32191 (0.1 μM) inhibited the responses to all of these compounds suggesting that they produce contraction by acting at TP receptors.

Sulprostone failed to elicit contraction in the human umbilical artery at concentrations up to 4.4 μM suggesting the absence of EP1 and EP3 receptors. Despite this, 17‐phenyltrinor PGE2 and GR63799 both induced contraction at concentrations above 1 μM, but the effects were sensitive to GR32191 (0.1 μM).

Fluprostenol had no effect on the human umbilical artery at concentrations up to 17 μM suggesting the absence of FP receptors. Cloprostenol was ineffective in two tissues, but caused contraction in one tissue at the highest concentration tested (1.7 μM). However, this response was abolished in the presence of GR32191 (0.1 μM).

The effects of four TP receptor antagonists were assessed by global non‐linear regression analysis. GR32191, SQ29548, SQ30741, and ICI192605 competitively inhibited responses to U46619 with pKb values of 8.0±0.1, 7.6±0.1, 7.0±0.2 and 8.1±0.1, respectively.

These results suggest that the human umbilical artery functionally expresses TP receptors, but not EP1, EP2 or FP receptors.

British Journal of Pharmacology (1999) 128, 1505–1512; doi:10.1038/sj.bjp.0702965
A novel anti‐diabetic drug, miglitol, markedly reduces myocardial infarct size in rabbits
Authors: Minatoguchi Shinya , Arai Masazumi , Uno Yoshihiro , Kariya Tatsuya , Nishida Yoshio , Hashimoto Kazuaki , Kawasaki Masanori , Takemura Genzou , Fujiwara Takako , Fujiwara Hisayoshi
Published: January 2005

We examined whether N‐hydroxyethyl‐1‐deoxynojirimycin (miglitol), a new human anti‐diabetic drug with effects to inhibit α‐1,6‐glucosidase glycogen debranching enzyme and reduce the glycogenolytic rate as well as to inhibit α‐1,4‐glucosidase, could reduce infarct size in the rabbit heart. Rabbits were subjected to 30‐min coronary occlusion followed by 48‐h reperfusion.

The infarct size as a percentage of area at risk was not reduced by pre‐ischaemic treatment with 1 mg kg−1 miglitol (42.7±4.0%, n=10) compared with the saline control group (41.7±2.3%, n=10). However, it was significantly and dose‐dependently reduced by pre‐ischaemic treatment with 5 or 10 mg kg−1 of miglitol (25.7±4.5%, n=10, and 14.6±2.4%, n=10, respectively) without altering the blood pressure, heart rate or blood glucose level. However, there was no evidence of an infarct‐size reducing effect after pre‐reperfusion treatment with 10 mg kg−1 of miglitol (35.0±3.0%, n=10).

Another 40 rabbits given 1, 5 and 10 mg kg−1 of miglitol or saline before ischaemia (n=10 in each) were sacrificed at 30 min of ischaemia for biochemical analysis. Miglitol preserved significantly the glycogen content, and attenuated significantly the lactate accumulation in a dose dependent manner in the ischaemic region at 30 min of ischaemia.

Pre‐ischaemic treatment, but not pre‐reperfusion treatment, with miglitol markedly reduced the myocardial infarct size, independently of blood pressure and heart rate. A dose‐dependent effect of miglitol on infarct size, glycogenolysis and lactate formation suggests that the mechanism may be related to the inhibition of glycogenolysis. Thus, miglitol may be beneficial for coronary heart disease as well as diabetes mellitus.

British Journal of Pharmacology (1999) 128, 1667–1672; doi:10.1038/sj.bjp.0702970
Nociceptin, Phe1ψ‐nociceptin1–13, nocistatin and prepronociceptin154–181 effects on calcium channel currents and a potassium current in rat locus coeruleus in vitro
Authors: Connor Mark , Vaughan Christopher W , Jennings Ernest A , Allen Richard G , Christie Macdonald J
Published: January 2005

The actions of the neuropeptide nociceptin, the putative nociceptin receptor antagonist [Phe1ψ(CH2‐NH)Gly2]‐nociceptin‐(1–13)NH2 (Phe1ψ‐nociceptin1–13) and the putative nociceptin precursor products nocistatin (rat prepronociceptin125–132) and rat prepronociceptin154–181 were examined on membrane properties of rat locus coeruleus (LC) neurons using whole cell patch clamp techniques.

Nociceptin inhibited IBa in all LC neurons, (pD2 of 8.9, maximum inhibition 50%). The inhibition of IBa by nociceptin was associated with slowing of the activation of IBa and could be significantly reversed by a strong depolarizing prepulse. Phe1ψ‐nociceptin1–13 also inhibited IBa in LC neurons (notional pD2 of 7.6, maximum inhibition 18%). Application of Phe1ψ‐nociceptin1–13 (1 μM) significantly occluded the subsequent effects of a co‐application of nociceptin (3 nM) on IBa.

As previously reported for nociceptin, Phe1ψ‐nociceptin1–13 caused an outward current in LC neurons voltage clamped at −60 mV (pD2 of 7.1, maximum current 50% of that of methionine enkephalin, 10 μM). The Phe1ψ‐nociceptin1–13 induced current reversed polarity at −112 mV and exhibited pronounced inward rectification. Phe1ψ‐nociceptin1–13 (1 μM) reversibly inhibited the current caused by nociceptin (300 nM) by 30%.

Neither nocistatin nor rat prepronociceptin154–181 inhibited IBa in LC neurons, or prevented the subsequent inhibition by nociceptin. Neither nocistatin or prepronociceptin154–181 affected the membrane properties of LC neurons.

This study demonstrates that nociceptin modulates somatic IBa in rat LC neurons. The putative ORL1 antagonist Phe1ψ‐nociceptin1–13 exhibited partial agonist activity at inhibiting IBa and opening K+ channels in LC. Other putative nociceptin precursor products were without effect on LC cells.

British Journal of Pharmacology (1999) 128, 1779–1787; doi:10.1038/sj.bjp.0702971
CGRP and adrenomedullin binding correlates with transcript levels for Calcitonin Receptor‐Like Receptor (CRLR) and Receptor Activity Modifying Proteins (RAMPs) in rat tissues
Authors: Chakravarty P , Suthar T P , Coppock H A , Nicholl C G , Bloom S R , Legon S , Smith D M
Published: January 2005

Putative receptors for CGRP and adrenomedullin have been investigated in the rat. Calcitonin Receptor‐Like Receptor (CRLR), in combination with Receptor Activity Modifying Proteins (RAMPs) is hypothesized to bind either CGRP or adrenomedullin. The receptors known as RDC1 and L1 have also been shown to bind CGRP and adrenomedullin respectively.

In this study it is shown that rat CRLR cDNA specifies a CGRP receptor when co‐transfected with RAMP‐1 cDNA and an adrenomedullin receptor when co‐transfected with either RAMP‐2 or RAMP‐3 cDNA in human embryonic kidney 293 cells.

CRLR, RAMP, RCD1 and L1 mRNA levels and CGRP and adrenomedullin receptor densities have been measured and correlated with each other in eight rat tissues selected for their distinctive patterns of CGRP and adrenomedullin binding.

The data are consistent with the predictions of the CRLR/RAMP model. CGRP binding correlates well with RAMP‐1 mRNA levels (R=1.0, P=0.007), adrenomedullin binding shows a tendency to vary with RAMP‐2 mRNA levels (R=0.85, P=0.14) and total binding is correlated with CRLR mRNA levels (R=0.94, P=0.03). The data do not support the hypothesis that RDC1 and L1 account for the majority of CGRP and adrenomedullin binding respectively.

British Journal of Pharmacology (2000) 130, 189–195; doi:10.1038/sj.bjp.0702975
Cardiovascular responses to angiotensins I and II in normotensive and hypertensive rats; effects of NO synthase inhibition or ET receptor antagonism
Authors: Gardiner S M , March J E , Kemp P A , Bennett T
Published: January 2005

We compared the cardiovascular responses to angiotensins (I and II), and any possible modulatory influences thereupon of nitric oxide (NO) or endothelin (ET) in conscious male, normotensive, Hannover Sprague‐Dawley (SD) rats, and hypertensive, heterozygous ((mRen‐2)27), transgenic (TG) rats.

The pressor effects of angiotensin I or of angiotensin II were not consistently different in SD and TG rats. The accompanying absolute reductions in renal and mesenteric vascular conductances were smaller in TG rats, but probably due to the baseline vasoconstriction in those animals.

Inhibition of NO synthase with L‐NAME had no significant effects on the pressor responses to angiotensin I or angiotensin II in either SD or TG rats. L‐NAME reduced the absolute, but not percentage, reductions in renal and mesenteric vascular conductances in response to angiotensin I and angiotensin II. L‐NAME abolished the hindquarters vasodilator effects of angiotensin I and angiotensin II in both strains of rat.

ET receptor antagonism (with SB209670) had no significant influence on the pressor or renal or mesenteric vasoconstrictor effects of angiotensin II in SD rats. In TG rats, the pressor responses to angiotensin II were unaffected by SB209670; the accompanying falls in renal and mesenteric vascular conductances were enhanced in absolute, but not in percentage terms.

These results provide no evidence for a buffering action of NO, or a modulatory influence of ET, on the pressor or vasoconstrictor effects of angiotensin I and/or angiotensin II in SD rats. Furthermore, there is no evidence for an altered sensitivity to angiotensin I or angiotensin II, and no evidence for a differential modulatory influence of either NO or ET in TG, compared to SD, rats.

British Journal of Pharmacology (1999) 128, 1795–1803; doi:10.1038/sj.bjp.0702978
Effects of ω‐conotoxin GVIA and diltiazem on double peaked vasoconstrictor responses to periarterial electric nerve stimulation in isolated canine splenic artery
Authors: Yang Xiao‐Ping , Chiba Shigetoshi
Published: January 2005

The actions of ω‐conotoxin (ω‐CTX) and diltiazem on adrenergic and purinergic components of double peaked vasoconstrictor responses to periarterial nerve stimulation have been investigated in the isolated, perfused canine splenic arterial preparation.

Double peaked vasoconstrictions (biphases of vasoconstrictors) were consistently observed in the conditions of 30 s trains of pulses at 1–10 Hz frequencies. ω‐CTX (1–30 nM) produced similar inhibitory effects on the first phase and second phase responses in a dose‐related manner. Thirty nM ω‐CTX almost completely inhibited the biphasic vasoconstrictions at any used frequencies but did not affect the vasoconstrictor responses to exogenous applied ATP (0.01–1 μmol) and noradrenaline (0.03–3 nmol).

Intraluminal application of a large dose of diltiazem (3–10 μM) also produced a dose‐dependent inhibitory effect on biphasic vasoconstrictions at any used frequencies. Three μM diltiazem exerted rather a larger inhibitory effect on the second phase than the first phase response at low frequencies (1–3 Hz), but a similar inhibition on first and second phasic responses at high frequencies (6–10 Hz). An extremely high dose of diltiazem (10 μM) almost completely inhibited the biphasic vasoconstrictor responses to nerve stimulation, and slightly inhibited the contractile responses to exogenous applied ATP (0.01–1 μmol) and noradrenaline (0.03–3 nmol).

The present results indicate that ω‐CTX selectively acts prejunctionally to inhibit the release of transmitters from sympathetic nerve terminals, and ω‐CTX‐sensitive calcium channels may produce a parallel controlling of purinergic and adrenergic components of sympathetic cotransmission. A large dose of diltiazem has inhibitory effects on both prejunctional and postjunctional sympathetic co‐transmission.

British Journal of Pharmacology (2000) 129, 47–52; doi:10.1038/sj.bjp.0702989
PF9404C, a new slow NO donor with beta receptor blocking properties
Authors: Villarroya Mercedes , Herrero Carlos J , Ruíz‐Nuño Ana , De Pascual Ricardo , Del Valle Mercedes , Michelena Pedro , Grau Manuel , Carrasco Emilio , López Manuela G , García Antonio G
Published: January 2005

PF9404C is the S‐S diesteroisomer of a novel blocker of beta adrenergic receptors with vasodilatory properties. It causes a concentration‐dependent relaxation of rat aorta helical strips pre‐contracted with 10−6 M noradrenaline (NA; IC50 33 nM). It was equipotent to nitroglycerin (NTG; IC50 49 nM), but much more potent than isosorbide dinitrate (ISD; IC50 15,000 nM).

Oxyhaemoglobin (10 μM) shifted to the right the concentration‐response curve for the relaxation induced by PF9404C (IC50 530 nM) or NTG (IC50 61 nM).

Either methylene blue (MB) or ODQ (1 μM each) largely prevented the vasorelaxing responses to increasing concentrations of PF9404C or NTG.

In rat aorta smooth muscle cells, PF9404C increased the formation of cyclic GMP from 3 pmol mg−1 protein in basal conditions, to 53 pmol mg−1 protein in 10 μM PF9404C. Neither metoprolol nor carvedilol enhanced cyclic GMP.

In the electrically driven guinea‐pig left atrium, PF9404C blocked the inotropic effects of isoprenaline in a concentration‐dependent manner. Its IC50 (30 nM) was similar to that for S‐propranolol (22.4 nM) and lower than the IC50s for metoprolol (120 nM) and atenolol (192 nM). The beta‐adrenergic ligand (−)‐[3H]‐CGP12177 (0.2 nM) was displaced from its binding to rat brain membranes with Ki of 7 nM, 17 nM, 170 nM and 1.2 μM respectively for PF9404C, S‐(−)propranolol, metoprolol, and atenolol.

The data are consistent with the idea that the S‐S diesteroisomer PF9404C, is a potent vasorelaxing agent, as well as a blocker of cardiac beta adrenergic receptors. The mechanism of its vasorelaxing effects involves the slow generation of NO. This molecule can, therefore, exhibit antihypertensive and cardioprotective actions through a double mechanism, NO donation and beta blockade.

British Journal of Pharmacology (1999) 128, 1713–1722; doi:10.1038/sj.bjp.0702992
Effects of diadenosine polyphosphates (ApnAs) and adenosine polyphospho guanosines (ApnGs) on rat mesenteric artery P2X receptor ion channels
Authors: Lewis C J , Gitterman D P , Schlüter H , Evans R J
Published: January 2005

Diadenosine polyphosphates (ApnAs, n=3–7) and adenosine polyphospho guanosines (ApnGs, n=3–6) are naturally occurring vasoconstrictor substances found in platelets. These vasoconstrictor actions are thought to be mediated through the activation of P2X receptors for ATP. The effects of ApnAs and ApnGs at P2X receptors on rat mesenteric arteries were determined in contraction studies and using the patch clamp technique on acutely dissociated artery smooth muscle cells.

P2X1 receptor immunoreactivity was detected in the smooth muscle layer of artery rings. The sensitivity to α,β‐methylene ATP and desensitizing nature of rat mesenteric artery P2X receptors correspond closely to those of recombinant P2X1 receptors.

Ap4A, Ap5A and Ap6A evoked concentration dependent P2X receptor inward currents which desensitized during the application of higher concentrations of agonist. The agonist order of potency was Ap5AAp6AAp4A>>Ap3A. Ap2A and Ap7A were ineffective. Similar results were obtained in contraction studies except for Ap7A which evoked a substantial contraction.

ApnGs (n=2–6)(30 μM) evoked P2X receptor inward currents in mesenteric artery smooth muscle cells. ApnGs (n=4–6) were less effective than the corresponding ApnA.

This study shows that at physiologically relevant concentrations ApnAs and ApnGs can mediate contraction of rat mesenteric arteries through the activation of P2X1‐like receptors. However the activity of the longer chain polyphosphates (n=6–7) may be overestimated in whole tissue studies due to metabolic breakdown to yield the P2X receptor agonists ATP and adenosine tetraphosphate.

British Journal of Pharmacology (2000) 129, 124–130; doi:10.1038/sj.bjp.0702993
Functional neuroimaging of cognition impaired by a classical antihistamine, d‐chlorpheniramine
Authors: Okamura Nobuyuki , Yanai Kazuhiko , Higuchi Makoto , Sakai Jun , Iwata Ren , Ido Tatsuo , Sasaki Hidetada , Watanabe Takehiko , Itoh Masatoshi
Published: January 2005

Antihistamine induced cognitive decline was evaluated using positron emission tomography (PET) measurement of histamine H1 receptor (H1R) occupancy and regional cerebral blood flow (rCBF).

Cognitive performance in attention‐demanding task deteriorated dose‐dependently and the effects were statistically significant after the treatment of 2 mg of d‐chlorpheniramine. There was no significant change in subjective sleepiness in the same dose.

The regional blockade of H1R was observed mainly in the frontal, temporal and anterior cingulate cortices, and the intravenous administration of d‐chlorpheniramine as a therapeutic dose (2 mg) blocked over 60% of H1R in the frontal cortices.

The results from activation study using visual discrimination tasks demonstrated that enhanced activity in the right prefrontal and anterior cingulate cortices as well as a decreased activity in the left temporal and frontal cortices and midbrain after the treatment of d‐chlorpheniramine.

There were no changes in global CBF for the subjects treated with 2 mg d‐chlorpheniramine (pre; 44.8±3.3 ml dl−1 min−1 vs post; 44.4±4.7 ml dl−1 min−1).

The results indicated that the attention system of human brain could be altered by therapeutic doses of H1R antagonists. These findings provide the information as to the potential risk of antihistamines in our daily activities.

British Journal of Pharmacology (2000) 129, 115–123; doi:10.1038/sj.bjp.0702994
Adenosine induces cyclic‐AMP formation and inhibits endothelin‐1 production/secretion in guinea‐pig tracheal epithelial cells through A2B adenosine receptors
Authors: Pelletier Stéphane , Dubé Jean , Villeneuve Annie , Gobeil Fernand , Bernier Sylvie G , Battistini Bruno , Guillemette Gaétan , Sirois Pierre
Published: January 2005

The adenosine receptor subtype mediating adenosine 3′ : 5′‐cyclic monophosphate (cyclic AMP) formation and the effect of its activation on endothelin‐1 (ET‐1) secretion were studied in primary cultures of tracheal epithelial cells.

Adenosine analogues showed the following rank order of potency (pD2 value) and intrinsic activity on the generation of cyclic AMP by tracheal epithelial cells: 5′‐N‐ethylcarboxyamidoadenosine (NECA, A1/A2A/A2B, pD2: 5.44±0.16)>adenosine (ADO, non selective, pD2: 4.99±0.09; 71±9% of NECA response) 2‐Cl‐adenosine (2CADO, non selective, pD2: 4.72±0.14; 65±9% of NECA response)>>>CGS21680 (A2A; inactive at up to 100 μM).

Cyclic AMP formation stimulated by NECA in guinea‐pig tracheal epithelial cells was inhibited by adenosine receptor antagonist with the following order of apparent affinity (pA2 value): Xanthine amine congeners (XAC, A2A/A2B, 7.89±0.22)>CGS15943 (A2A/A2B, 7.24±0.26)>ZM241385 (A2A, 6.69±0.14)>DPCPX (A1, 6.51±0.14)>3n‐propylxanthine (weak A2B, 4.30±0.10). This rank order of potency is typical for A2B‐adenosine receptor.

Adenosine decreased basal and LPS‐stimulated irET production in a concentration‐dependent manner. Moreover, NECA but not CGS21680 inhibited LPS‐induced irET production.

The inhibitory effect of NECA on LPS‐induced irET production was reversed by XAC (pA2=8.84±0.12) and DPCPX (pA2=8.10±0.22).

These results suggested that adenosine increased cyclic AMP formation and inhibited irET production/secretion by guinea‐pig tracheal epithelial cells through the activation of a functional adenosine receptor that is most likely the A2B subtype. This adenosine receptor may be involved in the regulation of the level of ET‐1 production/secretion by guinea‐pig tracheal epithelial cells in physiological as well as in pathophysiological conditions.

British Journal of Pharmacology (2000) 129, 243–250; doi:10.1038/sj.bjp.0702999
Effect of 18β‐glycyrrhetinic acid on electromechanical coupling in the guinea‐pig renal pelvis and ureter
Authors: Santicioli Paolo , Maggi Carlo Alberto
Published: January 2005

We have tested the effect of the gap junction inhibitor, 18β‐glycyrrhetinic acid (18βGA) on electromechanical coupling in the guinea‐pig renal pelvis and ureter by the sucrose gap technique.

In the ureter 18βGA (3–30 μM) produced a concentration‐dependent inhibition of the spike component of the action potential (AP) and reduced contraction evoked by electrical stimulation.

Neurokinin A (NKA) produced a slow depolarization with superimposed APs and phasic contractions of the ureter. 18βGA (30 μM) markedly inhibited the depolarization and APs evoked by NKA. However the contractile response was more sustained in the presence than in the absence of 18βGA. At 100 μM, 18βGA inhibited the mechanical responses to NKA.

KCl (80 mM) produced APs and phasic contractions followed by sustained depolarization and tonic contraction. At 30 μM 18βGA markedly inhibited the KCl‐evoked APs and phasic contractions without affecting the sustained responses. At 100 μM 18βGA inhibited the tonic contraction to KCl.

In the renal pelvis 18βGA (30 μM) inhibited the amplitude of pacemaker potentials and accompanying contractions and induced the appearance of low‐amplitude APs not associated with contraction.

We conclude that, up to 30 μM, the action of 18βGA is consistent with an inhibition of cell‐to‐cell electrical coupling via gap junctions. The single‐unit character of smooth muscles in the guinea‐pig upper urinary tract is partly converted to a multi‐unit pattern. At high concentrations 18βGA possesses non specific effects which limit its usefulness as a tool for studying the role of gap junctions in smooth muscles.

British Journal of Pharmacology (2000) 129, 163–169; doi:10.1038/sj.bjp.0703004
Modulation of airway smooth muscle tone by protease activated receptor‐1,‐2,‐3 and ‐4 in trachea isolated from influenza A virus‐infected mice
Authors: Lan Rommel S , Stewart Geoff A , Henry Peter J
Published: January 2005

Relaxant and contractile effects of the tethered ligand domain sequences of murine PAR‐1, PAR‐2, PAR‐3 and PAR‐4, and of the proteases thrombin and trypsin were examined in mouse isolated tracheal preparations. The epithelium‐ and cyclo‐oxygenase‐dependence of these effects and the potential modulatory effects of respiratory tract viral infection were also investigated.

In carbachol‐contracted preparations, trypsin, thrombin, and the tethered ligand domain sequences of murine PAR‐1 (SFFLRN‐NH2), PAR‐2 (SLIGRL‐NH2) and PAR‐4 (GYPGKF‐NH2), but not PAR‐3 (SFNGGP‐NH2), induced transient, relaxant responses that were abolished by the cyclo‐oxygenase inhibitor indomethacin.

Repeated administration of SFFLRN‐NH2, SLIGRL‐NH2 or GYPGKF‐NH2 (30 μM) was associated with markedly diminished relaxation responses (homologous desensitization), although there was no evidence of cross‐desensitization between these peptides.

The tethered ligand domain sequences for PAR‐1 and PAR‐4 induced a rapid, transient contractile response that preceded the relaxant response. Contractions were not inhibited by indomethacin and were not induced by either thrombin or trypsin.

Influenza A virus infection did not significantly affect the responses induced by either the proteases or peptides. Furthermore, epithelial disruption caused by mechanical rubbing had no significant effect on responses to these PAR activators in preparations from either virus‐ or sham‐infected mice.

In summary, the proteases trypsin and thrombin, and peptide activators of PAR‐1, PAR‐2 and PAR‐4 induced relaxant responses of mouse isolated tracheal smooth muscle preparations, which were mediated by a prostanoid, probably PGE2. Interestingly, PAR‐mediated relaxations were not significantly diminished following acute damage to the epithelium caused by mechanical rubbing and/or the respiratory tract viral pathogen, influenza A.

British Journal of Pharmacology (2000) 129, 63–70; doi:10.1038/sj.bjp.0703007
Regulation of β1‐ and β3‐adrenergic agonist‐stimulated lipolytic response in hyperthyroid and hypothyroid rat white adipocytes
Authors: Germack Renée , Starzec Anna , Perret Gérard Y
Published: January 2005

This study examined the effects of thyroid status on the lipolytic responses of rat white adipocytes to β‐adrenoceptor (β‐AR) stimulation. The β1‐ and β3‐AR mRNAs and proteins were measured by Northern and saturation analyses, respectively. Glycerol production and adenyl cyclase (AC) activity induced by various non‐selective and selective β1/β3‐AR agonists and drugs which act distal to the receptor in the signalling cascade were measured in cells from untreated, tri‐iodothyronine (T3)‐treated and thyroidectomized rats.

The β3‐AR density was enhanced (72%) by T3‐treatment and reduced (50%) by introduction of a hypothyroid state while β1‐AR number remained unaffected. The β1‐ and β3‐AR density was correlated with the specific mRNA level in all thyroid status.

The lipolytic responses to isoprenaline, noradrenaline (β1/β3/β3‐AR agonists) and BRL 37344 (β3‐AR agonist) were potentiated by 48, 58 and 48%, respectively in hyperthyroidism and reduced by about 80% in hypothyroidism.

T3‐treatment increased the maximal lipolytic response to the partial β3‐AR (CGP 12177) and β1‐AR (xamoterol) agonists by 234 and 260%, respectively, increasing their efficacy (intrinsic activity: 0.95 versus 0.43 and 1.02 versus 0.42). The maximal AC response to these agonists was increased by 84 and 58%, respectively, without changing their efficacy.

In the hypothyroid state, the maximal lipolytic and AC responses were decreased with CGP (0.17±0.03 versus 0.41±0.08 μmol glycerol/106 adipocytes; 0.048±0.005 versus 0.114±0.006 pmol cyclic AMP min−1 mg−1) but not changed with xamoterol.

The changes in lipolytic responses to postreceptor‐acting agents (forskolin, enprofylline and dibutenyl cyclic AMP, (Bu)2cAMP) suggest the modifications on receptor coupling and phosphodiesterase levels in both thyroid states.

Thyroid status affects lipolysis by modifying β3‐AR density and postreceptor events without changes in the β1‐AR functionality.

British Journal of Pharmacology (2000) 129, 448–456; doi:10.1038/sj.bjp.0703008