bluuebunny/crossref_metadata_2025 huggingface dataset:
Putative β4‐adrenoceptors in rat ventricle mediate increases in contractile force and cell Ca2+: comparison with atrial receptors and relationship to (−)‐[3H]‐CGP 12177 binding
Authors: Sarsero Doreen , Molenaar Peter , Kaumann Alberto J , Freestone Nicholas S
Published: January 2005

We identified putative β4‐adrenoceptors by radioligand binding, measured increases in ventricular contractile force by (−)‐CGP 12177 and (±)‐cyanopindolol and demonstrated increased Ca2+ transients by (−)‐CGP 12177 in rat cardiomyocytes.

(−)‐[3H]‐CGP 12177 labelled 13–22 fmol mg−1 protein ventricular β1, β2‐adrenoceptors (pKD ∼9.0) and 50–90 fmol mg−1 protein putative β4‐adrenoceptors (pKD ∼7.3). The affinity values (pKi) for (β1,β2‐) and putative β4‐adrenoceptors, estimated from binding inhibition, were (−)‐propranolol 8.4, 5.7; (−)‐bupranolol 9.7, 5.8; (±)‐cyanopindolol 10.0,7.4.

In left ventricular papillary muscle, in the presence of 30 μM 3‐isobutyl‐1‐methylxanthine, (−)‐CGP 12177 and (±)‐cyanopindolol caused positive inotropic effects, (pEC50, (−)‐CGP 12177, 7.6; (±)‐cyanopindolol, 7.0) which were antagonized by (−)‐bupranolol (pKB 6.7–7.0) and (−)‐CGP 20712A (pKB 6.3–6.6). The cardiostimulant effects of (−)‐CGP 12177 in papillary muscle, left and right atrium were antagonized by (±)‐cyanopindolol (pKP 7.0–7.4).

(−)‐CGP 12177 (1 μM) in the presence of 200 nM (−)‐propranolol increased Ca2+ transient amplitude by 56% in atrial myocytes, but only caused a marginal increase in ventricular myocytes. In the presence of 1 μM 3‐isobutyl‐1‐methylxanthine and 200 nM (−)‐propranolol, 1 μM (−)‐CGP 12177 caused a 73% increase in Ca2+ transient amplitude in ventricular myocytes. (−)‐CGP 12177 elicited arrhythmic transients in some atrial and ventricular myocytes.

Probably by preventing cyclic AMP hydrolysis, 3‐isobutyl‐1‐methylxanthine facilitates the inotropic function of ventricular putative β4‐adrenoceptors, suggesting coupling to Gs protein‐adenylyl cyclase. The receptor‐mediated increases in contractile force are related to increases of Ca2+ in atrial and ventricular myocytes. The agreement of binding affinities of agonists with cardiostimulant potencies is consistent with mediation through putative β4‐adrenoceptors labelled with (−)‐[3H]‐CGP 12177.

British Journal of Pharmacology (1999) 128, 1445–1460; doi:10.1038/sj.bjp.0702936
Inhibition of nuclear factor kappa B and induction of apoptosis in T‐lymphocytes by sulfasalazine
Authors: Liptay Susanne , Bachem Max , Häcker Georg , Adler Guido , Debatin Klaus M , Schmid Roland M
Published: January 2005

Chronic inflammatory diseases have been shown to be associated with NF‐κB activation and impaired apoptosis of immune cells. The aim of the present study was to investigate if sulfasalazine and its colonic metabolites 5‐aminosalicylic acid (5ASA) and sulfapyridine affect NF‐κB/Rel activation and viability of T‐lymphocytes.

Sulfasalazine inhibits NF‐κB/Rel activation in the murine T‐lymphocyte cell line RBL5 using electrophoretic mobility shift assays. In transfection assays sulfasalazine treatment for 4 h inhibits κB‐dependent transcription with an IC50 value of ∼0.625 mM.

Higher doses or prolonged treatment result in cell death of T‐lymphocytes in a dose‐ and time‐dependent manner. Cell death is caused by apoptosis as judged by DNA fragmentation, annexin V and Apo 2.7 staining. Induction of apoptosis is a fast event with 50% apoptotic cells after a 4 h incubation with 2.5 mM sulfasalazine. The ED50 value for apoptosis induction after 24 h treatment was ∼0.625 mM.

In contrast, 5ASA and sulfapyridine neither inhibit NF‐κB/Rel activation nor induce apoptosis in T‐lymphocytes at doses up to 5.0 mM.

These results demonstrate that sulfasalazine, but not 5ASA or sulfapyridine, strongly inhibits NF‐κB activation and potently induces apoptosis in T‐lymphocytes. Inhibition of NF‐κB/Rel activation and subsequent clearance of activated T‐lymphocytes by apoptosis might thus explain the beneficial effects of sulfasalazine in the treatment of chronic inflammatory disorders.

British Journal of Pharmacology (1999) 128, 1361–1369; doi:10.1038/sj.bjp.0702937
Activation of muscle nicotinic acetylcholine receptor channels by nicotinic and muscarinic agonists
Authors: Akk Gustav , Auerbach Anthony
Published: January 2005

The dose‐response parameters of recombinant mouse adult neuromuscular acetylcholine receptor channels (nAChR) activated by carbamylcholine, nicotine, muscarine and oxotremorine were measured. Rate constants for agonist association and dissociation, and channel opening and closing, were estimated from single‐channel kinetic analysis.

The dissociation equilibrium constants were (mM): ACh (0.16)<oxotremorine M (0.6)<carbamylcholine (0.8)<nicotine (2.6).

The gating equilibrium constants (opening/closing) were: ACh (45)>carbamylcholine (5.1)>oxotremorine M (0.6)>nicotine (0.5)>muscarine (0.15).

Rat neuronal α4β2 nAChR can be activated by all of the agonists. However, detailed kinetic analysis was impossible because the recordings lacked clusters representing the activity of a single receptor complex. Thus, the number of channels in the patch was unknown and the activation rate constants could not be determined.

Considering both receptor affinity and agonist efficacy, muscarine and oxotremorine are significant agonists of muscle‐type nAChR. The results are discussed in terms of structure‐function relationships at the nAChR transmitter binding site.

British Journal of Pharmacology (1999) 128, 1467–1476; doi:10.1038/sj.bjp.0702941
Novel cardiac protective effects of urea: from shark to rat
Authors: Wang Xintao , Wu Lingyun , Aouffen M'hamed , Mateescu Mircea‐Alexandru , Nadeau Réginald , Wang Rui
Published: January 2005

This study was carried out to investigate novel cardioprotective effects of urea and the underlying mechanisms. The cardiac functions under oxidative stress were evaluated using Langendorff perfused isolated heart.

Isolated dogfish shark hearts tolerated the oxidative stress generated by electrolysis (10 mA, 1 min) of the perfusion solution (n=4), and also showed normal cardiac functions during post‐ischaemia reperfusion (n=4). The high concentration of urea (350 mM) in the heart perfusate was indispensable for maintaining the normal cardiac functions of the shark heart.

Urea at 3–300 mM (n=4 for each group) protected the isolated rat heart against both electrolysis‐induced heart damage and post‐ischaemia reperfusion‐induced cardiac injury.

A concentration‐dependent scavenging effect of urea (3–300 mM, n=4 for each group) against electrolysis‐induced reactive oxygen species was also demonstrated in vitro.

Urea derivatives as hydroxyurea, dimethylurea, and thiourea had antioxidant cardioprotective effect against the electrolysis‐induced cardiac dysfunction of rat heart, but were not as effective as urea in suppressing the post‐ischaemia reperfusion injury.

Our results suggest that urea and its derivatives are potential antioxidant cardioprotective agents against oxidative stress‐induced myocardium damage including the post‐ischaemia reperfusion‐induced injury.

British Journal of Pharmacology (1999) 128, 1477–1484; doi:10.1038/sj.bjp.0702944
Inducible expression and pharmacology of the human excitatory amino acid transporter 2 subtype of L‐glutamate transporter
Authors: Dunlop J , Lou Z , Zhang Y , McIlvain H B
Published: January 2005

In this study we have examined the use of the ecdysone‐inducible mammalian expression system (Invitrogen) for the regulation of expression of the predominant L‐glutamate transporter EAAT2 (Excitatory Amino Acid Transporter) in HEK 293 cells.

HEK 293 cells which were stably transformed with the regulatory vector pVgRXR (EcR 293 cells) were used for transfection of the human EAAT2 cDNA using the inducible vector pIND and a clone designated HEK/EAAT2 was selected for further characterization.

Na+‐dependent L‐glutamate uptake activity (3.2 pmol min−1 mg−1) was observed in EcR 293 cells and this was increased approximately 2 fold in the uninduced HEK/EAAT2 cells, indicating a low level of basal EAAT2 activity in the absence of exogenous inducing agent. Exposure of HEK/EAAT2 cells to the ecdysone analogue Ponasterone A (10 μM for 24 h) resulted in a 10 fold increase in the Na+‐dependent activity.

L‐glutamate uptake into induced HEK/EAAT2 cells followed first‐order Michaelis‐Menten kinetics and Eadie‐Hofstee transformation of the saturable uptake data produced estimates of kinetic parameters as follows; Km 52.7±7.5 μM, Vmax 3.8±0.9 nmol min−1 mg−1 protein.

The pharmacological profile of the EAAT2 subtype was characterized using a series of L‐glutamate transport inhibitors and the rank order of inhibitory potency was similar to that described previously for the rat homologue GLT‐1 and in synaptosomal preparations from rat cortex.

Addition of the EAAT2 modulator arachidonic acid resulted in an enhancement (155±5% control in the presence of 30 μM) of the L‐glutamate transport capacity in the induced HEK/EAAT2 cells.

This study demonstrates that the expression of EAAT2 can be regulated in a mammalian cell line using the ecdysone‐inducible mammalian expression system.

British Journal of Pharmacology (1999) 128, 1485–1490; doi:10.1038/sj.bjp.0702945
Anaesthetic/amnesic agents disrupt beta frequency oscillations associated with potentiation of excitatory synaptic potentials in the rat hippocampal slice
Authors: Faulkner H J , Traub R D , Whittington M A
Published: January 2005

Anaesthetic agents produce disruption in cognitive function typified by reductions in sensory perception and memory formation. Oscillations within the EEG gamma and beta bands have been linked to sensory perception and memory and have been shown to be modified by anaesthetic agents.

Synchronous gamma oscillations generated by brief tetanic stimulation in two regions of hippocampal area CA1 in slices in vitro were seen to potentiate excitatory synaptic communication between the areas. This synaptic potentiation, was seen to contribute to a transition from gamma frequency (30–70 Hz) to beta frequency (12–30 Hz) oscillations.

Four drugs having anaesthetic/hypnotic and amnesic properties were tested on this synchronous gamma‐induced beta oscillation. Thiopental 10–200 μM, Diazepam 0.05–1.0 μM, Morphine 10–200 μM, and Ketamine 10–200 μM were all added to the bathing medium. Each drug markedly disrupted the formation of beta oscillations in a manner consistent with their primary modes of action. Thiopental and morphine disrupted synchrony of gamma oscillations and prevented potentiation of recurrent excitatory potentials measured in stratum oriens (fEPSPs). Neither diazepam, nor ketamine produced such marked changes in synchrony at gamma frequencies or reduction in potentiation of fEPSPs. However, each disrupted expression of subsequent beta oscillation via changes in the magnitude of inhibitory network gamma oscillations and the duration and magnitude of tetanus‐induced depolarization respectively.

The degree of disruption of fEPSP potentiation correlated quantitatively with the degree of disruption in synchrony between sites during gamma oscillations. The data indicate that synchronous gamma‐induced beta oscillations represent a mode of expression of excitatory synaptic potentiation in the hippocampus, and that anaesthetic/amnesic agents can disrupt this process markedly.

British Journal of Pharmacology (1999) 128, 1813–1825; doi:10.1038/sj.bjp.0702948
Inhibition of neuronal KV potassium currents by the antidepressant drug, fluoxetine
Authors: Yeung Shuk Yin , Millar Julie A , Mathie Alistair
Published: January 2005

The effect of the antidepressant drug, fluoxetine on neuronal delayed rectifier (KV) potassium (K) currents was investigated using perforated‐patch whole‐cell electrophysiological recording methods.

Fluoxetine was an effective inhibitor of KV currents in cerebellar granule neurons (CGNs) and also inhibited recombinant KV1.1 channels expressed in Chinese hamster ovary (CHO) cells.

Fluoxetine had an IC50 of 11 μM in CGNs but was slightly less potent on KV1.1 channels (IC50=55 μM). Interestingly, fluoxetine was a much more potent inhibitor of KV1.1 expressed in mammalian cells than has been found previously for the same homomeric channel expressed in Xenopus oocytes.

At concentrations that produced around 50% block, the shape of the KV currents in the presence of fluoxetine was simply scaled down when compared to control currents.

The effect of fluoxetine on KV currents in CGNs was neither voltage‐dependent nor dependent on the channels being in their open state. Both of these observations suggest that fluoxetine does not act as a simple open channel blocking agent.

It is concluded that block of KV currents in mammalian neurons can occur at therapeutic levels of fluoxetine. This could lead to an increase in neuronal excitability and this effect may contribute to the therapeutic antidepressant action of fluoxetine.

British Journal of Pharmacology (1999) 128, 1609–1615; doi:10.1038/sj.bjp.0702955
Tetrandrine ameliorates ischaemia‐reperfusion injury of rat myocardium through inhibition of neutrophil priming and activation
Authors: Shen Yuh‐Chiang , Chen Chieh‐Fu , Sung Yen‐Jen
Published: January 2005

We have previously shown that tetrandrine (TTD), a bisbenzyltetrahydroiosquinoline isolated from the Chinese herb Stephania tetrandra, inhibits neutrophil adhesion, Mac‐1 expression, and reactive oxygen species (ROS) production. To examine whether inhibition of neutrophil function may confer upon TTD the ability to prevent myocardial ischaemia‐reperfusion (MI/R) injury, experiments were performed on rats subjected to coronary ligation followed by reperfusion for induction of MI/R injury.

Intravenous administration of TTD (0.1 and 1.0 mg kg−1) 15 min prior to coronary ligation completely prevented MI/R‐associated mortality. TTD pretreatment also significantly reduced MI/R‐induced ventricular tachyarrhythmia, myocardial infarct size, and neutrophil infiltration.

However, TTD pretreatment did not influence mean arterial blood pressure, heart rate, or product of pressure‐rate, indicating that TTD extenuated MI/R through mechanisms independent of modulating haemodynamics or myocardial oxygen demand.

Peripheral blood neutrophils were isolated for ex vivo examination of shape change and Mac‐1 upregulation of neutrophils, two sensitive indicators of proinflammatory priming, as well as N‐formyl‐methionyl‐leucyl‐phenylalanine (fMLP)‐induced adhesion and ROS production, parameters commonly used for the assessment of neutrophil activation.

Neutrophils from MI/R animals showed significant shape change and Mac‐1 upregulation, both of which were prevented by TTD‐pretreatments. On the other hand, fMLP‐induced adhesion and ROS production of neutrophils were markedly enhanced by MI/R but diminished in TTD‐pretreated animals.

These data suggest that the protective effect of TTD against MI/R injury can be accounted for by inhibition of neutrophil priming and activation, thereby abolishing subsequent infiltration and ROS production that cause MI/R injury.

British Journal of Pharmacology (1999) 128, 1593–1601; doi:10.1038/sj.bjp.0702958
Bepridil differentially inhibits two delayed rectifier K+ currents, IKr and IKs, in guinea‐pig ventricular myocytes
Authors: Wang Jin‐Cheng , Kiyosue Tatsuto , Kiriyama Kuninori , Arita Makoto
Published: January 2005

We investigated the effects of bepridil on the two components of the delayed rectifier K+ current, i.e., the rapidly activating (IKr) and the slowly activating (IKs) currents using tight‐seal whole‐cell patch‐clamp techniques in guinea‐pig ventricular myocytes, under blockade of L‐type Ca2+ current with nitrendipine (5 μM) or D600 (1 μM).

Bepridil decreased IKs under blockade of IKr with E4031 (5 μM), in a concentration‐dependent manner. The concentration‐dependent inhibition of IKs by bepridil was fitted by a curve, assuming one‐to‐one interactions between the channel and the drug molecule. The concentration of half‐maximal inhibition (IC50) was found to be 6.2 μM.

The effect of bepridil on IKr was assessed using an envelope‐of‐tails test. In the control condition, a ratio of the tail current to the time‐dependent current measured during depolarization was large (>1) at shorter pulses (<200 ms), and it decreased to a steady state value of ∼0.4 with increases in the pulse duration. Bepridil at a concentration of 2 μM did not decrease this ratio at shorter pulses.

In a short‐pulse (duration=50 ms) experiment that largely activates IKr, the drug was found to block IKr in a cooperative manner (Hill coefficient=3.03) and the IC50 was 13.2 μM.

These results suggest that bepridil at a clinical therapeutic concentration (∼2 μM) selectively blocks IKs but does not inhibit IKr. This may relate to the characteristic frequency‐dependent effects of bepridil on the action potential duration (APD), e.g., the non‐reverse use‐dependent prolongation of APD.

British Journal of Pharmacology (1999) 128, 1733–1738; doi:10.1038/sj.bjp.0702959
Functional studies in atrium overexpressing A1‐adenosine receptors
Authors: Neumann Joachim , Vahlensieck Ute , Boknik Peter , Linck Bettina , Lüss Hartmut , Müller Frank U , Matherne G Paul , Schmitz Wilhelm
Published: January 2005

Adenosine and the A1‐adenosine receptor agonist R‐PIA, exerted a negative inotropic effect in isolated, electrically driven left atria of wild‐type mice.

In left atria of mice overexpressing the A1‐adenosine receptor, adenosine and R‐PIA exerted a positive inotropic effect.

The positive inotropic effect of adenosine and R‐PIA in transgenic atria could be blocked by the A1‐adenosine receptor antagonist DPCPX.

In the presence of isoprenaline, adenosine exerted a negative inotropic effect in wild‐type atria but a positive inotropic effect in atria from A1‐adenosine receptor overexpressing mice.

The rate of beating in right atria was lower in mice overexpressing A1‐adenosine receptors compared with wild‐type.

Adenosine exerted comparable negative chronotropic effects in right atria from both A1‐adenosine receptor overexpressing and wild‐type mice.

A1‐adenosine receptor overexpression in the mouse heart can reverse the inotropic but not the chronotropic effects of adenosine, implying different receptor‐effector coupling mechanisms.

British Journal of Pharmacology (1999) 128, 1623–1629; doi:10.1038/sj.bjp.0702963
Operational correlates of prostanoid TP receptor expression in human non‐pregnant myometrium are unaffected by excision site or menstrual cycle status of the donor
Authors: Senchyna Michelle , Crankshaw D J
Published: January 2005

Cumulative concentration‐effect curves for the selective prostanoid TP receptor agonist, U46619, were constructed in strips of human non‐pregnant myometrium grouped according to tissue excision site (top, lateral wall, lower uterine segment, sub‐serosal or sub‐endometrial), tissue orientation (strips cut either parallel or perpendicular to the serosa) and donor menstrual status (proliferative or secretory phase).

U46619 was excitatory in all tissues. There was no significant difference in either pEC50 or maximum response between groups (P<0.05). The range of pEC50 values was 6.8±0.1 (lateral wall, proliferative phase, n=5) to 7.1±0.3 (lateral wall, secretory phase, n=5). The range of maximum response values was 0.9±0.8 N cm−2 (lateral wall, proliferative phase, n=5) to 3.1±1.0 N cm−2 (lateral wall, secretory phase, n=5).

Saturation binding analyses were conducted using the radiolabelled TP receptor agonist, [125I]‐BOP. Binding parameters were estimated for membranes prepared from human non‐pregnant myometrium excised from the lateral wall and grouped according to donor menstrual status.

There were no significant differences in the mean pKd and [R]tot values for [125I]‐BOP binding between the two groups (proliferative phase: pKd=8.3±0.3, [R]tot=412±319 fmol mg protein−1, n=5; secretory phase: pKd=8.5±0.4, [R]tot=369±192 fmol mg protein−1, n=6; P<0.05).

These data indicate that U46619‐mediated responses in human non‐pregnant myometrium are not influenced by tissue excision site, tissue orientation or donor menstrual status and that [125I]‐BOP binding is not influenced by donor menstrual status. This suggests that the TP receptor population is homogeneous throughout the human non‐pregnant myometrium, and not subject to hormonal regulation.

British Journal of Pharmacology (1999) 128, 1524–1528; doi:10.1038/sj.bjp.0702964
Facilitation by 8‐OH‐DPAT of passive avoidance performance in rats after inactivation of 5‐HT1A receptors
Authors: Otano Ana , García‐Osta Ana , Ballaz Santiago , Frechilla Diana , Del Río Joaquín
Published: January 2005

Pretraining administration of 8‐hydroxy‐2‐di‐n‐propylamino‐tetralin (8‐OH‐DPAT 0.1 mg kg−1), a 5‐HT1A receptor agonist, or buspirone (1 mg kg−1), a 5‐HT1A receptor partial agonist, markedly impaired passive avoidance retention in rats 24 h later. The effect of 8‐OH‐DPAT was prevented by the 5‐HT1A receptor antagonists, NAN‐190 and WAY‐100635, at doses without any intrinsic effect.

N‐ethoxycarbonyl‐2‐ethoxy‐1,2‐dihydroquinoline (EEDQ 10 mg kg−1), an alkylating agent that inactivates different G‐protein coupled receptors, impaired retention performance when given 48 h pretraining. The disruptive effect of EEDQ was reversed by 8‐OH‐DPAT or buspirone, given 30 min before training.

Non‐specific actions did not account for 8‐OH‐DPAT‐induced reversal of the EEDQ effect since no significant difference in locomotor activity or in pain threshold was found between rats receiving EEDQ or EEDQ+8‐OH‐DPAT.

When NAN‐190 (1 mg kg−1) or WAY‐100635 (0.5 mg kg−1) were given before 8‐OH‐DPAT to EEDQ‐pretreated animals, the reversal by 8‐OH‐DPAT of EEDQ‐induced retention impairment was still more pronounced. However, no EEDQ reversal by 8‐OH‐DPAT was found when 5‐HT1A receptors were protected by WAY‐100635 (10 mg kg−1) 30 min before EEDQ.

In the hippocampus of EEDQ‐treated rats, 5‐HT7 receptors were less inactivated than 5‐HT1A receptors and significant increases were found in 5‐HT1A but not in 5‐HT7 receptor mRNA levels. Ritanserin and methiothepin (10 mg kg−1 each), antagonists with higher affinity at 5‐HT7 than at 5‐HT1A receptors, prevented the retention impairment induced by EEDQ but did not significantly protect against 5‐HT7 receptor inactivation.

The results indicate that the facilitatory effect of 8‐OH‐DPAT is not mediated through 5‐HT1A receptors and suggest that other 8‐OH‐DPAT‐sensitive receptors could be involved in the dual effect of 8‐OH‐DPAT on passive avoidance performance in rats.

British Journal of Pharmacology (1999) 128, 1691–1698; doi:10.1038/sj.bjp.0702974
An anti‐platelet agent, OPC‐29030, inhibits translocation of 12‐lipoxygenase and 12‐hydroxyeicosatetraenoic acid production in human platelets
Authors: Ozeki Yasushi , Nagamura Yoshie , Ito Hideki , Unemi Fumiko , Kimura Yukio , Igawa Takehiro , Kambayashi Jun‐ichi , Takahashi Yoshitaka , Yoshimoto Tanihiro
Published: January 2005

In human platelets, arachidonic acid is mainly metabolized by the two enzyme systems; cyclo‐oxygenase and 12‐lipoxygenase. Cyclo‐oxygenase produces prostaglandin H2 which is further converted to thromboxane B2. 12‐Lipoxygenase synthesizes 12(S)‐hydroperoxyeicosatetraenoic acid which is reduced to 12(S)‐hydroxyeicosatetraenoic acid (12(S)‐HETE).

An anti‐platelet compound, OPC‐29030, dose‐dependently inhibited 12(S)‐HETE production with an IC50 of 0.06±0.01 μM, but not synthesis of thromboxane B2 in human platelets. Although the compound suppressed 12(S)‐HETE production in human platelets, cytosolic 12‐lipoxygenase activity was not inhibited up to 10 μM. Essentially identical data were obtained with a 12‐lipoxygenase of human erythroleukaemia cells which had megakaryocyte/platelet‐like properties.

OPC‐29030 also suppressed production of 5(S)‐HETE, a 5‐lipoxygenase product, in rat basophilic leukaemia cells without inhibiting enzyme activity. It has been shown that 5‐lipoxygenase binds to membrane 5‐lipoxygenase‐activating protein (FLAP) to produce 5(S)‐HETE, and thus FLAP inhibitor suppresses cellular 5(S)‐HETE production.

A FLAP inhibitor, L‐655,238, suppressed platelet 12(S)‐HETE production, but had no effect on the 12‐lipoxygenase activity.

Western blot analysis showed that platelet 12‐lipoxygenase translocated from cytosol to membranes upon thrombin stimulation, and OPC‐29030 suppressed this process in a dose‐dependent manner.

These results suggest that the 12‐lipoxygenase of human platelets binds to FLAP or a similar protein, and OPC‐29030 suppresses 12(S)‐HETE production by inhibiting a certain step of the 12‐lipoxygenase translocation.

British Journal of Pharmacology (1999) 128, 1699–1704; doi:10.1038/sj.bjp.0702976
Selective nitrergic neurodegeneration in diabetes mellitus–a nitric oxide‐dependent phenomenon
Authors: Cellek Selim , Rodrigo José , Lobos Edgar , Fernández Patricia , Serrano Julia , Moncada Salvador
Published: January 2005

In vitro and in vivo studies have demonstrated a dysfunctional nitrergic system in diabetes mellitus, thus explaining the origin of diabetic impotence. However, the mechanism of this nitrergic defect is not understood.

In the penises of streptozotocin (STZ)‐induced diabetic rats, here, we show by immunohistochemistry that nitrergic nerves undergo selective degeneration since the noradrenergic nerves which have an anti‐erectile function in the penis remained intact.

Nitrergic relaxation responses in vitro and erectile responses to cavernous nerve stimulation in vivo were attenuated in these animals, whereas noradrenergic responses were enhanced.

Activity and protein amount of neuronal nitric oxide synthase (nNOS) were also reduced in the penile tissue of diabetic rats.

We, thus, hypothesized that NO in the nitrergic nerves may be involved in the nitrergic nerve damage, since only the nerves which contain neuronal NO synthase underwent degeneration.

We administered an inhibitor of NO synthase, NG‐nitro‐L‐arginine methyl ester (L‐NAME), in the drinking water of rats for up to 12 weeks following the establishment of diabetes with STZ.

Here we demonstrate that this compound protected the nitrergic nerves from morphological and functional impairment. Our results show that selective nitrergic degeneration in diabetes is NO‐dependent and suggest that inhibition of NO synthase is neuroprotective in this condition.

British Journal of Pharmacology (1999) 128, 1804–1812; doi:10.1038/sj.bjp.0702981
Nitric oxide synthase expression, enzyme activity and NO production during angiogenesis in the chick chorioallantoic membrane
Authors: Pipili‐Synetos Eva , Kritikou Sosanna , Papadimitriou Evangelia , Athanassiadou Aglaia , Flordellis C , Maragoudakis M E
Published: January 2005

In order to elucidate further the role of nitric oxide (NO) as an endogenous antiangiogenic mediator, mRNA expression of inducible nitric oxide synthase (iNOS), enzyme activity and production of NO were determined in the chick chorioallantoic membrane (CAM), an in vivo model of angiogenesis. In this model, maximum angiogenesis is reached between days 9–12 of chick embryo development. After that period, vascular density remains constant.

Inducible NO synthase (iNOS) mRNA expression, determined by reverse transcriptase polymerase chain reaction (RT–PCR), increased from the 8th day reaching a maximum (70% increase) at days 10–11.

NO synthase activity, determined as citrulline formation in the presence of calcium, also increased from day 8 reaching a maximum around day 10 (100% increase). Similar results were obtained in the absence of calcium suggesting that the NOS determined was the inducible form.

Nitric oxide production, determined as nitrites, increased from day 8 reaching a maximum around day 10 (64% increase) and remaining stable at day 13.

Finally, the bacterial lipopolysaccharide LPS (which activates transcriptionally iNOS), inhibited dose dependently angiogenesis in the CAM. These results in connection with previous findings from this laboratory, showing that NO inhibits angiogenesis in the CAM, suggest that increases in iNOS expression, enzyme activity and NO production closely parallel the progression of angiogenesis in the CAM, thus providing an endogenous brake to control this process.

British Journal of Pharmacology (2000) 129, 207–213; doi:10.1038/sj.bjp.0702986
Lipophilization of somatostatin analog RC‐160 with long chain fatty acid improves its antiproliferative and antiangiogenic activity in vitro
Authors: Dasgupta P , Mukherjee R
Published: January 2005

The therapeutic potential of the somatostatin analogue RC‐160 having antiproliferative activity, is limited by its short serum half life. To overcome this limitation, fatty acids namely butanoic acid and myristic acid were conjugated to the N‐terminal residue of RC‐160. The lipophilized derivatives of RC‐160 were synthesized, purified by reverse phase HPLC and characterized by ES‐mass spectroscopy. The antiproliferative activity of lipophilized derivatives of RC‐160 on the growth of MIA‐PaCa2 (human pancreatic carcinoma), DU145 (human prostate carcinoma), ECV304 (human umbilical chord endothelioma), as well as their antiangiogenic activity was evaluated in vitro. The relative stability of myristoyl‐RC‐160 towards degradation by proteases and serum was also determined.

Myristoyl‐RC‐160 exhibited significantly higher antiproliferative efficacy than RC‐160, on the above cell lines (P<0.01). Receptor binding assays, demonstrated that the affinity of RC‐160 towards somatostatin receptors remains unaltered by myristoylation. Unlike RC‐160, the myristoylated derivative was found to have significantly greater resistance to protease and serum degradation (P<0.01). Myristoyl‐RC‐160 exhibited significantly greater antiproliferative activity on ECV304, than RC‐160 (P<0.01). Myristoyl RC‐160 could also inhibit capillary tube formation more efficiently than RC‐160 in a dose dependent manner, suggesting that it possessed enhanced antiangiogenic activity in vitro (P<0.001).

Lipophilization of RC‐160 with long chain fatty acids like myristic acid endows it with improved antiproliferative and antiangiogenic activity, stability and therapeutic index.

British Journal of Pharmacology (2000) 129, 101–109; doi:10.1038/sj.bjp.0702990
Pharmacologic characterization of the oxytocin receptor in human uterine smooth muscle cells
Authors: Tahara Atsuo , Tsukada Junko , Tomura Yuichi , Wada Koh‐ichi , Kusayama Toshiyuki , Ishii Noe , Yatsu Takeyuki , Uchida Wataru , Tanaka Akihiro
Published: January 2005

[3H]‐oxytocin was used to characterize the oxytocin receptor found in human uterine smooth muscle cells (USMC). Specific binding of [3H]‐oxytocin to USMC plasma membranes was dependent upon time, temperature and membrane protein concentration.

Scatchard plot analysis of equilibrium binding data revealed the existence of a single class of high‐affinity binding sites with an apparent equilibrium dissociation constant (Kd) of 0.76 nM and a maximum receptor density (Bmax) of 153 fmol mg−1 protein. The Hill coefficient (nH) did not differ significantly from unity, suggesting binding to homogenous, non‐interacting receptor populations.

Competitive inhibition of [3H]‐oxytocin binding showed that oxytocin and vasopressin (AVP) receptor agonists and antagonists displaced [3H]‐oxytocin in a concentration‐dependent manner. The order of potencies for peptide agonists and antagonists was: oxytocin>[Asu1,6]‐oxytocin>AVP= atosiban>d(CH2)5Tyr(Me)AVP>[Thr4,Gly7]‐oxytocin>dDAVP, and for nonpeptide antagonists was: L‐371257>YM087>SR 49059>OPC‐21268>SR 121463A>OPC‐31260.

Oxytocin significantly induced concentration‐dependent increase in intracellular Ca2+ concentration ([Ca2+]i) and hyperplasia in USMC. The oxytocin receptor antagonists, atosiban and L‐371257, potently and concentration‐dependently inhibited oxytocin‐induced [Ca2+]i increase and hyperplasia. In contrast, the V1A receptor selective antagonist, SR 49059, and the V2 receptor selective antagonist, SR 121463A, did not potently inhibit oxytocin‐induced [Ca2+]i increase and hyperplasia. The potency order of antagonists in inhibiting oxytocin‐induced [Ca2+]i increase and hyperplasia was similar to that observed in radioligand binding assays.

In conclusion, these data provide evidence that the high‐affinity [3H]‐oxytocin binding site found in human USMC is a functional oxytocin receptor coupled to [Ca2+]i increase and cell growth. Thus human USMC may prove to be a valuable tool in further investigation of the physiologic and pathophysiologic roles of oxytocin in the uterus.

British Journal of Pharmacology (2000) 129, 131–139; doi:10.1038/sj.bjp.0702996
Involvement of cyclic AMP–PKA pathway in VIP‐induced, charybdotoxin‐sensitive relaxation of longitudinal muscle of the distal colon of Wistar‐ST rats
Authors: Kishi Masami , Takeuchi Tadayoshi , Katayama Hideo , Yamazaki Yasuko , Nishio Hideaki , Hata Fumiaki , Takewaki Tadashi
Published: January 2005

The intracellular mechanism of vasoactive intestinal peptide (VIP)‐induced, charybdotoxin (ChTx)‐sensitive relaxation of longitudinal muscle of the distal colon of Wistar‐ST rats was studied.

A single pulse or 100 pulses at 10 Hz of electrical field stimulation (EFS) induced rapid transient relaxation or that with a subsequent contraction of the longitudinal muscle in the presence of atropine and guanethidine, respectively.

Rp‐8 bromo cAMPS, an inhibitor of cyclic AMP dependent protein kinase (PKA), at 30 μM inhibited the relaxations induced by EFS with a single or 100 pulses maximally by about 80 or 60%, respectively. It also inhibited VIP (300 nM)‐induced relaxation by 82%.

VIP (100 nM–1 μM) increased the cyclic AMP content of longitudinal muscle myenteric plexus preparations obtained from the distal colon.

ChTx at 100 nM almost completely inhibited 8 bromo cyclic AMP‐induced relaxation of the distal segments.

EFS with two or three pulses at 10 Hz induced inhibitory junction potentials consisting of two phases, rapid and subsequent slow hyperpolarization in the membrane potential of longitudinal smooth muscle cells. Rp‐cAMPS, another inhibitor of PKA, inhibited the delayed slow hyperpolarization. It also inhibited the exogenously added VIP‐induced hyperpolarization of the cell membrane.

Thus, the present study suggests that activation of PKA via activation of VIP receptors is associated with activation of ChTx‐sensitive K+ channels in relaxation of longitudinal muscle of the distal colon of Wistar‐ST rats.

British Journal of Pharmacology (2000) 129, 140–146; doi:10.1038/sj.bjp.0702998
Effects of superoxide anion generators and thiol modulators on nitrergic transmission and relaxation to exogenous nitric oxide in the sheep urethra
Authors: Garcia‐Pascual A , Labadia A , Costa G , Triguero D
Published: January 2005

The effects of superoxide anion generators, the nitric oxide (NO) scavenger 2‐(4‐carboxyphenyl)‐4,4,5,5‐tetramethylimidazoine‐1‐oxyl 3‐oxide (carboxy‐PTIO), the specific guanylate cyclase inhibitor 1H‐[1,2,4]‐oxadiazole‐[4,3‐a]‐quinoxalin‐1‐one (ODQ), and thiol modulating agents were investigated on relaxations induced by nitrergic stimulation and exogenous NO addition in the sheep urethra.

Methylene blue (MB, 10 μM), pyrogallol (0.1 mM) and xanthine (X, 0.1 mM)/xanthine oxidase (XO, 0.1 u ml−1) inhibited NO‐mediated relaxations, without affecting those induced by nitrergic stimulation. This resistance was not diminished following inhibition of endogenous Cu/Zn superoxide dismutase (Cu/Zn SOD) with diethyldithiocarbamic acid (DETCA, 3 mM), which almost abolished tissue SOD activity.

Carboxy‐PTIO (0.1–0.5 mM) inhibited NO‐mediated relaxations but had no effect on responses to nitrergic stimulation, which were not changed by treatment with ascorbate oxidase (2 u ml−1).

Relaxations to NO were reduced, but not abolished, by ODQ (10 μM), while nitrergic responses were completely blocked.

The thiol modulators, ethacrynic acid (0.1 mM), diamide (1.5 mM), or 5,5′‐dithio‐bis (2‐nitrobenzoic acid) (DTNB, 0.5 mM), and subsequent treatment with dithiothreitol (DTT, 2 mM) had no effect on responses to nitrergic stimulation or NO. In contrast, N‐ethylmaleimide (NEM, 0.2 mM) markedly inhibited both relaxations.

L‐cysteine (L‐cys, 0.1 mM) had no effect on responses to NO, while it inhibited those to nitrergic stimulation, in a Cu/Zn SOD‐independent manner.

Our results do not support the view that the urethral nitrergic transmitter is free NO, and the possibility that another compound is acting as mediator still remains open.

British Journal of Pharmacology (2000) 129, 53–62; doi:10.1038/sj.bjp.0703000
Biphasic effects of NMDA on the motility of the rat portal vein
Authors: Rossetti Z L , Mameli M , Vargiu R , Fadda F , Mancinelli R
Published: January 2005

The effect of NMDA on the motility of the rat portal vein was studied in an isolated preparation. NMDA induced a concentration‐dependent (10−7–10−4 M) increase of the contraction frequency (maximum increase, 148±6% of control at NMDA 10−4 M).

The NMDA‐induced excitatory response was prevented by the competitive NMDA receptor antagonists (±)‐2‐Amino‐5‐phosphonopentanoic acid (AP‐5, 5×10−4 M) or (RS)‐3‐(2‐carboxypiperazine‐4‐yl) propyl‐1‐phosphonic acid (CPP, 10−4 M).

Tetrodotoxin (TTX, 10−6 M) or atropine (10−4 M) abolished the NMDA‐induced increase of the portal vein motility and reversed the excitatory effect to a concentration‐dependent inhibition (maximum inhibition, 52±8 and 29±7% of controls, respectively, at NMDA 10−3 M).

Removal of the endothelium abolished the NMDA‐induced inhibitory response. Sodium nitroprusside concentration‐dependently (10−7–10−5 M) inhibited the portal vein motility, while L‐NG‐nitro‐arginine methyl ester (L‐NAME, 10−4 M) reversed the inhibitory effect of NMDA (in the presence of TTX), restoring the portal vein spontaneous activity to control values.

These results show that NMDA modulates the portal vein motility in a biphasic manner: via indirect activation, through prejunctional NMDA receptors presumably located on intrinsic excitatory neuronal afferences, or via direct inhibition, through endothelial NMDA receptors activating the nitric oxide pathway. Overall these findings support the hypothesis of the existence of a peripheral glutamatergic innervation modulating the contractile activity of the rat portal vein.

British Journal of Pharmacology (2000) 129, 156–162; doi:10.1038/sj.bjp.0703002
Bradyzide, a potent non‐peptide B2 bradykinin receptor antagonist with long‐lasting oral activity in animal models of inflammatory hyperalgesia
Authors: Burgess Gillian M , Perkins Martin N , Rang Humphrey P , Campbell Elizabeth A , Brown Michael C , McIntyre Peter , Urban Laszlo , Dziadulewicz Edward K , Ritchie Timothy J , Hallett Allan , Snell Christopher R , Wrigglesworth Roger , Lee Wai , Davis Clare , Phagoo Steve B , Davis Andrew J , Phillips Elsa , Drake Gillian S , Hughes Glyn A , Dunstan Andrew , Bloomfield Graham C
Published: January 2005

Bradyzide is from a novel class of rodent‐selective non‐peptide B2 bradykinin antagonists (1‐(2‐Nitrophenyl)thiosemicarbazides).

Bradyzide has high affinity for the rodent B2 receptor, displacing [3H]‐bradykinin binding in NG108‐15 cells and in Cos‐7 cells expressing the rat receptor with KI values of 0.51±0.18 nM (n=3) and 0.89±0.27 nM (n=3), respectively.

Bradyzide is a competitive antagonist, inhibiting B2 receptor‐induced 45Ca efflux from NG108‐15 cells with a pKB of 8.0±0.16 (n=5) and a Schild slope of 1.05.

In the rat spinal cord and tail preparation, bradyzide inhibits bradykinin‐induced ventral root depolarizations (IC50 value; 1.6±0.05 nM (n=3)).

Bradyzide is much less potent at the human than at the rodent B2 receptor, displacing [3H]‐bradykinin binding in human fibroblasts and in Cos‐7 cells expressing the human B2 receptor with KI values of 393±90 nM (n=3) and 772±144 nM (n=3), respectively. Bradyzide inhibits bradykinin‐induced [3H]‐inositol trisphosphate (IP3) formation with IC50 values of 11.6±1.4 nM (n=3) at the rat and 2.4±0.3 μM (n=3) at the human receptor.

Bradyzide does not interact with a range of other receptors, including human and rat B1 bradykinin receptors.

Bradyzide is orally available and blocks bradykinin‐induced hypotension and plasma extravasation.

Bradyzide shows long‐lasting oral activity in rodent models of inflammatory hyperalgesia, reversing Freund's complete adjuvant (FCA)‐induced mechanical hyperalgesia in the rat knee joint (ED50, 0.84 μmol kg−1; duration of action >4 h). It is equipotent with morphine and diclofenac, and 1000 times more potent than paracetamol, its maximal effect exceeding that of the non‐steroidal anti‐inflammatory drugs (NSAIDs). Bradyzide does not exhibit tolerance when administered over 6 days.

In summary, bradyzide is a potent, orally active, antagonist of the B2 bradykinin receptor, with selectivity for the rodent over the human receptor.

British Journal of Pharmacology (2000) 129, 77–86; doi:10.1038/sj.bjp.0703012
Antagonism of calcium currents and neurotransmitter release by barium ions at frog motor nerve endings
Authors: Silinsky Eugene M
Published: January 2005

The effects of Ba2+ (0.1–2 mM) on the component of the perineural voltage change associated with nerve terminal calcium currents (prejunctional Ca2+ currents) were compared with the effects of this ion to antagonize calcium‐dependent acetylcholine (ACh) release. These experiments were made on isolated neuromuscular junctions of the frog.

In the presence of sufficient concentrations of K+ channel blockers to eliminate measurable prejunctional K+ currents, low concentrations of Ba2+ selectively antagonized prejunctional Ca2+ currents in normal Ca2+ solutions. Higher concentrations of Ba2+ also substantially reduced the Na+ component of the perineural waveform.

Ba2+ inhibited the prolonged prejunctional Ca2+ currents that developed in the presence of higher concentrations of K+ channel blockers.

Simultaneous measurements of the prejunctional Ca2+ currents and the electrophysiological correlates of ACh release (i.e. end‐plate potentials, EPPs) were made under conditions of modest K+ channel blockade. Under these conditions, Ba2+ generally produced simultaneous decreases in both Ca2+ currents and EPP amplitudes. In some instances, a prolongation of prejunctional Ca2+ currents and a transient increase in EPP amplitudes preceded the decreases in both electrophysiological events.

These results suggest that Ba2+ ions can antagonize the entry of calcium into motor nerve endings and this effect is likely to be responsible for the inhibitory effects of Ba2+ on evoked ACh release.

British Journal of Pharmacology (2000) 129, 360–366; doi:10.1038/sj.bjp.0703036
Mechanisms of AVP‐induced glucagon release in clonal α‐cells In‐R1‐G9: involvement of Ca2+‐dependent and ‐independent pathways
Authors: Yibchok‐anun Sirintorn , Cheng Henrique , Chen Ter‐Hsin , Hsu Walter H
Published: January 2005

The mechanisms underlying AVP‐induced increase in [Ca2+]i and glucagon release in clonal α‐cells In‐R1‐G9 were investigated.

AVP increased [Ca2+]i and glucagon release in a concentration‐dependent manner. After the administration of AVP, glucagon was released within 30 s, quickly reached the maximum within 2 min, and maintained a steady‐state concentration for at least 15 min.

In Ca2+‐containing medium, AVP increased [Ca2+]i in a biphasic pattern; a peak followed by a sustained plateau. In Ca2+‐free medium, the Ca2+ response to AVP became monophasic with lower amplitude and no plateau. Both the basal and AVP‐induced glucagon releases were lower in the absence than in the presence of extracellular Ca2+. When [Ca2+]i was stringently deprived by BAPTA, a Ca2+ chelator, AVP still significantly increased glucagon release.

Pretreatment with thapsigargin, a microsomal Ca2+ ATPase inhibitor, abolished both the Ca2+ peak and sustained plateau.

AVP increased intracellular concentration of IP3.

U‐73122 (8 μM), a phospholipase C inhibitor, abolished AVP‐induced increases in [Ca2+]i, but only reduced AVP‐induced glucagon release by 39%.

Pretreatment with nimodipine, an L‐type Ca2+ channel blocker failed to alter AVP‐induced glucagon release or increase in [Ca2+]i.

The results suggest that AVP causes glucagon release through both Ca2+‐dependent and ‐independent pathways. For the Ca2+‐dependent pathway, the Gq protein activates phospholipase C, which catalyzes the formation of IP3. IP3 induces Ca2+ release from the endoplasmic reticulum, which, in turn, triggers Ca2+ influx. Both Ca2+ release and Ca2+ influx may contribute to AVP‐induced glucagon release.

British Journal of Pharmacology (2000) 129, 257–264; doi:10.1038/sj.bjp.0703037
Role of tachykinin NK2 receptors in normal and altered rectal sensitivity in rats
Authors: Toulouse M , Coelho A M , Fioramonti J , Lecci A , Maggi C , Buéno L
Published: January 2005

Irritable bowel syndrome is characterized by visceral hyperalgesia commonly associated with stress and inflammatory processes. We investigated the role of tachykinin NK2 receptors in the ability of trinitrobenzenesulphonic acid (TNBS) and stress to enhance the sensitivity of the rat rectum to distension using a selective tachykinin NK2 receptor antagonist (MEN 11420).

Rats were fitted with electrodes implanted in the striated muscles of the abdomen. Rectal distension (RD) was performed with a balloon inflated by steps of 0.4 ml from 0 to 1.6 ml. Five groups were submitted to RD performed 3 days before and after intrarectal instillation of TNBS. Fifteen minutes before RD, rats were treated with saline or MEN 11420 (5–100 μg kg−1 i.v.). Two other groups, submitted to 2 h restraint or sham stress sessions were randomly treated i.v. with saline or MEN 11420 (10–200 μg kg−1) prior to RD applied 20 min later.

The basal response to RD was characterized by a significant increase in the number of abdominal contractions. This response occurred with a threshold volume of 0.8 ml and was dose‐dependently reduced by MEN 11420 (5–100 μg kg−1 i.v.). Rectal inflammation lowered the volume of distension producing abdominal contractions to 0.4 ml (allodynia). This effect was either reduced or suppressed by MEN 11420. A similar allodynia was observed after a stress session and this effect was reduced (49%) or suppressed by MEN 11420 at 200 and 100 μg kg−1, respectively.

Tachykinin NK2 receptors are involved in rectal hypersensitivity associated with inflammation and stress.

British Journal of Pharmacology (2000) 129, 193–199; doi:10.1038/sj.bjp.0703040
Tonic activation of A2A adenosine receptors unmasks, and of A1 receptors prevents, a facilitatory action of calcitonin gene‐related peptide in the rat hippocampus
Authors: Sebastião A M , Macedo M Paula , Ribeiro J A
Published: January 2005

We investigated how manipulations of the degree of activation of adenosine A1 and A2A receptors influences the action of the neuropeptide, calcitonin gene‐related peptide (CGRP) on synaptic transmission in hippocampal slices. Field excitatory post‐synaptic potentials (EPSPs) from the CA1 area were recorded.

When applied alone, CGRP (1–30 nM) was without effect on field EPSPs. However, CGRP (10–30 nM) significantly increased the field EPSP slope when applied to hippocampal slices in the presence of the A1 receptor antagonist, 1,3‐dipropyl‐8‐cyclopenthyl xanthine (DPCPX, 10 nM), or in the presence of the A2A adenosine receptor agonist CGS 21680 (10 nM).

The A2A receptor antagonist, ZM 241385 (10 nM) as well as adenosine deaminase (ADA, 2 U ml−1), prevented the enhancement of field EPSP slope caused by CGRP (30 nM) in the presence of DPCPX (10 nM), suggesting that this effect of CGRP requires the concomitant activation of A2A adenosine receptors by endogenous adenosine.

The protein kinase‐A inhibitors, N‐(2‐guanidinoethyl)‐5‐isoquinolinesulfonamide (HA‐1004, 10 μM) and adenosine 3′,5′‐cyclic monophosphorothioate, Rp‐isomer (Rp‐cAMPS, 50 μM), as well as the inhibitor of ATP‐sensitive potassium (KATP) channels, glibenclamide (30 μM), prevented the facilitation of synaptic transmission caused by CGRP (30 nM) in the presence of DPCPX (10 nM), suggesting that this effect of CGRP involves both KATP channels and protein kinase‐A.

It is concluded that the ability of CGRP to facilitate synaptic transmission in the CA1 area of the hippocampus is under tight control by adenosine, with tonic A1 receptor activation by endogenous adenosine ‘braking’ the action of CGRP, and the A2A receptors triggering this action.

British Journal of Pharmacology (2000) 129, 374–380; doi:10.1038/sj.bjp.0703048