bluuebunny/crossref_metadata_2025_split huggingface dataset:
Prevention by (±)‐8‐hydroxy‐2‐(di‐npropylamino)tetralin of both catalepsy and the rises in rat striatal dopamine metabolism caused by haloperidol
Authors: Andersen Heidi L. , Kilpatrick Ian C. 
Published: July 2012

The influence of (±)‐8‐hydroxy‐2‐(di‐n‐propylamino)tetralin (8‐OH‐DPAT) on haloperidol‐induced increases in the dopamine metabolites, 3,4‐dihydroxyphenylacetic acid (DOPAC) and 4‐hydroxy‐3‐methoxyphenylacetic acid (HVA), was measured in three microdissected brain regions of the rat following a quantitative assessment of catalepsy.
Haloperidol alone (2.66 μzmol kg−1, i.p.) caused a robust cataleptic response. Given 30 min after haloperidol, 8‐OH‐DPAT (76 or 760 nmol kg−1, s.c.) prevented catalepsy in 30% and 100% of rats, respectively.
Haloperidol significantly increased the DOPAC (by 2 to 4 fold) and HVA (by 3 to 7 fold) contents of the caudate‐putamen, nucleus accumbens and medial prefrontal cortex. Given alone, only the lower dose of 8‐OH‐DPAT caused a significant biochemical change, a doubling of cortical DOPAC.
In the cases where catalepsy was prevented by either dose of 8‐OH‐DPAT, the haloperidol‐induced increases in DOPAC and HVA were consistently lower in the caudate‐putamen. This pattern was true for the rise in cortical HVA but only in response to the lower dose of 8‐OH‐DPAT. In contrast, neither dose of 8‐OH‐DPAT was able to influence the haloperidol‐induced rises in cortical DOPAC. In the nucleus accumbens, 8‐OH‐DPAT did not affect the haloperidol‐induced increases in the dopamine metabolites, irrespective of the dose employed or the resulting behaviour. When catalepsy was not prevented, 8‐OH‐DPAT did not alter the neurochemical responses to haloperidol in any region.
These results suggest that part of the mechanism by which 8‐OH‐DPAT prevents haloperidol‐induced catalepsy is reflected by a reversal of the compensatory increase in meso‐striatal and/or meso‐cortical dopamine neuronal activity that normally accompanies postsynaptic dopamine receptor blockade with haloperidol.
Comparison of the uptake of [3H]‐gabapentin with the uptake of L‐[3H]‐leucine into rat brain synaptosomes
Authors: Thurlow Richard J. , Hill David R. , Woodruff G.N. 
Published: July 2012

Gabapentin is a novel anticonvulsant with an unknown mechanism of action. Homogenate binding studies described elsewhere have suggested that [3H]‐gabapentin binds to a site in brain similar to the large neutral amino acid (LNAA) uptake site, termed system‐L.
This study describes an investigation into the uptake of [3H]‐gabapentin into a crude synaptosomal preparation from cerebral cortex of rat brain. Characterization studies showed that [3H]‐gabapentin is taken up into synaptosomes by a system that is similar to that responsible for the uptake of L‐[3H]‐leucine. This system is sodium‐independent, temperature‐sensitive and requires ATP for function.
Kinetic studies of [3H]‐gabapentin uptake produced a Michaelis constant (KM = 160 μm) similar to that observed for L‐[3H]‐leucine (KM = 110.3 μm). Vmax values were 837.1 pmol mg−1 protein min−1 and 2.192 nmol mg−1 protein min−1 respectively.
Gabapentin and L‐leucine mutually inhibit their uptake. Lineweaver‐Burke plots of these data demonstrate that inhibition occurs by a competitive mechanism. Further to this the Dixon transformation of the data illustrates that these two substrates share a common uptake site by the similarity between their calculated Ki and KM values (gabapentin inhibition of L‐[3H]‐leucine uptake: Ki = 160 μm; L‐leucine inhibition of [3H]‐gabapentin uptake: Ki = 262 μm).
Studies into the effect of gabapentin, the system‐L‐specific ligand 2‐(—)‐endoamino‐bicycloheptane‐2‐carboxylic acid (BCH), and the system‐A‐specific ligand α‐(methyl‐amino)‐isobutyric acid (MeAIB), on the initial rate of uptake of [3H]‐glycine, L‐[3H]‐glutamate, L‐[3H]‐glutamine, and L‐[3H]‐leucine were performed. At 100 μm, gabapentin significantly inhibited initial rate of uptake of [3H]‐glycine (29%), L‐[3H]‐glutamate (22%) and L‐[3H]‐leucine (40%).
Gabapentin is taken up into synaptosomes by a system similar to system‐L, responsible for the uptake of large neutral amino acids. Gabapentin will also inhibit the uptake of certain excitatory amino acids in this synaptosomal preparation. The implications of these findings for the mechanism of action for gabapentin are unclear. The data presented here may suggest an intracellular site for mechanism of action for this compound. Similarly changes in levels of amino acid pools may be involved in the mechanism of gabapentin's anticonvulsant action.
The effect of dopamine D1 receptor stimulation on the up‐regulation of histamine H3‐receptors following destruction of the ascending dopaminergic neurones
Authors: Ryu Jong Hoon , Yanai Kazuhiko , Zhao Xiao‐Lan , Watanabe Takehiko 
Published: July 2012

The binding of [3H]‐(R)α‐methylhistamine and [3H]‐Nα‐methylhistamine to histamine H3‐receptors, [3H]‐SCH23390 to dopamine D1‐receptors, and [3H]‐YM09151‐2 to dopamine D2‐receptors was investigated by quantitative receptor autoradiography in the rat brain following 6‐hydroxydopamine injection into the substantia nigra.
The levels of [3H]‐(R)α‐methylhistamine binding sites in the denervated striatum and substantia nigra were significantly higher than those in the contralateral side from 1 week to 12 weeks after nigral lesions. The H3‐receptor binding was maximal at 3 weeks after nigral lesions and maintained until 12 weeks.
The increased number of histamine H3‐receptors was decreased to the level of the contralateral side by chronic treatment with a selective dopamine D1 agonist, SKF38393, but not modified by a selective dopamine D2 agonist, quinpirole.
Dopamine D1‐ and D2‐receptors in the striatum were similarly up‐regulated after unilateral nigral lesion. On the other hand, the number of dopamine D2‐receptors in the substantia nigra was markedly decreased after administration of 6‐hydroxydopamine.
The treatment with (S)α‐fluoromethylhistidine increased the H3‐receptor binding in both the ipsilateral and contralateral sides. As a result, the magnitude of the ratio of the H3‐receptor binding between ipsilateral and contralateral sides was partially attenuated by treatment with (S)‐α‐fluoromethylhistidine.
These results strongly suggest that the expression of histamine H3‐receptors in the striatum and substantia nigra is influenced through D1‐receptors by tonic nigrostriatal dopaminergic inputs.
Effects of hydroxyethylrutosides on hypoxia‐induced activation of human endothelial cells in vitro
Authors: Janssens Dominique , Michiels Carine , Arnould Thierry , Remacle José 
Published: July 2012

A clinically available mixture of hydroxyethylrutosides (HR) was examined as inhibitors of endothelial cell activation by hypoxia in vitro. Thus, the effects of HR on ATP depletion, phospholipase A2 activation and neutrophil adherence were investigated in hypoxia‐activated human umbilical vein endothelial cells in primary cell culture.
Our results show that HR inhibited two important steps of the activation of endothelial cells by hypoxia: the decrease in ATP content, which is the starting point of the process, and the activation of phospholipase A2 one enzyme responsible for the release of inflammatory mediators. This inhibition was dose‐dependent with 70 to 90% inhibition at 500 μg ml−1 of HR.
In addition, hypoxia‐activated endothelial cells increased their adhesiveness for neutrophils. This process could also be prevented in a dose‐dependent manner if endothelial cells were incubated in the presence of HR. This inhibition was confirmed by a morphological study.
In conclusion, the results of this study suggest that a possible explanation for the improvement in venous insufficiency by HR observed clinically could be their ability to inhibit the activation of endothelial cells during blood stasis.
Regulation of cytosolic calcium in skeletal muscle cells of the mdx mouse under conditions of stress
Authors: Leijendekker Wim J. , Passaquin Anne‐Catherine , Metzinger Laurent , Rüegg Urs T. 
Published: July 2012

In Duchenne muscular dystrophy (DMD) dysregulation of cytosolic calcium appears to be involved in the degeneration of skeletal muscle fibres. Therefore, we have studied the regulation of the free cytosolic calcium concentration ([Ca2+]c) under specific stress conditions in cultured myotubes isolated from the hind limbs of wild‐type (C57BL10) and dystrophin‐deficient mutant mdx mice. [Ca2+]c in the myotubes was estimated by the use of the Ca2+‐sensitive fluorescent dye, fura‐2.
Resting [Ca2+]c was similar in mdx and normal myotubes (35 ± 9 nM and 38 ± nM, respectively). However, when mdx myotubes were exposed to a high extracellular calcium concentration ([Ca2+]e) of 40 mM, the [Ca2+]c was elevated to 84 ± 29 nM, compared to 49 ± 7 nM in normal myotubes.
Lowering the osmolarity of the superfusion solution from 300 mOsm to 100 mOsm resulted also in a rise in [Ca2+]c which was about two times higher for mdx (243 ± 65 nM) than for C57BL10 (135 ± 37 nM). Replacing extracellular Ca2+ by EGTA (0.2 mM) prevented the rise in [Ca2+]c in both mdx and normal myotubes when exposed to the low osmolarity solution.
Gadolinium ion (50 μm), an inhibitor of Ca2+ entry, antagonized the rise in [Ca2+]c of myotubes superfused with 40 mM [Ca2+]c by 20–40% for both mdx and C57BL10 cells, but did not significantly reduce the rise in [Ca2+]c when the cells were exposed to the hypo‐osmotic buffer (100 mOsm).
Incubation of the cell culture for 3–5 days from the onset of induction of myotube formation with the membrane permeable protease inhibitor, calpeptin (50 μm) abolished the rise in [Ca2+]c in mdx myotubes upon exposure to hypo‐osmotic shock.
Treatment of the cell culture for 3–5 days with α‐methylprednisolone (PDN, 10 μm) attenuated the rise in [Ca2+]c following hypo‐osmotic stress for both normal and mdx myotubes by about 50%.
The results described here suggest an increased permeability of mdx myotubes to Ca2+ under specific stress conditions. The ameliorating effect of PDN on [Ca2+]c could explain, at least partly, the beneficial effect of this drug on DMD patients.
PPADS and suramin as antagonists at cloned P2Y‐ and P2U‐purinoceptors
Authors: Charlton Steven J. , Brown Colin A. , Weisman Gary A. , Turner John T. , Erb Laurie , Boarder Michael R. 
Published: July 2012

The effect of suramin and pyridoxalphosphate‐6‐azophenyl‐2′,4′‐disulphonic acid (PPADS) on the stimulation of phospholipase C in 1321N1 cells transfected with the human P2U‐purinoceptor (h‐P2U‐1321N1 cells) or with the turkey P2Y‐purinoceptor (t‐P2Y‐1321N1 cells) was investigated. 2‐Methylthioadenosine triphosphate (2MeSATP) was used as the agonist at t‐P2Y‐1321N1 cells and uridine triphosphate (UTP) at h‐P2U‐1321N1 cells.
Suramin caused a parallel shift to the right of the concentration‐response curves for 2MeSATP in the t‐P2Y‐1321N1 cells, yielding a Schild plot with a slope of 1.16 ± 0.08 and a pA2 value of 5.77 ± 0.11.
Suramin also caused a shift to the right of concentration‐response curves for UTP in the h‐P2U‐1321N1 cells, and on Schild plots gave a slope different from unity (1.57 ± 0.19) and an apparent pA2 value of 4.32 ± 0.13. Suramin was therefore a less potent antagonist at the P2U‐purinoceptor than the P2Y‐purinoceptor.
In the presence of the ectonucleotidase inhibitor, ARL 67156 (6‐N,N‐diethyl‐β,γ‐dibromomethylene‐D‐ATP) there was no significant difference in the EC50 or shapes of curves with either cell type, and no difference in pA2 values for suramin.
PPADS caused an increase in the EC50 for 2MeSATP in the t‐P2Y‐1321N1 cells. The Schild plot had a slope different from unity (0.55 ± 0.15) and an X‐intercept corresponding to an apparent pA2 of 5.98 ± 0.65.
PPADS up to 30 μm had no effect on the concentration‐response curve for UTP with the h‐P2U‐1321N1 cells.
In conclusion, suramin and PPADS show clear differences in their action at the 2 receptor types, in each case being substantially more effective as an antagonist at the P2Y‐purinoceptor than at the P2U‐purinoceptor. Ectonucleotidase breakdown had little influence on the nature of the responses at the two receptor types, or in their differential sensitivity to suramin.
Downregulation of nitrovasodilator‐induced cyclic GMP accumulation in cells exposed to endotoxin or interleukin‐1β
Authors: Papapetropoulos Andreas , Abou‐Mohamed Gamal , Marczin Nandor , Murad Ferid , Caldwell R. William , Catravas John D. 
Published: July 2012

Induction of nitric oxide synthase (iNOS) results in overproduction of nitric oxide (NO), which may be a principal cause of the massive vasodilatation and hypotension observed in septic shock. Since NO‐induced vasorelaxation is mediated via the soluble isoform of guanylate cyclase (sGC), the regulation of sGC activity during shock is of obvious importance, but yet poorly understood. The aim of the present study was to investigate the activation of sGC by sodium nitroprusside (SNP) before and after exposure of rat aortic smooth muscle cells to endotoxin (LPS) or interleukin‐1β (IL‐1β).
Exposure of rat aortic smooth muscle cells to SNP (10 μm) elicited up to 200 fold increases in cyclic GMP. This effect was attenuated by 30–70% in IL‐1β‐ or LPS‐pretreated cells, in a pretreatment time‐and IL‐1β‐ or LPS‐concentration‐dependent manner. When, however, cells were exposed to IL‐1β or LPS and then stimulated with the particulate guanylate cyclase activator, atriopeptin II, no reduction in cyclic GMP accumulation was observed.
Pretreatment of rats with LPS (5 mg kg−1, i.v.) for 6 h led to a decrease in aortic ring SNP‐induced cyclic GMP accumulation.
The IL‐1β‐induced reduction in SNP‐stimulated cyclic GMP accumulation in cultured cells was dependent on NO production, as arginine depletion abolished the downregulation of cyclic GMP accumulation in response to SNP.
Reverse‐transcriptase‐polymerase chain reaction analysis revealed that the ratio of steady state mRNA for the α1 subunit of sGC to glyceraldehyde phosphate dehydrogenase was decreased in LPS‐ or IL‐1β‐treated cells, as compared to vehicle‐treated cells.
Protein levels of the α1 sGC subunit remained unaltered upon exposure to LPS or IL‐1β, suggesting that the early decreased cyclic GMP accumulation in IL‐1β‐ or LPS‐pretreated cells was probably due to reduced sGC activation. Thus, the observed decreased responsiveness of sGC to NO stimulation following cytokine or LPS challenge may represent an important homeostatic mechanism to offset the extensive vasodilatation seen in sepsis.
Role of intracellular Ca2+ in the K channel opener action of CGRP in the guinea‐pig ureter
Authors: Maggi Carlo Alberto , Giuliani Sandro , Santicioli Paolo , Brading Alison F. 
Published: July 2012

The aim of this study was to assess the role of sarcoplasmic reticulum (SR) calcium (Ca2+) in the smooth muscle relaxant and hyperpolarizing actions of calcitonin gene‐related peptide (CGRP) in the guinea‐pig ureter.
CGRP (0.1 μm) rapidly and transiently reduced myogenic phasic contractions (twitches) produced by electrical field stimulation (EFS). Approximately 70% of the response to CGRP was antagonized by glibenclamide (1 μm).
Cyclopiazonic acid (CPA, 10 μm), ryanodine (100 μm) and thapsigargin (1 μm) reduced only the glibenclamide‐sensitive component of the response to CGRP (0.1 μm) but did not modify the mechanoinhibitory effect of cromakalim (3 μm). A low concentration of CPA (1 μm), assumed to produce a limited impairment of Ca2+ uptake from the stores, prolonged the duration of the inhibitory response to CGRP. Pre‐exposure to caffeine (5 mM) inhibited the suppression of twitches by CGRP or cromakalim.
When the frequency of EFS was increased, the suppression of twitches by CGRP was reduced. Under these conditions, CPA (1 μm) again prolonged the duration of the inhibitory response to CGRP.
CGRP (0.1 μm) and cromakalim (3 μm) markedly depressed the phasic component of contractions to 80 mM KCl. CPA (10 μm) antagonized the inhibitory effect of CGRP but not that of cromakalim. Inhibition of the tonic contraction to 80 mM KCl by CGRP was insensitive to CPA.
In sucrose gap experiments, a 5 min exposure to CGRP (0.1 μm) or cromakalim (3 μm) produced a sustained membrane hyperpolarization. Caffeine (5 mM) produced a glibenclamide‐sensitive transient hyperpolarization followed by a sustained depolarization. When tested in a Ca2+‐free medium the hyperpolarization produced by CGRP, cromakalim or caffeine was reduced. In normal Krebs, pre‐exposure to CPA (10 μm, 60 min) only abolished the hyperpolarization induced by CGRP. In contrast, 5 min after a caffeine challenge (5 mM) the hyperpolarizations induced by CGRP or cromakalim were reduced. The CGRP‐induced hyperpolarization was insensitive to apamin (0.1 μm) or charybdotoxin (0.1 μm).
We conclude that the K channel‐opening action of CGRP in the guinea‐pig ureter requires the mobilization of intracellular Ca2+ from a caffeine‐ and CPA‐sensitive store, leading to transient activation of glibenclamide‐sensitive K channels. The K channel‐opening action of caffeine appears to involve Ca2+ mobilization from a store which is insensitive to depletion by CPA.
Pharmacological analysis of dopamine stimulation of [35S]‐GTPγS binding via human D2short and D2long dopamine receptors expressed in recombinant cells
Authors: Gardner B. , Hall D.A. , Strange P.G. 
Published: July 2012

The activation of G‐proteins by agonist‐occupied D2 or D3 dopamine receptors in membranes from recombinant cells expressing the cloned receptors has been analysed by a [35S]‐guanosine 5′‐[γ‐thio] triphosphate ([35S]‐GTPγS) binding assay.
The rate of [35S]‐GTPγS binding was increased by dopamine in a dose‐dependent manner in membranes from CHO cells stably expressing either the D2short or D2long dopamine receptor.
The dopamine‐induced stimulation of [35S]‐GTPγS binding could be inhibited by a range of antagonists. Affinities for antagonists derived from the inhibition of the dopamine stimulation of [35S]‐GTPγS binding correlated very well with affinities derived from radioligand binding studies.
When the maximum [35S]‐GTPγS binding responses stimulated by dopamine acting at different receptor subtypes were compared, there was a tendency for the stimulation via the D2short receptor to be greater than via the D2long receptor and for the stimulation via the D3 dopamine receptor to be less than for either D2 receptor. These differences in maximal response were also seen when the inhibitory effects of dopamine on adenylyl cyclase via the three receptor subtypes were compared.
The stimulation of [35S]‐GTPγS binding by dopamine in membranes from recombinant cells therefore provides an excellent system for studying the molecular nature of agonism and the receptor/G‐protein interactions for these receptors.
Inhibition of a store‐operated Ca2+ entry pathway in human endothelial cells by the isoquinoline derivative LOE 908
Authors: Encabo A. , Romanin C. , Birke F.W. , Kukovetz W.R. , Groschner Klaus 
Published: July 2012

The novel cation channel blocker, LOE 908, was tested for its effects on Ca2+ entry and membrane currents activated by depletion of intracellular Ca2+ stores in human endothelial cells.
LOE 908 inhibited store‐operated Ca2+ entry induced by direct depletion of Ca2+ stores with 100 nM thapsigargin or 100 nM ionomycin with an EC50 of 2 μm and 4 μm, respectively.
LOE 908 did not affect thapsigargin‐ or ionomycin‐induced Ca2+ release from intracellular stores up to concentrations of 3 μm.
LOE 908 reversibly suppressed thapsigargin‐ as well as ionomycin‐induced whole‐cell membrane currents.
The LOE 908‐sensitive membrane conductance corresponded to a cation permeability of 5.5 and 6.9 fold selectivity for Ca2+ over K+ in the presence of thapsigargin and ionomycin, respectively.
Our results suggest that the isoquinoline, LOE 908 is a novel, potent inhibitor of the store‐operated (capacitive) Ca2+ entry pathway in endothelial cells.
The effect of the PKC inhibitor GF109203X on the release of Ca2+ from internal stores and Ca2+ entry in DDT1 MF‐2 cells
Authors: Sipma Henk , van der Zee Lucie , van den Akker Jan , den Hertog Adriaan , Nelemans Adriaan 
Published: July 2012

The effects of the specific protein kinase C (PKC) inhibitor, GF109203X, were measured on the cytoplasmic Ca2+ concentration ([Ca2+]i), and on histamine H1 receptor‐ and thapsigargin‐mediated increases in [Ca2+]i in DDT1 MF‐2 smooth muscle cells.
After pretreatment of cells with GF109203X (5 μm, 45 min), the histamine (100 μm)‐induced initial rise in [Ca2+]i, representing Ca2+ mobilization from internal stores, was inhibited (by 59 ± 7%). The slowly declining phase of the histamine induced Ca2+ response, reflecting Ca2+ entry, was enhanced (83 ± 26%) in the presence of the PKC inhibitor.
The histamine induced release of Ca2+ from internal stores, measured after blocking Ca2+ entry with LaCl3 was inhibited by GF109203X in a concentration‐dependent manner (IC50:3.1 ± 1.1 μm).
Histamine‐induced formation of inositol 1,4,5‐trisphosphate (Ins(1,4,5)P3) was not changed in the presence of GF109203X.
The PKC activating phorbol ester, phorbol 12‐myristate 13‐acetate (PMA, 1 μm), strongly reduced histamine‐induced Ins(1,4,5)P3 formation (58 ± 16%). This effect was reversed by GF109203X (5 μm). Furthermore, PMA diminished histamine evoked Ca2+ release (50 ± 6%) and blocked Ca2+ entry completely.
The rise in [Ca2+]i caused by blocking endoplasmic reticulum Ca2+‐ATPase with thapsigargin (1 μm), was strongly reduced (57 ± 3%) after pretreatment of cells with GF109203X. Downregulation of PKC by long‐term pretreatment of cells with PMA (1 μm, 48 h) did not abolish this effect of GF109203X (48 ± 3% inhibition).
In permeabilized DDT1 MF‐2 cells preloaded with 45Ca2+ in the presence of GF109203X, the amount of 45Ca2+ released by Ins(1,4,5)P3 (10 μm) was markedly reduced (42 ± 9%). GF109203X did not release Ca2+ itself and did not impair Ins(1,4,5)P3 receptor function.
Uptake of 45Ca2+ by intact cells, representing Ca2+ entry, was enhanced by GF109203X (65 ± 11%), by histamine (24 ± 6%) and also by thapsigargin (121 ± 10%). The GF109203X‐ and the thapsigargin‐induced uptake of 45Ca2+ were not additive.
These data suggest that GF109203X reduces the filling‐state of intracellular Ins(1,4,5)P3 sensitive Ca2+ stores by inhibiting the Ca2+ uptake into these stores, thereby promoting store‐dependent (capacitive) Ca2+ entry.