bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition of chemotaxis in A7r5 rat smooth muscle cells by a novel panel of inhibitors
Authors: Saxty B A , Yadollahi‐Farsani M , Kefalas P , Paul S , MacDermot J
Published: January 2005

Arginine‐specific ADP‐ribosyltransferase (ART) activity has been implicated in white cell chemotaxis. In this study, we examined the capacity of a panel of structurally unrelated inhibitors and pseudo‐substrates of ART to inhibit chemotaxis of A7r5 rat vascular smooth muscle cells in response to PDGF‐BB.

The IC50 values for nicotinamide (12 mM) and novobiocin (165 μM) were similar to those observed for inhibition of chemotaxis by human polymorphonuclear neutrophil leucocytes (PMN), whereas vitamins K3 (IC50=22 μM) and K1 (IC50=95 μM) were less potent than previously described in PMNs. The pseudo‐substrates for the enzyme (DEA‐BAG, agmatine and arginine‐methylester) also inhibited A7r5 chemotaxis, and in addition inhibited cell adhesion at similar concentrations. Vitamin K3 was unique among the inhibitors of ART, in that it also inhibited cell adhesion.

A rat ART1 transcript was amplified by rtPCR from rat skeletal muscle, and was noted to share 94% homology with the mouse ART1 cDNA sequence. No such transcript could be detected in A7r5 cells by Northern blot analysis or rtPCR.

Evidence for ART activity on the surface of A7r5 cells was investigated using 32P‐NAD+ as substrate, and labelled membrane proteins were observed with MWt values of 116, 100, 90 and 70 kDa. Exposure of the labelled proteins to phosphodiesterase yielded 32P‐AMP, and hydrolysis with NaOH yielded 32P‐NAD+. These results indicated that the labelled proteins were adducts with NAD+, and not the products of ART activity. The absence of ART catalytic activity in A7r5 cells was confirmed in protocols designed to show ADP‐ribosylation of agmatine.

We conclude that the chemotactic activity of A7r5 cells is independent of ART activity, and the mechanism whereby the novel panel of inhibitors reduced cell migration remains undefined.

British Journal of Pharmacology (1998) 125, 152–158; doi:10.1038/sj.bjp.0702027
Investigation on the mechanisms involved in the central protective effect of amylin on gastric ulcers in rats
Authors: Guidobono F , Pagani F , Ticozzi C , Sibilia V , Netti C
Published: January 2005

The mechanisms involved in the protective effect of amylin (administered into the brain ventricle, i.c.v.) on gastric ulcers induced by the oral administration of ethanol 50% (EtOH, 1 ml/rat) or indomethacin (indomethacin, 20 mg kg−1, at a dosing volume of 5 ml) were investigated in rats.

The possible involvement of endogenous nitric oxide (NO) in the beneficial effect of amylin against EtOH‐induced ulcers was examined. The inhibitor of NO‐synthesis, NG‐nitro‐L‐arginine methyl ester (L‐NAME, 70 mg kg−1, s.c.) was injected 30 min before amylin (2.2 μg/rat, i.c.v.) followed by EtOH after a further 30 min. Rats were sacrified 1 h after EtOH. L‐NAME completely removed the protective effect of amylin.

The interaction between amylin and gastric nonprotein sulfhydryl groups was studied. The rats were treated with N‐ethyl‐maleimide (NEM, 25 mg kg−1, s.c.) 30 min before amylin (2.2 μg/rat, i.c.v.) followed by EtOH 30 min after or by indomethacin 5 min after amylin. Rats were sacrified 1 h or 6 h respectively after EtOH or indomethacin. NEM counteracted the protective effect of amylin against EtOH‐induced ulcers but not against those provoked by indomethacin.

To determine whether amylin was able to promote ulcer healing, the peptide was injected 5 min after EtOH or 1 h after indomethacin. In the case of EtOH, the beneficial effect of amylin was lost whereas it was still effective on indomethacin‐induced ulcers.

The results indicate that: the mechanisms involved in the antiulcer effects of amylin are different in these two types of gastric lesions probably because of the different etiopathology of various types of ulcers. Endogenous NO and nonprotein sulfhydryl groups are involved in the mucosal protective effects of amylin on EtOH and not on indomethacin‐induced ulcers. Furthermore the effectiveness of amylin against indomethacin‐induced lesions when administered after the ulcerogenic process has started suggests that amylin is involved not only in the protection but also in the healing mechanisms in this type of ulcer.

British Journal of Pharmacology (1998) 125, 23–28; doi:10.1038/sj.bjp.0702029
Antithrombotic activity of a monoclonal antibody inducing the substrate form of plasminogen activator inhibitor type 1 in rat models of venous and arterial thrombosis
Authors: Berry C N , Lunven C , Lechaire I , Girardot C , O'Connor S E
Published: January 2005

Elevated plasminogen activator inhibitor 1 (PAI‐1) is a risk factor for thrombosis, and inhibitors of the interaction between PAI‐1 and tissue plasminogen activator (t‐PA) have antithrombotic and pro‐thrombolytic activity in animals. We describe the antithrombotic effects in the rat of a monoclonal antibody (MA33H1) which converts PAI‐1 to a non‐inhibitory substrate.

The activity of MA33H1 against rat PAI‐1 was confirmed using two‐chain t‐PA and a chromogenic substrate. MA33H1 was evaluated in rat venous (thromboplastin+stasis in the abdominal vena cava) and arterial (electric current applied to a carotid artery) thrombosis models. The effects on tail‐transection bleeding time were studied.

MA33H1 at 100 ng ml−1 inhibited both human (44.1%) and rat PAI‐1 (49.7%). This effect was concentration‐dependent. Its effect on human PAI‐1 was not significantly inhibited by 1 μg ml−1 fibrin or a ≈7 fold molar excess of vitronectin (1 nM). Inhibition of rat PAI‐1 was unchanged by fibrin, but vitronectin reduced inhibition from 0.5 nM.

In the venous thrombosis model, MA33H1 significantly reduced thrombus weights by 38 and 58.6% at 50 and 100 μg kg−1 min−1 i.v. respectively. This effect was inhibited by tranexamic acid. In the arterial model, MA33H1 significantly increased the delay to occlusive thrombus formation by 58 and 142% at 50 and 100 μg kg−1 min−1 i.v., and did not affect bleeding time at 300 μg kg−1 min−1 i.v.

Thus, a monoclonal antibody which transforms PAI‐1 to a t‐PA substrate prevents thrombus formation in the rat with no effect on bleeding time at a higher dose.

British Journal of Pharmacology (1998) 125, 29–34; doi:10.1038/sj.bjp.0702030
Structural determinants for binding to CGRP receptors expressed by human SK‐N‐MC and Col 29 cells: studies with chimeric and other peptides
Authors: Poyner David R , Soomets Ursel , Howitt Stephen G , Langel Ulo
Published: January 2005

Structure‐activity relationships for the binding of human α‐calcitonin gene‐related peptide 8–37 (hαCGRP8–37) have been investigated at the CGRP receptors expressed by human SK‐N‐MC (neuroblastoma) and Col 29 (colonic epithelia) cells by radioligand binding assays and functional assays (hαCGRP stimulation of adenylate cyclase).

On SK‐N‐MC cells the potency order was hαCGRP8–37>hαCGRP19–37=AC187>rat amylin8–37> hα[Tyr0]‐CGRP28–37 (apparent pKBs of 7.49±0.25, 5.89±0.20, 6.18±0.19, 5.85±0.19 and 5.25±0.07). The SK‐N‐MC receptor appeared CGRP1‐like.

On Col 29 cells, only hαCGRP8–37 of the above compounds was able to antagonize the actions of hαCGRP (apparent pKB=6.48±0.28). Its receptor appeared CGRP2‐like.

hα[Ala11,18]‐CGRP8–37, where the amphipathic nature of the N‐terminal α‐helix has been reduced, bound to SK‐N‐MC cells a 100 fold less strongly than hαCGRP8–37.

On SK‐N‐MC cells, hαCGRP8–18, 28–37 (M433) and mastoparan‐hαCGRP28–37 (M432) had apparent pKBs of 6.64±0.16 and 6.42±0.26, suggesting that residues 19–27 play a minor role in binding. The physico‐chemical properties of residues 8–18 may be more important than any specific side‐chain interactions.

M433 was almost as potent as hαCGRP8–37 on Col 29 cells (apparent pKB=6.17±0.20). Other antagonists were inactive.

British Journal of Pharmacology (1998) 124, 1659–1666; doi:10.1038/sj.bjp.0702032
A discriminant block among K+ channel types by phenytoin in neuroblastoma cells
Authors: Nobile M , Lagostena L
Published: January 2005

The action of the anticonvulsant drug phenytoin on K+ channels was investigated in neuroblastoma cells (N2A) by using the single‐channel patch‐clamp technique.

N2A cells expressed three types of delayed rectifier K+ channels, which were found to have a conductance of 10–20 pS in a `physiological' K+ gradient. When added to the external solution at concentrations ranging between 1 and 200 μM, phenytoin decreased single channel activity, whereas the unitary current amplitude was unaffected in all three types of channels.

The open probability of the biggest channel decreased, according to an exponential distribution of open and closed times, from 40% in control conditions to 10% in the presence of 50 μM phenytoin (Vm=40 mv). The reduction in the open‐channel probability was concentration‐dependent with a IC50=27.2±0.9 μM.

A transient type of K+ channel was identified that was affected by cumulative inactivation and had a conductance of a mean value equal to 26 pS. Finally, a voltage‐and Ca2+‐dependent K+ channel with a unitary conductance of 95 pS was recorded. Both the channel's amplitude and kinetics were unaffected by phenytoin.

These results confirm the phenytoin effect on K+ currents and suggest that the drug may be considered a selective blocker of delayed rectifier K+ channels.

British Journal of Pharmacology (1998) 124, 1698–1702; doi:10.1038/sj.bjp.0702035
Tumour necrosis factor‐α as a target of melanocortins in haemorrhagic shock, in the anaesthetized rat
Authors: Altavilla Domenica , Cainazzo Maria‐Michela , Squadrito Francesco , Guarini Salvatore , Bertolini Alfio , Bazzani Carla
Published: January 2005

The cytokine tumour necrosis factor‐α (TNF‐α) is involved (mostly through the activation of inducible nitric oxide synthase) in the pathogenesis of circulatory shock. On the other hand, melanocortin peptides are potent and effective in reversing haemorrhagic shock, both in animals (rat, dog) and in humans. This prompted us to study the influence of the melanocortin peptide ACTH‐(1–24) on the blood levels of TNF‐α in haemorrhage‐shocked rats and on the in vitro production of TNF‐α by lipopolysaccharide (LPS)‐activated macrophages. Plasma levels of TNF‐α were undetectable before starting bleeding and greatly increased 20 min after bleeding termination in saline‐treated rats. In rats treated with ACTH‐(1–24) the almost complete restoration of cardiovascular function was associated with markedly reduced levels of TNF‐α 20 min after bleeding termination. On the other hand, ACTH‐(1–24) did not influence TNF‐α plasma levels in sham‐operated, unbled rats. In vitro, ACTH‐(1–24) (25–100 nM) dose‐dependently reduced the LPS‐stimulated production of TNF‐α by peritoneal macrophages harvested from untreated, unbled rats. These results indicate that inhibition of TNF‐α overproduction may be an important component of the mechanism of action of melanocortins in reversing haemorrhagic shock.

British Journal of Pharmacology (1998) 124, 1587–1590; doi:10.1038/sj.bjp.0702038
Cytokine induction of NO synthase II in human DLD‐1 cells: roles of the JAK‐STAT, AP‐1 and NF‐κB‐signaling pathways
Authors: Kleinert Hartmut , Wallerath Thomas , Fritz Gerhard , Ihrig‐Biedert Irmgard , Rodriguez‐Pascual Fernando , Geller David A , Forstermann Ulrich
Published: January 2005

In human epithelial‐like DLD‐1 cells, nitric oxide synthase (NOS) II expression was induced by interferon‐γ (100 u ml−1) alone and, to a larger extent, by a cytokine mixture (CM) consisting of interferon‐γ, interleukin‐1β (50 u ml−1) and tumor necrosis factor‐α (10 ng ml−1).

CM‐induced NOS II expression was inhibited by tyrphostin B42 (mRNA down to 1%; nitrite production down to 0.5% at 300 μM) and tyrphostin A25 (mRNA down to 24%, nitrite production down to 1% at 200 μM), suggesting the involvement of janus kinase 2 (JAK‐2). Tyrphostin B42 also blocked the CM‐induced JAK‐2 phosphorylation (kinase assay) and reduced the CM‐stimulated STAT1α binding activity (gel shift analysis).

CM reduced the nuclear binding activity of transcription factor AP‐1. A heterogenous group of compounds, that stimulated the expression of c‐fos/c‐jun, enhanced the nuclear binding activity of AP‐1. This group includes the protein phosphatase inhibitors calyculin A, okadaic acid, and phenylarsine oxide, as well as the inhibitor of translation anisomycin. All of these compounds reduced CM‐induced NOS II mRNA expression (to 9% at 50 nM calyculin A; to 28% at 500 nM okadaic acid; to 18% at 10 μM phenylarsine oxide; and to 19% at 100 ng ml−1 anisomycin) without changing NOS II mRNA stability. In cotransfection experiments, overexpression of c‐Jun and c‐Fos reduced promoter activity of a 7 kb DNA fragment of the 5′‐flanking sequence of the human NOS II gene to 63%.

Nuclear extracts from resting DLD‐1 cells showed significant binding activity for transcription factor NF‐κB, which was only slightly enhanced by CM. The NF‐κB inhibitors dexamethasone (1 μM), 3,4‐dichloroisocoumarin (50 μM), panepoxydone (5 μg ml−1) and pyrrolidine dithiocarbamate (100 μM) produced no inhibition of CM‐induced NOS II induction.

We conclude that in human DLD‐1 cells, the interferon‐γ–JAK‐2‐STAT1α pathway is important for NOS II induction. AP‐1 (that is downregulated by CM) seems to be a negative regulator of NOS II expression. NF‐κB, which is probably important for basal activity of the human NOS II promoter, is unlikely to function as a major effector of CM in DLD‐1 cells.

British Journal of Pharmacology (1998) 125, 193–201; doi:10.1038/sj.bjp.0702039
The transport of the anti‐HIV drug, 2′,3′‐didehydro‐3′‐deoxythymidine (D4T), across the blood‐brain and blood‐cerebrospinal fluid barriers
Authors: Thomas Sarah A , Segal Malcolm B
Published: January 2005

The brain is a site of infection, viral replication and sanctuary for HIV‐1. The treatment of HIV‐1 infection therefore requires that an effective agent be delivered to the brain. 2′,3′‐Didehydro‐3′‐deoxythymidine (D4T) is a nucleoside analogue which has been shown to have beneficial clinical effects in the treatment of HIV infection. However, although D4T has been detected in human CSF, the ability of this drug to cross both the blood‐brain and blood‐cerebrospinal fluid (CSF) barriers and gain entrance into the brain tissue is not known.

This study examined the CNS entry of D4T by means of the bilateral vascular brain perfusion technique in the anaesthetized guinea‐pig.

The results indicated that [3H]‐D4T had a limited ability to cross the blood‐brain barrier (BBB), which was not significantly greater than D‐[14C]‐mannitol (a slowly penetrating marker molecule). Although D4T was found to cross the blood‐CSF barrier, the presence of D4T in the CSF did not reflect levels of the drug in the brain tissue.

These results can be related to the measured low lipophilicity of D4T, the higher paracellular permeability characteristics of the choroid plexus (blood‐CSF barrier) compared to the BBB, and the sink action nature of the CSF to the brain tissue.

In conclusion, these animal studies suggest that D4T may only penetrate the brain tissue to a limited extent and consideration should be given to these findings in the clinical situation.

British Journal of Pharmacology (1998) 125, 49–54; doi:10.1038/sj.bjp.0702044
Endothelin‐1 stimulates sodium‐dependent calcium efflux from bovine adrenal chromaffin cells in culture
Authors: Houchi Hitoshi , Yoshizumi Masanori , Tsuchiya Koichiro , Hirose Masao , Kitagawa Tetsuya , Kujime Toshihide , Shimizu Eiji , Niwa Yasuharu , Minakuchi Kazuo , Tamaki Toshiaki
Published: January 2005

The effect of endothelin (ET)‐1 on Ca2+ efflux from cultured bovine adrenal chromaffin cells was examined. ET‐1 (10−7 M) significantly increased intracellular free Ca2+ level ([Ca2+]i), 45Ca2+ uptake and catecholamine secretion in the cells. 2. ET‐1 stimulated the efflux of 45Ca2+ from the cells preloaded with 45Ca2+ in a concentration‐dependent manner (10−9–10−7 M). This stimulatory effect was inhibited by ETB receptor antagonist BQ788, but not by ETA receptor antagonist BQ123. Selective ETB receptor agonists Suc‐[Glu9, Ala11,15]‐ET‐1 and sarafotoxin S6c (SRTX) also stimulated 45Ca2+ efflux from the cells.

ET‐1, Suc‐[Glu9, Ala11,15]‐ET‐1 and SRTX increased the level of cyclic GMP in the adrenal chromaffin cells. ET‐1 induced an increase in the nitric oxide (NO) level in the cells. The stimulatory effects by which ET‐1 increases NO level and 45Ca2+ efflux were inhibited by NG‐monomethyl‐L‐arginine acetate (L‐NMMA), a competitive inhibitor of NO synthase.

The 45Ca2+ efflux stimulated by ET‐1 was inhibited by deprivation of extracellular Na+, but not by deprivation of Ca2+.

These results suggest that ET‐1 stimulates an extracellular Na+‐dependent Ca2+ efflux through the activation of NO synthase in cultured bovine adrenal chromaffin cells.

British Journal of Pharmacology (1998) 125, 55–60; doi:10.1038/sj.bjp.0702047
Involvement of barium‐sensitive K+ channels in endothelium‐dependent vasodilation produced by hypercapnia in rat mesenteric vascular beds
Authors: Okazaki Kaoru , Endou Masayuki , Okumura Fukuichiro
Published: January 2005

We examined the vasodilatory effect of hypercapnia in the rat isolated mesenteric vascular bed. The preparation was perfused constantly (5 ml min−1 with oxygenated Krebs‐Ringer solution, and the perfusion pressure was measured. In order to keep the extracellular pH (pHe) constant (around 7.35) against a change in CO2, adequate amounts of NaHCO3 were added to Krebs‐Ringer solution.

In the endothelium intact preparations, an increase in CO2 from 2.5% to 10% in increments of 2.5% decreased the 10 μM phenylephrine (PE)‐produced increase in the perfusion pressure in a concentration‐dependent manner. Denudation of the endothelium by CHAPS (3‐[(3‐cholamidopropyl)‐dimethylammonio]‐l‐propanesulphonate) (5 mg l−1, 90 s perfusion) abolished the vasodilatory effect of hypercapnia.

An increase in CO2 from 5% to 10% reduced the increases in the perfusion pressure produced by 10 μM PE and 400 nM U‐46619 by 48% and 44%, respectively. NG‐monomethyl‐L‐arginine (100 μM) and indomethacin (10 μM) did not affect the vasodilatory effect of hypercapnia, whereas the vasodilatory response of the preparation to hypercapnia disappeared when the preparation was contracted by 60 mM K+ instead of PE or U‐46619.

The vasodilatory effect of hypercapnia observed in the PE‐ or U‐46619‐precontracted preparation was affected by neither tetraethylammonium (1 mM), apamin (500 μM), glibenclamide (10 μM), nor 4‐aminopyridine (1.5 mM). On the other hand, pretreatment with Ba2+ at a concentration of 0.3 mM abolished the hypercapnia‐produced vasodilation.

An increase in the concentration of K+ in Krebs‐Ringer solution from 4.5 mM to 12.5 mM in increments of 2 mM reduced the PE‐produced increase in the perfusion pressure in a concentration‐dependent manner. Pretreatment of the preparations with not only Ba2+ (0.3 mM) but also CHAPS abolished the vasodilatory effect of K+.

The results suggest that an increase in CO2 produces vasodilation by an endothelium‐dependent mechanism in the rat mesenteric vascular bed. The membrane hyperpolarization of the endothelial cell by an activation of the inward rectifier K+ channel seems to be the mechanism underlying the hypercapnia‐produced vasodilation. Neither nitric oxide nor prostaglandins are involved in this response.

British Journal of Pharmacology (1998) 125, 168–174; doi:10.1038/sj.bjp.0702048
Enhancement of glycine receptor function by ethanol: role of phosphorylation
Authors: Paola Mascia Maria , Wick Marilee J , Martinez Larry D , Harris R Adron
Published: January 2005

The effects of several kinase inhibitors (staurosporine, GF 109203X, H89, KN62, genistein) and of the phosphatase inhibitor calyculin A were studied on the ethanol potentiation and on the function of homomeric α1 glycine receptor expressed in Xenopus oocytes using a two electrode voltage clamp recording technique.

The function of the homomeric α1 glycine receptor was not modified in Xenopus oocytes pretreated with kinase inhibitors or with the phosphatase inhibitor calyculin A.

The potentiation of the glycine receptor function induced by ethanol (10–200 mM) was significantly reduced in Xenopus oocytes pretreated with the PKC inhibitors staurosporine or GF 109203X.

No differences in propofol (2.5 μM) or halothane (250 μM) actions were found after exposure of Xenopus oocytes to staurosporine.

No differences in ethanol sensitivity were found after exposure of Xenopus oocytes expressing glycine α1 receptors to H89, KN62, genistein or to the phosphatase inhibitor calyculin A.

The mutant α1 (S391A), in which the PKC phosphorylation site at serine 391 was mutated to alanine, was less sensitive to the effects of ethanol than was the α1 wild type receptor. Moreover, the ethanol potentiation of the glycine receptor function was not affected by treatment with staurosporine in oocytes expressing α1 (S391A).

The splice variant of the α1 glycine receptor subunit, α1ins, containing eight additional amino acids and a potential phosphorylation site for PKA, did not differ from wild type for sensitivity to ethanol.

These results indicate that phosphorylation by PKC of the homomeric α1 glycine receptor subunit modulates ethanol potentiation, but not the function of the glycine receptor.

British Journal of Pharmacology (1998) 125, 263–270; doi:10.1038/sj.bjp.0702054
5‐Hydroxytryptamine receptors mediating vasoconstriction and vasodilation in perinatal and adult rabbit small pulmonary arteries
Authors: Morecroft Ian , MacLean Margaret R
Published: January 2005

Vasoconstrictor responses to 5‐HT, 5‐carboxamidotryptamine (5‐CT, 5‐HT1 receptor agonist), α‐methyl‐5‐HT (5‐HT2 receptor agonist) and sumatriptan (5‐HT1D/1B receptor agonist) were studied in fetal, 0–24 h, 4 day, 7 day and adult rabbit pulmonary resistance arteries (PRAs), alone and in the presence of the NO synthase inhibitor Nω‐nitro‐L‐arginine methylester (L‐NAME). The effect of the selective 5‐HT receptor antagonists ketanserin (5‐HT2A receptor) and GR55562 (5‐HT1B/1D receptor) on vasoconstrictor responses to 5‐HT were studied in the presence of L‐NAME. Vasodilator responses to 5‐CT were also studied in pre‐contracted PRAs.

5‐HT and α‐methyl‐5‐HT were equipotent in causing contraction in the PRAs at each age (e.g. pEC50s for 5‐HT and α‐methyl‐5‐HT were 6.74±0.13 and 6.63±0.22 respectively in adult vessels). In the perinatal PRAs, sumatriptan and 5‐CT produced negligible contractions, but in adult PRAs, 5‐CT and sumatriptan were potent agonists with pEC50s of 6.05±0.3 and 5.70±0.20 respectively.

L‐NAME markedly increased the maximum response to 5‐HT in the 0–24 h, 4 day and 7 day vessels and increased 5‐HT potency in the 4‐, 7‐day‐old and adult rabbit vessels.

In perinatal vessels, responses to 5‐HT, with L‐NAME present, were antagonized by ketanserin (30 nM and 0.1 μM) but not GR55562 (1 μM). A small ketanserin‐resistant, GR55562‐sensitive component was observed at 0–24 h. In adult vessels, both ketanserin and GR55562 inhibited 5‐HT‐induced responses.

Vasodilator responses to 5‐CT were observed in pre‐contracted PRAs from 4‐ and 7‐day‐old rabbits but not in the fetus, 0–24 h old or adult rabbit vessels. At 4 days the vasodilator response was inhibited both by L‐NAME and GR55562. At 7 days the response was only partly blocked by L‐NAME and resistant to GR55562. The L‐NAME resistant component was antagonized by the 5‐HT7 receptor antagonist spiperone (1 μM).

The results suggest that 5‐HT2A‐receptors mediate vasoconstriction in perinatal vessels whilst the 5‐HT1D or 5‐HT1B receptor contributes in adult rabbit vessels. The 5‐HT1D or 5‐HT1B receptor mediates NO‐dependent vasodilation in vessels from rabbits at 4 days of age whilst 5‐HT7 receptors mediate NO‐independent vasodilation by 7 days.

British Journal of Pharmacology (1998) 125, 69–78; doi:10.1038/sj.bjp.0702055
Prostanoid receptors of the EP3 subtype mediate inhibition of evoked [3H]acetylcholine release from isolated human bronchi
Authors: Reinheimer Torsten , Harnack Eva , Racke Kurt , Wessler Ignaz
Published: January 2005

The release of neuronal [3H]acetylcholine (ACh) from isolated human bronchi after labelling with [3H]choline was measured to investigate the effects of prostanoids.

A first period of electrical field stimulation (S1) caused a [3H]ACh release of 320±70 and 200±40 Becquerel (Bq) g−1 in epithelium‐denuded and epithelium‐containing bronchi respectively (P>0.05). Subsequent periods of electrical stimulation (Sn, n=2, 3, and 4) released less [3H]ACh, i.e. decreasing Sn/S1 values were obtained (0.76±0.09, 0.68±0.07 and 0.40±0.04, respectively).

Cumulative concentrations (1–1000 nM) of EP‐receptor agonists like prostaglandin E2, nocloprost, and sulprostone (EP1 and EP3 selective) inhibited evoked [3H]ACh release in a concentration dependent manner with IC50 values between 4–14 nM and maximal inhibition of about 70%.

The inhibition of evoked [3H]ACh release by prostaglandin E2, nocloprost and sulprostone was not affected by the DP‐, EP1‐ and EP2‐receptor antagonist AH6809 at a concentration of 3 μM, i.e. a 3–30 times greater concentration than its affinity (pA2 values) at the respective receptors.

Circaprost (IP‐receptor agonist; 1–100 nM), iloprost (IP‐ and EP1‐receptor agonist; 10‐1000 nM) and U‐46619 (TP‐receptor agonist; 100–1000 nM) did not significantly affect [3H]ACh release.

Blockade of cyclooxygenase by 3 μM indomethacin did not significantly modulate evoked [3H]ACh release in epithelium‐containing and epithelium‐denuded bronchi. Likewise, the combined cyclo‐ and lipoxygenase inhibitor BW‐755C (20 μM) did not affect evoked [3H]ACh release.

In conclusion, applied prostanoids appear to inhibit [3H]ACh release in epithelium‐denuded human bronchi under the present in vitro conditions, most likely via prejunctional prostanoid receptors of the EP3 subtype.

British Journal of Pharmacology (1998) 125, 271–276; doi:10.1038/sj.bjp.0702057
Augmented myocardial ischaemia by nicotine – Mechanisms and their possible significance
Authors: Schrör Karsten , Zimmermann Katja C , Tannhäuser Roman
Published: January 2005

To study the effect of nicotine on the severity of experimental myocardial ischaemia, Langendorff hearts of rabbits (n=7–12 per group) were subjected to 2 h of low‐flow ischaemia followed by 1 h of reperfusion.

Infusion of nicotine (100 ng ml−1) caused only minor changes in non‐ischaemic conditions but a significant (P<0.05) increase in end‐diastolic pressure (LVEDP), loss of creatine kinase (CK) and troponin (TnT) as well as increase in noradrenaline (NA) overflow in reperfused ischaemic hearts.

RT–PCR was done on total RNA for mRNA expression of the constitutive (COX‐1) and inducible cyclooxygenase (COX‐2). There was no COX‐2 in non‐ischaemic hearts but a significant expression in ischaemia (n=5) which was further increased by nicotine. These data were confirmed at the protein level by Western blotting and additionally shown that COX‐1 remained unchanged.

There was a marked increase in prostacyclin (PGI2) and a 2 fold increase in NA overflow which were both stimulated by nicotine.

The aggravating effects of nicotine on myocardial ischaemia (CK release) as well as the expression of COX‐2 mRNA were prevented by pretreatment with the β‐blocker pindolol (1 μM).

The data demonstrate marked deleterious actions of nicotine in reperfused ischaemic hearts. These actions are probably related to the increase in catecholamine overflow, are β‐receptor‐mediated and involve enhanced gene expression of COX‐2.

British Journal of Pharmacology (1998) 125, 79–86; doi:10.1038/sj.bjp.0702061
Glycine induces a novel form of long‐term potentiation in the superficial layers of the superior colliculus
Authors: Platt Bettina , Bate Joanne R , von Linstow Roloff Eva , Withington Deborah J
Published: January 2005

The mammalian superior colliculus (SC) is a midbrain nucleus containing space maps of different sensory modalities which show various forms of age‐ and activity‐dependent plasticity in vivo and in vitro. In the present study, we aimed to characterize the role of glycine (Gly) receptors in the SC, and we observed that application of glycine (Gly; 500 μM and 3 mM) for 7 min to SC slices of adult guinea‐pigs caused a novel form of long‐term potentiation (termed LTPgly) of evoked excitatory postsynaptic potentials recorded in the superficial layers.

The strength of potentiation was found to be concentration‐dependent and partially independent from synaptic stimulation.

LTPgly did not involve NMDA receptor activation as proven by the lack of inhibition by 100 μM D,L‐2‐amino‐5‐phosphonovaleric acid (APV) and 10 μM MK‐801.

LTPgly could only be masked but not prevented by strychnine (100 μM) and remained undisturbed in the presence of picrotoxin (100 μM).

Inhibition of carbonic anhydrase by acetazolamide (20 μM) had no effect on LTPgly suggesting that the excitatory action of Gly is not due to a differential breakdown of the Cl−/HCO3− gradients.

As indicated by the inhibition of LTPgly of the fEPSP slope by the L‐type calcium channel blocker nifedipine (20 μM), voltage‐dependent calcium channels are the source for Ca2+ elevation as the intracellular trigger.

Our data provide the first evidence for a role of Gly in SC synaptic transmission. They illustrate a so far unknown action of Gly which can lead to long‐lasting changes of synaptic efficacy and which is not mediated via NMDA‐related or strychnine‐sensitive binding sites.

British Journal of Pharmacology (1998) 125, 293–300; doi:10.1038/sj.bjp.0702062
Catecholamine transport by the organic cation transporter type 1 (OCT1)
Authors: Breidert Tilo , Spitzenberger Folker , Gründemann Dirk , Schömig Edgar
Published: January 2005

Liver and kidney extract adrenaline and noradrenaline from the circulation by a mechanism which does not seem to be one of the classical catecholamine transporters. The hypothesis that OCT1 is involved–the organic cation transporter type 1 which exists in rat kidney and liver–was tested.

Based on human embryonic kidney cells (293), we constructed a cell line which stably expresses OCT1r (293OCT1r cells). Transfection with OCT1 resulted in a transport activity not only for prototypical known substrates of OCT1 such as 3H‐1‐methyl‐4‐phenylpyridinium and 14C‐tetraethylammonium but also for the catecholamines 3H‐adrenaline, 3H‐noradrenaline (3H‐NA) and 3H‐dopamine (3H‐DA), the indoleamine 3H‐5‐hydroxytryptamine (3H‐5HT) as well as the indirect sympathomimetic 14C‐tyramine.

For 3H‐DA, 3H‐5HT and 3H‐NA, at non‐saturating concentrations, the rate constants for inwardly directed substrate flux (kin) were 6.9±0.8, 3.1±0.2, and 1.2±0.1 μl min−1 mg protein−1. In wild type cells (293WT) the corresponding kin's were considerably lower, being 0.94±0.40, 0.47±0.08 and 0.23±0.05 μl min−1 mg protein−1 (n=12). The indirectly determined half‐saturating concentrations of DA, 5HT, and NA were 1.1 (95% c.i.: 0.8, 1.4), 0.65 (0.49, 0.86), and 2.8 (2.1, 3.7) mmol l−1 (n=3).

Specific 3H‐DA uptake in 293OCT1r cells was resistant to cocaine (1 μmol l−1), 3H‐5HT uptake was resistant to citalopram (300 nmol l−1) and 3H‐NA uptake was resistant to desipramine (100 nmoll−1), corticosterone (1 μmol l−1), and reserpine (10 nmol l−1) which rules out the involvement of classical transporters for biogenic amines.

The findings demonstrate that OCT1 efficiently transports catecholamines and other biogenic amines and support the hypothesis that OCT1 is responsible for hepatic and renal inactivation of circulating catecholamines.

British Journal of Pharmacology (1998) 125, 218–224; doi:10.1038/sj.bjp.0702065
Actions of novel antidiabetic thiazolidinedione, T‐174, in animal models of non‐insulin‐dependent diabetes mellitus (NIDDM) and in cultured muscle cells
Authors: Arakawa Kenji , Ishihara Tomomi , Aoto Masamichi , Inamasu Masanori , Saito Akira , Ikezawa Katsuo
Published: January 2005

The antihyperglycaemic effect and the possible mechanism of action of T‐174, a novel thiazolidinedione derivative, was determined in vivo and in vitro.

Oral administration of T‐174 markedly improved hyperglycaemia, hyperinsulinaemia, hyperlipidaemia, and glucose intolerance in genetically obese and diabetic yellow KK (KK‐Ay) mice (0.2–15.5 mg kg−1 day−1, for 7 days) and Zucker fatty rats (1.4–11.4 mg kg−1 day−1, for 6 days). The ED50 values for the glucose lowering action of T‐174 and pioglitazone, another thiazolidinedione antidiabetic, were 1.8 and 29 mg kg−1 day−1, respectively in KK‐Ay mice; T‐174 was about 16 times more potent than pioglitazone.

The hypoglycaemic effect of exogenous insulin in KK‐Ay mice was enhanced after the administration of T‐174. A hyperinsulinaemic euglycaemic clamp study in Zucker fatty rats showed an amelioration of whole‐body insulin resistance by the T‐174 treatment.

Insulin‐stimulated glucose metabolism was enhanced in adipocytes from KK‐Ay mice treated with T‐174. The insulin receptor number of the adipocytes was increased without a change in the affinity of the receptor.

The hypomagnesaemia in KK‐Ay mice was completely restored by T‐174.

In cultured L6 myotubes, glucose consumption and [3H]‐2‐deoxy‐glucose transport were enhanced by T‐174 (EC50; 6 and 4 μM, respectively). Combination of insulin with T‐174 was additive to stimulate glucose disposal.

These results suggest that the antihyperglycaemic effect of T‐174 was mediated by enhanced insulin action. This was associated with amelioration of the hypomagnesaemia and T‐174 directly increased basal and insulin‐stimulated glucose utilization by cultured muscle cells.

British Journal of Pharmacology (1998) 125, 429–436; doi:10.1038/sj.bjp.0702066
Nociceptin inhibits non‐adrenergic non‐cholinergic contraction in guinea‐pig airway
Authors: Shah S , Page C P , Spina D
Published: January 2005

Electrical field stimulation (EFS) of guinea‐pig isolated main bronchi induced a non‐adrenergic non‐cholinergic (NANC) contractile response. Nociceptin (0.01–1 μM) significantly inhibited the contractile response to EFS (P<0.01), but not to capsaicin (P>0.05).

The μ‐, δ‐ and κ‐opioid receptor antagonists, naloxone (0.3 μM), naltrindole (3 μM) and nor‐binaltorphimine (1 μM), respectively, did not significantly affect the inhibitory effect of nociceptin (0.03 μM; P>0.05).

The novel nociceptin antagonist, [Phe1ψ(CH2‐NH)Gly2]nociceptin(1–13)NH2 (0.03–1 μM); the σ ligands, carbetapentane (30 μM), 3‐phenylpiperidine (30–100 μM) and (+)‐cyclazocine (10–100 μM) significantly reversed the inhibitory effect of nociceptin (0.03 μM, P<0.05). In contrast, rimcazole, did not significantly reverse the inhibitory effect of nociceptin (0.03 μM) at any concentration tested (P>0.05).

EFS of guinea‐pig bronchial preparations significantly increased SP‐LI release above basal SP‐LI (P<0.05). In the presence of nociceptin (1 μM), EFS induced a significant increase in SP‐LI release above basal SP‐LI release (P<0.05). Nociceptin caused a 59±11% (n=5) inhibition of EFS‐induced release of SP‐LI.

Nociceptin reduces the release of sensory neuropeptides induced by EFS, but not capsaicin, from guinea‐pig airways. These experiments provide further evidence for a role for nociceptin in regulating the release of sensory neuropeptides in response to EFS.

British Journal of Pharmacology (1998) 125, 510–516; doi:10.1038/sj.bjp.0702068
Investigation of the functional role played by the chemokine monocyte chemoattractant protein‐1 in interleukin‐1‐induced murine peritonitis
Authors: Ajuebor Maureen N , Gibbs Linda , Flower Roderick J , Das Anuk M , Perretti Mauro
Published: January 2005

Intraperitoneal (i.p.) injection of murine recombinant IL‐1β (mrIL‐1β) produced a dose‐dependent (0.5–50 ng) and time‐related (0.5–2 h) secretion of murine monocyte chemoattractant protein‐1 (mMCP‐1; 3–4 ng per cavity) in the lavage fluids. MCP‐1 mRNA could also be detected in the cell pellets by reverse transcriptase‐polymerase chain reaction (RT‐PCR).

MCP‐1 levels were reduced by more than 90% by co‐administration of IL‐1 receptor antagonist (10 μg) (n=6, P<0.05). In contrast, an IL‐1 mutant with low affinity for IL‐1 receptor type I, termed yIL‐1βΔ4 (50 ng), produced only a modest release of the chemokine. Treatment of mice with dexamethasone (DEX) (∼1 mg kg−1 s.c.) reduced mrIL‐1β‐induced mMCP‐1 gene expression (apparent total inhibition) and protein release in the lavage fluids (∼40% reduction; n=10; P<0.05). Drastic reductions in the numbers of residential macrophages or mast cells did not modify the levels of mMCP‐1 recovered in the lavage fluids.

Injection of mrIL‐1β produced neutrophil accumulation into the peritoneal cavities (maximal at 4 h with 1.42±0.15×106 cells per mouse). Co‐injection of a specific polyclonal antibody against mMCP‐1 reduced this process by more than 50% (n=6; P<0.05). In conclusion, we studied the mechanisms leading to the specific release of the CC chemokine mMCP‐1 after in vivo administration of mrIL‐1β.

British Journal of Pharmacology (1998) 125, 319–326; doi:10.1038/sj.bjp.0702071
Inhibitory effects of mesoionic 3‐aryl substituted oxatriazole‐5‐imine derivatives on vascular smooth muscle cell mitogenesis and proliferation in vitro
Authors: Lähteenmäki Tuula , Sievi Eeva , Vapaatalo Heikki
Published: January 2005

The effects of oxatriazole‐type (GEA 3162 and GEA 5624) nitric oxide (NO) donors on mitogenesis and proliferation were studied in vascular smooth muscle cell (VSMC) culture. The effects of the GEA‐compounds were compared with well‐known NO‐donors 3‐morpholinosydnonimine (SIN‐1) and S‐nitroso‐N‐acetylpenicillamine (SNAP).

All NO‐donors released NO and increased the production of cyclic GMP concentration‐dependently. The production of cyclic GMP was inhibited by the guanylate cyclase inhibitor, ODQ (1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one).

The NO‐donors inhibited basal and serum‐induced DNA synthesis concentration‐dependently. The GEA‐compounds were needed in concentrations 10 times lower than SIN‐1 and SNAP. GEA 3162, SIN‐1 and SNAP were also able to inhibit serum‐induced cell proliferation. GEA 5624 was ineffective. The antimitogenic effect of NO‐donors was not reduced by inhibiting the guanylate cyclase.

These results suggest that NO inhibits serum‐induced DNA synthesis and proliferation of VSMC by a cyclic GMP‐independent mechanism. The oxatriazole‐type NO‐donor GEA 3162 was found to be a more potent inhibitor of mitogenesis and cell proliferation than SIN‐1 and SNAP.

British Journal of Pharmacology (1998) 125, 402–408; doi:10.1038/sj.bjp.0702076
Inhibition of the gap junctional component of endothelium‐dependent relaxations in rabbit iliac artery by 18‐α glycyrrhetinic acid
Authors: Taylor Hannah J , Chaytor Andrew T , Evans W Howard , Griffith Tudor M
Published: January 2005

The gap junction inhibitor 18‐α‐glycyrrhetinic acid (α‐GA, 100 μM) attenuated endothelium‐dependent relaxations to acetylcholine and cyclopiazonic acid by ∼20% in rings of pre‐constricted rabbit iliac artery. The nitric oxide synthase inhibitor NG‐nitro‐L‐arginine methyl ester (L‐NAME, 300 μM) inhibited relaxations to both agents by ∼65% and these were further attenuated by α‐GA to <10% of control. In endothelium‐denuded preparations, relaxations to sodium nitroprusside were not affected by α‐GA. Heterocellular gap junctional communication may therefore account for nitric oxide‐independent relaxations evoked both by receptor‐dependent and ‐independent mechanisms in rabbit iliac artery.

British Journal of Pharmacology (1998) 125, 1–3; doi:10.1038/sj.bjp.0702078
Enhanced expression of G protein‐coupled receptor kinase 2 selectively increases the sensitivity of A2A adenosine receptors to agonist‐induced desensitization
Authors: Mundell Stuart J , Luty Jason S , Willets Jon , Benovic Jeffrey L , Kelly Eamonn
Published: January 2005

G protein‐coupled receptor kinases (GRKs) are thought to be important in mediating the agonist‐induced phosphorylation and consequent desensitization of G protein‐coupled receptor (GPCR) responses. We have previously shown that stable expression of a dominant negative mutant G protein‐ coupled receptor kinase 2 (GRK2) construct in NG108‐15 mouse neuroblastoma × rat glioma cells suppresses the agonist‐induced desensitization of A2A and A2B adenosine receptor‐stimulated adenylyl cyclase activity (Mundell et al., 1997). To further determine the role of GRK2 in agonist‐induced desensitization of these adenosine receptors, we stably overexpressed wild type GRK2 in NG108‐15 cells.

In homogenates prepared from cells overexpressing GRK2, the acute stimulation of adenylyl cyclase by activation of A2A and A2B adenosine receptors was markedly reduced, but could be reversed by pretreating the cells with AD (adenosine deaminase), to remove extracellular adenosine from the medium. On the other hand, acute stimulation of adenylyl cyclase by secretin, iloprost, NaF and forskolin was the same in GRK2 overexpressing cells and plasmid‐transfected control cells.

Cells overexpressing GRK2 were more sensitive to adenosine receptor agonist‐induced desensitization than plasmid‐transfected control cells. This effect was selective since the agonist sensitivity of desensitization for secretin and IP‐prostanoid receptor‐stimulated adenylyl cyclase activity was not affected by GRK2 overexpression.

These results further implicate GRK2 as the likely mechanism by which A2 adenosine receptors undergo short‐term desensitization in NG108‐15 cells, and indicate that even when overexpressed, GRK2 retains its substrate specificity for native receptors in intact cells. Furthermore, the susceptibility of GPCRs to desensitization appears to depend on the level of GRK expression, such that in cells that express high levels of GRK2, low agonist concentrations may be sufficient to trigger GRK‐mediated desensitization.

British Journal of Pharmacology (1998) 125, 347–356; doi:10.1038/sj.bjp.0702081
Characterization of the P2 receptors on the human umbilical vein endothelial cell line ECV304
Authors: Conant Alan R , Fisher Michael J , McLennan Alexander G , Simpson Alec W M
Published: January 2005

To characterize the P2 receptors present on the human umbilical vein endothelial‐derived cell line, ECV304, cytosolic Ca2+, ([Ca2+]c), responses were recorded in single cells and in cell suspensions to a series of nucleotides and nucleotide agonists.

Concentration response curves were obtained in fura‐2‐loaded ECV304 cell suspensions, with EC50 values of 4.2 μM for ATP, 2.5 μM for UTP and 14 μM for adenosine‐5′‐O‐(3‐thio)triphosphate (ATPγS). EC50 values for 2‐methylthioATP, ADP, adenosine‐5′‐O‐(2‐thio)diphosphate (ADPβS) and AMP were 0.5 μM, 3.5 μM, 15 μM and 4.7 μM respectively, but maximal [Ca2+]c responses were less than those produced by a maximal addition of ATP/UTP. ECV304 cells were unresponsive to UDP and β,γ,methyleneATP.

Cross‐desensitization studies on ECV304 cells suggested that ATP and UTP recognized the same receptor. However, ADP recognized a receptor distinct from the UTP‐sensitive receptor and AMP recognized a third distinct receptor.

ECV304 [Ca2+]c responses to 2‐methylthioATP were inhibited in the presence of 30 μM pyridoxalphosphate‐6‐azophenyl‐2′,4′‐disulphonic acid (PPADS), whereas [Ca2+]c responses to UTP were unaffected by this treatment.

ECV304 cells responded to the diadenosine polyphosphate Ap3A with rises in [Ca2+]c. Apparent responses to Ap4A, Ap5A and Ap6A, were shown to be due to a minor nucleotide contaminant that could be removed by pre‐treatment of the diadenosine samples with either alkaline phosphatase or apyrase.

ECV304 cells display a pharmacology consistent with the presence of at least two P2 receptors; a P2Y2 receptor insensitive to the diadenosine polyphosphates and a P2Y1 receptor sensitive to Ap3A. In addition, ECV304 cells respond to AMP with increases in [Ca2+]c via an as yet uncharacterized receptor.

British Journal of Pharmacology (1998) 125, 357–364; doi:10.1038/sj.bjp.0702082
LF 16.0335, a novel potent and selective nonpeptide antagonist of the human bradykinin B2 receptor
Authors: Pruneau Didier , Luccarini Jean‐Michel , Fouchet Chantal , Defrêne Evelyne , Franck Rose‐Marie , Loillier Bruno , Duclos Hervé , Robert Claude , Cremers Béatrice , Bélichard Pierre , Paquet Jean‐Luc
Published: January 2005

In the present paper, we describe the in vitro pharmacological properties of LF 16.0335 (1‐[[3‐[(2,4‐dimethylquinolin‐8‐yl)oxymethyl]‐2,4‐dichloro‐phenyl]sulphonyl] ‐2(S) ‐ [[4 ‐[4‐(aminoiminomethyl)phenylcarbonyl]piperazin‐1‐yl]carbonyl]pyrrolidine), a novel and potent nonpeptide antagonist of the human bradykinin (BK) B2 receptor.

LF 16.0335 displaced [3H]‐BK binding to membrane preparations from CHO cells expressing the cloned human B2 receptor, INT 407 cells and human umbilical vein with Ki values of 0.84±0.39 nM, 1.26±0.68 nM and 2.34±0.36 nM, respectively.

In saturation binding studies performed in INT 407 cell membranes in the presence or absence of LF 16.0335, Bmax values of [3H]‐BK were not significantly changed suggesting that LF 16.0335 behaves as a competitive antagonist.

LF 16.0335 had no affinity for the cloned human kinin B1 receptor stably expressed in 293 cells. In addition, this compound at 1 μM did not significantly bind to a range of 40 different membrane receptors and eight ion channels except muscarinic M2 and M1 receptors for which an IC50 value of 0.9 and 1 μM was obtained.

BK stimulates in a concentration‐dependent manner phosphoinositosides (IPs) production in cultured INT 407 cells. Concentration‐response‐curves to BK were shifted to the right in the presence of LF 16.0335 (0.1 μM) without reduction of the maximum. LF 16.0335 inhibited the concentration‐contraction curve to BK in the human umbilical vein giving a pA2 value of 8.30±0.30 with a Schild plot slope that was not different from unity.

These results demonstrate that LF 16.0335 is a potent, selective and competitive antagonist of the human bradykinin B2 receptor.

British Journal of Pharmacology (1998) 125, 365–372; doi:10.1038/sj.bjp.0702083
Modulation of the vagal bradycardia evoked by stimulation of upper airway receptors by central 5‐HT1 receptors in anaesthetized rabbits
Authors: Dando Simon B , Skinner Matthew R , Jordan David , Ramage Andrew G
Published: January 2005

The effects of central application of 5‐HT1A and 5‐HT1B/1D receptor ligands on the reflex bradycardia, apnoea, renal sympathoexcitation and pressor response evoked by stimulating upper airway receptors with smoke in atenolol‐pretreated anaesthetized rabbits were studied.

Intracisternal administration of the 5‐HT1A receptor antagonists WAY‐100635 (100 μg kg−1) and (−)pindolol (100 μg kg−1) significantly reduced the smoke‐induced bradycardia, attenuated the pressor response and in the case of (−)pindolol, sympathetic nerve activity. The same dose of WAY‐100635 i.v. was without effect.

Buspirone (200 μg kg−1, i.c.) potentiated the reflex bradycardia. This action was prevented if the animals were pretreated with WAY‐100635 (100 μg kg−1, i.v.)

(+)8‐OH‐DPAT (25 μg kg−1, i.c.) attenuated the evoked bradycardia, pressor response, apnoea and renal sympathoexcitation. The attenuation of the apnoea and renal sympathoexcitation, but not the bradycardia or pressor response was prevented in animals pretreated with WAY‐100635 (100 μg kg−1, i.v.). The attenuation of the reflex bradycardia and the reduction in the renal sympathoexcitation were reduced by pretreatment with the 5‐HT1B/1D receptor antagonist GR127935 (100 μg kg−1, i.v.).

In WAY‐100635 (100 μg kg−1, i.v.) pretreated animals, sumatriptan (a 5‐HT1B/1D receptor agonist) reduced the reflex bradycardia and the pressor response. The 5‐HT1B/1D receptor antagonist GR127935 (20 μg kg−1, i.c. or 100 μg kg−1, i.v.) had no effect on the reflex responses.

In conclusion, the present data are consistent with the hypothesis that activation of central 5‐HT1A receptors potentiate whilst activation of 5‐HT1B/1D receptors attenuate the reflex activation of cardiac preganglionic vagal motoneurones evoked by stimulation of upper airway receptors with smoke in rabbits.

British Journal of Pharmacology (1998) 125, 409–417; doi:10.1038/sj.bjp.0702085