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M Lafon-Cazal

Publications and source records attributed to M Lafon-Cazal.

At least 19 recordsLinked to original sources
PubMed2003

Neuroprotective activity of antazoline against neuronal damage induced by limbic status epilepticus.

Imidazoline drugs exert neuroprotective effects in cerebral ischaemia models. They also have effects against mouse cerebellar and striatal neuronal death induced by N-methyl-D-aspartate (NMDA) through the blockade of NMDA currents. Here, we investigated the effects of antazoline on NMDA toxicity and current in rat hippocampal neuronal cultures, and on an in vivo model of status epilepticus. In hippocampal cultures, antazoline (30 microM) decreased NMDA-mediated neurotoxicity and also blocked the NMDA current with voltage-dependent and fast-reversible action (inhibition by 85+/-3% at -60 mV). Status epilepticus was induced by injecting pilocarpine (200 nmol) directly into the right pyriform cortex of male adult rats. The rats then received immediately three consecutive i.p. injections at 30-min intervals of either PBS (control group) or antazoline at 10 mg/kg (low-dose group) or at 45 mg/kg (high-dose group). During the 6-h recording, status epilepticus lasted more than 200 min in all groups. In the high-dose group only, seizures completely ceased 1 h after the third injection of antazoline, then started again 1 h later. Rats were killed 1 week later, and Cresyl Violet-stained sections of their brain were analysed for damage quantification. On the ipsilateral side to the pilocarpine injection, pyriform cortex and hippocampal CA1 and CA3 areas were significantly protected in both antazoline-treated groups, whilst prepyriform and entorhinal cortices were only in the high-dose group. On the contralateral side to the pilocarpine injection, only the hippocampal CA3 area was significantly protected in the low-dose group, but all investigated structures were in the high-dose group. In conclusion, antazoline is a potent neuroprotective drug in different models of neuronal primary culture, as previously shown in striatal and cerebellar granule neurons [Neuropharmacology 39 (2000) 2244], and here in hippocampal neurons. Antazoline is also neuroprotective in vivo in the intra-pyriform pilocarpine-induced status epilepticus model.

Animals↗
PubMed2000

Imidazoline-induced neuroprotective effects result from blockade of NMDA receptor channels in neuronal cultures.

Imidazolines have been shown to be neuroprotective in focal and global ischemia in the rat. However, their mechanism of action is still unclear. We have studied the neuroprotective effects of imidazolines against NMDA-induced neuronal death and hypoxic insult in cerebellar and striatal neuronal cultures. All of the imidazolines tested decreased the NMDA-mediated neurotoxicity in a non-competitive manner. Antazoline was the most effective (IC(50) of 5 microM, maximal neuroprotection reaching 90% at 100 microM). The neuroprotective effects were still present when the imidazolines were applied during the post-insult period. Antazoline, idazoxan and guanabenz also showed neuroprotective effects against hypoxia-induced neuronal death (neuroprotection reaching 95% for antazoline at 100 microM). Antazoline was still active if applied during the reoxygenation period (15% neuroprotection). To determine the mechanism of the neuroprotective effects, the possible interaction of imidazolines with NMDA receptors was studied. Imidazolines dose-dependently and non-competitively inhibited NMDA currents. As found for the neuroprotective effects, antazoline was the most effective imidazoline, with an IC(50) of 4 microM and a maximal inhibition of 90% at 100 microM. This blockade was rapid, reversible and voltage-dependent. We compared these effects to those of the classical non-competitive antagonist of NMDA channels, MK-801. In contrast to imidazolines, blockade of the NMDA current by MK-801 was voltage-independent and reversible only at positive potentials. When co-applied with MK-801, antazoline prevented the long lasting blockade of the NMDA current by MK-801. These results are consistent with the existence of overlapping binding sites for these drugs on the NMDA receptor channel. They indicate that imidazolines exert a strong neuroprotective effect against excitotoxicity and hypoxia in cerebellar and striatal primary neuronal cultures by inhibiting NMDA receptors. Since these effects were non-competitive, imidazolines appear to be interesting new drugs with therapeutic potential.

Animals↗
PubMed1999

mGluR7-like receptor and GABA(B) receptor activation enhance neurotoxic effects of N-methyl-D-aspartate in cultured mouse striatal GABAergic neurones.

Presynaptic metabotropic glutamate receptors (mGluRs) of group III constitute possible targets for putative neuroprotective drugs acting against glutamate excitotoxic insults. Indeed, in glutamatergic cerebellar granule neurones in culture, high concentrations of L-2-amino-4-phosphonobutyrate (L-AP4, above 0.3 mM, thus activating mGluR7) inhibit NMDA-induced cell death. In contrast, in striatal cultures which are enriched in GABAergic neurones, we show that high concentrations of L-AP4 increased neuronal death in control as well as in NMDA-stimulated cultures. Moreover, similar results were obtained with the GABA(B)R agonist. baclofen. Both the neuroprotective effects in cerebellar granule cells and the neurotoxic effects in striatal neurones were mediated via Gi-Go-coupled mGluRs, suggesting that these effects were probably mediated by mGluR7a or b and GABA(B)R expressed in these neurones. In striatal neurones, we found that L-AP4 and baclofen inhibited both basal and NMDA-stimulated GABA release. These inhibitions of GABA release may be responsible for the increase in basal and NMDA-stimulated neuronal death. Indeed, blockade of GABA(A) receptors with bicuculline increased neuronal death of control and NMDA-treated striatal cultures. Taken together, these results suggest that L-AP4 and baclofen, via mGluR7 and GABA(B)R, reduced the neuroprotective effect of GABA present in striatal cultures acting via GABA(A) receptors. Although caution must be taken when extrapolating from in vitro to in vivo situations, the present experiments and the recent observations that mGluR7 and GABA(B)R are expressed in heterologous synapses, should be taken into consideration when evaluating the neuroprotective action of future mGluR7 specific agonists or GABA(B)R specific antagonists.

Animals↗
PubMed1999

mGluR7-like metabotropic glutamate receptors inhibit NMDA-mediated excitotoxicity in cultured mouse cerebellar granule neurons.

Glutamate-induced glutamate release may be involved in the delayed neuronal death induced by N-methyl-D-aspartate (NMDA). In order to examine a possible modulatory effect of the presynaptic group III mGluRs on glutamate excitotoxicity, the effect of L-2-amino-4-phosphonobutyrate (L-AP4) was examined on NMDA-induced delayed death of mouse cerebellar granule neurons in culture. We found that L-AP4, at high concentration (in the millimolar range), inhibited in a non-competitive manner the NMDA-induced toxicity. This effect was mimicked by high concentration of L-serine-o-phosphate (L-SOP), and was inhibited by pertussis toxin (PTX) indicating the involvement of a Gi/o protein. This suggests the involvement of mGluR7 in the L-AP4 effect, and this was consistent with the detection of both mGluR7 protein and mRNA in these cultured neurons. To examine the mechanism of the L-AP4-induced protection from excitotoxic damage, the effect of L-AP4 on glutamate release was examined. L-AP4 (> or = 1 mM) noncompetitively inhibited by more than 60% the glutamate release induced by NMDA during the insult. We also observed that the 10-min NMDA receptor stimulation resulted in a dramatic increase in the extracellular glutamate concentration reaching 6000% of the control value 24 h after the insult. This large increase was also inhibited when NMDA was applied in the presence of > or = 1 mM L-AP4. Part of the L-AP4-induced protection from excitotoxic damage of granule neurons may therefore result from the inhibition of the vicious cycle: dying cells release glutamate, glutamate induced cell death. The present results add to the hypothesis that presynaptic mGluRs, probably mGluR7, may be the targets of drugs decreasing glutamate release and then neuronal death observed in some pathological situations.

Animals↗
PubMed1997

Different routes of Ca2+ influx in NMDA-mediated generation of nitric oxide and arachidonic acid.

Nitric oxide and arachidonic acid act as inter- and intracellular messengers in the central nervous system. It is well known that the NMDA-mediated generation of nitric oxide and arachidonic acid is dependent on extracellular Ca2+. However, the role of voltage-dependent calcium channels (VDCCs) in this regard is poorly understood. We report here that NMDA-mediated nitric oxide production in striatal neuron cultures is blocked (80%) by the L-type VDCC antagonist nifedipine, but not by omega-conotoxin or omega-agatoxin IVA, antagonists of the N- and P-type VDCCs respectively. By contrast, none of the VDCC antagonists inhibited the NMDA-mediated release of arachidonic acid. These data indicate that permeation through different Ca2+ channels is responsible for the production of arachidonic acid and nitric oxide in striatal neurons.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1996

The CaM-kinase II inhibitor KN-62 blocks NMDA but not kainate stimulation of NO synthesis.

We have studied the effect of CaM-kinase II inhibition induced by KN-62 on NO synthesis mediated by the activation of NMDA and kainate receptors in striatal neurones. KN-62 partially inhibited NMDA-mediated NO synthesis but the effect of kainate on NO production was unaffected by the specific CaM-kinase II inhibitor. Ionomycin-induced cGMP production and the NMDA-mediated superoxide generation by nNOS were also inhibited by KN-62. Since we determined the NO synthesis via its ability to increase intracellular cGMP, we checked that the kinase inhibitor was unable to block the cGMP production induced by a NO-donor like 3-morpholinosydnonimine (SIN-1). In conclusion, these results indicate that, depending on the glutamatergic receptors involved, CaM-kinase II could participate in the regulation of NO synthesis in striatal neurones.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1995

Involvement of divalent ions in the nitric oxide-induced blockade of N-methyl-D-aspartate receptors in cerebellar granule cells.

We have previously shown that nitric oxide blocks the N-methyl-D-aspartate (NMDA) receptor without affecting the agonist binding site. We now report that in cerebellar granule cells nitric oxide decreases the NMDA channel conductance and open probability, in voltage-dependent and -independent manners, respectively, by acting on an extracellular site different from the redox, glycine, and pH modulatory sites of the receptor-channel complex. This inhibition is not additive with those of Mg2+ and Zn2+. Moreover, removal of trace concentrations of metal ions in the external medium by means of metal ion-chelators significantly reduced the inhibitory action of nitric oxide on NMDA currents. These results indicate that divalent ions are required for the blockade of NMDA receptors by NO donors.

Animals↗
PubMed1994

Glutamate receptors induce a burst of superoxide via activation of nitric oxide synthase in arginine-depleted neurons.

We have previously shown in cultured cerebellar granule neurons (Lafon-Cazal, M., Pietri, S., Culcasi, M., and Bockaert, J. (1993) Nature 364, 535-537) that upon N-methyl-D-aspartate stimulation, a nitric oxide synthase (NOS)-independent, arachidonic acid-dependent generation of superoxide free radicals (O2-.) is observed after a lag time of 10-15 min. Using the electron spin resonance spin trapping technique, we show that N-methyl-D-aspartate stimulation produced a more rapid burst of O2-. in L-arginine (L-Arg)-depleted neurons. These O2-. radicals are synthesized by NOS. KCl and kainate, which also stimulated NOS in these neurons, produced this rapid burst of O2-., which was blocked as follows: (a) in the presence of L-NG-nitro-arginine (L-Narg), and (b) by L-Arg repletion. This burst of O2-. was arachidonic acid-independent, and its time course was similar to that of nitric oxide production. It was also responsible for a weak but significant cell death that was suppressed by L-Narg and L-Arg.

Amino Acid Oxidoreductases↗
PubMed1994

Blockade of nitric oxide synthesis by tyrosine kinase inhibitors in neurones.

In striatal neurones in culture, N-methyl-D-aspartate-(NMDA), kainate-(Kai) and K(+)-dependent cGMP production is entirely mediated via nitric oxide (NO). Low concentrations of lavendustin-A (< or = 0.3 microM), a highly specific tyrosine kinase inhibitor, reduced irreversibly and in a time-dependent manner NMDA-stimulated cGMP production. After a preincubation period of 20 min with lavendustin-A (0.3 microM), the inhibition of NMDA-induced cGMP production was equal to 56 +/- 8% (n = 6). After the same preincubation period, the IC50 of the lavendustin-A blockade was 30 +/- 15 nM. Genistein, another tyrosine kinase inhibitor also inhibited NMDA-dependent cGMP production with high potencies (< or = 3 microM). Whatever the tyrosine kinase inhibitor tested, the basal cGMP production remained unaffected. Kai-, K(+)-, and ionomycin-induced cGMP production was also inhibited by lavendustin-A, and genistein. In contrast, tyrosine kinase inhibitors were unable to block NO donor-induced cGMP production. Using patch clamp experiments, we have also found that lavendustin-A (0.3-1 microM), the most potent tyrosine kinase inhibitor used, (a) did not reduce the NMDA receptor-mediated current, (b) only slighly affected Kai receptor-mediated current (16.4 +/- 3.4% inhibition) and (c) had a marked effect on voltage-sensitive Ca2+ channel- (VSCC) mediated currents (44.4 +/- 4.9% inhibition). A reduction in VSCC activity certainly explains the inhibition of K(+)-, Kai- and possibly part of the NMDA-induced cGMP production.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1993

NMDA-dependent superoxide production and neurotoxicity.

Neuronal injury resulting from acute brain insults and some neurodegenerative diseases implicates N-methyl-D-aspartate (NMDA) glutamate receptors. The fact that antioxidants reduce some types of brain damage suggests that oxygen radicals may have a role. It has been shown that mutations in Cu/Zn-superoxide dismutase (SOD), an enzyme catalysing superoxide (O2.-) detoxification in the cell, are linked to a familial form of amyotrophic lateral sclerosis (ALS). Here we report that O2.- is produced upon NMDA receptor stimulation in cultured cerebellar granule cells. Electron paramagnetic resonance was used to assess O2.- production that was due in part to the release of arachidonic acid. Activation of kainic acid receptors, or voltage-sensitive Ca2+ channels, did not produce detectable O2.-. We also find that the nitrone DMPO (5,5-dimethyl pyrroline 1-oxide), used as a spin trap, is more efficient than the nitric oxide synthase inhibitor, L-NG-nitro-arginine, in reducing NMDA-induced neuronal death in these cultures.

Amino Acid Oxidoreductases↗
PubMed1993

Nitric oxide, superoxide and peroxynitrite: putative mediators of NMDA-induced cell death in cerebellar granule cells.

In this study, we analysed the implication of superoxide (O2-.) and nitric oxide (NO.) free radicals and their resulting product peroxynitrite (ONOO-) in the neuronal death induced by the activation of the glutamatergic receptor of the N-methyl-D-aspartate (NMDA) subtype using cultured cerebellar granule cells. The NOl donor SIN-1 (3-morpholinosydnonimine N-ethylcarbamide), at concentrations which produced a much higher guanylate cyclase activation (i.e. NO. concentration) than NMDA, was not neurotoxic and did not increase the NMDA-induced neuronal death. The absence of involvement of NO. in NMDA-induced neuronal death was confirmed by the ineffectiveness of L-NG-nitroarginine (L-Narg) as a neuroprotective compound. Electron paramagnetic resonance (EPR) experiments, using 5,5-dimethyl pyrroline 1-oxide (DMPO) as a spin trap, indicated that NMDA receptor stimulation led to the generation of O2-. from at least 15-30 min. The generation of O2-. by xanthine (XA)-xanthine oxidase (XO) induced a neuronal death similar to that of NMDA. XA-XO-induced neuronal death was suppressed by addition of either superoxide dismutase (SOD) plus catalase (CAT), or DMPO in the incubation medium. In contrast, NMDA-induced neuronal death was widely blocked by DMPO and other spin trap compounds, but not by SOD +/- CAT. XA-XO-induced neuronal death was not potentiated by SIN-1 indicating that ONOO- is not more toxic than O2-. in our neuronal model.

Amino Acid Oxidoreductases↗
PubMed1993

Non-classical glutamate receptors, blocked by both NMDA and non-NMDA antagonists, stimulate nitric oxide production in neurons.

In striatal neurons in primary culture, kainate and domoate stimulated cGMP production, whereas two other analogs of glutamate which act at non-NMDA receptors, alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionate (AMPA) and quisqualate were ineffective. However, both agonists stimulated cGMP accumulation on neurons pretreated with concanavalin A, a lectin which is known to prevent desensitization of AMPA receptors. We show here that such a treatment also potentiated the kainate-stimulated cGMP production. Responses induced by all agonists of non-NMDA receptors tested were mediated by nitric oxide (NO) production, since they were inhibited by haemoglobin, an NO scavenger, and two competitive inhibitors of NO-synthase L-NG-monomethylarginine and L-NG-nitro-arginine, the effects of both inhibitors being reversed by an excess of L-arginine. The rank order of potency of the agonists tested (domoate > kainate approximately AMPA approximately quisqualate) suggests that a kainate receptor subtype triggers NO production in striatal neurons. Surprisingly, response evoked by maximally effective concentrations of kainate, quisqualate and AMPA on concanavalin A-treated neurons were partially antagonized by two non-competitive antagonists of NMDA receptors, MK-801 and phencyclidine, and by Mg2+ ions, which block NMDA-operated channels. However, in neurons which had not been treated with concanavalin A, kainate-induced NO production was not inhibited by these antagonists. These results suggest that, in addition to kainate receptor subtype, another glutamate receptor subtype which may be composed of both kainate and NMDA receptor subunits and which is desensitized by kainate, AMPA and quisqualate, is involved in NO production.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1992

Measurement of gamma-enolase release, a new method for selective quantification of neurotoxicity independently from glial lysis.

We have developed a sensitive enzymatic-immunoassay to quantify the level of gamma-enolase (a specific neuronal enzyme) which is released from cultured cells after exposure to various toxins. We show that this method can estimate selectively neuronal cell death without significantly interfering with glial cell death. Indeed, no gamma-enolase is released when glial cells are killed with free-radical producing agents. Experiments comparing the levels of neuronal cell death induced by NMDA or free-radical producing drugs, performed either by measuring gamma-enolase release or using the classical fluorescein diacetate method, yielded similar results. In addition to selectively follow neuronal death in a mixed population of neurons and glial cells, this method provides a way of determining the cell death kinetics from a single culture dish, since enolase can be measured on small samples taken from the culture medium. Finally, we propose these two methods as being complementary and useful neuronal and other cellular death indexes and also to understand the complex problem of glial influence on neuronal survival or death.

Animals↗
PubMed1992

A nitric oxide (NO) synthase inhibitor accelerates amygdala kindling.

In response to NMDA receptor activation, hippocampal, striatal and cerebellar neurons synthesize nitric oxide (NO), which in turn elevates cGMP levels via guanylate cyclase. NO is increasingly being considered as a transsynaptic retrograde messenger, involved in neuronal plasticity. The effect of an inhibitor of NO synthase, L-NG-nitroarginine (NOArg), was studied on amygdala kindling and on kindled seizures in rats. NOArg increased kindling rate, particularly in its initial period, but did not modify seizure severity in previously kindled rats, although we have no definitive explanation for this effect. However, an enhanced post-synaptic excitability could be attributed to the blockade of the negative feed-back exerted by NO on the NMDA receptor.

Amino Acid Oxidoreductases↗
PubMed1985

Pharmacological characterization of octopamine-sensitive adenylate cyclase in the flight muscle of Locusta migratoria L.

Octopamine stimulates (20-30-fold) the adenylate cyclase activity in a broken cell preparation of locust flight muscle. This stimulation is mediated by one receptor with an apparent affinity of 3.3 X 10(-6) M. The hydroxyl group in the para position on phenylethanolamine was absolutely necessary to obtain an agonist whereas the meta hydroxyl group or the presence of a catechol almost suppressed the activity. Similar pharmacological profiles were obtained on other locust muscles, i.e. mandibular and extensor tibiae muscles. The affinities of a large series of agonists and antagonists for the octopamine receptor coupled with an adenylate cyclase were compared to those reported for octopamine 1, 2A and 2B receptors based on physiological studies in the locust extensor tibiae muscle. It appears that the octopamine receptor coupled with adenylate cyclase is likely to be identical with the octopamine 2A receptor mediating the increase in the amplitude of slow motoneuron twitch tension. The results of the pharmacological experiments are discussed, in particular concerning the possible relationship between the octopamine receptor and alpha 1- and alpha 2-adrenoceptors.

Adenylyl Cyclases↗
PubMed1984

In vitro occurrence of m-octopamine in the cultured cephalic ganglion of Locusta migratoria L. after L-dopa administration.

Cephalic ganglia of the locust Locusta migratoria L. were cultured in the presence of L-DOPA and inhibitors of dopa decarboxylase or dopamine beta hydroxylase. The addition of L-DOPA to the culture medium resulted in a marked increase of m-octopamine, following higher levels of dopamine. L-DOPA produced an increase of m-tyramine. RO 44602 considerably reduced the levels of p and m-octopamines, m-tyramine, dopamine and noradrenaline while fusaric acid reduced only those of p and m-octopamines, m-tyramine and noradrenaline. Though not normally found in the locust nervous system, m-octopamine appears to be closely related to catecholamines and to be produced via their biosynthesizing enzymes through a hypothetical dehydroxylation step.

Animals↗
PubMed1982

[Neuroendocrine control of blood lipids in the locust, Locusta migratoria].

In order to determine the best conditions, the influence of various parameters on the haemolymph lipid concentration were studied. These parameters are the age, the sex and the feeding of the animals, the time and the number of the haemolymph sample-taking and the temperature of the locust culture. A large in vivo increase in haemolymph lipid concentration was obtained in locusts which received extracts of the whole CC and of their glandular or neurohemal lobes. Reversely, a decrease in this concentration was obtained in locusts operated 7 days before (cardiacectomy or glandular lobe removal). Moreover the pars intercerebralis extracts increased the level of haemolymph lipids. We conclude that adipokinetic factors are present, both in the glandular lobes of the CC and in their neurohemal lobes. It is likely that the latter partly originate from the pars intercerebralis. Results of allatectomy and injections of corpora allata extracts led to the conclusion that corpora allata contain an adipokinetic factor, the juvenile hormone. and factors that inhibit the haemolymph lipid concentration. Finally, from different injections of neurotransmitters and drugs it is argued that it is mainly octopamine which is involved in the mechanism governing the increase of the level of haemolymph lipids.

Animals↗