bluuebunny/crossref_metadata_2025 huggingface dataset:
mGluR‐evoked augmentation of receptor‐mediated cyclic AMP formation in neonatal and adult rat striatum
Authors: Cartmell Jayne , Schaffhauser Hervé , Wichmann Jürgen , Mutel Vincent
Published: August 2006

The effects of selective agonists at group I, II and III metabotropic glutamate receptors (mGluRs) on adenosine A2 receptor‐mediated cyclic AMP formation were compared in cross‐chopped slices of adult and neonatal (8 days old) rat striatum, in the presence of 1 u ml−1 adenosine deaminase.

The group II selective agonist, (2S,1R,2R,3R)‐2‐(2,3‐dicarboxycyclopropyl)glycine (DCG‐IV), elicited a potentiation of 5′‐N‐ethylcarboxamidoadenosine (NECA)‐stimulated cyclic AMP production with similar potencies in adult (EC50 value 122±35 nM) and neonatal (EC50 value 285±6 nM) brain. In contrast, the group I selective agonist (S)‐dihydroxyphenylglycine ((S)‐DHPG) augmented the NECA cyclic AMP response in neonatal striatum (EC50 value 9±1 μM), but at a concentration of 100 μM, (S)‐DHPG failed to affect the NECA response in adult striatal slices.

The potentiation evoked by (S)‐DHPG was specific for group I mGluRs as (2S,3S,4S,)‐2‐methyl‐2‐(carboxycyclopropyl)glycine (MCCG), a group II antagonist, was ineffective on the (S)‐DHPG (100 μM) response at a concentration (500 μM) which reversed a similar augmentation elicited by DCG‐IV (300 nM). Furthermore, a protein kinase C inhibitor (Ro 31‐8220, 10 μM) markedly reversed the effect of (S)‐DHPG without affecting the response to DCG‐IV.

The mGluR agonist (2S,3S,4S,)‐α‐(carboxycyclopropyl)glycine (L‐CCG‐I), elicited a greater potentiation of NECA‐stimulated cyclic AMP production in neonatal striatum in comparison with that observed in adult rat brain. Moreover, EC50 values obtained from adult and neonatal striatum were 2±1 μM and 9±1 μM, respectively. These differences in potency might reflect co‐activation of both group I and group II mGluRs by L‐CCG‐I in neonatal striatum.

Distinct patterns of mGluR expression in various brain areas might account for previous conflicting data on the nature of the mGluR able to evoke such potentiated responses.
Electrically‐evoked dopamine and acetylcholine release from rat striatal slices perfused without magnesium: regulation by glutamate acting on NMDA receptors
Authors: Jin Shaoyu , Fredholm Bertil B
Published: August 2006

Rat striatal slices, preincubated with [3H]‐dopamine and [14C]‐choline, were continuously superfused and electrically stimulated. Electrically evoked release of [3H]‐dopamine and [14C]‐acetylcholine (ACh) was not significantly changed by elimination of Mg2+ from superfusion buffer, but the basal release of [3H]‐dopamine was doubled.

Kynurenic acid (100–800 μM) caused, in the absence but not presence of Mg2+, a concentration‐dependent decrease in the evoked release of these two transmitters. The addition of glycine reversed the inhibition of the evoked release of both transmitters caused by kynurenic acid (400 μM) in a concentration‐dependent manner. In addition, glycine increased the evoked release of [3H]‐dopamine via a site inhibitable by strychnine (1 μM).

Another two antagonists at N‐methyl‐D‐aspartate (NMDA) receptors, 2‐amino‐5‐phosphonovaleric acid and dizocilpine, also decreased significantly the evoked release of the two transmitters in a concentration‐dependent manner in the absence, but not presence of Mg2+. By contrast, an antagonist of non‐NMDA receptors, 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (10 μM) significantly decreased the evoked release of the two transmitters in the presence, but not in the absence of Mg2+.

Electrical field stimulation evoked release of endogenous adenosine, and this release tended to be higher in the absence of Mg2+. However, the addition of a selective adenosine A1 receptor antagonist 8‐cyclopentyl‐1,3‐dipropylxanthine (200 nM) did not influence the evoked release of the two transmitters, showing that the released adenosine is of little importance in controlling ACh and dopamine release from striatal slices. Non‐NMDA receptors may play a similar role when Mg2+ ions are present.

The results indicate that NMDA receptors activated in the absence of Mg2+ participate in the electrically‐evoked release of [3H]‐dopamine and [14C]‐ACh from the striatum.
Interactions between loreclezole, chlormethiazole and pentobarbitone at GABAA receptors: functional and binding studies
Authors: Zhong Yu , Simmonds Michael A
Published: August 2006

Interations were investigated between loreclezole, chlormethiazole and pentobarbitone as potentiators of depolarization responses mediated by γ‐aminobutyric acidA (GABAA) receptors on afferent nerve terminals in the rat cuneate nucleus in vitro. These drugs were also compared as modulators of [3H]‐flunitrazepam (FNZ) binding to synaptic membranes prepared from rat whole brain homogenate.

In rat cuneate nucleus slices, the drugs shifted muscimol log dose–response lines to the left in an approximately parallel fashion with the result that 200 μM chlormethiazole potentiated muscimol responses by 0.567±0.037 log unit (mean±s.e.mean, n=4) while loreclezole gave a maximal potentiation at 10 μM of only 0.121±0.037 (n=6) log unit and 0.071±0.039 (n=22) at 50 μM.

While 50 μM chlormethiazole and 30 μM pentobarbitone showed no significant interactions between each other when potentiating muscimol responses in combination, 50 μM loreclezole in combination with either chlormethiazole or pentobarbitone attenuated their potentiating effects, possibly by inducing desensitization of GABAA receptors.

In the [3H]‐FNZ binding studies on well‐washed membranes, loreclezole enhanced binding to a maximum of 47.3±2.83% of control (mean±s.e.mean, n=3) at 300 μM. Scatchard analysis revealed no change in Bmax but a decrease in KD for [3H]‐FNZ from 3.9±0.29 nM to 2.7±0.10 nM (mean±s.e.mean, n=4) in the presence of 100 μM loreclezole. In contrast, 100 μM chlormethiazole caused no potentiation. A small component of the enhancement by loreclezole could be blocked by 100 μM bicuculline and could also be blocked by 100 μM chlormethiazole. It seems likely that the effects on [3H]‐FNZ binding are due predominantly to direct actions of the drugs on the GABAA receptor and are separate from the GABA‐potentiating effects.

The results indicate distinctly different profiles of action for loreclezole, chlormethiazole and pentobarbitone on GABAA receptors.
Effect of oxytocin as a partial agonist at vasoconstrictor vasopressin receptors on the human isolated uterine artery
Authors: Jovanović Aleksandar , Jovanović Sofija , Tulić Ivan , Grbović Leposava
Published: August 2006

The effect of oxytocin on endothelium‐intact and endothelium‐denuded segments of the human uterine artery rings was investigated.

In both types of preparation oxytocin induced contraction of human uterine artery with similar potency and efficacy (pEC50 values: 6.95±0.05 vs 7.06±0.01; maximal response values: 61±4.1% vs 63±5.1% for arteries with and without endothelium, respectively).

In contrast, human uterine arteries, both intact and denuded of endothelium, did not respond to the addition of the selective oxytocin receptor agonist, [Thr4, Gly7]oxytocin (10 nM–1 μM).

The vasopressin receptor antagonists, [d(CH2)5Tyr(Me)]AVP (10–100 nM) and [d(CH2)5,D‐Ile2,Ile4]AVP (300 nM–3 μM) produced parallel rightward shifts of the curves for oxytocin. The Schild plots constrained to a slope of unity gave the following −log KB values: [d(CH2)5Tyr(Me)] AVP vs [d(CH2)5,D‐Ile2,Ile4] AVP 9.24 vs 6.91 and 9.26 vs 6.84 for human uterine artery with intact and those denuded of endothelium, respectively. In contrast, in both types of preparations the oxytocin receptor antagonist, [d(CH2)5Tyr(OMe), 2Orn8]vasotocin (1 μM), did not significantly affect oxytocin‐induced contractions.

The calculated pKA values for oxytocin itself also did not differ between preparations: 6.56 and 6.43 for human uterine artery with and without endothelium, respectively. In both types of preparations, the receptor reserve (KA/EC50) was close to unity (intact vs denuded: 3.9 vs 3.0).

It is concluded that, in human uterine artery, oxytocin induces contractions that are not modulated by the endothelium. It is likely that oxytocin acts as a partial agonist on human uterine artery, regardless of the endothelial condition. On the basis of differential antagonists affinity and affinity of oxytocin itself, it is probable that receptors involved in oxytocin‐induced contraction in human uterine arteries belong to the V1A vasopressin receptors.
The mechanisms of enhancement and inhibition of field stimulation responses of guinea‐pig vas deferens by prostacyclin analogues
Authors: Tam Fiona S F , Chan Kam‐ming , Bourreau Jean‐Pierre , Jones Robert L
Published: August 2006

In the guinea‐pig isolated vas deferens preparation bathed in Tyrode's solution, the prostacyclin analogues, cicaprost, TEI‐9063, iloprost, taprostene and benzodioxane‐prostacyclin, enhanced twitch responses to submaximal electrical field stimulation (20%‐EFS). The high potency of cicaprost (EC150=1.3 nM) and the relative potencies of the analogues (equi‐effective molar ratios=1.0, 0.85, 1.6, 17 and 82, respectively) suggest the involvement of a prostacyclin (IP‐) receptor.

Maximum enhancement induced by cicaprost in 2.5 mM K+ Krebs‐Henseleit solution was similar to that in Tyrode solution (2.7 mM K+), but was progressively reduced as the K+ concentration was increased to 3.9, 5.9 and 11.9 mM. There was also a greater tendency for the other prostacyclin analogues to inhibit EFS responses in 5.9 mM standard K+ Krebs‐Henseleit solution; this may be attributed to their agonist actions on presynaptic EP3‐receptors resulting in inhibition of transmitter release.

The EFS enhancing action of cicaprost was not affected by the α1‐adrenoceptor antagonist prazosin (100 and 1000 nM). Cicaprost (20 and 200 nM) did not affect contractile responses of the vas deferens to either ATP (5 μM) or α,β‐methylene ATP (1 μM) in the presence of tetrodotoxin (TTX, 100 nM). In addition, enhancement by cicaprost of responses to higher concentrations of ATP (30 and 300 μM) in the absence of TTX, as shown previously by others, was not seen. Prostaglandin E2 (PGE2, 10 nM) and another prostacyclin analogue TEI‐3356 (20 nM) enhanced purinoceptor agonist responses. Unexpectedly, TTX (0.1 and 1 μM) partially inhibited contractions elicited by 10–1000 μM ATP; contractions elicited by 1–3 μM ATP were unaffected. Further studies are required to establish whether a pre‐ or post‐synaptic mechanism is involved.

In a separate series of experiments, cicaprost (5–250 nM), TEI‐9063 (3–300 nM), 4‐aminopyridine (10–100 μM) and tetraethylammonium (100–1000 μM) enhanced both 20%‐EFS responses and the accompanying overflow of noradrenaline to a similar extent. In further experiments with the EP1‐receptor antagonist AH 6809, TEI‐3356 (1.0–100 nM) and the EP3‐receptor agonist, sulprostone (0.1–1.0 nM) inhibited both maximal EFS responses and noradrenaline overflow, thus confirming previous reports of the high activity of TEI‐3356 at the EP3‐receptor. Cicaprost had no significant effect on noradrenaline overflow at 10 and 100 nM, but produced a modest inhibition at 640 nM.

In conclusion, our studies show that prostacyclin analogues (particularly TEI‐3356) can inhibit EFS responses of the guinea‐pig vas deferens by acting as agonists at presynaptic EP3‐receptors. Prostacyclin analogues (particularly cicaprost and TEI‐9063) can also enhance EFS responses through activation of IP‐receptors. The mechanism of the enhancement has not been rigorously established but from our results we favour a presynaptic action to increase transmitter release.
ACE inhibitor potentiation of bradykinin‐induced venoconstriction
Authors: Hecker Markus , Blaukat Andree , Bara Agnieszka T , Müller‐Esterl Werner , Busse Rudi
Published: August 2006

Angiotensin‐converting enzyme (ACE) inhibitors exert their cardiovascular effects not only by preventing the formation of angiotensin II (AII), but also by promoting the accumulation of bradykinin in or at the vessel wall. In addition, certain ACE inhibitors have been shown to augment the vasodilator response to bradykinin, presumably by an interaction at the level of the B2 receptor. We have investigated whether this is a specific effect of the ACE inhibitor class of compounds in isolated endothelium‐denuded segments of the rabbit jugular vein where bradykinin elicits a constrictor response which is exclusively mediated by activation of the B2 receptor.

Moexiprilat and ramiprilat ( 3 nM) enhanced the constrictor response to bradykinin three to four fold. Captopril and enalaprilat were less active by approximately one and quinaprilat by two orders of magnitude. Moexiprilat and ramiprilat, on the other hand, had no effect on the constrictor response to AII or the dilator response to acetylcholine.

The bradykinin‐potentiating effect of the ACE inhibitors was not mimicked by inhibitors of amino‐, carboxy‐, metallo‐ or serine peptidases or the synthetic ACE substrate, hippuryl‐L‐histidyl‐L‐leucine, at a concentration which almost abolished the residual ACE activity in the vessel wall. In contrast, angiotensin‐(1–7) (10 μM), an angiotensin I metabolite, significantly enhanced the constrictor response to bradykinin.

Ramiprilat did not alter the binding of [3H]‐bradykinin to a membrane fraction prepared from endothelium‐denuded rabbit jugular veins or to cultured fibroblasts, and there was no ACE inhibitor‐sensitive, bradykinin‐induced cleavage of the B2 receptor in cultured endothelial cells.

These findings demonstrate that ACE inhibitors selectively potentiate the B2 receptor‐mediated vascular effects of bradykinin. Their relative efficacy appears to be independent of their ACE‐inhibiting properties and might be related to differences in molecule structure. Moreover, the potentiation of the biological activity of bradykinin by this class of compounds does not seem to be mediated by a shift in affinity of the B2 receptor or a prevention of its desensitization, but may involve an increase in the intrinsic activity of unoccupied B2 receptor molecules.
Stellettamide‐A, a novel inhibitor of calmodulin, isolated from a marine sponge
Authors: Abe Yoshinori , Saito Shin‐ya , Hori Masatoshi , Ozaki Hiroshi , Fusetani Nobuhiro , Karaki Hideaki
Published: August 2006

Stellettamide A (ST‐A), a novel marine toxin isolated from a marine sponge, inhibited high K+(72.7 mM)‐induced contraction in the smooth muscle of guinea‐pig taenia coli with an IC50 of 88 μM.

In the taenia permeabilized with Triton X‐100, ST‐A inhibited Ca2+ (3 and 10 μM)‐induced contractions with an IC50 of 46 μM for 3 μM Ca2+ and 105 μM for 10 μM Ca2+. In the permeabilized taenia, calyculin‐A (300 nM), a potent inhibitor of type‐1 and type‐2A phosphatases, induced sustained contraction in the absence of Ca2+. ST‐A had no effect on this contraction.

ST‐A inhibited Mg2+‐ATPase activity in native actomyosin prepared from chicken gizzard with an IC50 of 25 μM.

In a reconstituted smooth muscle contractile system containing calmodulin, myosin light chain (MLC) and MLC kinase, ST‐A inhibited MLC phosphorylation with an IC50 of 152 μM. The inhibitory effect of ST‐A was antagonized by increasing the concentration of calmodulin.

ST‐A inhibited calmodulin activity, assessed by Ca2+/calmodulin‐dependent enzymes, (Ca2+‐Mg2+)‐ATPase of erythrocyte membrane, with an IC50 of 100 μM and phosphodiesterase prepared from bovine cardiac muscle with an IC50 of 52 μM. The inhibitory effect on phosphodiesterase activity was antagonized by increasing the calmodulin concentration.

Interaction between ST‐A and calmodulin was demonstrated by instantaneous quenching of the intrinsic tyrosine fluorescence of calmodulin by ST‐A (3–300 μM). Similar results were obtained in the presence or absence of Ca2+ suggesting that ST‐A binds to calmodulin and that Ca2+ is not essential for the binding of ST‐A to calmodulin.

These results suggest that ST‐A, isolated from marine metabolites, is a novel inhibitor of calmodulin.
The involvement of tumour necrosis factor‐α in the protective effects of 17β oestradiol in splanchnic ischaemia‐reperfusion injury
Authors: Squadrito Francesco , Altavilla Domenica , Squadrito Giovanni , Campo Giuseppe M. , Arlotta Mariarita , Arcoraci Vincenzo , Minutoli Letteria , Saitta Antonino , Caputi Achille P.
Published: August 2006

Tumour necrosis factor‐α (TNF‐α) is a cytokine that is implicated in the pathogenesis of ischaemic states and atherosclerosis. We tested the hypothesis that the vasoprotective effects of the oestrogens may be mediated in vivo by inhibition of the formation of TNF‐α.

Anaesthetized rats, subjected to total occlusion of the superior mesenteric artery and the coeliac trunk for 45 min developed a severe shock state resulting in a fatal outcome within 75–90 min after the release of occlusion. Sham‐operated animals were used as controls.

Splanchnic artery occlusion (SAO) shocked rats had a marked hypotension, enhanced levels of TNF‐α in serum and macrophages, leukopenia and increased ileal leukocyte accumulation, studied by means of myeloperoxidase activity (MPO). Furthermore, aortae from SAO rats showed a marked hyporeactivity to phenylephrine (PE, 1 nM–10 μM), reduced responsiveness to acetylcholine (ACh, 10 nM–10 μM) and an increased staining for intercellular adhesion molecule‐1 (ICAM‐1).

In vivo administration of 17β oestradiol (500 μg kg−1, i.m., three hours before the induction of SAO) increased survival rate (100%, 4 h after SAO), enhanced mean arterial blood pressure; reduced serum TNF‐α (25±5 u ml−1 vs 379±16 u ml−1), ameliorated leukopaenia and reduced ileal MPO (0.7±0.02 u 10−3 g−1 tissue vs 4.2±0.4 u 10−3 g−1 tissue). Furthermore aortae from SAO rats treated with 17β oestradiol exhibited a greater contractile response to phenylephrine, improved responsiveness to ACh and a blunted staining of ICAM‐1. Finally 17β oestradiol, added in vitro to peritoneal macrophages collected from untreated SAO rats, significantly reduced TNF‐α production.

Our results suggest that inhibition of TNF‐αin vivo may explain, at least in part, the vasoprotective effects of oestrogens.

British Journal of Pharmacology (1997) 121, 1782–1788; doi:10.1038/sj.bjp.0701288
Effects of Ca2+ channel blocker neurotoxins on transmitter release and presynaptic currents at the mouse neuromuscular junction
Authors: Katz Eleonora , Protti Darío A. , Ferro Pablo A. , Rosato Siri Marcelo D. , Uchitel Osvaldo D.
Published: August 2006

The effects of the voltage‐dependent calcium channel (VDCC) blockers ω‐agatoxin IVA (ω‐AgaIVA), ω‐conotoxin GVIA (ω‐CgTx), ω‐conotoxin MVIIC (ω‐MVIIC) and ω‐conotoxin MVIID (ω‐MVIID) were evaluated on transmitter release in the mouse diaphragm preparation. The effects of ω‐AgaIVA and ω‐MVIIC were also evaluated on the perineurial calcium and calcium‐dependent potassium currents, ICa and IK(Ca), respectively, in the mouse levator auris preparation.

The P‐ and Q‐type VDCC blocker ω‐AgaIVA (100 nM) and P‐ Q‐ and N‐type channel blockers ω‐MVIIC (1 μM) and ω‐MVIID (3 μM) strongly reduced transmitter release (>80–90% blockade) whereas the selective N‐type channel blocker ω‐CgTx (5 μM) was ineffective.

The process of release was much more sensitive to ω‐MVIIC (IC50=39 nM) than to ω‐MVIID (IC50=1.4 μM). After almost completely blocking transmitter release (quantal content ∼0.3% of its control value) with 3 μMω‐MVIIC, elevating the external [Ca2+] from 2 to 10 mM induced an increase of ∼20 fold on the quantal content of the endplate potential (e.p.p.) (from 0.2±0.04 to 4.8±1.4).

Nerve‐evoked transmitter release in a low Ca2+‐high Mg2+ medium (low release probability, quantal content = 2±0.1) had the same sensitivity to ω‐AgaIVA (IC50=16.8 nM) as that in normal saline solutions. In addition, K+‐evoked transmitter release was also highly sensitive to the action of this toxin (IC50=11.5 nM; 100 nM >95% blockade). The action of ω‐AgaIVA on transmitter release could be reversed by toxin washout if the experiments were carried out at 31–33°C. Conversely, the effect of ω‐AgaIVA persisted even after two hours of toxin washout at room temperature.

Both the calcium and calcium‐dependent potassium presynaptic currents, ICa and IK(Ca), respectively, were highly sensitive to low concentrations (10–30 nM) of ω‐AgaIVA. The ICa and the IK(Ca) were also strongly reduced by 1 μMω‐MVIIC. The most marked difference between the action of these two toxins was the long incubation times required to achieve maximal effects with ω‐MVIIC.

In summary these results provide more evidence that synaptic transmission at the mammalian neuromuscular junction is mediated by Ca2+ entry through P‐ and/or Q‐type calcium channels.

British Journal of Pharmacology (1997) 121, 1531–1540; doi:10.1038/sj.bjp.0701290
Influence of AMPA/kainate receptors on extracellular 5‐hydroxytryptamine in rat midbrain raphe and forebrain
Authors: Tao Rui , Ma Zhiyuan , Auerbach Sidney B.
Published: August 2006

The regulation of 5‐hydroxytryptamine (5‐HT) release by excitatory amino acid (EAA) receptors was examined by use of microdialysis in the CNS of freely behaving rats. Extracellular 5‐HT was measured in the dorsal raphe nucleus (DRN), median raphe nucleus (MRN), nucleus accumbens, hypothalamus, frontal cortex, dorsal and ventral hippocampus.

Local infusion of kainate produced increases in extracellular 5‐HT in the DRN and MRN. Kainate infusion into forebrain sites had a less potent effect.

In further studies of the DRN and nucleus accumbens, kainate‐induced increases in extracellular 5‐HT were blocked by the EAA receptor antagonists, kynurenate and 6,7‐dinitroquinoxaline‐2,3‐dione (DNQX).

The effect of infusing kainate into the DRN or nucleus accumbens was attenuated or abolished by tetrodotoxin (TTX), suggesting that the increase in extracellular 5‐HT is dependent on 5‐HT neuronal activity. In contrast, ibotenate‐induced lesion of intrinsic neurones did not attenuate the effect of infusing kainate into the nucleus accumbens. Thus, the effect of kainate in the nucleus accumbens does not depend on intrinsic neurones.

Infusion of α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolaproprionate (AMPA) into the DRN and nucleus accumbens induced nonsignificant changes in extracellular 5‐HT. Cyclothiazide and diazoxide, which attenuate receptor desensitization, greatly enhanced the effect of AMPA on 5‐HT in the DRN, but not in the nucleus accumbens.

In conclusion, AMPA/kainate receptors regulate 5‐HT in the raphe and in forebrain sites.

British Journal of Pharmacology (1997) 121, 1707–1715; doi:10.1038/sj.bjp.0701292
Characterization of the Ca2+ responses evoked by ATP and other nucleotides in mammalian brain astrocytes
Authors: Centemeri Carlo , Bolego Chiara , Abbracchio Maria P. , Cattabeni Flaminio , Puglisi Lina , Burnstock Geoffrey , Nicosia Simonetta
Published: August 2006

This study was aimed at characterizing ATP‐induced rises in cytosolic free calcium ion, [Ca2+]i, in a population of rat striatal astrocytes loaded with the fluorescent Ca2+ probe Fura2, by means of fluorescence spectrometry.

ATP triggered a fast and transient elevation of [Ca2+]i in a concentration‐dependent manner. The responses of the purine analogues 2‐methylthio‐ATP (2‐meSATP), adenosine‐5′‐O‐(2‐thiodiphosphate) (ADPβS), as well as uridine‐5′‐triphosphate (UTP) resembled that of ATP, while α,β‐methylene‐ATP (α,β‐meATP) and β,γ‐methylene‐ATP (β,γ‐meATP) were totally ineffective.

Suramin (50 μM) had only a minor effect on the ATP response, whereas pyridoxal phosphate‐6‐azophenyl‐2′,4′‐disulphonic acid (PPADS) (5 μM) significantly depressed the maximum response.

Extracellular Ca2+ did not contribute to the observed [Ca2+]i rise: removing calcium from the extracellular medium (with 1 mM EGTA) or blocking its influx by means of either Ni2+ (1 mM) or Mn2+ (1 mM) did not modify the nucleotide responses.

Furthermore, after preincubation with 10 μM thapsigargin, the nucleotide‐evoked [Ca2+]i increments were completely abolished. In contrast, 10 mM caffeine did not affect the responses, suggesting that thapsigargin‐, but not caffeine/ryanodine‐sensitive stores are involved.

Both application of the G‐protein blocker guanosine‐5′‐O‐(2‐thiodiphosphate) (GDPβS) (1 mM) and preincubation with pertussis toxin (PTx) (350 ng ml−1) partially inhibited the nucleotide‐mediated responses. Moreover, the phospholipase C (PLC) inhibitor U‐73122, but not its inactive stereoisomer U‐73343 (5 μM), significantly reduced the ATP‐evoked [Ca2+]i rise.

In conclusion, our results suggest that, in rat striatal astrocytes, ATP‐elicited elevation of [Ca2+]i is due solely to release from intracellular stores and is mediated by a G‐protein‐linked P2Y receptor, partially sensitive to PTx and coupled to PLC.

British Journal of Pharmacology (1997) 121, 1700–1706; doi:10.1038/sj.bjp.0701293
Characterization of the signalling pathways involved in ATP and basic fibroblast growth factor‐induced astrogliosis
Authors: Bolego Chiara , Ceruti Stefania , Brambilla Roberta , Puglisi Lina , Cattabeni Flaminio , Burnstock Geoffrey , Abbracchio Maria P.
Published: August 2006

A brief challenge of rat astrocytes with either α,β‐methyleneATP (α,β‐meATP) or basic fibroblast growth factor (bFGF) resulted, three days later, in morphological differentiation of cells, as shown by marked elongation of astrocytic processes. The P2 receptor antagonist suramin prevented α,β‐meATP‐ but not bFGF‐induced astrocytic elongation. Similar effects on astrocytic elongation were also observed with ATP and other P2 receptor agonists (β,γmeATP, ADPβS, 2meSATP and, to a lesser extent, UTP).

Pertussis toxin completely abolished α,β‐meATP‐ but not bFGF‐induced effects. No effects were exerted by α,β‐meATP on cyclic AMP production; similarly, neomycin had no effects on elongation of processes induced by the purine analogue, suggesting that adenylyl cyclase and phospholipase C are probably not involved in α,β‐meATP‐induced effects (see also the accompanying paper by Centemeri et al., 1997). The tyrosine‐kinase inhibitor genistein greatly reduced bFGF‐ but not α,β‐meATP‐induced astrocytic elongation.

Challenge of cultures with α,β‐meATP rapidly and concentration‐dependently increased [3H]‐arachidonic acid (AA) release from cells, suggesting that activation of phospholipase A2 (PLA2) may be involved in the long‐term functional effects evoked by purine analogues. Consistently, exogenously added AA markedly elongated astrocytic processes. Moreover, various PLA2 inhibitors (e.g. mepacrine and dexamethasone) prevented both the early α,β‐meATP‐induced [3H]‐AA release and/or the associated long‐term morphological changes, without affecting the astrocytic elongation induced by bFGF. Finally, the protein kinase C (PKC) inhibitor H7 fully abolished α,β‐meATP‐ but not bFGF‐induced effects.

Both α,β‐meATP and bFGF rapidly and transiently induced the nuclear accumulation of Fos and Jun. Both c‐fos and c‐jun induction by the purine analogue could be fully prevented by pretreatment with suramin. In contrast, the effects of bFGF were unaffected by this P2 receptor antagonist.

It was concluded that α,β‐meATP‐ and bFGF‐morphological differentiation of astrocytes occurs via independent transductional pathways. For the purine analogue, signalling involves a Gi/Go protein‐coupled P2Y‐receptor which may be linked to activation of PLA2 (involvement of an arachidonate‐sensitive PKC is speculated); for bFGF, a tyrosine kinase receptor is involved. Both pathways merge on some common intracellular target, as suggested by induction of primary response genes, which in turn may regulate late response genes mediating long‐term phenotypic changes of astroglial cells.

These findings implicate P2 receptors as novel targets for the pharmacological regulation of reactive astrogliosis, which has intriguing implications in nervous system diseases characterized by degenerative events.

British Journal of Pharmacology (1997) 121, 1692–1699; doi:10.1038/sj.bjp.0701294
Evidence that the substance P‐induced enhancement of pacemaking in lymphatics of the guinea‐pig mesentery occurs through endothelial release of thromboxane A2
Authors: Rayner Sharyn E. , Van Helden Dirk F.
Published: August 2006

In vitro studies were performed to examine the mechanisms underlying substance P‐induced enhancement of constriction rate in guinea‐pig mesenteric lymphatic vessels.

Substance P caused an endothelium‐dependent increase in lymphatic constriction frequency which was first significant at a concentration of 1 nM (115±3% of control, n=11) with 1 μM, the highest concentration tested, increasing the rate to 153±4% of control (n=9).

Repetitive 5 min applications of substance P (1 μM) caused tachyphylaxis with tissue responsiveness tending to decrease (by an average of 23%) and significantly decreasing (by 72%) for application at intervals of 30 and 10 min, respectively.

The competitive antagonist of tachykinin receptors, spantide (5 μM) and the specific NK1 receptor antagonist, WIN51708 (10 μM) both prevented the enhancement of constriction rate induced by 1 μM substance P.

Endothelial cells loaded with the Ca2+ sensing fluophore, fluo 3/AM did not display a detectable change in [Ca2+]i upon application of 1 μM substance P.

Inhibition of nitric oxide synthase by NG nitro‐L‐arginine (L‐NOARG; 100 μM) had no significant effect on the response induced by 1 μM substance P.

The enhancement of constriction rate induced by 1 μM substance P was prevented by the cyclo‐oxygenase inhibitor, indomethacin (3 μM), the thromboxane A2 synthase inhibitor, imidazole (50 μM), and the thromboxane A2 receptor antagonist, SQ29548 (0.3 μM).

The stable analogue of thromboxane A2, U46619 (0.1 μM) significantly increased the constriction rate of lymphangions with or without endothelium, an effect which was prevented by SQ29548 (0.3 μM).

Treatment with pertussis toxin (PTx; 100 ng ml−1) completely abolished the response to 1 μM substance P without inhibiting either the perfusion‐induced constriction or the U46619‐induced enhancement of constriction rate.

Application of the phospholipase A2 inhibitor, antiflammin‐1 (1 nM) prevented the enhancement of lymphatic pumping induced by substance P (1 μM), without inhibiting the response to either U46619 (0.1 μM) or acetylcholine (10 μM).

The data support the hypothesis that the substance P‐induced increase in pumping rate is mediated via the endothelium through NK1 receptors coupled by a PTx sensitive G‐protein to phospholipase A2 and resulting in generation of the arachidonic acid metabolite, thromboxane A2, this serving as the diffusible activator.

British Journal of Pharmacology (1997) 121, 1589–1596; doi:10.1038/sj.bjp.0701306
Hypoglycaemic effects of the novel antidiabetic agent repaglinide in rats and dogs
Authors: Mark Michael , Grell Wolfgang
Published: August 2006

Repaglinide, a novel compound with a nonsulphonylurea structure, is currently being clinically tested as a therapeutic agent. In the present study, the hypoglycaemic effects of repaglinide in rats and dogs were investigated.

Whereas the R‐enantiomer, AG‐EE 624 ZW, showed only weak hypoglycaemic activity, the S‐enantiomer, repaglinide, turned out to be a potent hypoglycaemic compound in rats after oral as well as after intravenous administration. Only 50% of the dose of repaglinide was needed to be equieffective with the racemic mixture AG‐EE 388 ZW. The corresponding ED50 values calculated for the effects after 120 min p.a. (intravenous administration) were 3.4 μg kg−1 (repaglinide) and 6 μg kg−1 (AG‐EE 388 ZW).

When compared to glimepiride or glibenclamide, repaglinide displayed a 18 to 25 times higher potency in fasted rats. The ED50 values calculated for the effects after 120 min p.a. (oral administration) were 10 μg kg−1 (repaglinide), 182 μg kg−1 (glimepiride) and 255 μg kg−1 (glibenclamide).

In glucose loaded rats (0.5, 1.0, 2.0 and 3.0 g kg−1 glucose, p.o.) repaglinide exerted a very strong antihyperglycaemic activity which was even more pronounced than under normoglycaemic conditions. So for a reduction in blood glucose of 1 mmol l−1, 10.3, 9.3, 7.0 8.4 and 7.2 μg kg−1 repaglinide were needed after glucose loads of 0.0, 0.5, 1.0, 2.0 and 3.0 g kg−1, respectively.

In beagle dogs repaglinide again showed a pronounced hypoglycaemic effect (ED50 28.3 μg kg−1) which lasted for up to 24 h. However, insulin levels were only transiently increased.

The in vivo data presented are well supported by recently published in vitro findings. From its activity profile, repaglinide appears to be a promising new therapeutic agent.

British Journal of Pharmacology (1997) 121, 1597–1604; doi:10.1038/sj.bjp.0701307
Inhibitory effect of a new steroidal saponin, OSW‐1, on ovarian functions in rats
Authors: Tamura Kazuhiro , Honda Hideo , Mimaki Yoshihiro , Sashida Yutaka , Kogo Hiroshi
Published: August 2006

This study was undertaken to determine the effects of OSW‐1 (3β, 16β, 17α‐trihydroxycholest‐5‐en‐22‐one 16‐O‐(2‐O‐4‐methoxybenzoyl‐β‐D‐xylopyranosyl)‐(1→3)‐(2‐O‐acetyl‐α‐L‐arabinopyranoside)) on the pituitary‐ovarian system and the functions of aortic smooth muscle.

A single s.c. injection of OSW‐1 (9 μg kg−1) on the morning of pro‐oestrus inhibited the occurrence of the expected next pro‐oestrus, whereas administration of OSW‐1 at a dose of 4.5 μg kg−1 did not affect the oestrous cycle. OSW‐1 treatment on the day of dioestrus‐l did not affect the oestrous cycle.

At doses of 4.5 and 9 μg kg−1 OSW‐1, the serum oestradiol (E2) levels at the expected next pro‐oestrus were significantly lower than in control (pro‐oestrus). The serum luteinizing hormone (LH) levels 4 days after 9 μg kg−1 OSW‐1 treatment were also markedly lower than those of control. OSW‐1 (4.5 μg kg−1) did not affect the levels of inhibin, progesterone and gonadotrophins on the same day.

OSW‐1 did not inhibit the preovulatory LH surge which occurs on the afternoon of pro‐oestrus day.

The expression of mRNA coding for the cholesterol side chain cleavage cytochrome P‐450 (p450scc), an ovarian steroidal limiting enzyme, was suppressed at 24 and 96 h after OSW‐1 treatment.

Administration of OSW‐1 (9 μg kg−1) tended to reduce the relaxation of isolated thoracic aorta ring preparations induced by acetylcholine, while there was no difference in the relaxation induced by sodium nitroprusside.

Our results show that OSW‐1 inhibits ovarian E2 secretion and that the decrease in E2 secretion may contribute to its effects on the oestrous cycle and the sensitivity of the thoracic aorta to relaxation. The decrease in the levels of ovarian steroids induced by OSW‐1 may be due to its direct inhibitory action on the gene expression of the steroidal enzyme and on the proliferation of granulosa cells in the ovary.

British Journal of Pharmacology (1997) 121, 1796–1802; doi:10.1038/sj.bjp.0701309
Long lasting smooth muscle relaxation by a novel PACAP analogue in guinea‐pig and primate airways in vitro
Authors: Yoshihara Shigemi , Lindén Anders , Kashimoto Kazuhisa , Nagano Yumiko , Ichimura Tohju , Nadel Jay A.
Published: August 2006

We compared the relaxant effect of pituitary adenylate cyclase activating peptide (PACAP) 1–27 with that of a newly developed PACAP 1–27 analogue, [Arg15,20,21Leu17]‐PACAP‐Gly‐Lys‐Arg‐NH2, in the guinea‐pig trachea and primate bronchi in vitro (n=4–5).

In the guinea‐pig trachea precontracted by a submaximally effective carbachol concentration (0.1 μM), cumulative administration of PACAP 1–27 and the β2‐adrenoceptor agonist salbutamol (3 nM–3 μM) caused significant and concentration‐dependent smooth muscle relaxation, with salbutamol being approximately one log‐step more potent in this model. However, in primate bronchi precontracted by carbachol (0.1 μM), cumulative administration of PACAP 1–27 and salbutamol caused concentration‐dependent smooth muscle relaxation with very similar potencies and maximum relaxant effects.

In the guinea‐pig trachea, non‐cumulative administration of the PACAP 1–27 analogue and the original PACAP 1–27 (0.3–3 μM) caused concentration‐dependent relaxation with a very similar maximum relaxant effect and potency. However, the onset and offset of action was markedly slower for the PACAP 1–27 analogue than for the original PACAP 1–27 (>90% versus <10% of peak relaxation remaining 6 h after administration). Separate experiments confirmed that the PACAP 1–27 analogue also caused significant relaxation with slower onset and offset of action than did the original PACAP 1–27 in primate bronchi.

Peptidase inhibition by captopril (10 μM) and phosphoramidon (1 μM) significantly increased the maximum relaxant effect and duration of action of PACAP 1–27 but not of the PACAP 1–27 analogue, during the 3 h of observation in the guinea‐pig trachea.

We conclude that [Arg15,20,21Leu17]‐PACAP‐Gly‐Lys‐Arg‐NH2 produces significant, concentration‐dependent and sustained airway smooth muscle relaxation in vitro. The sustained relaxant effect is due, at least in part, to the PACAP 1–27 analogue being less susceptible to cleavage by peptidases than the original peptide PACAP 1–27.

British Journal of Pharmacology (1997) 121, 1730–1734; doi:10.1038/sj.bjp.0701310
Comparison of the effects of sibutramine and other monoamine reuptake inhibitors on food intake in the rat
Authors: Jackson Helen C. , Needham Andrew M. , Hutchins Lisa J. , Mazurkiewicz Sarah E. , Heal David J.
Published: August 2006

The effects of the potent 5‐hydroxytryptamine (5‐HT) and noradrenaline reuptake inhibitor (serotonin‐noradrenaline reuptake inhibitor, SNRI), sibutramine, on the cumulative food intake of freely‐feeding male Sprague‐Dawley rats during an 8 h dark period were investigated and compared to those of the selective 5‐HT reuptake inhibitor (selective serotonin reuptake inhibitor, SSRI), fluoxetine; the selective noradrenaline reuptake inhibitor, nisoxetine; the 5‐HT and noradrenaline reuptake inhibitors, venlafaxine and duloxetine; and the 5‐HT releaser and 5‐HT reuptake inhibitor, (+)‐fenfluramine.

Sibutramine (3 and 10 mg kg−1, p.o.) and (+)‐fenfluramine (1 and 3 mg kg−1, p.o.) produced a significant, dose‐dependent decrease in food intake over the 8 h dark period. These responses became apparent within the first 2 h following drug administration.

Fluoxetine (3, 10 and 30 mg kg−1, p.o.), and nisoxetine (3, 10 and 30 mg kg−1, p.o.) had no significant effect on food intake during the 8 h dark period. However, a combination of fluoxetine and nisoxetine (30 mg kg−1, p.o., of each) significantly decreased food intake 2 and 8 h after drug administration.

Venlafaxine (100 and 300 mg kg−1, p.o.) and duloxetine (30 mg kg−1, p.o.) also significantly decreased food intake in the 2 and 8 h following drug administration.

The results of this study demonstrate that inhibition of 5‐HT and noradrenaline reuptake by sibutramine, venlafaxine, duloxetine, or by a combination of fluoxetine and nisoxetine, markedly reduces food intake in freely‐feeding rats and suggest that this may be a novel approach for the treatment of obesity.

British Journal of Pharmacology (1997) 121, 1758–1762; doi:10.1038/sj.bjp.0701312
Catecholamine modulatory effects of nepicastat (RS‐25560‐197), a novel, potent and selective inhibitor of dopamine‐β‐hydroxylase
Authors: Stanley William C. , Li Bin , Bonhaus Douglas W. , Johnson Lowell G. , Lee Keiho , Porter Seth , Walker Keith , Martinez Greg , Eglen Richard M. , Whiting Roger L. , Hegde Sharath S.
Published: August 2006

Inhibitory modulation of sympathetic nerve function may have a favourable impact on the progression of congestive heart failure. Nepicastat is a novel inhibitor of dopamine‐β‐hydroxylase, the enzyme which catalyses the conversion of dopamine to noradrenaline in sympathetic nerves. The in vitro pharmacology and in vivo catecholamine modulatory effects of nepicastat were investigated in the present study.

Nepicastat produced concentration‐dependent inhibition of bovine (IC50=8.5±0.8 nM) and human (IC50=9.0±0.8  nM)dopamine‐β‐hydroxylase. The corresponding R‐enantiomer (RS‐25560‐198) was approximately 2–3 fold less potent than nepicastat. Nepicastat had negligible affinity (>10 μM) for twelve other enzymes and thirteen neurotransmitter receptors.

Administration of nepicastat to spontaneously hypertensive rats (SHRs) (three consecutive doses of either 3, 10, 30 or 100 mg kg−1, p.o.; 12 h apart) or beagle dogs (0.05, 0.5, 1.5 or 5 mg kg−1, p.o.; b.i.d., for 5 days) produced dose‐dependent decreases in noradrenaline content, increases in dopamine content and increases in dopamine/noradrenaline ratio in the artery (mesenteric or renal), left ventricle and cerebral cortex. At the highest dose studied, the decreases in tissue noradrenaline were 47%, 35% and 42% (in SHRs) and 88%, 91% and 96% (in dogs) in the artery, left ventricle and cerebral cortex, respectively. When tested at 30 mg kg−1, p.o., in SHRs, nepicastat produced significantly greater changes in noradrenaline and dopamine content, as compared to the R‐enantiomer (RS‐25560‐198), in the mesenteric artery and left ventricle.

Administration of nepicastat (2 mg kg−1, b.i.d, p.o.) to beagle dogs for 15 days produced significant decreases in plasma concentrations of noradrenaline and increases in plasma concentrations of dopamine and dopamine/noradrenaline ratio. The peak reduction (52%) in plasma concentration of noradrenaline and the peak increase (646%) in plasma concentration of dopamine were observed on day‐6 and day‐7 of dosing, respectively.

The findings of this study suggest that nepicastat is a potent, selective and orally active inhibitor of dopamine‐β‐hydroxylase which produces gradual modulation of the sympathetic nervous system by inhibiting the biosynthesis of noradrenaline. This drug may, therefore, be of value in the treatment of cardiovascular disorders associated with over‐activation of the sympathetic nervous system, such as congestive heart failure.

British Journal of Pharmacology (1997) 121, 1803–1809; doi:10.1038/sj.bjp.0701315
Gabapentin (neurontin) and S‐(+)‐3‐isobutylgaba represent a novel class of selective antihyperalgesic agents
Authors: Field M. J. , Oles R. J. , Lewis A. S. , McCleary S , Hughes J , Singh L
Published: August 2006

Gabapentin (neurontin) is a novel antiepileptic agent that binds to the α2δ subunit of voltage‐dependent calcium channels. The only other compound known to possess affinity for this recognition site is the (S)‐(+)‐enantiomer of 3‐isobutylgaba. However, the corresponding (R)‐(−)‐enantiomer is 10 fold weaker. The present study evaluates the activity of gabapentin and the two enantiomers of 3‐isobutylgaba in formalin and carrageenan‐induced inflammatory pain models.

In the rat formalin test, S‐(+)‐3‐isobutylgaba (1–100 mg kg−1) and gabapentin (10–300 mg kg−1) dose‐dependently inhibited the late phase of the nociceptive response with respective minimum effective doses (MED) of 10 and 30 mg kg−1, s.c. This antihyperalgesic action of gabapentin was insensitive to naloxone (0.1–10.0 mg kg−1, s.c.). In contrast, the R‐(−)‐enantiomer of 3‐isobutylgaba (1–100 mg kg−1) produced a modest inhibition of the late phase at the highest dose of 100 mg kg−1. However, none of the compounds showed any effect during the early phase of the response.

The s.c. administration of either S‐(+)‐3‐isobutylgaba (1–30 mg kg−1) or gabapentin (10–100 mg kg−1), after the development of peak carrageenan‐induced thermal hyperalgesia, dose‐dependently antagonized the maintenance of this response with MED of 3 and 30 mg kg−1, respectively. Similar administration of the two compounds also blocked maintenance of carrageenan‐induced mechanical hyperalgesia with MED of 3 and 10 mg kg−1, respectively. In contrast, R‐(−)‐3‐isobutylgaba failed to show any effect in the two hyperalgesia models.

The intrathecal administration of gabapentin dose‐dependently (1–100 μg/animal) blocked carrageenan‐induced mechanical hyperalgesia. In contrast, administration of similar doses of gabapentin into the inflamed paw was ineffective at blocking this response.

Unlike morphine, the repeated administration of gabapentin (100 mg kg−1 at start and culminating to 400 mg kg−1) over 6 days did not lead to the induction of tolerance to its antihyperalgesic action in the formalin test. Furthermore, the morphine tolerance did not cross generalize to gabapentin. The s.c. administration of gabapentin (10–300 mg kg−1), R‐(−) (3–100 mg kg−1) or S‐(+)‐3‐isobutylgaba (3–100 mg kg−1) failed to inhibit gastrointestinal motility, as measured by the charcoal meal test in the rat. Moreover, the three compounds (1–100 mg kg−1, s.c.) did not generalize to the morphine discriminative stimulus. Gabapentin (30–300 mg kg−1) and S‐(+)‐isobutylgaba (1–100 mg kg−1) showed sedative/ataxic properties only at the highest dose tested in the rota‐rod apparatus.

Gabapentin (30–300 mg kg−1, s.c.) failed to show an antinociceptive action in transient pain models. It is concluded that gabapentin represents a novel class of antihyperalgesic agents.

British Journal of Pharmacology (1997) 121, 1513–1522; doi:10.1038/sj.bjp.0701320
Reduction of urinary 8‐epi‐prostaglandin F2α during cyclo‐oxygenase inhibition in rats but not in man
Authors: Bachi Angela , Brambilla Raffaella , Fanelli Roberto , Bianchi Roberto , Zuccato Ettore , Chiabrando Chiara
Published: August 2006

8‐epi‐prostaglandin (PG) F2α, a major F2 isoprostane, is produced in vivo by free radical‐dependent peroxidation of lipid‐esterified arachidonic acid. Both cyclo‐oxygenase isoforms (COX‐1 and COX‐2) may also form free 8‐epi‐PGF2α as a minor product. It has been recently seen in human volunteers that the overall basal formation of 8‐epi‐PGF2αin vivo is mostly COX‐independent and urinary 8‐epi‐PGF2α is therefore an accurate marker of ‘basal’ oxidative stress in vivo.

To test the validity of this marker in the rat, we evaluated in vivo the effect of COX inhibition on the formation of 8‐epi‐PGF2α vs prostanoids. Two structurally unrelated COX inhibitors (naproxen: 30 mg kg−1 day−1; indomethacin: 4 mg kg−1 day−1) were given i.p. to rats kept in metabolic cages. In vivo formation of 8‐epi‐PGF2α was assessed by measuring its urinary excretion. Prostanoid biosynthesis was assessed by measuring urinary excretion of major metabolites of thromboxane (TX) and prostacyclin (2,3‐dinor‐TXB1 and 2,3‐dinor‐6‐keto‐PGF1α). All compounds were selectively measured by immunopurification/gas chromatography‐mass spectrometry.

Naproxen reduced urinary excretion of 2,3‐dinor‐TXB1 and 2,3‐dinor‐6‐keto‐PGF1α but, unexpectedly, also that of 8‐epi‐PGF2α (82, 49 and 52% inhibition, respectively). Indomethacin had a similar effect (77, 69 and 55% inhibition). Esterified 8‐epi‐PGF2α in liver and plasma remained unchanged after indomethacin.

These findings prompted us to re‐assess the contribution of COX activity to the systemic production of 8‐epi‐PGF2α in man. We gave naproxen (1 g day−1) to healthy subjects (four nonsmokers and four smokers). Urinary 8‐epi‐PGF2α remained unchanged in the two groups (9.63±0.99 before vs 10.24±1.01 after and 20.14±3.00 vs 19.03±2.45 ng h−1 1.73 m−2), whereas there was a marked reduction of major urinary metabolites of thromboxane and prostacyclin (about 90% for both 11‐dehydro‐TXB2 and 2,3‐dinor‐TXB2; >50% for 2,3‐dinor‐6‐keto‐PGF1α).

To investigate whether rat COX‐1 produces 8‐epi‐PGF2α more efficiently than human COX‐1, we measured the ex vivo formation of 8‐epi‐PGF2α and TXB2 simultaneously in whole clotting blood. Serum levels of 8‐epi‐PGF2α and TXB2 were similar in rats and man.

We conclude that a significant amount of COX‐dependent 8‐epi‐PGF2α is present in rat but not in human urine under normal conditions. This implies that urinary 8‐epi‐PGF2α cannot be used as an index of near‐basal oxidant stress in rats. On the other hand, our data further confirm the validity of this marker in man.

British Journal of Pharmacology (1997) 121, 1770–1774; doi:10.1038/sj.bjp.0701321