bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of brainstem adenosine A1 receptors in the cardiovascular response to hypothalamic defence area stimulation in the anaesthetized rat
Authors: St. Lambert J.H. , Dashwood M.R. , Spyer K.M. 
Published: July 2012

The role of centrally located adenosine A1 receptors in the cardiovascular changes associated with the hypothalamic defence response has been investigated by in vitro autoradiography and the intraventricular application of an A1 receptor antagonist.
8‐Cyclopentyl‐1,3‐dipropylxanthine (DPCPX), a highly selective adenosine A1 antagonist and its vehicle, ethanol, were administered directly into the posterior portion of the fourth ventricle of α‐chloralose anaesthetized, paralysed and artificially ventilated rats.
DPCPX (0.01 to 0.3 mg kg−1) caused a dose‐dependent decrease in the magnitude of the evoked pressor response (from −13 to −23 mmHg) elicited on hypothalamic defence area stimulation at a dose 10 fold lower than that required to produce an equivalent effect following systemic administration whilst ethanol, the vehicle, had no effect.
In vitro autoradiography revealed a heterogeneous distribution of adenosine A1 binding sites in the lower brainstem of rats. Image analysis showed the ventrolateral medulla to have the highest density of A1 receptors. Intermediate levels of binding were seen in caudal regions of the nucleus tractus solitarii and the hypoglossal nucleus.
These data imply that a proportion of the cardiovascular response to hypothalamic defence area stimulation are produced by the activation of adenosine A1 receptors localized close to the surface of, or adjacent to, the fourth ventricle in the immediate vicinity of the injection site.
Involvement of platelet cyclic GMP but not cyclic AMP suppression in leukocyte‐dependent platelet adhesion to endothelial cells induced by platelet‐activating factor in vitro
Authors: Hirafuji Masahiko , Nezu Akihiro , Shinoda; Hisashi , Minami Masaru 
Published: July 2012

Incubation of endothelial cells with platelets in the absence or the presence of PAF (10 μm) markedly increased platelet cyclic AMP levels, which were significantly decreased by indomethacin (3 μm). Co‐incubation of endothelial cells and platelets with polymorphonuclear leukocytes (PMNs) did not change the platelet cyclic AMP levels.
Incubation of endothelial cells with platelets in the absence of PAF increased platelet cyclic GMP levels, which were increased 3.5 fold by PAF. These cyclic GMP levels were significantly decreased by NG‐nitro‐L‐arginine (100 μm), and completely by methylene blue (10 μm). When endothelial cells and platelets were co‐incubated with PMNs, the cyclic GMP level in the cell mixture was 42.5 and 65.3% lower than that in endothelial cells and platelets without and with PAF stimulation, respectively.
PAF induced platelet adhesion to endothelial cells only when PMNs were present. Methylene blue dose‐dependently potentiated the PMN‐dependent platelet adhesion induced by PAF, although it had no effect in the absence of PMNs.
Sodium nitroprusside and 8‐bromo cyclic GMP but not dibutyryl cyclic AMP significantly, although partially, inhibited the platelet adhesion. Inhibition of cyclic GMP‐specific phosphodiesterase by zaprinast slightly inhibited the PMN‐induced platelet adhesion and potentiated the inhibitory effect of 8‐bromo cyclic GMP, while these drugs markedly inhibited the adhesion of platelet aggregates induced by PMN sonicates.
These results suggest that the impairment by activated PMNs of EDRF‐induced platelet cyclic GMP formation is involved in part in the mechanism of PMN‐dependent platelet adhesion to endothelial cells induced by PAF in vitro. The precise mechanism still remains to be clarified.
Structure activity studies of mast cell activation and hypotension induced by neuropeptide Y (NPY), centrally truncated and C‐terminal NPY analogues
Authors: Cross L.J. Mark , Beck‐Sickinger Annette G. , Bienert Michael , Gaida Wolfram , Jung Günther , Krause Eberhard , Ennis Madeleine 
Published: July 2012

Neuropeptide‐induced histamine release is thought to occur via receptor‐independent mechanisms, with net charge and lipophilicity being important factors.
In this study, the histamine releasing ability of neuropeptide Y (NPY), two C‐terminal segments of NPY and 13 centrally truncated NPY analogues was examined. These results were compared with the ability of the peptides to bind to the Y2 receptor in the rabbit kidney membrane model and with their hypotensive actions in the anaesthetized‐rat model.
All analogues tested, with the exception of [Glu4,25,33,35]‐NPY(1–4)‐Ahx‐(25–36) and [Asp4,25,33,35]NPY(1–4)‐Ahx‐(25–36) which were devoid of histamine releasing activity, evoked a dose‐dependent histamine release but there were marked differences between the peptides. The native peptide was the least active.
Histamine release was not linked to the ability of the peptides to displace NPY from Y2 receptors. There was a statistical correlation between the hypotensive effects expressed as ED10 values (μmol kg−1, which induced a blood pressure decrease of 10 mmHg) and the EC25 for histamine release (r = 0.62, P = 0.04), although histamine release may not be the sole determinant of the alterations in blood pressure.
There was a strong negative correlation between EC25 for histamine release and net positive charge (r = −0.93, P = 5.7 × 10−7), i.e. increasing the net positive charge caused greater histamine release. However, there was a 12 fold difference in activity amongst the most positively charged analogues (+ 5). Helicity did not correlate with histamine releasing ability.
In the development of NPY‐related drugs the avoidance of compounds with net positive charge is recommended.
A study of tolerance to apomorphine
Authors: Montastruc Jean‐Louis , Llau Marie‐Elise , Senard Jean‐Michel , Tran Marie‐Antoinette , Rascol Olivier , Montastruc Paul 
Published: July 2012

The present study was designed to investigate tolerance to several pharmacological effects of apomorphine.
Changes in blood pressure, heart rate, plasma noradrenaline levels, rectal temperature, respiratory rate and retching plus vomiting were compared after administration of apomorphine (200 μg kg−1, i.v. as a bolus) or saline at different time intervals (30, 120 and 720 min) in four groups of chloralose‐anaesthetized dogs.
The first administration of apomorphine induced a significant decrease in blood pressure and rectal temperature, a marked rise in heart rate with no change in noradrenaline plasma levels or respiratory rate. Emesis occurred in 71% of the animals.
A second administration of apomorphine 30 min later failed to modify blood pressure or heart rate. In contrast, the magnitude of apomorphine‐induced changes in blood pressure and heart rate was similar to that observed after the first administration when apomorphine was given 120 or 720 min later.
The apomorphine‐induced decrease in rectal temperature evoked by a second dose of apomorphine was less marked when given 30 and 120 min after the first dose and unchanged when given 720 min later.
The number of animals exhibiting retching and vomiting was lower when apomorphine was reinjected after 30 min than when the time between two successive injections of apomorphine was 120 or 720 min.
These results show that tolerance to apomorphine involves its cardiovascular, hypothermic and emetic effects. The time course of tolerance to repeated injections of apomorphine is longer for its hypothermic than for its hypotensive or emetic effects. This suggests a tissue‐specific regulation of D2 dopamine receptors to repeated injections of apomorphine.
Effects of trimetazidine on pHi regulation in the rat isolated ventricular myocyte
Authors: Lagadic‐Gossmann Dominique , Le Prigent Karine , Feuvray Danielle 
Published: July 2012

We have examined the effects of trimetazidine (TMZ) on intracellular pH (pHi) regulation in rat isolated ventricular myocytes. pHi was recorded ratiometrically by use of the pH‐sensitive fluoroprobe, carboxy‐SNARF‐1 (carboxy‐seminaphtorhodafluor).
Following an intracellular acid load (induced by 10 mM NH4Cl removal), pHi recovery in HEPES‐ buffered Tyrode solution was significantly slowed down upon application of 0.3 mM TMZ only when myocytes were pretreated for 5 h 30 min (slowing by ∼ 50%; P < 0.01). This effect of TMZ on pHi recovery was shown to be not only time‐ but also dose‐dependent with a large, quickly reversible, effect obtained with 1 mM TMZ applied for 2–3 h (slowing by ∼ 64%; P 0.001). This slowing of pHi recovery was also associated with a decrease of the NH4+ removal‐induced acidification.
Relationship between intracellular intrinsic buffering power (βi) and pHi was assessed in absence or presence of TMZ (0.3 mM or 1 mM). As expected, βi increased roughly linearly with a decrease in pHi in all cases. However, both concentrations of TMZ significantly increased βi (by ∼ 55 and 65% at pHi 7.1, respectively).
When Na+/H+ exchange was inhibited by dimethyl amiloride (DMA; 40 μm), trimetazidine (1 mM) did not change the H+ flux estimated at pHi 7.1 (0.31 ± 0.03 mequiv 1−1 min−1, n = 5, control, versus 0.30 ± 0.025 mequiv 1−1 min−1, n = 5, TMZ), ruling out any effect of TMZ on background acid loading.
Acid efflux carried by Na+/H+ exchange was significantly decreased only when myocytes were pretreated with 1 mM TMZ, for 2–3 h (JeH = 2.86 ± 0.38 mequiv 1−1 min−1, n = 26, control, versus 1.66 ± 0.26 mequiv 1−1 min−1, n = 10, TMZ, estimated at pHi 7.1; P < 0.05).
In conclusion, the present work demonstrates that, following an intracellular acid load in HEPES‐ buffered medium, trimetazidine slows down pHi recovery in rat isolated ventricular myocytes, primarily through an increase of βi. An effect on Na+/H+ exchange is also detected but only after long‐term incubation of the myocytes with TMZ.
The effects of purine compounds on the isolated aorta of the frog Rana temporaria
Authors: Knight Gillian E. , Burnstock Geoffrey 
Published: July 2012

In the isolated aorta of the frog, Rana temporaria, adenosine concentration‐dependently, endothelium‐independently relaxed adrenaline pre‐constricted vessels. None of the adenosine analogues including D‐5′‐(N‐ethylcarboxamide) adenosine (NECA), R‐ and S‐N6‐(2‐phenylisopropyl) adenosine (R‐and S‐PIA) and 2‐chloroadenosine (2‐CA), or the more selective A1, A2 and A3 agonists cyclopentyladenosine (CPA), CGS 21680 and N6‐(3‐iodobenzyl) adenosine‐5′‐N‐methylcarboxamide (IB‐MECA) respectively, had any effect.
The non‐selective adenosine antagonist, 8‐p‐sulphophenyl‐theophylline (8‐pSPT; 30 μm) failed to inhibit adenosine relaxations, as did NG‐nitro‐L‐arginine methyl ester (L‐NAME; 0.1 mM) and indomethacin (30 μm).
Adenosine 5′‐triphosphate (ATP), α,β‐methylene ATP (α,β‐MeATP), β,γ‐methylene ATP MeATP), 2‐methylthio ATP (2‐MeSATP) and uridine 5′‐triphosphate (UTP) all concentration‐dependently contracted the frog aorta. ATP and α,β‐MeATP were equipotent and more potent than UTP and β,γ‐MeATP; 2‐MeSATP had little activity.
The P2‐purinoceptor antagonist, suramin (0.1 mM) inhibited contractions to α,β‐MeATP but not to ATP. Pyridoxalphosphate‐6‐azophenyl‐2′,4′‐disulphonic acid (PPADS; 30 μm) also inhibited contractions to α,β‐MeATP but not to ATP. Contractions to ATP were, however, inhibited by indomethacin (30 μm).
In conclusion, in the frog aorta there appears to be a novel subclass of P1‐purinoceptor mediating vasodilatation, although like the A3 subclass it is not blocked by methylxanthines; a P2‐purinoceptor mediates vasoconstriction which resembles a P2X subtype, based on the agonist potency of α,β‐MeATP being more potent than 2‐MeSATP (UTP has moderate activity) and PPADS is an effective antagonist. There is no evidence for the presence of a P2Y‐purinoceptor, mediating vasodilatation, in this preparation.
Binding sites for α‐trinositol (inositol 1,2,6‐trisphosphate) in porcine tissues; comparison with Ins(1,4,5)P3 and Ins(1,3,4,5)P4‐binding sites
Authors: Stricker Rolf , Westerberg Eva , Reiser Georg 
Published: July 2012

The molecular mechanism of action of the inositol trisphosphate isomer, α‐trinositol (Ins(1,2,6)P3) which has potential therapeutic use in treatment of inflammation and burn oedema, is still unclear. Therefore we have studied binding sites for α‐trinositol in different tissues.
In membranes from pig cerebellum, liver, kidney, heart, and spleen, the density of specific [3H]‐α‐trinositol binding sites was maximal at pH 5.0. Cerebellum and spleen showed only one binding site (cerebellum KD = 9.1 μm, spleen KD = 7.3 μm). In the other tissues, there were a high‐affinity site (heart KD = 70 nM, liver KD = 790 nM and kidney KD = 1800 nM), besides a low‐affinity site with a KD ranging between 32 and 120 μm. In cerebellar membranes, the affinity and density (107 pmol mg−1 protein) of α‐trinositol binding sites were not affected by phosphate (0 to 25 mM).
Binding of Ins(1,4,5)P3 and Ins(1,3,4,5)P4 to membranes from different porcine tissues was also determined. Ins(1,3,4,5)P4, the isomer stereochemically related to α‐trinositol, binds with an affinity of 1.2 nM in cerebellum, but in the other tissues the binding site density was too low to determine the affinity. With cerebellar membranes heterologous displacement of [3H]‐Ins(1,3,4,5)P4 by α‐trinositol yielded a K1 of 11 μm. The Ins(1,4,5)P3 receptor displayed an affinity of 15 nM in cerebellum and of 5 to 7 nM in the other tissues investigated.
The solubilized Ins(1,3,4,5)P4 receptor preparation from cerebellum did not show Ins(1,2,6)P3 binding. Ins(1,2,6)P3 binding was found in the pellet obtained after solubilization of the membranes with the detergent Brij 58.
Thus, in different tissues α‐trinositol binds to proteins with different affinity. They are obviously not related to binding sites for Ins (1,4,5)P3 or for Ins(1,3,4,5)P4. Future experiments have to unravel the identity of the binding protein(s) for α‐trinositol.
Characterization of putative 5‐ht7 receptors mediating direct relaxation in Cynomolgus monkey isolated jugular vein
Authors: Leung E. , Walsh L.K.M. , Pulido‐Rios M.T. , Eglen R.M. 
Published: July 2012

5‐Hydroxytryptamine (5‐HT) receptors mediating contraction and relaxation are present in Cynomolgus monkey isolated jugular vein denuded of endothelium.
In the absence of spasmogen, α‐methyl‐5‐HT and sumatriptan contracted the tissues with potency values (pEC50) of 6.8 (n=2) and 6.4 ± 0.1 (mean ± s.e. mean, n=3), respectively. In contrast, 5‐HT caused an initial contraction (10 nM‐1 μm), followed by relaxation (1 μm‐32 μm). The contractile effect of α‐methyl‐5‐HT was antagonized by ketanserin with a pKB value of 8.1 (n=2). 5‐Carboxamidotryptamine (5‐CT), 5‐methoxytryptamine (5‐MeOT) and 8‐OH‐DPAT did not contract or relax the tissues in the absence of spasmogen.
In tissues precontracted with U46619 (10 nM) and in the presence of 5‐HT1A, 5‐HT1B, 5‐HT2A, 5‐HT3, and 5‐HT4 receptor blockade, 5‐CT and 5‐MeOT caused endothelium‐independent relaxation with potency values of 7.5±0.1 (n=21) and 5.7±0.1 (n=4), respectively. The potency of 5‐HT was 7.2 (n=2) while α‐methyl‐5‐HT did not start to relax the tissues below a concentration of 10 μm.
Relaxations elicited by 5‐CT were antagonized by the following compounds (with pKB values in parentheses): methiothepin (9.7), mesulergine (8.1), metergoline (8.0), clozapine (7.8), mianserin (7.7), spiperone (7.3), ritanserin (7.1), methysergide (7.0) and ketanserin (5.7).
It is concluded that the 5‐HT receptor mediating endothelium‐independent relaxation may be a functional correlate of the putative 5‐ht7 receptor.
Endothelin‐1 and the periaqueductal gray area of the rat: an autoradiographic and functional pharmacological study
Authors: D'Amico Michele , Dashwood Michael R. , Warner Timothy D. 
Published: July 2012

. Endothelin‐1 (ET‐1) injected centrally induces pressor effects and associated haemodynamic changes. Here we have evaluated the effects on systemic and regional cardiovascular parameters of injection of ET‐1 into the periaqueductal gray (PAG) area of anaesthetized rats. In addition, we have used the ETA receptor‐selective antagonist, FR 139317, the ETB receptor‐selective antagonist, BQ‐788, and the ETA/ ETB receptor non‐selective antagonist, SB 209670, to identify the receptor(s) mediating these effects. We have also used in vitro autoradiography to identify binding sites for ET‐1 in the PAG.
. In vitro autoradiography showed dense binding of [125I]‐PD 151242 (for ETA receptors) in the PAG area, with the binding sites being homogeneously distributed within the dorsal, lateral and ventral subregions. Tissues incubated with [125I]‐BQ 3020 (for ETB receptors) had little binding.
. Injection of ET‐1 (0.1, 1 and 10 pmol per rat) in the dorsolateral PAG area significantly increased, in a dose‐dependent manner the mean arterial blood pressure (MAP). The highest dose of ET‐1 (10 pmol) also decreased the heart rate by 18±1%, n=6 (P>0.05). Increases in blood pressure induced by ET‐1 (1 pmol; 31±6.6 mmHg, n=6) were greatly reduced by pre‐administration to the PAG area of FR 139317 (5 nmol per rat) or SB 209670 (3 nmol per rat) (97 and 94%, respectively), but were unaffected by BQ‐788 (5 nmol per rat). Similarly, FR 139317 and SB 209670 prevented the decrease in heart rate induced by ET‐1 while BQ‐788 did not affect it.
. Injection of ET‐1 to the PAG area caused falls in renal blood flow (RBF) as measured by an ultrasonic flow probe, and increased renal vascular resistance (RVR). Pre‐treatment of the PAG with FR 139317 or SB 209670, but not with BQ‐788, prevented this ET‐1‐induced effect.
. Injection of ET‐1 (10 pmol) also increased total peripheral resistance (TPR; control, 2.39±0.2 mmHg ml−1 min 100 g body weight) by 100±9% (n=5) and reduced the cardiac output (CO; control, 94.7±3.1 ml min−1) by 30±3% (n=5), as determined by radioactive microspheres. Vascular resistances were increased in other organs, such as skeletal muscle (88±5%, n=4), the colon (55±7%, n=4) and the stomach (47±3%, n=4). Pretreatment of the PAG area with FR 139317 or SB 209670 reduced the increases in TPR and vascular resistance, and the reduction in CO caused by ET‐1. BQ‐788 did not affect the responses to ET‐1.
. Thus, there are predominantly ETA binding sites within the PAG area and injection of ET‐1 into the PAG area causes complex haemodynamic changes which are sensitive to ETA receptor antagonism. ETA receptors are, therefore, the predominant mediators of the actions of ET‐1 in the PAG of the rat.
Relative potencies of metal ions on transmitter release at mouse motor nerve terminals
Authors: Porter V.A. , Wray D. 
Published: July 2012

. The effects of a range of metal ions were systematically studied at the mouse neuromuscular junction in order to investigate the type of calcium channel present at the nerve terminal.
. Endplate potentials and miniature endplate potentials were recorded from the phrenic nerve diaphragm muscle preparation with glass microelectrodes.
. Endplate potential amplitudes and quantal contents were reduced by manganese (IC50 220 μm), cadmium (IC50 11 μm), cobalt (IC50 340 μm), and nickel (IC50 420 μm). Miniature endplate potentials were not affected by these ions at concentrations equal to the IC50S. Gadolinium did not reduce endplate potentials up to 100 μm.
. Comparisons made with known channel types in neuroblastoma cell lines suggest that the calcium channels at the motor nerve terminal are different from those types studied in the cell lines, although most similarity is shown to the high‐voltage activated calcium channel types.
Effects of delayed treatment with nafronyl oxalate on microsphere embolism‐induced changes in monoamine levels of rat brain regions
Authors: Takagi Norio , Miyake Keiko , Ohiwa Akiko , Nukaga Reiko , Takeo Satoshi 
Published: July 2012

. The present study was undertaken to examine the effects of delayed treatment with nafronyl oxalate (nafronyl), a cerebral vasodilator, on monoamine neurotransmitters of brain regions in the microsphere‐embolized rat.
. Microsphere embolism was induced by injecting 900 microspheres with a diameter of 48 μm into the right internal carotid artery of rats. Microsphere‐embolized rats were treated with nafronyl, 15 mg kg−1, i.p., twice daily from the first to the 5th day. Levels of monoamines and their metabolites in the cerebral cortex, striatum, and hippocampus were measured on days 3 and 5 after the operation by a high‐performance liquid chromatograph with electrochemical detection. In vivo tyrosine or tryptophan hydroxylation was estimated by measurement of the accumulation of 3,4‐dihydroxyphenylalanine or 5‐ hydroxy‐1‐tryptophan after administration of 3‐hydroxybenzylhydrazine dihydrochloride, an inhibitor of aromatic L‐amino acid decarboxylase.
. Microsphere embolism induced decreases in dopamine, noradrenaline and 5‐hydroxytryptamine in three brain regions of the right hemisphere on days 3 and 5. In the left hemisphere, the monoamines were reduced, but to a lesser degree than in the right hemisphere. On days 3 and 5, the decrease in the monoamines of the right hemisphere was attenuated by nafronyl treatment except for noradrenaline on day 3. The decrease in the monoamines levels in the left hemisphere was almost completely prevented by nafronyl treatment.
. On day 3 after microsphere embolism, in vivo tyrosine and tryptophan hydroxylation was lower than the pre‐embolic value in all three brain regions. Treatment of the embolized rats with nafronyl significantly attenuated the decrease in in vivo tyrosine and tryptophan hydroxylation in the ipsilateral hemisphere, but not hippocampal tryptophan hydroxylation.
. The results suggested that treatment with nafronyl improves or attenuates changes in monoamine neurotransmitter metabolism of the brain regions impaired by microsphere embolism. The mechanisms underlying this effect may be attributed to preservation of the ability to synthesize monoamines when the brain is ischaemic or oligaemic.