bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanisms of the cutaneous vasodilator response to local external pressure application in rats: involvement of CGRP, neurokinins, prostaglandins and NO
Authors: Fromy Bérengère , Merzeau Sandra , Abraham Pierre , Saumet Jean‐Louis
Published: January 2005

Local pressure‐induced vasodilation (PIV) is a neural vasodilator response to non‐nociceptive externally applied pressure in the skin, previously described in humans. We first determined whether PIV exists in rats and depends on capsaicin‐sensitive fibres as it does in humans. We then examined the mediators involved in the efferent pathway of PIV.

Cutaneous blood flow was measured by laser Doppler flowmetry during 11.1 Pa s−1 increases in local applied pressure in anaesthetized rats. The involvement of capsaicin‐sensitive fibres in PIV was tested in rats treated neonatally with capsaicin. To antagonize CGRP, neurokinin‐1, −2, or −3 receptors, different groups of rats were treated with CGRP8–37, SR140333, SR48968 or SR142801, respectively. Prostaglandins involvement was tested with indomethacin treatment. To inhibit nitric oxide synthase (NOS) activity or specific neuronal NOS, rats were treated with NG‐nitro‐L‐arginine or 7‐nitroindazole, respectively.

PIV was found in rats, as in humans. PIV was abolished by neonatal treatment with capsaicin and by administration of CGRP8–37 but remained unchanged with SR140333, SR48968 and SR142801 treatments. Prostaglandin inhibition resulted in a significant decrease in PIV. Inhibition of NOS abolished PIV, whereas inhibition of neuronal NOS caused a diminution of PIV.

These data suggest that PIV depends on capsaicin‐sensitive fibres in rats, as in humans. It appears that CGRP plays a major role in the PIV, whereas neurokinins have no role. Furthermore, PIV involves a contribution from prostaglandins and depends on endothelial NO, whereas neuronal NO has a smaller role.

British Journal of Pharmacology (2000) 131, 1161–1171; doi:10.1038/sj.bjp.0703685
Pharmacology and autoradiography of human DP prostanoid receptors using [3H]‐BWA868C, a DP receptor‐selective antagonist radioligand
Authors: Sharif N A , Williams G W , Davis T L
Published: January 2005

A potent and highly selective DP prostanoid receptor antagonist radioligand, [3H]‐cyclohexyl‐N‐BWA868C (3‐benzyl‐5‐(6‐carboxyhexyl)‐1‐(2‐cyclohexyl‐2‐hydroxyethyl‐amino) hydantoin, ([3H]‐BWA868C)), has been generated for receptor binding and autoradiographic studies.

Specific [3H]‐BWA868C binding to human platelet membranes achieved equilibrium within 60 min at 23°C and constituted up to 95% of the total binding. The association (K+1) and dissociation (K−1) rate constants of binding were 0.758±0.064 min−1, mmol and 0.0042±0.0002 min−1, respectively, yielding dissociation constants (KDs) of 5.66±0.44 nM (n=4).

Specific [3H]‐BWA868C bound to DP receptors with a high affinity (KD=1.45±0.01 nM, n=3) and to a finite, saturable number of binding sites (Bmax=21.1±0.6 nmol g−1 wet weight).

DP receptor class prostanoids (e.g. ZK118182, BW245C, BWA868C, PGD2) exhibited high (nanomolar) affinities for [3H]‐BWA868C binding, while prostanoids selective for EP, FP, IP and TP receptors showed a low (micromolar) affinity.

Specific DP receptor binding sites were autoradiographically localized on the ciliary epithelium/process, longitudinal and circular ciliary muscles, retinal choroid and iris in human eye sections using [3H]‐BWA868C. While [3H]‐PGD2 yielded similar quantitative distribution of DP receptors as [3H]‐BWA868C, the level of non‐specific binding observed with [3H]‐PGD2 was significantly greater than that observed with [3H]‐BWA868C.

It is concluded that [3H]‐BWA868C is a high‐affinity and very specific DP receptor radioligand capable of selectively labelling the DP receptor. [3H]‐BWA868C may prove useful for future homogenate‐based and autoradiographic studies on the DP receptor.

British Journal of Pharmacology (2000) 131, 1025–1038; doi:10.1038/sj.bjp.0703686
Histamine depolarizes cholinergic interneurones in the rat striatum via a H1‐receptor mediated action
Authors: Bell M I , Richardson P J , Lee K
Published: January 2005

Whole‐cell patch clamp recordings were made from rat striatal cholinergic interneurones in slices of brain tissue in vitro. Bath application of histamine (EC50 6.3 μM) was found to rapidly and reversibly depolarize these neurones through the induction of an inward current at −60 mV.

The effects of histamine were mimicked by the H1 receptor agonist 2‐thiazolylethylamine (50 μM) and selectively inhibited by pre‐incubation with the H1 receptor antagonist triprolidine (1 μM).

Ion substitution experiments under voltage clamp conditions revealed that the histamine activated current was comprised of two components. One component was sensitive to the concentration of extracellular Na+, whilst the other component was inhibited by intracellular Cs+ or extracellular Ba2+.

In situ hybridization experiments revealed that the majority of cholinergic interneurones in the rat striatum express the histamine H1 receptor but few neurones express H2 receptors. These findings were confirmed using single cell RT–PCR.

It is concluded that histamine depolarizes cholinergic interneurones in the rat striatum via a H1‐receptor mediated mechanism.

British Journal of Pharmacology (2000) 131, 1135–1142; doi:10.1038/sj.bjp.0703692
Role of EDHF in the vasodilatory effect of loop diuretics in guinea‐pig mesenteric resistance arteries
Authors: Pourageaud Fabrice , Bappel‐Gozalbes Catherine , Marthan Roger , Freslon Jean‐Louis
Published: January 2005

Relaxing effect of loop diuretics, piretanide and furosemide in comparison with acetylcholine (ACh) was investigated in guinea‐pig isolated mesenteric resistance arteries.

Concentration‐response curves to ACh (0.001–10 μM) and diuretics (0.0001–1 μM) were constructed in noradrenaline (10–30 μM)‐precontracted arteries incubated either in normal physiological salt solution (PSS) or in 30 mM KCl PSS (K‐PSS).

In PSS, maximal relaxations (Rmax) and pD2 to ACh were 87±2% and 7.1±0.1 (n=10). L‐NG‐nitro‐arginine methyl ester (L‐NAME, 100 μM) reduced Rmax by 20% (P<0.01, n=7) and pD2 by 10% (P<0.01). In contrast, indomethacin (10 μM) increased Rmax by 19% (P<0.01, n=8) and pD2 by 10% (P<0.05). Combination of L‐NAME+indomethacin reversed the effect observed with either of these inhibitors used alone. In K‐PSS, Rmax was attenuated by 40% (P<0.001, n=6) compared to PSS. L‐NAME reduced Rmax by 65% (P<0.01, n=5) and increased pD2 by 15 fold. L‐NAME+indomethacin suppressed the resistant relaxation.

In PSS+L‐NAME+indomethacin, inhibitors of small (SKCa; apamin, 0.1 μM) and large (BKCa; iberiotoxin and charybdotoxin, 0.1 μM) conductance Ca2+‐sensitive K−‐channels used alone had little effect on the ACh‐response. Combination of apamin+iberiotoxin reduced Rmax by 40% (P<0.05, n=7) while apamin+charybdotoxin fully abolished the resistant relaxation.

In PSS, piretanide and furosemide induced relaxation with Rmax: 89±3% vs 84±5% and pD2: 8.5±0.1 vs 7.7±0.2 (P<0.01) for piretanide (n=11) and furosemide (n=10), respectively. Endothelial abrasion suppressed relaxation to diuretics. L‐NAME and indomethacin used alone or in combination did not significantly modify the response to diuretics.

In K‐PSS, piretanide‐induced relaxation was abolished whereas that to furosemide was reduced by 70% (P<0.001, n=9) compared to PSS and was suppressed by L‐NAME+indomethacin. In PSS+L‐NAME+indomethacin, apamin slightly reduced relaxation to diuretics whereas charybdotoxin or iberiotoxin abolished the response.

These results indicate that ACh‐evoked relaxation is mediated by both NO/PGl2‐dependent and ‐independent mechanisms. The EDHF‐dependent component relies on activation of Ca2+‐activated K+ channels, is sensitive to a combination of apamin+charybdotoxin and to a smaller degree to a combination of apamin+iberiotoxin. Loop diuretic‐induced relaxation is endothelium‐dependent, appears to be mediated by NO, PGl2 and EDHF for furosemide and EDHF only for piretanide. For the two diuretics, opening of BKCa channels may be involved in the relaxation.

British Journal of Pharmacology (2000) 131, 1211–1219; doi:10.1038/sj.bjp.0703693
Alteration of the [Ca2+]i‐force relationship during the vasorelaxation induced by a Ca2+ channel blocker SR33805 in the porcine coronary artery
Authors: Ieiri Satoshi , Hirano Katsuya , Nishimura Junji , Suita Sachiyo , Kanaide Hideo
Published: January 2005

The mechanism of vasorelaxation induced by SR33805 was investigated by simultaneously monitoring the cytosolic Ca2+ concentration ([Ca2+]i) and force, and by determining level of myosin light chain (MLC) phosphorylation in the medial strip of the porcine coronary artery.

SR33805 inhibited the sustained increases in [Ca2+]i and force (IC50; 3.2±1.0 and 49.4±27.5 nM, respectively) induced by 118 mM K+‐depolarization. There was about a 10 fold difference in the inhibitory potency between [Ca2+]i and force.

SR33805 completely inhibited the [Ca2+]i elevation induced by a thromboxane A2 analogue, U46619 and histamine, at concentrations (1 μM) higher than those required for the complete inhibition of K+‐depolarization induced [Ca2+]i elevation.

SR33805 had no effect on the [Ca2+]i elevation induced by histamine or caffeine in the absence of extracellular Ca2+.

SR33805 caused a leftward shift of the [Ca2+]i‐force relationship of the contraction induced by cumulative application of extracellular Ca2+ during 118 mM K+‐depolarization. The relationship between [Ca2+]i and MLC phosphorylation also shifted to the left by SR33805, while the relationship between MLC phosphorylation and force remained unaffected.

In conclusion, SR33805 caused an apparent leftward shift of the [Ca2+]i‐force relationship, accompanied by a greater degree of MLC phosphorylation for a given level of [Ca2+]i. The mechanism of this leftward shift, however, still remains to be elucidated.

British Journal of Pharmacology (2000) 131, 1597–1606; doi:10.1038/sj.bjp.0703721
The effect of selective and non‐selective phosphodiesterase inhibitors on allergen‐ and leukotriene C4‐induced contractions in passively sensitized human airways
Authors: Schmidt Dunja T , Watson Nikki , Dent Gordon , Rühlmann Elke , Branscheid Detlev , Magnussen Helgo , Rabe Klaus F
Published: January 2005

Non‐selective inhibitors of cyclic nucleotide phosphodiesterase (PDE) block allergen‐induced contraction of passively sensitized human airways in vitro by a dual mechanism involving a direct relaxant effect on smooth muscle and inhibition of histamine and cysteinyl leukotriene (LT) release from airways. We investigated the effects of non‐selective PDE inhibitors and selective inhibitors of PDE3 and PDE4 in order to determine the involvement of PDE isoenzymes in the suppression of allergic bronchoconstriction.

Macroscopically normal airways from 76 patients were sensitized with IgE‐rich sera (>250 u ml−1) containing specific antibodies against allergen (Dermatophagoides farinae). Contractile responses of bronchial rings were assessed using standard organ bath techniques.

Passive sensitization caused increased contractile responses to allergen, histamine and LTC4. Non‐selective PDE inhibitors (theophylline, 3‐isobutyl‐1‐methylxanthine [IBMX]), a PDE3‐selective inhibitor (motapizone), PDE4‐selective inhibitors (RP73401, rolipram, AWD 12‐281) and a mixed PDE3/4 inhibitor (zardaverine) all significantly relaxed inherent bronchial tone at resting tension and to a similar degree. Theophylline, IBMX, zardaverine and the combination of motapizone and RP73401 inhibited the contractile responses to allergen and LTC4. Pre‐treatment with motapizone, RP73401, rolipram or the methylxanthine adenosine receptor antagonist, 8‐phenyltheophylline, did not significantly decrease responses to either allergen or LTC4.

We conclude that combined inhibition of PDE3 and PDE4, but not selective inhibition of either isoenzyme or antagonism of adenosine receptors, is effective in suppressing allergen‐induced contractions of passively sensitized human airways. The relationship between allergen‐ and LTC4‐induced responses suggests that PDE inhibitors with PDE3 and PDE4 selectivity are likely to act in part through inhibition of mediator release and not simply through direct relaxant actions on airway smooth muscle.

British Journal of Pharmacology (2000) 131, 1607–1618; doi:10.1038/sj.bjp.0703725
Inhibitory action of brotizolam on circadian and light‐induced Per1 and Per2 expression in the hamster suprachiasmatic nucleus
Authors: Yokota Shin‐ichi , Horikawa Kazumasa , Akiyama Masashi , Moriya Takahiro , Ebihara Shizufumi , Komuro Goyo , Ohta Tatsuro , Shibata Shigenobu
Published: January 2005

Triazolam reportedly causes phase advances in hamster wheel‐running rhythm after injection during subjective daytime. However, it is unclear whether benzodiazepine affects the Per gene expression accompanying a behavioural phase shift.

Brotizolam (0.5–10 mg kg−1) induced large phase advances in hamster rhythm when injected during mid‐subjective daytime (circadian time 6 or 9), but not at circadian time 0, 3 or 15.

Brotizolam (5 mg kg−1) significantly reduced the expression of Per1 and Per2 in the suprachiasmatic nucleus 1 and 2 h after injection at circadian time 6, and slightly reduced them at circadian time 20.

Injection of 8‐OH‐DPAT (5 mg kg−1) at subjective daytime induced similar phase advances with a reduction of Per1 and Per2 expression. Co‐administration of brotizolam with 8‐OH DPAT failed to potentiate the 8‐OH DPAT‐induced phase advances and reduced Per expression.

Both phase advance and rapid induction of Per1 and Per2 in the suprachiasmatic nucleus after light exposure (5 lux, 15 min) at circadian time 20 was strongly attenuated by co‐treatment with brotizolam 5 mg kg−1.

The present results strongly suggest that reduction of Per1 and/or Per2 expression during subjective daytime by brotizolam may be an important step in causing a behavioural phase advance. The co‐administration experiment suggests that common mechanism(s) are involved in brotizolam‐ or 8‐OH DPAT‐induced phase advances and the reduction of Per gene expression.

These results suggest that brotizolam is not only a good drug for insomnia but also a drug capable of facilitating re‐entrainment like melatonin.

British Journal of Pharmacology (2000) 131, 1739–1747; doi:10.1038/sj.bjp.0703735
Modification of adenosine modulation of synaptic transmission in the hippocampus of aged rats
Authors: Sebastião A M , Cunha R A , De Mendonça A , Ribeiro J A
Published: January 2005

We compared the modulation of synaptic transmission by adenosine A1 receptors in the hippocampus of aged (24 months) and young adult rats (6 weeks).

The adenosine A1 receptor agonist, N6‐cyclopentyladenosine, was less potent (P<0.05) to inhibit synaptic transmission in aged (EC50=53 nM) than young adult (EC50=14 nM) hippocampal slices, these effects being prevented by the A1 receptor antagonist, 1,3‐dipropyl‐8‐cyclopentylxanthine (DPCPX).

In contrast with the lower effect of the A1 receptor agonist, it was observed that blockade of A1 receptors with DPCPX (50 nM), or removal of endogenous extracellular adenosine with adenosine deaminase (2 u ml−1), caused a more pronounced disinhibition of synaptic transmission in aged rats. Also consistent with a more intense A1 receptor‐mediated inhibitory tonus by endogenous adenosine in aged rats was the finding that to fully prevent the depression of synaptic transmission induced by 3 min hypoxia, a higher concentration of DPCPX was required in slices from aged (100 nM) than from young (50 nM) rats.

It is concluded that in hippocampal slices of aged rats the efficiency of A1 receptors to modulate synaptic transmission is reduced, but this may be compensated by an enhanced inhibitory tonus by endogenous adenosine.

British Journal of Pharmacology (2000) 131, 1629–1634; doi:10.1038/sj.bjp.0703736
Role of selectins on IgE‐mediated skin reaction
Authors: Wada Yukihisa , Kuzuhara Akemi , Hanamura Mikiko , Kida Rie , Yoshinaka Tsuyoshi , Saito Tadayuki
Published: January 2005

Selectins play an important role on leukocytes infiltration into inflammatory tissues. To understand the role of selectins, we investigated the effects of selectin‐IgG chimeras and anti selectin antibodies on the murine IgE‐mediated skin inflammation model.

Biphasic skin reactions were induced by intradermal challenge with ovalbumin (OA) to ears of actively sensitized mice. This reaction was characterized by immediate and late phase responses observed as which were induced via a rapid increase in capillary permeability and leukocyte infiltration, respectively. The expression of E‐selectin mRNA was significantly increased to reach its highest level at 2 h after OA challenge.

E‐, P‐, and L‐selectin‐IgG chimeras inhibited the late phase responses, i.e. ear swelling, neutrophil infiltration and eosinophil infiltration at 24 h after OA challenge in a dose‐dependent manner at dose range of 0.1–10 mg kg−1, i.v. Antiselectin antibodies did not inhibit the increase of ear swelling. But anti E‐ and P‐selectin antibodies significantly inhibited neutrophil infiltration and eosinophil infiltration.

These results indicate that selectins play an important role on the late phase response of the murine IgE‐mediated skin inflammation model by mediating inflammatory cell adhesion to endothelium.

British Journal of Pharmacology (2000) 131, 1531–1536; doi:10.1038/sj.bjp.0703739
4‐Aminopyridine affects rat arterial smooth muscle BKCa currents by changing intracellular pH
Authors: Petkova‐Kirova Polina , Gagov Hristo , Krien Ulrike , Duridanova Dessislava , Noack Thomas , Schubert Rudolf
Published: January 2005

The hypothesis whether or not 4‐AP can affect vascular smooth muscle BKCa currents was tested using the patch‐clamp technique, pH‐ and calcium‐fluorimetry, and freshly isolated rat arterial smooth muscle cells.

Application of 4‐AP reversibly inhibited BKCa currents at an intracellular calcium ([Ca]i) of 250 nM with a half‐block of 2.5 mM at +50 mV.

The presence of 2 μM thapsigargin, 10 μM heparin, and 10 μM ryanodine did not alter the effect of 4‐AP on BKCa currents at [Ca]i 250 nM.

At [Ca]i<100 nM 4‐AP did not inhibit BKCa currents.

Application of 4‐AP to the intracellular or extracellular side of excised BKCa channels did not alter channel activity or channel amplitude.

Replacement of the pH‐sensitive calcium buffer EGTA by the pH‐insensitive calcium buffer BAPTA in the intracellular solution turned the 4‐AP‐induced inhibition of BKCa currents into a stimulation at [Ca]i 250 nM.

Application of 4‐AP to single cells increased intracellular pH, which was accompanied by a reduction of [Ca]i in EGTA‐loaded cells and a stable [Ca]i in BAPTA‐loaded cells.

Thus, these results suggest that in isolated vascular smooth muscle cells at [Ca]i>100 nM 4‐AP affects BKCa currents via an alteration of intracellular pH.

British Journal of Pharmacology (2000) 131, 1643–1650; doi:10.1038/sj.bjp.0703742
Multiple P2Y receptor subtypes in the apical membranes of polarized epithelial cells
Authors: McAlroy H L , Ahmed S , Day S M , Baines D L , Wong H Y , Yip C Y , Ko W H , Wilson S M , Collett A
Published: January 2005

Apical ATP, ATP, UTP and UDP evoked transient increases in short circuit current (ISC, a direct measure of transepithelial ion transport) in confluent Caco‐2 cells grown on permeable supports. These responses were mediated by a population of at least three pharmacologically distinct receptors.

Experiments using cells grown on glass coverslips showed that ATP and UTP consistently increased intracellular free calcium ([Ca2+]i) whilst sensitivity to UDP was variable. Cross desensitization experiments suggested that the responses to UTP and ATP were mediated by a common receptor population.

Messenger RNA transcripts corresponding to the P2Y2, P2Y4 and P2Y6 receptors genes were detected in cells grown on Transwell membranes by the reverse transcriptase–polymerase chain reaction. Identical results were obtained for cells grown on glass.

Experiments in which ISC and [Ca2+]i were monitored simultaneously in cells on Transwell membranes, confirmed that apical ATP and UTP increased both parameters and showed that the UDP‐evoked increase in ISC was accompanied by a [Ca2+]i‐signal.

Ionomycin consistently increased [Ca2+]i in such polarized cells but caused no discernible change in ISC. However, subsequent application of apical ATP or UTP evoked a small rise in ISC but no rise in [Ca2+]i. UDP evoked no such response.

As well as evoking increases in [Ca2+]i, the ATP/UTP‐sensitive receptors present in Caco‐2 cells thus allow direct control over ion channels in the apical membrane. The UDP‐sensitive receptors, however, appear to simply evoke a rise in [Ca2+]i.

British Journal of Pharmacology (2000) 131, 1651–1658; doi:10.1038/sj.bjp.0703743
Blockade of μ‐opioid receptors reveals the hyperalgesic effect of orphanin FQ/nociceptin in the rat hot plate test
Authors: Lutfy Kabirullah , Maidment Nigel T
Published: January 2005

Orphanin FQ (OFQ, also known as nociceptin) has been proposed to oppose the antinociceptive effect of endogenous opioid peptides in the brain. We sought to determine whether, conversely, the endogenous opioid peptides counteract a pronociceptive action of OFQ.

In testing this hypothesis, naloxone, a non‐selective opioid receptor antagonist, was used to block the action of endogenous opioid peptides. We then examined whether OFQ would produce hyperalgesia in the absence of such an endogenous opioidergic tone.

Neither naloxone (1 mg kg−1; s.c.) nor OFQ (up to 30 nmol; i.c.v.) alone induced any significant change in mean hot plate latency. However, OFQ dose‐dependently produced hyperalgesia in rats pretreated with naloxone, implying that OFQ can indeed produce hyperalgesia once an endogenous opioidergic tone is inhibited.

In subsequent studies, we used subtype selective opioid receptor antagonists to determine which class of opioid receptor is involved in this response. The effect of naloxone was reproduced using the selective μ‐opioid receptor antagonist CTOP (D‐Phe‐Cyc‐Tyr‐D‐Trp‐Orn‐Thr‐Pen‐Thr‐NH2), but not by administration of the δ‐opioid receptor antagonist, naltrindole (NTI) or the κ‐opioid receptor antagonist nor‐binaltorphimine (nor‐BNI).

These results suggest that endogenous opioid peptides acting at the μ‐, but not κ‐ or δ‐opioid receptor may be counteracting the hyperalgesic effect of OFQ in rats.

British Journal of Pharmacology (2000) 131, 1684–1688; doi:10.1038/sj.bjp.0703746
Endotoxin sensitization to kinin B1 receptor agonist in a non‐human primate model: haemodynamic and pro‐inflammatory effects
Authors: DeBlois Denis , Horlick Robert A
Published: January 2005

Although endotoxaemia induces kinin B1 receptors in several animal models, this condition is not documented in primates. This study examined the up‐regulation of haemodynamic and pro‐inflammatory responses to the B1 agonist des‐Arg10‐kallidin (dKD) in a non‐human primate model.

Green monkeys (Cercopithecus aethiops St Kitts) received lipopolysaccharide (LPS; 90 μg kg−1) or saline intravenously. After 4 h, anaesthetized monkeys were canulated via the carotid artery to monitor blood pressure changes following intra‐arterial injections of dKD or the B2 agonist bradykinin (BK). Oedema induced by subcutaneous kinin administration was evaluated as the increase in ventral skin folds in anaesthetized monkeys injected with captopril at 4 h to 56 days post‐LPS.

LPS increased rectal temperature but did not affect blood pressure after 4 h. dKD reduced blood pressure (Emax: 27±4 mmHg; EC50: 130 pmol kg−1) and increased heart rate (Emax: 33 b.p.m.) only after LPS. In contrast, the dose‐dependent fall in blood pressure with BK was comparable in all groups. The selective B1 antagonist [Leu9]dKD (75 ng kg−1 min−1, intravenously) abolished responses to dKD but not BK.

dKD injection induced oedema dose‐dependently (2.4±0.1 mm at 150 nmol) only following LPS (at 4 h to 12 days but not 56 days). In contrast, BK‐induced oedema was present and stable in all monkeys. Co‐administration of [Leu9]dKD (150 nmol) significantly reduced oedema induced by dKD (50 nmol).

These results suggest LPS up‐regulation of B1 receptor effects in green monkeys. This non‐human primate model may be suitable for testing new, selective B1 antagonists with therapeutic potential as anti‐inflammatory agents.

British Journal of Pharmacology (2001) 132, 327–335; doi:10.1038/sj.bjp.0703748
Ecto‐alkaline phosphatase in NG108‐15 cells : a key enzyme mediating P1 antagonist‐sensitive ATP response
Authors: Ohkubo Satoko , Kimura Junko , Matsuoka Isao
Published: January 2005

We previously demonstrated that extracellular adenine nucleotides induced cyclic AMP elevation through local adenosine production at the membrane surface and subsequent activation of adenosine A2A receptors in NG108‐15 cells. Furthermore, the adenosine formation was found to be mediated by an ecto‐enzyme distinct from the ecto‐5′‐nucleotidase (CD73). In this study, we investigated the properties of the ecto‐AMP phosphohydrolase activity in NG108‐15 cells.

NG108‐15 cells hydrolyzed AMP to adenosine with the KM value of 18.8±2.2 μM and Vmax of 5.3±1.6 nmol min−1 106 cells−1. This activity was suppressed at pH 6.5, but markedly increased at pH 8.5.

The AMP hydrolysis was blocked by levamisole, an alkaline phosphatase (ALP) inhibitor. NG108‐15 cells released orthophosphate from 2′‐ and 3′‐AMP as well as from ribose‐5‐phosphate and β‐glycerophosphate, indicating that NG108‐15 cells express ecto‐ALP.

The cyclic AMP accumulation induced by several adenine nucleotides was inhibited by levamisole, p‐nitrophenylphosphate and β‐glycerophosphate, with a parallel decrease in the extracellular adenosine formation.

Reverse transcriptase polymerase chain reaction analysis revealed that NG108‐15 cells express mRNA for the tissue‐nonspecific isozyme of ALP.

These results demonstrate that AMP phosphohydrolase activity in NG108‐15 cells is due to ecto‐ALP, and suggest that this enzyme plays an essential role for the P1 antagonist‐sensitive ATP‐induced cyclic AMP accumulation in NG108‐15 cells.

British Journal of Pharmacology (2000) 131, 1667–1672; doi:10.1038/sj.bjp.0703750
Circadian variation in the activity of the 5‐HT1B autoreceptor in the region of the suprachiasmatic nucleus, measured by microdialysis in the conscious freely‐moving rat
Authors: Garabette M L , Martin K F , Redfern P H
Published: January 2005

Intracerebral microdialysis was used to examine the function of the terminal 5‐hydroxytryptamine1B (5‐HT1B) autoreceptor in the region of the suprachiasmatic nuclei (SCN) of freely moving conscious rats at six time points or zeitgeber times (ZTs) across the light:dark cycle.

Infusion of the 5‐HT1A/1B agonist 5‐methoxy‐3‐(1,2,3,6‐tetrahydro‐4‐pyridyl)‐1H‐indole (RU24969) (1 μM) via the microdialysis probe produced a decrease in 5‐HT output when applied at ZTs 3, 6, 15 and 21 (69.8±11.9, 59±11.7, 43.9±17.2 and 45.7±17.0% respectively). At ZTs 9 and 18 RU24969 (1 μm) failed to affect the 5‐HT output significantly (28.0±11 and 32.8±24.6% decrease respectively).

The profile of inhibition of 5‐HT output following infusion of RU24969 (1 μM) at ZT 6 was unaffected by concurrent infusion of the specific 5‐HT1A antagonist N‐[2‐[4‐(2‐methoxyphenyl)‐1‐piperazinyl]ethyl]‐N‐(2‐pyridinyl)cyclohexanecarboxamide trihydrochloride (WAY100635) (1 μM) (52.48±17.5% decrease).

The data demonstrate a circadian rhythm in the activity of the 5‐HT1B autoreceptor in the region of the SCN.

British Journal of Pharmacology (2000) 131, 1569–1576; doi:10.1038/sj.bjp.0703753
Characterization of [3H]‐CGP54626A binding to heterodimeric GABAB receptors stably expressed in mammalian cells
Authors: Green Andrew , Walls Steven , Wise Alan , Green Richard H , Martin Amanda K , Marshall Fiona H
Published: January 2005

Functional human GABAB(1a,2) and GABAB(1b,2) receptors have been stably expressed in mammalian CHO K1 cells.

Detailed characterization of GABAB ligand binding at each of the receptors has been compared using [3H]‐CGP54626A. In cell membranes fractions, [3H]‐CGP54626A bound to a single site with a KD of 1.51±1.12 nM, Bmax of 2.02±0.17 pmoles mg protein−1 and 0.86±0.20 nM, Bmax of 5.19±0.57 pmoles mg protein−1 for GABAB(1a,2) and GABAB(1b,2) respectively.

In competition binding assays the rank order was identical for both GABAB receptors. For known GABAB agonists the rank order was CGP27492>SKF97541=CGP46381>GABA>Baclofen and for GABAB antagonists the rank order was CGP54262A>CGP55845>CGP52432>SCH 50911>CGP51176>CGP36742=CGP35348 2‐OH Saclofen ABPA.

The allosteric effect of calcium cations was also investigated. The effect of removal of CaCl2 from the binding assay conditions was ligand dependent to either cause a decrease in ligand affinity or to have no significant effect. However, these effects were similar for both GABAB receptors.

A whole cell, scintillation proximity binding assay was used to determine agonist affinity at exclusively heterodimeric GABAB receptors. In competition assays, the rank order was the same for both GABAB(1a,2) and GABAB(1b,2) and consistent with that seen with cell membrane fractions.

These data suggest that, in terms of ligand binding, the currently identified isoforms of the GABAB receptor are pharmacologically indistinguishable.

British Journal of Pharmacology (2000) 131, 1766–1774; doi:10.1038/sj.bjp.0703755
Properties of P2X and P2Y receptors are dependent on artery diameter in the rat mesenteric bed
Authors: Gitterman D P , Evans R J
Published: January 2005

P2 receptor mediated contractile responses have been characterized in different diameter arteries from the rat mesenteric arterial vasculature (first, second to third and fifth to sixth order for large, medium and small arteries) using wire myograph and diamtrak video imaging.

α,β‐methylene ATP (α,β‐meATP) evoked transient concentration‐dependent contractions in mesenteric arteries with EC50 values of 0.4, 2.5 and 107 μM for small, medium and large arteries respectively.

Suramin (10–100 μM) produced substantial parallel rightward shifts of the concentration‐response curve to α,β‐meATP in small and medium‐sized arteries with pA2 of 5.1. Responses in large vessels were unaffected by suramin.

Immunohistochemical analysis of arterial sections revealed no substantial differences in expression patterns of P2X receptors between different sizes of artery. P2X1 receptors were expressed at high levels, P2X4 and P2X5 receptors were also detected on smooth muscle. The P2X receptor response is dominated by P2X1 receptor in small and medium arteries but the nature of the receptor mediating the suramin insensitive α,β‐meATP mediated response in large arteries is unclear.

The P2Y receptor agonist UTP was significantly more potent in small than in medium or large arteries (EC50 values: 15.0 μM small, 88.5 μM diamtrak medium 1.6 mM myography medium and 1.4 mM large). Responses in both small and medium‐sized vessels were reduced by suramin (30–100 μM). The sensitivity to UTP and suramin indicates the presence of P2Y2 receptors.

This study shows that P2 receptors do not have a homogenous phenotype throughout the mesenteric vascular bed and that the properties depend on artery size.

British Journal of Pharmacology (2000) 131, 1561–1568; doi:10.1038/sj.bjp.0703760
Antiplatelet action of R‐99224, an active metabolite of a novel thienopyridine‐type Gi‐linked P2T antagonist, CS‐747
Authors: Sugidachi Atsuhiro , Asai Fumitoshi , Yoneda Kenji , Iwamura Ryo , Ogawa Taketoshi , Otsuguro Ken‐ichi , Koike Hiroyuki
Published: January 2005

CS‐747 is a novel thienopyridine‐type platelet ADP inhibitor which lacks in vitro activity. This study examined pharmacological profiles of R‐99224, a hepatic metabolite of CS‐747.

R‐99224 produced a concentration‐dependent inhibition of in vitro platelet aggregation in washed human platelets (0.03 – 1 μg ml−1), which was relatively specific to ADP compared to collagen and thrombin.

R‐99224 (0.1 – 3 μg ml−1) also elicited a similar inhibition of ADP‐induced aggregation in rat platelets. The inhibition by R‐99224 (10 μg ml−1) persisted even after platelets were washed three times. Intravenous injection of R‐99224 (0.1 – 3 mg kg−1) to rats resulted in a dose‐dependent inhibition of ex vivo ADP‐induced platelet aggregation.

R‐99224 (0.1 – 100 μM) decreased binding of [3H]‐2‐methylthio‐ADP ([3H]‐2‐MeS‐ADP), a stable ligand for platelet ADP receptors, to washed human platelets. The inhibition by R‐99224 reached a plateau at a concentration of 3 μM (1.4 μg ml−1), but complete inhibition was not achieved even at the highest concentration used (100 μM).

R‐99224 (10 μM) in combination with ARL‐66096 (0.3 μM), an ATP analogue‐type Gi‐linked P2T receptor antagonist, produced no additional inhibition of [3H]‐2‐MeS‐ADP binding. In contrast, [3H]‐2‐MeS‐ADP binding was completely abolished by R‐99224 (10 μM) in combination with A3P5PS (300 μM), a selective P2Y1 antagonist, suggesting that R‐99224 selectively binds to the Gi‐linked P2T receptor.

R‐99224 (0.01 – 3 μg ml−1) inhibited ADP‐induced [125I]‐fibrinogen binding to human platelets in a concentration‐dependent manner. R‐99224 (0.1 – 1 μg ml−1) also inhibited the ADP‐induced decrease in cyclic AMP levels in PGE1‐stimulated platelets, whereas the agent did not affect ADP (10 μM)‐induced Ca2+ mobilization.

These findings suggest that R‐99224 is a selective and irreversible antagonist of Gi‐linked P2T receptors and that R‐99224 is a responsible molecule for in vivo actions of CS‐747.

British Journal of Pharmacology (2001) 132, 47–54; doi:10.1038/sj.bjp.0703761
Sumatriptan elicits both constriction and dilation in human and bovine brain intracortical arterioles
Authors: Elhusseiny A , Hamel E
Published: January 2005

Little is known about serotonin (5‐HT) receptors present on brain microvessels that are innervated by brainstem serotonergic neurons. Using 5‐HT, sumatriptan and subtype selective 5‐HT1 receptor agonists and/or the 5‐HT1 receptor antagonist GR127935, we characterized the 5‐HT receptors involved in regulating microvascular tone of pressurized intracortical arterioles (∼40 – 50 μm) isolated from human and bovine cerebral cortex. The role of nitric oxide (NO) on these responses was assessed with the Nω‐nitro‐L‐arginine (L‐NNA, 10−5 M), an inhibitor of NO synthesis. Bovine pial arteries were studied for comparative purposes.

At spontaneous tone, 5‐HT induced a dose‐dependent constriction of human and bovine microarteries (respective pD2 values of 7.3±0.2 and 6.9±0.1); a response potently inhibited by GR127935 (pIC50 value of 8.5±0.1) in bovine microvessels.

In both species, the 5‐HT1 receptor agonist sumatriptan induced a biphasic response consisting of a small but significant dilation at low concentrations (1 and/or 10 nM) followed by a constriction at higher doses (pD2 for contraction of 6.9±0.1 and 6.6±0.2 in human and bovine vessels, respectively). Pre‐incubation with L‐NNA abolished the sumatriptan‐induced dilation and significantly shifted the dose‐response of the constriction curve to the left. In contrast, the selective 5‐HT1D (PNU‐109291) and 5‐HT1F (LY344864) receptor agonists were devoid of any vasomotor effect.

In bovine pial vessels, 5‐HT and sumatriptan elicited potent constrictions (respective pD2 of 7.2±0.1 and 6.6±0.1), a weak dilation being occasionally observed at low sumatriptan concentrations.

A significant negative correlation was observed between pial and intracortical vessels diameter and the extent of the dilatory response to 10−9 M sumatriptan. Together, these results indicate that sumatriptan, most likely via activation of distinctly localized microvascular 5‐HT1B receptors, can induce a constriction and/or a dilation which is sensitive to inhibition of NO synthesis and dependent on the size and, possibly, the existing tone of the vessels.

British Journal of Pharmacology (2001) 132, 55–62; doi:10.1038/sj.bjp.0703763
In various tumour cell lines the peptide bradykinin B2 receptor antagonist, Hoe 140 (Icatibant), may act as mitogenic agonist
Authors: Drube Sebastian , Liebmann Claus
Published: January 2005

This study examined the mitogenic effects of bradykinin (BK, Arg‐Pro‐Pro‐Gly‐Phe‐Ser‐Pro‐Phe‐Arg), the peptide bradykinin B2 receptor antagonist Hoe 140 (D‐Arg0[Hyp3‐Thi6‐D‐Tic7‐Oic8]BK, and the orally active, nonpeptide B2 receptor antagonist FR 173657 ((E)‐3‐(6‐acetamido‐3‐pyridyl)‐N‐[N‐2‐4‐dichloro‐3‐[(2‐methyl‐8‐quinolinyl) oxymethyl]phenyl]‐N‐methylaminocarbonyl‐methyl]acrylamide) in three different human tumour cell lines: the small cell lung carcinoma (SCLC) cell line H‐69, the breast carcinoma cell line EFM‐192A, and the colon carcinoma cell line SW‐480.

In these cell lines activation of mitogen‐activated protein kinase (MAPK) is involved in BK‐induced stimulation of cell proliferation and may be mediated by both Gq proteins (SW‐480) and Gi proteins (EFM‐192A; H‐69).

In these cells BK as well as Hoe 140 increased the rate of DNA synthesis measured with the [3H]‐thymidine uptake assay. Hoe 140 did neither antagonize nor potentiate the effect of BK. FR 173657 did not stimulate [3H]‐thymidine incorporation but clearly antagonized the mitogenic effects of BK as well as Hoe 140. In H‐69 cells, FR 173657 induced a decrease in the basal rate of DNA synthesis.

In all three cell lines BK and Hoe 140 stimulated the activity of MAPK. Their effect on MAPK activity was completely abolished by FR 173657 which itself did not increase the activity of MAPK. In H‐69 cells, the basal activity of MAPK was slightly inhibited by FR 173657.

In the cell lines SW‐480 and H‐69 both BK and Hoe 140 but not FR 173657 stimulated phosphatidylinositol hydrolysis. In H‐69 cells, FR 173657 decreased basal inositol phosphate formation.

Our results show that in certain tumour cell lines the classical peptide B2 receptor antagonist, Hoe 140, may act as mitogenic B2 receptor agonist whereas the nonpeptide B2 receptor antagonist, FR 173657, does not. In H‐69 cells FR 173657 was found to exhibit properties of an inverse agonist.

British Journal of Pharmacology (2000) 131, 1553–1560; doi:10.1038/sj.bjp.0703764
Cardiovascular effects of endothelin‐1 and endothelin antagonists in conscious, hypertensive ((mRen‐2)27) rats
Authors: Gardiner S M , March J E , Kemp P A , Bennett T
Published: January 2005

SB 209670 is a potent antagonist of the vasoconstrictor (ETA‐ and ETB‐receptor‐mediated) and vasodilator (ETB‐receptor‐mediated) effects of endothelin, whereas SB 234551 is relatively selective for the constrictor (ETA‐receptor‐mediated) effects. Since we had previously found SB 209670 exerted antihypertensive, vasodilator effects in conscious, heterozygous, transgenic ((mRen‐2)27) (abbreviated to TG) rats, here we compared the two antagonists in that model, and assessed their chronic effects on responses to exogenous endothelin‐1. We did this to test our global hypothesis, namely, that SB 209670, but not SB 234551, would cause inhibition of the depressor effects of exogenous endothelin‐1 in vivo, and that this differential effect would be associated with a more marked antihypertensive action of SB 234551 in TG rats.

SB 209670 and SB 234551 (infused for 50 h) exerted similar, sustained, antihypertensive effects in TG rats.

The antihypertensive effects of the antagonists occurred at times when the pressor effects of exogenous endothelin‐1 were not significantly inhibited. Furthermore, SB 234551 did not exert a greater antihypertensive effect than SB 209670 at a time (i.e., 2–4 h) when the depressor effects of endothelin‐1 were abolished by the latter, but not by the former (although this differential action was lost after 24 h infusion).

The results caused us to reject the hypothesis that selective antagonism of the vasoconstrictor effects of endothelin‐1 would result in SB 234551 exerting a greater antihypertensive effect than SB 209670 in TG rats.

British Journal of Pharmacology (2000) 131, 1732–1738; doi:10.1038/sj.bjp.0703767
Impaired vasodilator response to organic nitrates in isolated basilar arteries
Authors: Martens Dorothee , Kojda Georg
Published: January 2005

The differential responsiveness of various sections and regions in the vascular system to the vasodilator activity of organic nitrates is important for the beneficial antiischaemic effects of these drugs. In this study we examined the vasodilator activity of organic nitrates in cerebral arteries, where vasodilation causes substantial nitrate induced headache.

Isolated porcine basilar and coronary arteries were subjected to increasing concentrations of glyceryl trinitrate (GTN), isosorbide‐5‐nitrate (ISMN) and pentaerythritol tetranitrate (PETN). S‐nitroso‐N‐acetyl‐D,L‐penicillamine (SNAP) and endothelium‐dependent vasodilation was investigated for comparison purpose.

The vasodilator potency (halfmaximal effective concentration in −logM) of GTN (4.33±0.1, n=8), ISMN (1.61±0.07, n=7) and PETN (>10 μM, n=7) in basilar arteries was more than 100 fold lower than that of GTN (6.52±0.06, n=12), ISMN (3.66±0.08, n=10) and PETN (6.3±0.13, n=8) observed in coronary arteries.

In striking contrast, the vasodilator potency of SNAP (halfmaximal effective concentration in −logM) was almost similar in basilar (7.76±0.05, n=7) and coronary arteries (7.59±0.05, n=9). Likewise, no difference in endothelium dependent relaxation was observed.

Denudation of the endothelium resulted in a small increase of the vasodilator potency (halfmaximal effective concentration in −logM) of GTN (4.84±0.09, n=7, P<0.03) in basilar arteries and similar results were obtained in the presence of the NO‐synthase inhibitor Nω‐nitro‐L‐arginine (4.59±0.05, n=9, P<0.03).

These results suggest that cerebral conductance blood vessels such as porcine basilar arteries seems to have a reduced expression and/or activity of certain cellular enzymatic electron transport systems such as cytochrome P450 enzymes, which are necessary to bioconvert organic nitrates to NO.

British Journal of Pharmacology (2001) 132, 30–36; doi:10.1038/sj.bjp.0703768
Pre‐ and postjunctional protective effect of neocuproine on the nitrergic neurotransmitter in the mouse gastric fundus
Authors: De Man Joris G , Moreels Tom G , De Winter Benedicte Y , Herman Arnold G , Pelckmans Paul A
Published: January 2005

Electrical field stimulation (EFS) of non‐adrenergic non‐cholinergic nerves of the mouse gastric fundus induced frequency‐dependent transient relaxations which were mimicked by nitric oxide (NO), added as acidified NaNO2. The NO donors S‐nitrosocysteine, S‐nitrosoglutathione, SIN‐1 and hydroxylamine induced sustained concentration‐dependent relaxations. The NO synthase blocker L‐nitro arginine (L‐NOARG; 300 μM) abolished the relaxations to EFS without affecting the relaxations to NO.

The copper(I) chelator neocuproine (10 μM) enhanced the relaxations to EFS and NO but inhibited those to S‐nitrosocysteine and S‐nitrosoglutathione. Neocuproine potentiated the relaxations to SIN‐1, which releases NO extracellularly, without affecting the relaxations to hydroxylamine, which releases NO intracellularly.

The potentiating effect of neocuproine on the relaxations to EFS was more pronounced after inhibition of catalase with 3‐amino‐1,2,4‐triazole (1 mM) but not after inhibition of Cu/Zn superoxide dismutase (SOD) with diethyl dithiocarbamic acid (DETCA, 1 mM). The potentiating effect of neocuproine on relaxations to NO was not altered by 3‐amino‐1,2,4‐triazole or DETCA treatment.

The relaxations to EFS were significantly inhibited by the oxidants hydrogen peroxide (70 μM) and duroquinone (10 μM) but only after inhibition of catalase with 3‐amino‐1,2,4‐triazole or after inhibition of Cu/ZnSOD with DETCA respectively.

Our results suggest that neocuproine can act as an antioxidant in the mouse gastric fundus and that both catalase and Cu/ZnSOD protect the nitrergic neurotransmitter from oxidative breakdown. Since inhibition of catalase but not inhibition of Cu/ZnSOD potentiated the effect of neocuproine on relaxations to EFS without affecting the relaxations to NO, catalase may protect the nitrergic neurotransmitter mainly at a prejunctional site whereas Cu/ZnSOD protects at a postjunctional site.

British Journal of Pharmacology (2001) 132, 277–285; doi:10.1038/sj.bjp.0703772
Potentiation of cytokine induction of group IIA phospholipase A2 in rat mesangial cells by ATP and adenosine via the A2A adenosine receptor
Authors: Scholz‐Pedretti Kirsten , Pfeilschifter Josef , Kaszkin Marietta
Published: January 2005

In rat mesangial cells extracellular nucleotides were found to increase arachidonic acid release by a cytosolic phospholipase A2 through the P2Y2 purinergic receptor.

In this study we investigated the effects of ATP and UTP on interleukin‐1β (IL‐1β)‐induced mRNA expression and activity of group IIA phospholipase A2 (sPLA2‐IIA) in rat mesangial cells.

Treatment of cells for 24 h with extracellular ATP potentiated IL‐1β‐stimulated sPLA2‐IIA induction, whereas UTP had no effect.

We obtained the following evidence that the P2Y2 receptor is not involved in the potentiation of sPLA2‐IIA induction: (i) ATP‐γ‐S had no enhancing effect; (ii) suramin, a P2 receptor antagonist, did not inhibit ATP‐mediated potentiation; (iii) inhibition of degradation of extracellular nucleotides by the 5′‐ectonucleotidase inhibitor AOPCP did not enhance sPLA2‐IIA induction and (iv) adenosine deaminase treatment completely abolished the ATP‐mediated potentiation of sPLA2‐IIA induction.

In contrast, treatment of mesangial cells with adenosine or the A2A receptor agonist CGS 21680 mimicked the effects of ATP in enhancing IL‐1β‐stimulated sPLA2‐IIA induction, whereas the specific A2A receptor antagonist ZM 241385 completely abolished the potentiating effect of ATP or adenosine.

The protein kinase A inhibitor Rp‐8‐Br‐cyclic AMPS dose‐dependently inhibited the enhancing effect of ATP or adenosine indicating the participation of an adenosine receptor‐mediated cyclic AMP‐dependent signalling pathway.

These data indicate that ATP mediates proinflammatory long‐term effects in rat mesangial cells via its degradation product adenosine through the A2A receptor resulting in potentiation of sPLA2‐IIA induction.

British Journal of Pharmacology (2001) 132, 37–46; doi:10.1038/sj.bjp.0703774
Role of PGE2 in protease‐activated receptor‐1, −2 and −4 mediated relaxation in the mouse isolated trachea
Authors: Lan Rommel S , Knight Darryl A , Stewart Geoff A , Henry Peter J
Published: January 2005

The potential mediator role of the prostanoid PGE2 in airway smooth muscle relaxations induced by peptidic and proteolytic activators of PAR‐1, PAR‐2, PAR‐3 and PAR‐4 was investigated in carbachol‐precontracted mouse isolated tracheal segments.

The tethered ligand domain sequences of murine PAR‐1 (SFFLRN‐NH2), PAR‐2 (SLIGRL‐NH2) and PAR‐4 (GYPGKF‐NH2), but not PAR‐3 (SFNGGP‐NH2), induced smooth muscle relaxation that was abolished by the non‐selective cyclo‐oxygenase (COX) inhibitor, indomethacin. The relative order for mean peak relaxation was SLIGRL‐NH2>GYPGKF‐NH2 ∼amp; SFFLRN‐NH2>SFNGGP‐NH2.

SFFLRN‐NH2, SLIGRL‐NH2 and GYPGKF‐NH2, but not SFNGGP‐NH2, induced significant PGE2 release that was abolished by indomethacin. Like that for relaxation, the relative order for mean PGE2 release was SLIGRL‐NH2>GYPGKF‐NH2>SFFLRN‐NH2>SFNGGP‐NH2.

In dose‐response studies, SLIGRL‐NH2 induced concentration‐dependent increases in PGE2 release (EC50=20.4 μM) and smooth muscle relaxation (EC50=15.8 μM).

The selective COX‐2 inhibitor, nimesulide, but not the COX‐1 inhibitor valeryl salicylate, significantly attenuated SLIGRL‐NH2‐induced smooth muscle relaxation and PGE2 release.

Exogenously applied PGE2 induced potent smooth muscle relaxation (EC50=60.3 nM) that was inhibited by the mixed DP/EP1/EP2 prostanoid receptor antagonist, AH6809. SLIGRL‐NH2‐induced relaxation was also significantly inhibited by AH6809.

In summary, the results of this study strongly suggest that PAR‐mediated relaxation in murine tracheal smooth muscle is dependent on the generation of the spasmolytic prostanoid, PGE2. PAR‐stimulated PGE2 release appears to be generated preferentially by COX‐2 rather than COX‐1, and induces relaxation via activation of the EP2 receptor.

British Journal of Pharmacology (2001) 132, 93–100; doi:10.1038/sj.bjp.0703776