bluuebunny/crossref_metadata_2025 huggingface dataset:
Vascular endothelial growth factor attenuates trauma‐induced injury in rats
Authors: Campbell Barry , Chuhran Craig , Lefer Allan M
Published: January 2005

Endothelial dysfunction and loss of nitric oxide (NO) is an integral part of the initiation and maintenance of the inflammatory process such as that occurring in traumatic shock, and is considered responsible for much of the trauma induced microvascular injury.

We investigated the effects of a vascular endothelial growth factor (VEGF) in a rat model of traumatic shock. Pentobarbital‐anaesthetized rats subjected to Noble‐Collip drum trauma developed a shock state characterized by marked hypotension and a 93% mortality rate with a mean survival time of 108±10 min in 14 rats. Accompanying these effects was a significant degree of endothelial dysfunction and a markedly elevated intestinal myeloperoxidase (MPO) activity.

Treatment with 125 μg kg−1 VEGF administered intravenously 18 h pre‐trauma, increased survival rate to 67% (P<0.01), and prolonged survival time to 252±24 min in 12 rats (P<0.01). VEGF also significantly preserved the endothelium‐dependent relaxation to ACh indicating a preservation of endothelium‐derived NO.

Our results indicate that endothelial dysfunction with its accompanying loss of NO plays an important role in tissue injury associated with trauma, and that preservation of NO is beneficial in traumatic shock. The mechanisms of the protective effect of VEGF in trauma involves preservation of eNOS function and diminished neutrophil accumulation resulting in reduced neutrophil‐mediated tissue injury.

British Journal of Pharmacology (2000) 129, 71–76; doi:10.1038/sj.bjp.0703010
Evidence that activation of central 5‐HT2B receptors causes renal sympathoexcitation in anaesthetized rats
Authors: Knowles Ian D , Ramage Andrew G
Published: January 2005

The effects of injections i.c.v. of α‐methyl‐5‐(2‐thienylmethoxy)‐1H‐indole‐3‐ethanamine (BW723C86; 0.02–2 μmol kg−1), a 5‐HT2B receptor agonist, on renal sympathetic and phrenic nerve activity, mean arterial blood pressure and heart rate were investigated in α‐chloralose anaesthetized rats pretreated with a peripherally acting 5‐HT2 receptor antagonist.

BW723C86 i.c.v. caused a dose‐related increase in renal nerve activity reaching a maximum of 67±6%, which at the highest dose was associated with a small and maintained fall in mean arterial blood pressure of 7±3 mmHg. These changes were not associated with any significant changes in heart rate or phrenic nerve activity.

BW723C86‐evoked increases in renal nerve activity and hypotension were attenuated by pretreatment (i.c.v.) with SB204741 (300 nmol kg−1; a 5‐HT2B receptor antagonist) but not by the same dose (i.c.v.) of ketanserin (a 5‐HT2A receptor antagonist) or RS102221 (a 5‐HT2C receptor antagonist). None of these antagonists alone had any effect on the variables being measured.

It is concluded that central 5‐HT2B receptors may play a selective role in the control of sympathetic supply to the kidney, which could be important in the central mechanisms involved in blood volume regulation.

British Journal of Pharmacology (2000) 129, 177–183; doi:10.1038/sj.bjp.0703011
Sustained ethanol inhibition of native AMPA receptors on medial septum/diagonal band (MS/DB) neurons
Authors: Frye Gerald D , Fincher Annette
Published: January 2005

The direct impact of ethanol on native, non‐NMDA glutamate receptors was examined in acutely isolated MS/DB neurons from rat. The impact of ethanol functional tolerance and physical dependence on non‐NMDA receptor function was also determined.

Non‐NMDA receptors were defined pharmacologically as predominantly the AMPA subtype, because both AMPA‐ or kainate‐activated currents were blocked by GYKI 52466, a selective AMPA receptor antagonist. The relative magnitude of potentiation of AMPA‐activated currents by 10 or 100 μM cyclothiazide was consistent with recombinant AMPA flop‐subtype receptors. Finally, the selective kainate receptor agonist, SYM 8021, induced little current in MS/DB neurons.

AMPA receptor currents when activated by kainate were sensitive to ethanol, showing inhibition of ∼5–50% when 10–300 mM ethanol and kainate were briefly co‐applied (3 s). Ethanol (100 mM) also inhibited both the initial transient peak and sustained currents activated by AMPA. Inhibition was sustained during continuous ethanol superfusions of 5 min, suggesting a lack of acute tolerance to ethanol‐induced AMPA receptor blockade.

Rapid application of 3–3000 μM kainate activated concentration‐dependent currents in MS/DB neurons from Control and Ethanol Dependent animals that were not significantly different. Also, direct ethanol inhibition (300 mM) of kainate‐activated currents was not reduced by ethanol dependence, suggesting a lack of functional tolerance.

These results suggest that native AMPA receptors on MS/DB neurons are inhibited by pharmacologically‐relevant concentrations of ethanol. However, these receptors, unlike NMDA receptors, do not undergo adaptation with sustained ethanol exposure sufficient to induce physical dependence.

British Journal of Pharmacology (2000) 129, 87–94; doi:10.1038/sj.bjp.0703039
Voltage‐dependent block of native AMPA receptor channels by dicationic compounds
Authors: Tikhonov D B , Samoilova M V , Buldakova S L , Gmiro V E , Magazanik L G
Published: January 2005

The kinetics of open channel block of GluR2‐containing and GluR2‐lacking AMPA receptors (AMPAR) by dicationic compounds (IEM‐1460, IEM‐1754, and IEM‐1925) have been studied in rat hippocampal neurones using whole‐cell patch clamp recording and concentration‐jump techniques. Neurones were isolated from hippocampal slices by vibrodissociation.

The dicationic compounds were approximately 100–200 times more potent as blockers of GluR2‐lacking AMPAR than as blockers of GluR2‐containing AMPAR. The subunit specificity of channel block is determined by the blocking rate constant of a dicationic compound, whereas differences in unblocking rate constants account for differences in potency.

Hyperpolarization may decrease the block produced by IEM‐1460 and IEM‐1754 block due to the voltage‐dependence of the unblocking rate constants for these compounds. This suggests that dicationic compounds permeate the AMPAR channel at negative membrane potentials. The effect was particularly apparent for GluR2‐lacking AMPAR. These findings indicate that the presence of GluR2‐subunit(s) in AMPAR hinders the binding of the cationic compounds and their permeation through the channel.

The most potent compound tested was IEM‐1925. The presence of a phenylcyclohexyl moiety instead of an adamantane moiety, as in IEM‐1460 and IEM1754, is probably responsible for the higher potency of IEM‐1925. Dicationic compounds are important not only as pharmacological tools, but also as templates for the synthesis of new selective AMPAR blockers which may be potential therapeutic agents.

British Journal of Pharmacology (2000) 129, 265–274; doi:10.1038/sj.bjp.0703043
ADP can induce aggregation of human platelets via both P2Y1 and P2T receptors
Authors: Jarvis G E , Humphries R G , Robertson M J , Leff P
Published: January 2005

In the present study we have investigated the roles of P2Y1 and P2T receptor subtypes in adenosine 5′‐diphosphate (ADP)‐induced aggregation of human platelets in heparinized platelet rich plasma.

The response to ADP can be characterized as the initial rate or the maximum or final extent of aggregation. The response profile is determined by the concentration of ADP used, being transient at lower and sustained at higher concentrations.

The P2Y1 receptor antagonist, adenosine‐3′‐phosphate‐5′‐phosphate (A3P5P) competitively antagonized the initial rate of aggregation (pKB 5.47) and transformed the response profile to a slowly developing but sustained response. Both maximum and final extents were also inhibited by A3P5P although not in a competitive manner (Schild slope <1).

The P2T receptor antagonist, AR‐C67085, competitively antagonized the final extent of aggregation (pKB 8.54), transforming the response profile to one of rapid, transient aggregation. Its effect on maximum extent (the most widely used index of aggregation) was complex, and further supported the involvement of both receptor subtypes in the aggregation response.

ADP‐induced aggregation is a complex phenomenon, the nature of which is determined by the relative occupancy of the two receptor subtypes. While P2Y1 receptor activation causes a rapid and transient aggregation, the extent of sustained aggregation is determined by the level of P2T receptor occupancy. Hence, detailed analysis of the aggregation response is essential to correctly define the purinergic pharmacology of the platelet and interpretation of results is critically dependent on the response index chosen.

British Journal of Pharmacology (2000) 129, 275–282; doi:10.1038/sj.bjp.0703046
The endogenous lipid anandamide is a full agonist at the human vanilloid receptor (hVR1)
Authors: Smart D , Gunthorpe M J , Jerman J C , Nasir S , Gray J , Muir A I , Chambers J K , Randall A D , Davis J B
Published: January 2005

The endogenous cannabinoid anandamide was identified as an agonist for the recombinant human VR1 (hVR1) by screening a large array of bioactive substances using a FLIPR‐based calcium assay. Further electrophysiological studies showed that anandamide (10 or 100 μM) and capsaicin (1 μM) produced similar inward currents in hVR1 transfected, but not in parental, HEK293 cells. These currents were abolished by capsazepine (1 μM). In the FLIPR anandamide and capsaicin were full agonists at hVR1, with pEC50 values of 5.94±0.06 (n=5) and 7.13±0.11 (n=8) respectively. The response to anandamide was inhibited by capsazepine (pKB of 7.40±0.02, n=6), but not by the cannabinoid receptor antagonists AM630 or AM281. Furthermore, pretreatment with capsaicin desensitized the anandamide‐induced calcium response and vice versa. In conclusion, this study has demonstrated for the first time that anandamide acts as a full agonist at the human VR1.

British Journal of Pharmacology (2000) 129, 227–230; doi:10.1038/sj.bjp.0703050
Modulation by bicuculline and penicillin of the block by t‐butyl‐bicyclo‐phosphorothionate (TBPS) of GABAA‐receptor mediated Cl−‐current responses in rat striatal neurones
Authors: Behrends Jan C
Published: January 2005

T‐butyl‐bicyclo‐phosphorothionate (TBPS) is a prototypical representative of the cage‐convulsants which act through a use‐dependent block of the GABAA‐receptor‐ionophore complex. Using current recordings from cultured neurones of rat striatum the manner was investigated in which two antagonists, bicuculline and penicillin, presumably acting at the agonist binding site and in the ionic channel, respectively, modify the rate of block by TBPS.

Penicillin (5 or 10 mM) did not slow the rate of block by TBPS, but produced a significant enhancement of block rate, which, however, was inversely related to the degree of antagonism by penicillin of the GABA‐induced current.

Bicuculline (10 μM) reduced the rate of block by TBPS. However, this effect was 3 fold weaker than its GABA‐antagonistic action. The slowing of block rate and the current antagonism exhibited a biphasic, positive‐negative relationship. Co‐application of bicuculline (100 μM) in a concentration that produced nearly complete antagonism and TBPS (10 μM) resulted in a marked (∼40%) reduction of subsequent GABA response amplitudes compatible with a direct, bicuculline‐induced conformational change in the receptor required for the binding of and block by TBPS.

The lack of protection afforded by the channel blocker penicillin as well as the lack of correlation between bicuculline antagonism of the Cl−‐current and its efficiency in protecting against TBPS block is evidence against an open channel blocking mechanism for TBPS. TBPS does, therefore, not appear to gain access to its binding site via the open pore but through alternative routes regulated from the agonist binding site.

British Journal of Pharmacology (2000) 129, 402–408; doi:10.1038/sj.bjp.0703063
Ontogenic aspects of D1 receptor coupling to G proteins and regulation of rat jejunal Na+, K+ ATPase activity and electrolyte transport
Authors: Vieira‐Coelho M A , Soares‐da‐Silva P
Published: January 2005

The present study examined the effect of dopamine on rat jejunal electrolyte transport (rheogenic transport and Na+, K+‐ATPase activity) in adult (60‐day old) and young (20‐day old) animals.

In young rats, dopamine, in the presence of phentolamine, produced an increase in jejunal Isc, this being completely abolished by SKF 83566, and not changed by S‐sulpiride. SKF 38393, but not quinerolane, also increased Isc; this effect was abolished by SKF 83566 and ouabain, but not by furosemide. In adult rats, dopamine in the presence of phentolamine (0.2 μM) decreased Isc.

Na+, K+‐ATPase activity in isolated jejunal epithelial cells from adult rats was 2.4 fold that in young rats. In the presence of phentolamine, both dopamine and SKF 38393, but not quinerolane, significantly decreased jejunal Na+, K+‐ATPase activity in young animals but not in adult animals.

Binding [3H]‐Sch 23390 to membranes of jejunal mucosa revealed the presence of a single class of receptors in both young and adult rats, with similar KD and Bmax values.

GTPγS and cholera toxin inhibited jejunal Na+, K+‐ATPase activity in young, but not in adult rats. Co‐incubation of pertussis toxin with dopamine was found to potentiate the inhibitory effects of dopamine upon the enzyme in both young and adult rats.

Regulation of Na+, K+‐ATPase activity by cholera toxin‐sensitive G proteins is absent in adult animals, and such difference may explain the failure of dopamine to inhibit intestinal Na+, K+‐ATPase activity in adult rats.

British Journal of Pharmacology (2000) 129, 573–581; doi:10.1038/sj.bjp.0703065
On the mechanism of d‐amphetamine‐induced changes in glutamate, ascorbic acid and uric acid release in the striatum of freely moving rats
Authors: Miele Maddalena , Mura Maria A , Enrico Paolo , Esposito Giovanni , Serra Pier A , Migheli Rossana , Zangani Danilo , Miele Egidio , Desole Maria S
Published: January 2005

The effects of systemic, intrastriatal or intranigral administration of d‐amphetamine on glutamate, aspartate, ascorbic acid (AA), uric acid, dopamine (DA), dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5‐hydroxyindoleacetic acid (5‐HIAA) concentrations in dialysates from the striatum of freely‐moving rats were evaluated using microdialysis.

d‐Amphetamine (2 mg kg−1) given subcutaneously (s.c.) increased DA, AA and uric acid and decreased DOPAC+HVA, glutamate and aspartate dialysate concentrations over a 3 h period after d‐amphetamine. 5‐HIAA concentrations were unaffected. Individual changes in glutamate and AA dialysate concentrations were negatively correlated.

d‐Amphetamine (0.2 mM), given intrastriatally, increased DA and decreased DOPAC+HVA and aspartate dialysate concentrations, but failed to change those of glutamate, AA uric acid or 5‐HIAA, over a 2 h period after d‐amphetamine. Haloperidol (0.1 mM), given intrastriatally, increased aspartate concentrations without affecting those of glutamate or AA.

d‐Amphetamine (0.2 mM), given intranigrally, increased AA and uric acid dialysate concentrations and decreased those of glutamate, aspartate and DA; DOPAC+HVA and 5‐HIAA concentrations were unaffected.

These results suggest that d‐amphetamine‐induced increases in AA and uric acid and decreases in glutamate concentrations are triggered at nigral sites. The changes in aspartate levels may be evoked by at least two mechanisms: striatal (mediated by inhibitory dopaminergic receptors) and nigral (activation of amino acid carrier‐mediated uptake).

British Journal of Pharmacology (2000) 129, 582–588; doi:10.1038/sj.bjp.0703066
Gamma‐aminobutyric acid (GABA) transport across human intestinal epithelial (Caco‐2) cell monolayers
Authors: Thwaites David T , Basterfield Laura , McCleave Peter M J , Carter Simon M , Simmons Nicholas L
Published: January 2005

Transintestinal absorption of gamma‐aminobutyric acid (GABA) via a pH‐dependent mechanism is demonstrated in the model human intestinal epithelial cell line Caco‐2.

Experiments with BCECF [2′,7′,‐bis(2‐carboxyethyl)‐5(6)‐carboxyfluorescein]‐loaded Caco‐2 cells demonstrate that GABA transport across the apical membrane is coupled to proton flow into the cell.

Short‐circuit current (ISC) measurements using Caco‐2 cell monolayers under voltage‐clamped conditions demonstrate that pH‐dependent GABA transport is a rheogenic process even in the absence of extracellular Na+, consistent with H+/GABA symport.

A range of GABA analogues were tested for their abilities to: (a) inhibit pH‐dependent [3H]GABA uptake across the apical membrane; (b) stimulate H+ flow across the apical surface of BCECF‐loaded Caco‐2 cell monolayers; (c) increase inward ISC across voltage‐clamped Caco‐2 cell monolayers.

Nipecotic acid, isonipecotic acid, D,L‐β‐aminobutyric acid, and 3‐amino‐1‐propanesulphonic acid each caused a marked acidification of intracellular pH and an increase in ISC when superfused at the apical surface of Caco‐2 cell monolayers. In contrast L‐α‐amino‐n‐butyric acid failed to induce proton flow or ISC. The ability of these compounds to induce proton or current flow across the apical surface of this intestinal epithelium was closely related to the relative inhibitory effects on [3H]GABA uptake.

These observations demonstrate H+/GABA symport and suggest that this transport mechanism may be accessible as a route for oral absorption of therapeutically‐useful GABA analogues.

British Journal of Pharmacology (2000) 129, 457–464; doi:10.1038/sj.bjp.0703069
The gastric H,K‐ATPase blocker lansoprazole is an inhibitor of chloride channels
Authors: Schmarda Andreas , Dinkhauser Patrick , Gschwentner Martin , Ritter Markus , Fürst Johannes , Scandella Elke , Wöll Ewald , Laich Andreas , Rossmann Heidi , Seidler Ursula , Lang Florian , Paulmichl Markus
Published: January 2005

It was postulated that swelling dependent chloride channels are involved in the proton secretion of parietal cells. Since omeprazole, lansoprazole and its acid activated sulphenamide form AG2000 are structurally related to phenol derivatives known to block swelling dependent chloride channels, we set out to test, whether these substances – which are known to block the H,K‐ATPase – could also lead to an inhibition of swelling‐dependent chloride channels. Swelling‐dependent chloride channels – characterized in many different cell types – show highly conserved biophysical and pharmacological features, therefore we investigated the effect of omeprazole, lansoprazole and its acid activated sulphenamide form AG2000 on swelling‐dependent chloride channels elicited in fibroblasts, after the reduction of the extracellular osmolarity.

Omeprazole, lansoprazole and its acid activated sulphenamide form AG2000 are able to block swelling‐dependent chloride channels (IClswell).

Lansoprazole and its protonated metabolite AG2000 act on at least two different sites of the IClswell protein: on an extracellular site which seems to be in a functional proximity to the nucleotide binding site, and on an intracellular site which allows the formation of disulfide‐bridges.

The inhibition of the proton pump and the simultaneous blocking of chloride channels by omeprazole, lansoprazole and its acid activated sulphenamide form AG2000, as described here could be an effective mode to restrict proton secretion in parietal cells.

British Journal of Pharmacology (2000) 129, 598–604; doi:10.1038/sj.bjp.0703070
Protein phosphatase‐protein kinase interplay modulates α1b‐adrenoceptor phosphorylation: effects of okadaic acid
Authors: Alcántara‐Hernández Rocío , Vázquez‐Prado José , García‐Sáinz J Adolfo
Published: January 2005

In the present work we studied the effect of protein phosphatase inhibitors on the phosphorylation state and function of α1b‐adrenoceptors.

Okadaic acid increased receptor phosphorylation in a time‐ and concentration‐dependent fashion (maximum at 30 min, EC50 of 30 nM). Other inhibitors of protein phosphatases (calyculin A, tautomycin and cypermethrin) mimicked this effect.

Staurosporine and Ro 31‐8220, inhibitors of protein kinase C, blocked the effect of okadaic acid on receptor phosphorylation. Neither genistein nor wortmannin altered the effect of okadaic acid.

The intense adrenoceptor phosphorylation induced by okadaic acid altered the adrenoceptor‐G protein coupling, as evidenced by a small decreased noradrenaline‐stimulated [35S]GTPγS binding. Okadaic acid did not alter the noradrenaline‐stimulated increases in intracellular calcium or the production of inositol trisphosphate.

Our data indicate that inhibition of protein phosphatases increases the phosphorylation state of α1b‐adrenoceptors; this effect seems to involve protein kinase C. In spite of inducing an intense receptor phosphorylation, okadaic acid alters α1b‐adrenergic actions to a much lesser extent than the direct activation of protein kinase C by phorbol myristate acetate.

British Journal of Pharmacology (2000) 129, 724–730; doi:10.1038/sj.bjp.0703073
Participation of mitogen‐activated protein kinase in thapsigargin‐ and TPA‐induced histamine production in murine macrophage RAW 264.7 cells
Authors: Shiraishi Muneshige , Hirasawa Noriyasu , Kobayashi Yuriko , Oikawa Shinji , Murakami Akira , Ohuchi Kazuo
Published: January 2005

Stimulation of the murine macrophage cell line RAW 264.7 with thapsigargin, an endomembrane Ca2+‐ATPase inhibitor, induced histamine production in a time‐ and concentration‐dependent manner.

The protein kinase C activator, 12‐O‐tetradecanoylphorbol 13‐acetate (TPA), also enhanced histamine production.

α‐Fluoromethylhistidine, a suicide substrate of L‐histidine decarboxylase (HDC), suppressed the thapsigargin (30 nM)‐ and TPA (30 nM)‐induced histamine production.

Both thapsigargin (30 nM) and TPA (30 nM) induced phosphorylation of p44/p42 MAP kinase and p38 MAP kinase.

PD98059, a specific inhibitor of MEK‐1 which phosphorylates p44/p42 MAP kinase, strongly suppressed both the thapsigargin (30 nM)‐ and TPA (30 nM)‐induced histamine production, whereas SB203580, a specific inhibitor of p38 MAP kinase, inhibited them only partially.

The other MEK‐1 inhibitor, U‐0126, also inhibited both the thapsigargin‐ and TPA‐induced histamine production in a concentration‐dependent manner.

Thapsigargin (30 nM) and TPA (30 nM) increased the levels of HDC mRNA at 4 h, but PD98059 suppressed both the thapsigargin‐ and TPA‐induced increases in the HDC mRNA level.

These findings indicate that thapsigargin and TPA induce histamine production in RAW 264.7 cells by increasing the level of HDC mRNA, and that both the thapsigargin‐ and TPA‐induced histamine production are regulated largely by p44/p42 MAP kinase and partially by p38 MAP kinase.

British Journal of Pharmacology (2000) 129, 515–524; doi:10.1038/sj.bjp.0703085
The actions of ether, alcohol and alkane general anaesthetics on GABAA and glycine receptors and the effects of TM2 and TM3 mutations
Authors: Krasowski Matthew D , Harrison Neil L
Published: January 2005

The actions of 13 general anaesthetics (diethyl ether, enflurane, isoflurane, methoxyflurane, sevoflurane, chloral hydrate, trifluoroethanol, tribromoethanol, tert‐butanol, chloretone, brometone, trichloroethylene, and α‐chloralose) were studied on agonist‐activated Cl− currents at human GABAA α2β1, glycine α1, and GABAC ρ1 receptors expressed in human embryonic kidney 293 cells.

All 13 anaesthetics enhanced responses to submaximal (EC20) concentrations of agonist at GABAA and glycine receptors, except α‐chloralose, which did not enhance responses at the glycine α1 receptor. None of the anaesthetics studied potentiated GABA responses at the GABAC ρ1 receptor.

Potentiation of submaximal agonist currents by the anaesthetics was studied at GABAA and glycine receptors harbouring mutations in putative transmembrane domains 2 and 3 within GABAA α2, β1, or glycine α1 receptor subunits: GABAA α2(S270I)β1, α2(A291W)β1, α2β1(S265I), and α2β1(M286W); glycine α1(S267I) and α1(A288W). For all anaesthetics studied except α‐chloralose, at least one of the mutations above abolished drug potentiation of agonist responses at GABAA and glycine receptors.

α‐Chloralose produced efficacious direct activation of the GABAA α2β1 receptor (a ‘GABA‐mimetic’ effect). The other 12 anaesthetics produced minimal or no direct activation of GABAA and glycine receptors. A non‐anaesthetic isomer of α‐chloralose, β‐chloralose, was inactive at GABAA and glycine receptors and did not antagonize the actions of α‐chloralose at GABAA receptors.

The implications of these findings for the molecular mechanisms of action of general anaesthetics at GABAA and glycine receptors are discussed.

British Journal of Pharmacology (2000) 129, 731–743; doi:10.1038/sj.bjp.0703087
Investigation of the interaction between nitric oxide and vasoactive intestinal polypeptide in the guinea‐pig gastric fundus
Authors: Dick J M C , Van Geldre L A , Timmermans J P , Lefebvre R A
Published: January 2005

The interaction between nitric oxide (NO) and vasoactive intestinal polypeptide (VIP) was investigated in isolated circular smooth muscle cells and strips of the guinea‐pig gastric fundus.

VIP induced a concentration‐dependent inhibition of carbachol‐induced contraction in smooth muscle cells with a maximum at 10−6 M. The relaxation by 10−6 M VIP was inhibited for 79.1±5.8% (mean±s.e.mean) by the NO‐synthase (NOS) inhibitor L‐NG‐nitroarginine (L‐NOARG; 10−4 M) in a L‐arginine reversible way. Also the inducible NOS (iNOS) selective inhibitor N‐(3‐(acetaminomethyl)‐benzyl)acetamide (1400 W; 10−6 M) inhibited the VIP‐induced relaxation, but its inhibitory effect was not reversed by L‐arginine.

When cells were incubated with the guanylyl cyclase inhibitor 1H‐(1,2,4)oxadiazolo(4,3‐a)quinoxalin‐1‐one (ODQ, 10−6 M), the protein kinase A‐inhibitor (R)‐p‐cyclic adenosine‐3′,5′‐monophosphothioate ((R)‐p‐cAMPS, 10−6 M) and the glucocorticoid dexamethasone (10−5 M), the relaxant effect of VIP was decreased by respectively 80.9±7.6, 77.0±11.6 and 87.1±4.5%.

In circular smooth muscle strips of the guinea‐pig gastric fundus, the VIP (10−9–10−7 M)‐induced relaxations were not significantly influenced by 10−4 M L‐NOARG, 10−6 M 1400 W, 10−6 M ODQ and 10−5 M dexamethasone.

These results suggest that iNOS, possibly induced by the procedure to prepare the smooth muscle cells, is involved in the relaxant effect of VIP in isolated smooth muscle cells but not in smooth muscle strips of the guinea‐pig gastric fundus. This study illustrates the importance of the experimental method when studying the influence of NOS inhibitors on the relaxation induced by VIP in gastrointestinal smooth muscle preparations.

British Journal of Pharmacology (2000) 129, 751–763; doi:10.1038/sj.bjp.0703089
β1‐, β2‐ and atypical β‐adrenoceptor‐mediated relaxation in rat isolated aorta
Authors: Brawley L , Shaw A M , MacDonald A
Published: January 2005

β‐adrenoceptor‐mediated relaxation was investigated in ring preparations of rat isolated thoracic aorta. Rings were pre‐constricted with a sub‐maximal concentration of noradrenaline (1 μM) and relaxant responses to cumulative concentrations of β‐adrenoceptor agonists obtained.

The concentration‐response curve (CRC) to isoprenaline was shifted to the right by propranolol (0.3 μM) with a steepening of the slope. Estimation of the magnitude of the shift from EC50 values gave a pA2 of 7.6. Selective β1‐ and β2‐adrenoceptor antagonists, CGP 20712A (0.1 μM) and ICI 118551 (0.1 μM), respectively, produced 4 and 14 fold shifts of the isoprenaline CRC.

Atypical β‐adrenoceptor agonists also produced concentration‐dependent relaxation of aortic rings. The order of potency of the β‐adrenoceptor agonists was (−log EC50): isoprenaline (6.25)>cyanopindolol (5.59)>isoprenaline+propranolol (5.11)>CGP 12177A (4.40)>ZD 2079 (4.24)>ZM 215001 (4.07)>BRL 37344 (3.89). Relaxation to CGP 12177A and ZM 215001 was unaffected by propranolol (0.3 μM).

SR 59230A (1 μM) and cyanopindolol (1 μM), β3‐adrenoceptor antagonists, had no effect on the isoprenaline (in the presence of propranolol) or CGP 12177A CRCs. Bupranolol and CGP 20712A, at μM concentrations (β4‐adrenceptor antagonists), inhibited responses to isoprenaline (in the presence of propranolol) and CGP 12177A.

In conclusion, atypical β‐adrenoceptors co‐exist with β1‐ and β2‐adrenoceptors in rat aorta. Although non‐conventional partial agonists and selective β3‐adrenoceptor agonist cause relaxation, the vascular atypical β‐adrenoceptor does not appear to correspond to the β3‐adrenoceptor. There are, however, similarities with the putative β4‐adrenoceptor.

British Journal of Pharmacology (2000) 129, 637–644; doi:10.1038/sj.bjp.0703091
Differential effects of ethanol on glycine uptake mediated by the recombinant GLYT1 and GLYT2 glycine transporters
Authors: Núñez Enrique , López‐Corcuera Beatriz , Martínez‐Maza Rodrigo , Aragón Carmen
Published: January 2005

The effects of ethanol on the function of recombinant glycine transporter 1 (GLYT1) and glycine transporter 2 (GLYT2) have been investigated.

GLYT1b and GLYT2a isoforms stably expressed in human embryonic kidney 293 (HEK 293) cells showed a differential behaviour in the presence of ethanol; only the GLYT2a isoform was acutely inhibited.

The ‘cut‐off’ (alcohols with four carbons) displayed by the n‐alkanols on GLYT2a indicates that a specific binding site for ethanol exists on GLYT2a or on a GLYT2a‐interacting protein.

The non‐competitive inhibition of GLYT2a indicates an allosteric modulation by ethanol of GLYT2a activity.

Chronic treatment with ethanol caused differential adaptive responses on the activity and the membrane expression levels of these transporters. The neuronal GLYT2a isoform decreased in activity and surface expression and the mainly glial GLYT1b isoform slightly increased in function and surface density.

These changes may be involved in some of the modifications of glycinergic or glutamatergic neurotransmitter systems produced by ethanol intoxication.

British Journal of Pharmacology (2000) 129, 802–810; doi:10.1038/sj.bjp.0703100
Effects of selective inhibitors of cyclo‐oxygenase‐1 (COX‐1) and cyclo‐oxygenase‐2 (COX‐2) on the spontaneous myogenic contractions in the upper urinary tract of the guinea‐pig and rat
Authors: Davidson M E , Lang R J
Published: January 2005

The role of cyclo‐oxygenase‐1 (COX‐1) and cyclo‐oxygenase‐2 (COX‐2) in the upper urinary tract of the guinea‐pig and rat was examined using simultaneous tension recordings of the proximal and distal regions of the renal pelvis and the ureter.

The guinea‐pig upper urinary tract contracted at a frequency (7.52±0.3 min−1 at 35°C) significantly lower than the frequency in the proximal renal pelvis (21.6±1.3 min−1) and in the distal renal pelvis and ureter (20.2±1.4 min−1) of the rat (at 30°C).

Indomethacin (1 μM for 60 min), decreased the motility index (amplitude×frequency) (MI) in all three regions of the guinea‐pig upper urinary tract, an effect which mainly arose from a decrease in the frequency of contractions. In the rat, indomethacin (1–30 μM for 60 min) significantly decreased the MI calculated in the proximal renal pelvis (30 μM indomethacin), and in the distal renal pelvis (10 μM indomethacin), arising from a significant decrease in the amplitude of contractions.

The COX‐1 inhibitor, valeryl salicylate (VSA) (5–100 μM for 60 min), had no effect on either the amplitude or frequency of contractions in the guinea‐pig upper urinary tract. In contrast, VSA increased the force of contractions in the proximal and distal renal pelvis of the rat, whilst having little effect on the frequency of contractions.

The COX‐2 inhibitor, NS‐398 (10–100 nM for 60 min) reduced the MI in the guinea‐pig upper urinary tract in a concentration‐dependent manner. The MIs calculated for the proximal renal pelvis, distal renal pelvis and ureter, were decreased by 72, 64 and 72% respectively, in 100 nM NS‐398. NS‐398 (10–100 nM) had no effect on any of the three parameters measured in either the proximal or distal renal pelvis of the rat.

These data suggest that endogenously‐released prostaglandins (PGs) maintain the myogenic contractility of the upper urinary tract in both the guinea‐pig and rat. Moreover COX‐2 is the primary enzyme involved in synthesizing PGs in the guinea‐pig upper urinary tract, while COX‐1 appears to be the predominantly active enzyme in the rat.

British Journal of Pharmacology (2000) 129, 661–670; doi:10.1038/sj.bjp.0703104
Clotrimazole inhibits the recombinant human cardiac L‐type Ca2+channel α1Csubunit
Authors: Fearon I M , Ball S G , Peers C
Published: January 2005

Clotrimazole (CLT) is an antimycotic agent with a potential role in the treatment of cancer. Whole‐cell patch clamp recordings and Fura‐2 AM fluorescence measurements were used to investigate the inhibition by CLT of recombinant human cardiac L‐type Ca2+channel α1Csubunits, stably expressed in human embryonic kidney (HEK 293) cells.

CLT (100 nmol l−1to 25 μmol l−1) reduced Ca2+channel currents in a concentration‐dependent manner. Inhibition was neither use‐ or voltage‐dependent. The effects of CLT were rapid and maximal effects were attained within 3 min. Application of CLT also caused an acceleration of apparent Ca2+channel current inactivation.

Basal current density and the degree of inhibition due to CLT were not significantly altered by pretreating cells with 3 mmol l−11‐aminobenzotriazole for 1 h, or by dialysing cells for 10 min with 2 mmol l−1α‐napthoflavoneviathe patch pipette, suggesting that the inhibitory action of CLT was not due to inhibition of cytochromeP‐450.

CLT (10 μmol l−1) did not influence [Ca2+]i, as determined by Fura‐2 AM fluorescence measurements.

Dialysing cells for 10 min with the non‐specific serine/threonine kinase inhibitor H‐7 (10 μmol l−1) was without effect on basal current density or on the inhibitory response to 10 μmol l−1CLT, indicating that CLT is not actingviaan indirect effect on these kinases.

These data suggest that CLT exerts a direct blocking effect on the α1Csubunit at therapeutic concentrations. This effect may explain the abbreviation of the action potential duration by CLT observed in cardiac myocytes.

British Journal of Pharmacology(2000)129, 547–554; doi:10.1038/sj.bjp.0703106
Apamin‐sensitive, non‐nitric oxide (NO) endothelium‐dependent relaxations to bradykinin in the bovine isolated coronary artery: no role for cytochrome P450 and K+
Authors: Drummond Grant R , Selemidis Stavros , Cocks Thomas M
Published: January 2005

Since cytochrome P450‐derived metabolites of arachidonic acid and K+ have been implicated in endothelium‐derived hyperpolarizing factor (EDHF)‐dependent responses, the aim of this study was to determine whether such factors contribute to non‐nitric oxide (NO), endothelium‐dependent relaxation to bradykinin (BK) in bovine isolated coronary artery.

In rings of artery contracted with U46619 and treated with indomethacin (3 μM) and NG‐nitro‐L‐arginine (L‐NOARG; 100 μM), relaxation to BK (0.01 nM‐0.3 μM) was blocked by ∼60% after inhibition of K+ channels with either high extracellular K+ (high [K+]o; 15–67 mM) or apamin (0.3 μM).

Ouabain (1 μM), an inhibitor of Na+/K+‐ATPase, decreased the sensitivity to BK without affecting the maximum response. In L‐NOARG‐treated rings, ouabain had no further effect on the relaxation to BK. An inhibitor of inward‐rectifying K+ channels, Ba2+ (30 μM), had no effect on relaxations to BK in the absence or presence of either L‐NOARG or ouabain.

KCl (2.5–10 mM) elicited small relaxations (∼20%) that were abolished by nifedipine (0.3 μM) and ouabain.

Both the high [K+]o/apamin‐sensitive relaxation to BK, and the relaxation to the KATP channel‐opener, levcromakalim (0.6 μM), were unaffected by the cytochrome P450 inhibitor, 7‐ethoxyresorufin (10 μM), or by co‐treatment with a phospholipase A2 inhibitor, arachidonyl trifluoromethyl ketone (AACOCF3; 3 μM) and a diacylglycerol (DAG)‐lipase inhibitor, 1,6‐bis‐(cyclohexyloximinocarbonylamino)‐hexane (RHC 80267; 30 μM). The non‐NO/high [K+]o‐insensitive, ∼40% relaxation to BK was, however, abolished by these treatments.

Therefore, neither cytochrome P450‐derived metabolites of arachidonic acid nor K+ appear to mediate the EDHF‐like relaxation to BK (i.e the non‐NO, high [K+]o/apamin‐sensitive component) in bovine coronary arteries. Cytochrome P450‐derived metabolites may be released at higher BK concentrations to act in parallel with NO and the high [K+]o/apamin‐sensitive mechanism.

British Journal of Pharmacology (2000) 129, 811–819; doi:10.1038/sj.bjp.0703107
The effects of Z13752A, a combined ACE/NEP inhibitor, on responses to coronary artery occlusion; a primary protective role for bradykinin
Authors: Rastegar Mohamed Ali , Marchini Francesco , Morazzoni Gabrielle , Végh Agnes , Papp Julius Gy , Parratt James R
Published: January 2005

The effects on the responses to coronary artery occlusion of a combined ACE/NEP inhibitor (Z13752A) were examined in anaesthetized dogs.

A 1 h infusion of Z13752A (128 μg kg−1 min−1 intravenously) decreased arterial blood pressure (by 11±3%; P<0.05) and increased coronary blood flow (by 12±4%, P<0.05). There were no other significant haemodynamic changes.

Z13752A inhibited both NEP and ACE enzymes both in dog plasma and in tissue (lung ACE; kidney NEP). Pressor responses to angiotensin I in vivo were inhibited and systemic vasodilator responses to bradykinin were potentiated.

When the left anterior descending coronary artery was occluded for 25 min, Z13752A markedly reduced the severity of the resultant ventricular arrhythmias. No ventricular fibrillation (VF) occurred (compared to 7/16 in the controls; P<0.05), and ventricular tachycardia (VT) was reduced (VT in 2/9 dogs treated with Z13752A cp. 16/16 of controls; episodes of VT 0.2±0.1 c.p. 10.7±3.3; P<0.05).

Reperfusion of the ischaemic myocardium led to VF in all control dogs but occurred less frequently in dogs given Z13752A (survival from the combined ischaemia‐reperfusion insult 67% c.p. 0% in controls; P<0.05).

Z13752A reduced two other indices of ischaemia severity; epicardial ST‐segment elevation and inhomogeneity of electrical activation.

These protective effects of Z13752A during ischaemia and reperfusion were abolished by the administration of icatibant (0.3 mg kg−1, i.v.) a selective antagonist of bradykinin at B2 receptors; the ischaemic changes in dogs given both icatibant and Z13752A were similar to those in the controls.

We conclude that this ACE/NEP inhibitor is effective at reducing the consequences of coronary artery occlusion in this canine model and that this protection is primarily due to potentiation of released bradykinin.

British Journal of Pharmacology (2000) 129, 671–680; doi:10.1038/sj.bjp.0703109
Hamster pancreatic beta cell lines with altered sensitivity towards apoptotic signalling by phosphatase inhibitors
Authors: Krautheim Andrea , Brechlin Peter , Becker Klaus , Winkler Monika , Steinfelder Hans Jürgen
Published: January 2005

Specific inhibitors of serine/threonine phosphatases like okadaic acid can induce apoptotic cell death in the pancreatic beta cell line HIT. Cultivation in stepwise increased concentrations of okadaic acid enabled the isolation of HIT100R cells which proliferate at 100 nMokadaic acid (8–10 times the initially lethal concentration).

These two cell lines were used to characterize the events triggered by okadaic acid that led to apoptosis. Biochemical markers, e.g. cytochrome c release from mitochondria and increase of caspase‐3‐like activity, revealed that induction of apoptosis by 100 nMokadaic acid in parental HIT cells started with the release of cytochrome c. In HIT100R cells 500 nMokadaic acid were necessary to induce alterations comparable to those observed with 100 nMokadaic acid in non‐resistant HIT cells.

In contrast to okadaic acid, the potency of the structurally different phosphatase inhibitor cantharidic acid to induce cytochrome c release, increase of caspase‐3‐like activity and DNA fragmentation was comparable in HIT and HIT100R cells. Thus, no cross‐resistance between these phosphatase inhibitors seemed to exist.

Phosphatase activity in extracts from HIT and HIT100R cells did not differ in its total amount or in its sensitivity for okadaic acid.

Since higher concentrations of okadaic acid were needed to induce apoptosis in HIT100R cells, a compromised intracellular accumulation of the toxin appeared likely. Functional and structural analysis revealed that this was achieved by the development of the multidrug resistance phenotype in HIT100R cells. The underlying mechanism appeared to be the enhanced expression of thepgp1but not thepgp2gene.

British Journal of Pharmacology(2000)129, 687–694; doi:10.1038/sj.bjp.0703113
In vivo venodilator action of fenoldopam, a dopamine D1‐receptor agonist
Authors: Ng Sylvia S W , Pang Catherine C Y
Published: January 2005

The effects of the dopamine D1‐receptor agonist fenoldopam were compared with those of the D2‐receptor agonist R(−)‐propylnorapomorphine and vehicle on mean arterial pressure (MAP), mean circulatory filling pressure (MCFP, the driving force of venous return), arterial resistance (Ra), venous resistance (Rv), heart rate (HR) and cardiac output (CO) in groups of thiobutabarbitone‐anaesthetized rats pre‐treated with i.v. injection of mecamylamine (3.7 μmol kg−1) and continuously infused with noradrenaline (6.8 nmol kg−1 min−1).

The vehicle did not alter any haemodynamic variables. All doses of fenoldopam (0.5, 2 and 16 μg kg−1 min−1) reduced MAP, Ra and Rv, and increased CO. At the highest dose, fenoldopam also increased HR and reduced MCFP.

All doses of R(−)‐propylnorapomorphine (0.5, 2 and 16 μg kg−1 min−1) increased MAP but did not significantly alter CO, Rv and MCFP. Both Ra and HR were increased by the highest dose of R(−)‐propylnorapomorphine.

Our results indicate that fenoldopam reduces MAP and MCFP, and markedly increases CO through reductions of arterial and venous resistances. The effects of fenoldopam in dilating arterial resistance and capacitance vessels were similar. In contrast, R(−)‐propylnorapomorphine elevates MAP through an increase in arterial resistance but has minimal effects on CO, MCFP and venous resistance. Both drugs have a small direct, positive chronotropic action at the highest dose.

British Journal of Pharmacology (2000) 129, 853–858; doi:10.1038/sj.bjp.0703119
Pressor response to pulsatile compression of the rostral ventrolateral medulla mediated by nitric oxide and c‐fos expression
Authors: Morimoto Satoshi , Sasaki Susumu , Miki Shigeyuki , Kawa Tetsuyoshi , Itoh Hiroshi , Nakata Tetsuo , Takeda Kazuo , Nakagawa Masao
Published: January 2005

It has been reported that neurovascular compression of the rostral ventrolateral medulla might be causally related to essential hypertension. Recently, we found that pulsatile compression of the rostral ventrolateral medulla increases sympathetic nerve activity and elevates arterial pressure via activation of glutamate receptors in rats. We also found that increases in sympathetic and cardiovascular activities by microinjection of L‐glutamate into the rostral ventrolateral medulla are mediated by c‐fos expression‐related substance(s) following activation of the nitric oxide‐cyclic GMP pathway.

Herein, we investigated whether responses to pulsatile compression are mediated by local activation of the nitric oxide‐cyclic GMP pathway and/or c‐fos expression‐related substance(s) in rats.

Increases in arterial pressure (15±1 mmHg), heart rate (9±1 b.p.m.), and sympathetic nerve activity (% change: 8.5±1.1%) induced by pulsatile compression were partially but significantly inhibited after local microinjection of a nitric oxide synthase inhibitor, L‐NG‐nitroarginine methyl ester (8±2 mmHg, 1±1 b.p.m., 4.0±1.3%; P<0.05 vs compression without pretreatment) or 7‐nitroindazole (7±2 mmHg, 2±1 b.p.m., 4.0±1.5%; P<0.05), or a soluble guanylate cyclase inhibitor, methylene blue (9±1 mmHg, 4±1 b.p.m., 4.1±1.4%; P<0.05). In addition, increases in arterial pressure, heart rate, and sympathetic nerve activity by pulsatile compression were significantly reduced 6 h after microinjection of antisense oligodeoxynucleotide to c‐fos mRNA (2±2 mmHg, 2±1 b.p.m., 1.0±1.0%; P<0.05 vs sense oligodeoxynucleotide).

These results suggest that increases in sympathetic and cardiovascular activities induced by pulsatile compression of the rostral ventrolateral medulla are mediated, at least in part, by local activation of the nitric oxide‐cyclic GMP pathway and c‐fos expression‐related substance(s) in rats.

British Journal of Pharmacology (2000) 129, 859–864; doi:10.1038/sj.bjp.0703121
Dexamethasone attenuates the depressor response induced by neuropeptide Y microinjected into the nucleus tractus solitarius in rats
Authors: Ouyang Ming , Wang Shao
Published: January 2005

An investigation was made of the effect of dexamethasone (Dex) injection into the nucleus tractus solitarius (NTS) on the cardiovascular response to neuropeptide Y in rats.

Dex (39 pmol) injected into the NTS inhibited the hypotension and bradycardia caused by NPY (5 pmol) with a short latency (10 min) and a long duration of action (up to 4 h).

The rapid inhibition by Dex (39 pmol) of the cardiovascular response to NPY was not blocked by pretreatment with the glucocorticoid receptor blocker, RU38486 (47 or 117 pmol respectively), but was reversed by bicuculline (30 pmol).

Microiontophoresis of NPY (0.01 mM, pH 6.5) into the NTS increased the spontaneous firing of the majority (68.4%) of baroreflex‐excited cells, but decreased the firing of most (73.7%) baroreflex‐inhibited cells. In contrast, Dex (0.02 M, pH 6.5) decreased the spontaneous firing of the majority of baroreflex‐excited cells (42.1% of normal response) and decreased the inhibition of baroreflex‐inhibited cells (47.5% of normal response). The responses of the majority of baroreceptive cells to NPY were blocked by iontophoretic administration of Dex.

Dex (200 μM) increased the delayed rectifier outward K+ current by 31.4±1.1% (n=5), whereas NPY alone, at a concentration of 1.5 μM, inhibited the current by 28.6±0.8% (n=5). In the presence of Dex (200 μM), addition of NPY (1.5 μM) had no effect on the current.

In conclusion, NTS‐administered‐Dex attenuated the cardiovascular response to NPY injected into the same area via a rapid membrane effect, which was mediated by an action on GABAA receptors and on the delayed rectifier outward K+ channel.

British Journal of Pharmacology (2000) 129, 865–870; doi:10.1038/sj.bjp.0703122