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J Glowinski

Publications and source records attributed to J Glowinski.

At least 73 records · Page 4Linked to original sources
PubMed1998

Direct and indirect presynaptic control of dopamine release by excitatory amino acids.

Dopamine (DA) release from nerve terminals of the nigrostriatal DA neurons not only depends on the activity of nigral DA cells but also on presynaptic regulation. Glutamatergic neurons of cortical origin play a prominent role in these presynaptic regulations. The direct glutamatergic presynaptic control of DA release is mediated by N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazole-4-propionate (AMPA) receptors, located on DA nerve terminals. In addition, by acting on striatal target cells, these glutamatergic neurons contribute also to indirect regulations of DA release involving several transmitters such as GABA, acetylcholine and neuropeptides. Diffusible messengers such as nitric oxide (NO) or arachidonic acid (AA) which are particularly formed under the stimulation of NMDA receptors may also participate to the regulation of DA release. In the present study, it will be shown that the co-application of NMDA and carbachol synergistically increases the release of [3H]-DA and that this effect is reduced by mepacrine or 4-bromophenacylbromide (10(-7) M), two inhibitors of PLA2. Therefore endogenously released AA induced by the co-stimulation of NMDA and cholinergic receptors seems to be involved, at least partly, in the release of DA.

Animals↗
PubMed1998

Distinct modifications by neurokinin1 (SR140333) and neurokinin2 (SR48968) tachykinin receptor antagonists of the N-methyl-D-aspartate-evoked release of acetylcholine in striosomes and matrix of the rat striatum.

The effects of SR140333 and SR48968 (neurokinin1 and neurokinin2 tachykinin receptor antagonists, respectively) on the N-methyl-D-aspartate-evoked release of [3H]acetylcholine (previously formed from [3H]choline) were investigated in striosome-enriched areas and in the matrix of the rat striatum using an in vitro microsuperfusion method. In both striatal compartments, SR140333 and SR48968 did not modify the 50 microM N-methyl-D-aspartate-evoked release of [3H]acetylcholine. However, in low concentrations, both SR140333 (0.1 microM to 1 pM) and SR48968 (0.1 microM to 0.1 nM) markedly enhanced the 1 mM N-methyl-D-aspartate (+10 microM D-serine)-evoked release of [3H]acetylcholine in striosome-enriched areas. These responses were dopamine-dependent since they were not observed any more following the local blockade of D2 receptors by sulpiride or of dopamine synthesis by alpha-methyl-p-tyrosine. A dopamine-dependent disinhibitory effect (of lower amplitude) on the 1 mM N-methyl-D-aspartate (+10 microM D-serine)-evoked release of [3H]acetylcholine was also induced by SR48968 (0.1 microM to 0.1 nM) (but not by SR140333) in the matrix. In addition, in the matrix, as shown only in the presence of alpha-methyl-p-tyrosine, both SR140333 and SR48968 reduced the 1 mM N-methyl-D-aspartate (+10 microM D-serine)-evoked response and these non-dopamine-mediated inhibitory effects only occurred at the highest tested concentration (0.1 microM) of the antagonists. Indicating the specificity of these responses, the effects of SR140333 were reproduced by RP67580, another neurokinin1 receptor antagonist and, as expected from previous binding studies, corresponding SR140333 and SR48968 enantiomers were without effect. These results suggest that under potent stimulation of N-methyl-D-aspartate receptors, endogenously released substance P and neurokinin A (or related tachykinins) regulate differently the N-methyl-D-aspartate-evoked release of [3H]acetylcholine in striosomes and in the matrix. The inhibitory effects of these tachykinins on the evoked release of [3H]acetylcholine are mediated by dopamine. On the contrary, their facilitatory responses are only observed in the matrix under blockade of dopamine transmission.

Acetylcholine↗
PubMed1998

Functional coupling of the NK1 tachykinin receptor to phospholipase D in chinese hamster ovary cells and astrocytoma cells.

In [3H]myristic acid-prelabeled Chinese hamster ovary cells stably expressing the rat NK1 tachykinin receptor, the selective NK1 agonist [Pro9]substance P ([Pro9]SP) time and concentration dependently stimulated the formation of [3H]phosphatidylethanol in the presence of ethanol. This [Pro9]SP-induced activation of phospholipase D (PLD) was blocked by NK1 receptor antagonists and poorly or not mimicked by NK2 and NK3 agonists, respectively. In confirmation of previous observations, [Pro9]SP also stimulated the hydrolysis of phosphoinositides, the release of arachidonic acid, and the formation of cyclic AMP (cAMP). All these [Pro9]SP-evoked responses could be mimicked by aluminum fluoride, but they remained unaffected in cells pretreated with pertussis toxin, suggesting that a Gi/Go protein is not involved in these different signaling pathways. The activation of PLD by [Pro9]SP was sensitive to external calcium and required an active protein kinase C because the inhibition of this kinase (Ro 31-8220) or its down-regulation (long-term treatment with a phorbol ester) abolished the response. In contrast, a cAMP-dependent process was not involved in the activation of PLD because the [Pro9]SP-evoked response was neither affected by Rp-8-bromoadenosine 3',5'-cyclic monophosphorothioate nor mimicked by cAMP-generating compounds (cholera toxin or forskolin) or by 8-bromo-cyclic AMP. A functional coupling of NK1 receptors to PLD was also demonstrated in the human astrocytoma cell line U 373 MG stimulated by SP or [Pro9]SP. These results suggest that PLD activation could be an additional signaling pathway involved in the mechanism of action of SP in target cells expressing NK1 receptors.

Animals↗
PubMed1998

Endothelin induces a calcium-dependent phosphorylation of PEA-15 in intact astrocytes: identification of Ser104 and Ser116 phosphorylated, respectively, by protein kinase C and calcium/calmodulin kinase II in vitro.

PEA-15 (phosphoprotein enriched in astrocytes, Mr = 15,000) is an acidic serine-phosphorylated protein highly expressed in the CNS, where it can play a protective role against cytokine-induced apoptosis. PEA-15 is a major substrate for protein kinase C. Endothelins, which are known to exert pleiotropic effects on astrocytes, were used to analyze further the processes involved in PEA-15 phosphorylation. Endothelin-1 or endothelin-3 (0.1 microM) induced a robust phosphorylation of PEA-15 that was abolished by the removal of extracellular calcium, but only diminished by inhibitors of protein kinase C. Microsequencing of phosphopeptides generated by digestion of PEA-15 following endothelin-1 treatment identified two phosphorylated residues: Ser104, previously recognized as the protein kinase C site, and a novel phosphoserine, Ser116, located in a consensus motif for either protein kinase casein kinase II or calcium/calmodulin-dependent protein kinase II (CaMKII). Partly purified PEA-15 was a substrate in vitro for CaMKII, but not for casein kinase II. Two-dimensional phosphopeptide mapping demonstrated that the site phosphorylated in vitro by CaMKII was also phosphorylated in intact astrocytes in response to endothelin. CaMKII phosphorylated selectively Ser116 and had no effect on Ser104, but in vitro phosphorylation by CaMKII appeared to facilitate further phosphorylation by protein kinase C. Treatment of intact astrocytes with okadaic acid enhanced the phosphorylation of the CaMKII site. These results demonstrate that PEA-15 is phosphorylated in astrocytes by CaMKII (or a related kinase) and by protein kinase C in response to endothelin.

Amino Acid Sequence↗
PubMed1997

Pyruvate protects neurons against hydrogen peroxide-induced toxicity.

Hydrogen peroxide (H2O2) is suspected to be involved in numerous brain pathologies such as neurodegenerative diseases or in acute injury such as ischemia or trauma. In this study, we examined the ability of pyruvate to improve the survival of cultured striatal neurons exposed for 30 min to H2O2, as estimated 24 hr later by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazoliumbromide assay. Pyruvate strongly protected neurons against both H2O2 added to the external medium and H2O2 endogenously produced through the redox cycling of the experimental quinone menadione. The neuroprotective effect of pyruvate appeared to result rather from the ability of alpha-ketoacids to undergo nonenzymatic decarboxylation in the presence of H2O2 than from an improvement of energy metabolism. Indeed, several other alpha-ketoacids, including alpha-ketobutyrate, which is not an energy substrate, reproduced the neuroprotective effect of pyruvate. In contrast, lactate, a neuronal energy substrate, did not protect neurons from H2O2. Optimal neuroprotection was achieved with relatively low concentrations of pyruvate (</=1 mM), whereas at high concentration (10 mM) pyruvate was ineffective. This paradox could result from the cytosolic acidification induced by the cotransport of pyruvate and protons into neurons. Indeed, cytosolic acidification both enhanced the H2O2-induced neurotoxicity and decreased the rate of pyruvate decarboxylation by H2O2. Together, these results indicate that pyruvate efficiently protects neurons against both exogenous and endogenous H2O2. Its low toxicity and its capacity to cross the blood-brain barrier open a new therapeutic perspective in brain pathologies in which H2O2 is involved.

Animals↗
PubMed1997

Neurons promote macrophage proliferation by producing transforming growth factor-beta2.

The infiltration of bone marrow-derived macrophages into the CNS contributes to growth and reactions of microglia during development or after brain injury. The proliferation of microglial cells is stimulated by colony-stimulating factor 1 (CSF-1), an astrocyte-produced growth factor that acts on mononuclear phagocytes. In the present study, we have shown, using an in vitro model system, that rodent neurons obtained from the developing cerebral cortex produce a soluble factor that strongly enhances the proliferation of macrophages cultured in the presence of CSF-1. Both macrophages isolated from the developing brain and those from the adult bone marrow were stimulated. Kinetic analyses of [3H]thymidine incorporation into macrophages indicated that their response to the neuron-derived factor involved a shortening of the cycle of proliferating cells. The effect of neurons on macrophages was blocked in the presence of antibodies neutralizing transforming growth factor-beta2 (TGF-beta2), whereas recombinant TGF-beta2 stimulated macrophage proliferation in the presence of CSF-1. Neuronal secretion of TGF-beta2 was confirmed by reverse transcription-PCR detection of TGF-beta2 transcripts and immunodetection of the protein within neurons and in their culture medium. In situ hybridization and immunohistochemical experiments showed neuronal expression of TGF-beta2 in sections of cerebral cortex obtained from 6-d-old rats, an age at which extensive developmental recruitment of macrophages occurs in this cerebral region. Altogether, our results provide direct evidence that neurons have the capacity to promote brain macrophage proliferation and demonstrate the role of TGF-beta2 in this neuronal function.

Animals↗
PubMed1997

Glutamate-dependent phosphorylation of elongation factor-2 and inhibition of protein synthesis in neurons.

Postischemic delayed neuronal death is attributed to excitotoxic activation of glutamate receptors. It is preceded by a persistent inhibition of protein synthesis, the molecular basis of which is not known. Here we have examined in cortical neurons in culture the regulation by glutamate of phosphorylation of eukaryotic elongation factor-2 (eEF-2) by eEF-2 kinase, a Ca2+/calmodulin-dependent enzyme. Using a phosphorylation state-specific antibody, we show that glutamate, which triggers a large influx of Ca2+, enhances dramatically the phosphorylation of eEF-2. On the basis of kinetic and pharmacological analysis, we demonstrate a close correlation among the increase in cytosolic Ca2+ concentration, the degree of eEF-2 phosphorylation, and the inhibition of protein synthesis. A 30 min treatment with NMDA induced a transient phosphorylation of eEF-2 and delayed neuronal death. However, pharmacological inhibition of protein translation was not neurotoxic by itself and protected neurons against the toxicity evoked by low concentrations of NMDA. Thus, phosphorylation of eEF-2 and the resulting depression of protein translation may have protective effects against excitotoxicity and open new perspectives for understanding long-term effects of glutamate.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1997

Interleukin-1 enhances the ATP-evoked release of arachidonic acid from mouse astrocytes.

During neuropathological states associated with inflammation, the levels of cytokines such as interleukin-1beta (IL-1beta) are increased. Several studies have suggested that the neuronal damage observed in pathogenesis implicating IL-1beta are caused by an alteration in the neurochemical interactions between neurons and astrocytes. We report here that treating striatal astrocytes in primary culture with IL-1beta for 22-24 hr enhances the ATP-evoked release of arachidonic acid (AA) with no effect on the ATP-induced accumulation of inositol phosphates. The molecular mechanism responsible for this effect involves the expression of P2Y2 receptors (a subtype of purinoceptor activated by ATP) and cytosolic phospholipase A2 (cPLA2, an enzyme that mediates AA release). Indeed, P2Y2 antisense oligonucleotides reduce the ATP-evoked release of AA only from IL-1beta-treated astrocytes. Further, both the amount of cPLA2 (as assessed by Western blotting) and the release of AA resulting from direct activation of cPLA2 increased fourfold in cells treated with IL-1beta. We also report evidence indicating that the coupling of newly expressed P2Y2 receptors to cPLA2 is dependent on PKC activity. These results suggest that during inflammatory conditions, IL-1beta reveals a functional P2Y2 signaling pathway in astrocytes that results in a dramatic increase in the levels of free AA. This pathway may thus contribute to the neuronal loss associated with cerebral ischemia or traumatic brain injury.

Adenosine Triphosphate↗
PubMed1997

Mechanism involved in initiation and propagation of receptor-induced intercellular calcium signaling in cultured rat astrocytes.

The mechanisms involved in the initiation and the propagation of intercellular calcium signaling (calcium waves) were studied in cultured rat astrocytes. The analysis of calcium waves, induced either by mechanical stimulation or by focal application of ionomycin, indicated that initiation was dependent on the presence of external calcium. In addition, pharmacological experiments indicate that intercellular propagation required PLC activation, integrity of IP3-sensitive internal calcium stores, and functional gap junctions. An extracellular action of ATP or glutamate and participation of voltage-dependent Ca2+ channels were tested by using enzymatic degradation, receptor antagonists, and channel blockers, respectively. Because neither the speed of propagation nor the extent of the calcium waves was affected by these treatments, these alternate mechanisms were excluded from playing a role in intercellular calcium signaling. Biochemical assays and focal applications of several agonists (methoxamine, carbachol, glutamate) of membrane receptors to neurotransmitters and peptides (endothelin 1) demonstrated that their ability to trigger regenerative calcium waves depended on phospholipase C activity and inositol phosphate production. Thus, in rat astrocytes, initiation and propagation of calcium waves involve a sequence of intra- and intercellular steps in which phospholipase C, inositol trisphosphate, internal calcium stores, and gap junction channels play a critical role. The identification of these different events allows us to determine several targets at which the level of long-range signaling in astrocytes may be controlled.

Animals↗
PubMed1997

[Epidemiological aspects of osteoarticular tuberculosis in adults. Retrospective study of 206 cases diagnosed in the Paris area from 1980 to 1994].

OBJECTIVES: The aim of this study was to determine the epidemiologic features of bone and joint tuberculosis in the Paris area from 1980 to 1994. METHODS: This retrospective study included 206 cases of confirmed bone and joint tuberculosis (in situ specimen) diagnosed from 1980 to 1994 in 7 hospital units (mainly rheumatology clinics) in Paris and suburban areas. RESULTS: The number of cases increased by a mean 12 per year from 1980 to 1989 then by 17 cases per year from 1990 to 1994. In both 1993 and 1994 there were 21 cases per year. The percentage of immigrant patients was 53% from 1980 to 1989 then reached 74% for 1990-1994, predominantly in subjects from black Africa. Only one patient in the series had human immunodeficiency virus (HIV) infection. A favoring factor was found in 23% of the immigrant and in 45% of the native French patients. Mean age was 37 years in immigrants and 58 years in French patients. Compared with French patients, immigrants had a higher rate of multifocal bone and joint tuberculosis, peripheral osteitis and spondylitus. CONCLUSION: Our findings suggest that the incidence of bone and joint tuberculosis has increased in Paris in 1993 and 1994. Two populations are especially susceptible: the elderly and/or immunodepressed French population and immigrants coming from endemic zones. The role or HIV infection was minimal in this predominantly rheumatology series.

Adult↗
PubMed1997

Potency and selectivity of the tachykinin NK3 receptor antagonist SR 142801.

Binding studies indicated that tachykinin NK3 binding sites in peripheral (ileum) and central (cerebral cortex) tissues of the guinea pig exhibit similar pharmacological properties. They also confirmed that the tachykinin NK3 receptor antagonist (S)-(N)-(1-(3-(1-benzoyl-3-(3,4-dichlorophenyl)piperidin-3-yl) propyl)-4-phenylpiperidin-4-yl)-N-methylacetamide (SR 142801) has a higher affinity for tachykinin NK3 binding sites in the guinea pig than in the rat. SR 142801 exhibited a much lower affinity for tachykinin NK2 and NK1 binding sites. SR 142801 was shown to be a potent uncompetitive antagonist of the senktide-induced formation of [3H]inositol monophosphate in slices from the guinea-pig ileum (apparent KB = 3.2 nM, 51% reduction of the maximal response), a functional test for tachykinin NK3 receptors. In agreement with results of binding studies, the effect of SR 142801 was stereoselective since its enantiomer SR 142806 was much less potent. In the rat urinary bladder, a tissue devoid of tachykinin NK3 receptors, SR 142801 was without effect on the [Pro9]substance P- or the septide-induced formation of [3H]inositol monophosphate but it slightly reduced the response of the tachykinin NK2 receptor agonist [Lys5,MeLeu9,Nle10]neurokinin A-(4-10) (KB = 339 nM). Altogether, these data indicate that SR 142801 is a highly selective tachykinin NK3 receptor antagonist which is more potent in the guinea pig than in the rat.

Animals↗
PubMed1997

Nicotine inhibits slowly inactivating K+ currents in rat cultured striatal neurons.

As shown on cultured striatal neurons recorded in whole-cell configuration, both acetylcholine (in the presence of atropine) and nicotine reduced voltage-dependent outward currents. Although, at early postnatal ages, outward currents in these cells are mainly carried by rapidly and slowly inactivating K+ channels, these inhibitions resulted from a selective and reversible effect on the slowly inactivating K+ conductance (IK+). This action was blocked by the nicotinic antagonist dihydro-beta-erythroïdine and reproduced by nicotinic agonists. When neurons were recorded under current-clamp conditions, nicotine increased reversibly their firing rate generated by step depolarizations. Therefore, in addition to its well documented muscarinic effects, acetylcholine also controls K+ currents in striatal neurons through mechanisms mediated by nicotinic receptors.

Acetylcholine↗
PubMed1997

Substance P(6-11) and natural tachykinins interact with septide-sensitive tachykinin receptors coupled to a phospholipase C in the rat urinary bladder.

The rat urinary bladder possesses NK1, NK2 (but not NK3) and 'septide-sensitive' tachykinin receptors coupled to a phospholipase C. The present study performed with SR48968 (10(-6) M) to avoid any interaction of the tested peptides with NK2 receptors, indicates that substance P(6-11) (with a high potency), neurokinin A, neurokinin B and to a lesser extent neuropeptide K (with a lower potency) stimulate [3H]-inositol monophosphate ([3H]-IP1) formation in this tissue by acting on the 'septide-sensitive' tachykinin receptors. Substance P(6-11) had little affinity for NK1 binding sites and stimulated [3H]-IP1 formation with an EC50 value and a maximal amplitude similar to those of septide. As previously observed with septide, this maximal response of substance P(6-11) (insensitive to 10(-6) M SR48968) which was about three-fold that of substance P, was blocked by the NK1 receptor antagonist RP67580 and prevented by [Pro9]substance P (NK1 receptor agonist). Similarly, substance P and several substance P C-terminal fragments prevented the substance P(6-11)-evoked response. In addition, neurokinin A, neuropeptide K and neurokinin B induced SR48968-resistant responses which exhibited a maximal amplitude similar to that of substance P (6-11) and were blocked by RP67580 and totally or partially (neuropeptide K) prevented by [Pro9]substance P.

Analgesics↗
PubMed1997

Position of the ventral pallidum in the rat prefrontal cortex-basal ganglia circuit.

The ventral pallidum receives major inputs from the nucleus accumbens, a striatal region related to the prefrontal cortex. The ventral pallidum, through its projections to the mediodorsal nucleus of the thalamus, has been considered as the main output structure of the prefrontal-basal ganglia circuits. However, as shown recently, the ventral pallidum also sends efferents to the subthalamic nucleus and the substantia nigra, suggesting that it could participate in intrinsic basal ganglia circuits. The aim of the present investigation was to determine the position of the ventral pallidum in the prefrontal-basal ganglia circuit originating from the prelimbic and medial orbital areas. Following injections of biocytin (an anterograde tracer) into the region of the core of the nucleus accumbens receiving excitatory inputs from the prelimbic and medial orbital areas, axonal terminal fields were observed in a delineated dorsal region of the ventral pallidum. When the biocytin injections were made into this ventral pallidal region, anterogradely labelled fibres were observed in both the dorsomedial substantia nigra pars reticulata and the medial subthalamic nucleus, but not in the mediodorsal nucleus of the thalamus. Confirming these anatomical observations, electrical stimulation of the core of the nucleus accumbens induced an inhibition of the spontaneous activity (D=34.9+/-13.3 ms, L=9.2+/-3.3 ms) in 46.5% of the ventral pallidal cells. Among these responding cells, 43% were antidromically driven from the subthalamic nucleus, 30% from the substantia nigra pars reticulata and only 6% from the mediodorsal nucleus of the thalamus. These data demonstrate that the region of the ventral pallidum involved in the prefrontal cortex-basal ganglia circuit originating from the prelimbic and medial orbital areas represents essentially a ventral subcommissural extension of the external segment of the globus pallidus since it exhibits similar extrinsic connections and functional characteristics. In conclusion, in this prelimbic and medial orbital channel, the ventral pallidum cannot be considered as a major output structure but is essentially involved in intrinsic basal ganglia circuits.

Animals↗
PubMed1997

N-methyl-D-aspartate-evoked release of [3H]acetylcholine in striatal compartments of the rat: regulatory roles of dopamine and GABA.

The N-methyl-D-aspartate-evoked release of [3H]acetylcholine previously formed from [3H]choline was estimated in striosome- (identified by [3H]naloxone binding) or matrix-enriched areas of the rat striatum using an in vitro microsuperfusion procedure. Experiments were performed in either the absence or the presence of dopaminergic and/or GABAergic receptor antagonists. Although the cell bodies of the cholinergic interneurons were mainly found in the matrix, in the absence of magnesium, N-methyl-D-aspartate (50 microM) stimulated the release of [3H]acetylcholine in both striatal compartments. These responses were blocked by either magnesium, dizocilpine maleate, 7-chlorokynurenate or tetrodotoxin. N-Methyl-D-aspartate responses were concentration-dependent, but the 1 mM N-methyl-D-aspartate response was higher in striosomes than in the matrix. The co-application of D-serine (10 microM) enhanced the 10 microM N-methyl-D-aspartate response in both compartments, but reduced those induced by 1 mM N-methyl-D-aspartate, this reduction being higher in striosomes. The blockade of dopaminergic transmission with the D2 and D1 dopaminergic receptor antagonists, (-)-sulpiride (1 microM) and SCH23390 (1 microM), was without effect on the 50 microM N-methyl-D-aspartate-evoked release of [3H]acetylcholine, but markedly enhanced the 1 mM N-methyl-D-aspartate+D-serine-evoked response in striosomes and to a lesser extent in the matrix. Disinhibitory responses of similar amplitude were observed not only in striosomes but also in the matrix when (-)-sulpiride was used alone, while SCH23390 alone enhanced the 1 mM N-methyl-D-aspartate+D-serine response only in striosomes and to a lower extent than (-)-sulpiride. These results indicate that D2 receptors are mainly involved in the inhibitory effect of dopamine on the 1 mM N-methyl-D-aspartate+D-serine-evoked release of [3H]acetylcholine. They also show that the stimulation of D1 receptors can either reduce (striosomes) or enhance (matrix) this response, since in the latter case the effect induced by the combined application of the D1 and D2 receptor antagonists was smaller than that observed with the D2 receptor antagonist alone. Indicating that released GABA facilitates N-methyl-D-aspartate responses, the blockade of GABAA receptors with bicuculline (5 microM) reduced the 50 microM N-methyl-D-aspartate-evoked release of [3H]acetylcholine in both striatal compartments and the 1 mM N-methyl-D-aspartate+D-serine response in the matrix. These effects result from an inhibition by GABA of the evoked release of dopamine, since the reducing effects of bicuculline on N-methyl-D-aspartate responses were not observed under the complete blockade of dopaminergic transmission by the D1 and D2 receptor antagonists. Further demonstrating a facilitatory role of GABA in the control of N-methyl-D-aspartate-evoked release of [3H]acetylcholine, in the presence of bicuculline, (-)-sulpiride and SCH23390 alone or in combination enhanced, in both compartments, the responses induced not only by 1 mM N-methyl-D-aspartate+D-serine, but also by 50 microM N-methyl-D-aspartate.

Acetylcholine↗
PubMed1997

Endothelin stimulates phospholipase D in striatal astrocytes.

In primary cultures of mouse striatal astrocytes prelabeled with [3H]myristic acid, endothelin (ET)-1 induced a time-dependent formation of [3H]phosphatidic acid and [3H]diacylglycerol. In the presence of ethanol, a production of [3H]phosphatidylethanol was observed, indicating the activation of a phospholipase D (PLD). ET-1 and ET-3 were equipotent in stimulating PLD activity (EC50 = 2-5 nM). Pretreatment of the cells with pertussis toxin partially abolished the effect of ET-1, indicating the involvement of a Gi/G(o) protein. Inhibition of protein kinase C by Ro 31-8220 or down-regulation of the kinase by a long-time treatment with phorbol 12-myristate 13-acetate (PMA) totally abolished the ET-1-induced stimulation of PLD. In contrast, a cyclic AMP-dependent process is not involved in the activation of PLD, because the ET-1-evoked formation of [3H]phosphatidylethanol was not affected when cells were coincubated with either isoproterenol, 8-bromo-cyclic AMP, or forskolin. Acute treatment with PMA also stimulated PLD through a protein kinase C-dependent process. However, the ET-1 and PMA responses were additive. Furthermore, the ET-1-evoked response, contrary to that of PMA, totally dependent on the presence of extracellular calcium. These results suggest that at least two distinct mechanisms are involved in the control of PLD activity in striatal astrocytes. Finally, ET-1, ET-3, and PMA also stimulated PLD in astrocytes from the mesencephalon, the cerebral cortex, and the hippocampus.

Animals↗
PubMed1997

High affinity binding of [3H]propionyl-[Met(O2)11]substance P(7-11), a tritiated septide-like peptide, in Chinese hamster ovary cells expressing human neurokinin-1 receptors and in rat submandibular glands.

Propionyl-[Met(O2)11]substance P(7-11) [ALIE-124 or propionyl-[Met(O2)11]SP(7-11)] has been designed as a septide-like ligand adequate for tritiation and, therefore, adequate for binding studies. In Chinese hamster ovary (CHO) cells expressing human tachykinin neurokinin (NK)-1 receptors, ALIE-124 displaced [3H][Pro9]substance P (SP) from its binding site at micromolar concentrations. However, ALIE-124 stimulated phosphatidylinositol hydrolysis, as previously shown for septide-like peptides. With [3H]ALIE-124 (95 Ci/mmol), we have been able to reveal a high affinity binding site in CHO cells (Kd = 6.6 +/- 1.0 nM), with a low maximal binding capacity. [3H]ALIE-124 specific maximal binding represented only 15-20% of that observed with [3H][Pro9]SP in CHO cells. Septide-like peptides, including septide and NKA, were potent competitors (in the nanomolar range) of [3H]ALIE-124 specific binding site. Interestingly, SP and [Pro9]SP were also potent competitors, with 10-fold greater potency for sites labeled with [3H]ALIE-124 than for sites labeled with [3H][Pro9]SP. The NK-1 antagonist RP 67580 also showed a higher potency for [3H]ALIE-124 than for [3H][Pro9]SP-specific binding sites. NKB and [Lys5,methyl-Leu9,Nle10]NKA(4-10) displaced [3H]ALIE-124 binding but with lower potency, whereas senktide had no affinity. The existence of [3H]ALIE-124 specific binding sites was also demonstrated in rat submandibular gland. In this tissue, [3H]ALIE-124 specific maximal binding was higher, reaching 40-50% of that achieved with [3H][Pro9]SP.

Animals↗