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Kilbride SM, Gluchowska SA, Telford JE, O'Sullivan C, Davey GP. High-level inhibition of mitochondrial complexes III and IV is required to increase glutamate release from the nerve terminal. Mol Neurodegener 2011; 6:53. [PMID: 21791084 PMCID: PMC3169489 DOI: 10.1186/1750-1326-6-53] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Accepted: 07/26/2011] [Indexed: 11/10/2022] Open
Abstract
Background The activities of mitochondrial complex III (ubiquinol-cytochrome c reductase, EC 1.10.2.2) and complex IV (cytochrome c oxidase EC 1.9.3.1) are reduced by 30-70% in Huntington's disease and Alzheimer's disease, respectively, and are associated with excitotoxic cell death in these disorders. In this study, we investigated the control that complexes III and complex IV exert on glutamate release from the isolated nerve terminal. Results Inhibition of complex III activity by 60-90% was necessary for a major increase in the rate of Ca2+-independent glutamate release to occur from isolated nerve terminals (synaptosomes) depolarized with 4-aminopyridine or KCl. Similarly, an 85-90% inhibition of complex IV activity was required before a major increase in the rate of Ca2+-independent glutamate release from depolarized synaptosomes was observed. Inhibition of complex III and IV activities by ~ 60% and above was required before rates of glutamate efflux from polarized synaptosomes were increased. Conclusions These results suggest that nerve terminal mitochondria possess high reserves of complex III and IV activity and that high inhibition thresholds must be reached before excess glutamate is released from the nerve terminal. The implications of the results in the context of the relationship between electron transport chain enzyme deficiencies and excitotoxicity in neurodegenerative disorders are discussed.
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Affiliation(s)
- Seán M Kilbride
- School of Biochemistry and Immunology & Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin 2, Ireland.
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2
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Kilbride SM, Telford JE, Tipton KF, Davey GP. Partial inhibition of complex I activity increases Ca-independent glutamate release rates from depolarized synaptosomes. J Neurochem 2008; 106:826-34. [PMID: 18445136 DOI: 10.1111/j.1471-4159.2008.05441.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Mitochondria have been implicated in the pathogenesis of several neurodegenerative disorders and, in particular, complex I (NADH:ubiquinone oxidoreductase, EC 1.6.5.3) activity has been shown to be partially reduced in postmortem studies of the substantia nigra of Parkinson's disease patients. The present study examines the effect of partial inhibition of complex I activity on glutamate release from rat brain synaptosomes. Following a 40% inhibition of complex I activity with rotenone, it was found that Ca(2+)-independent release of glutamate increased from synaptosomes depolarized with 4-aminopyridine. Highest rates of glutamate release were found to occur between 60-90% complex I inhibition. A similar pattern of increase was shown to occur in synaptosomes depolarized with KCl. The increase in glutamate release was found to correlate to a significant decrease in ATP. Inhibition of complex I activity by 40% was also shown to cause a significant collapse in mitochondrial membrane potential (Deltapsi(m)). These results suggest that partial inhibition of complex I activity in in situ mitochondria is sufficient to significantly increase release of glutamate from the pre-synaptic nerve terminal. The relevance of these results in the context of excitotoxicity and the pathogenesis of neurodegenerative disorders is discussed.
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Affiliation(s)
- Seán M Kilbride
- School of Biochemistry and Immunology & Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland
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3
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Deferoxamine decreases the excitatory amino acid levels and improves the histological outcome in the hippocampus of neonatal rats after hypoxia–ischemia. Pharmacol Res 2008; 57:73-8. [DOI: 10.1016/j.phrs.2007.12.003] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2007] [Revised: 12/10/2007] [Accepted: 12/18/2007] [Indexed: 11/19/2022]
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4
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Sundström E, Mo LL. Mechanisms of glutamate release in the rat spinal cord slices during metabolic inhibition. J Neurotrauma 2002; 19:257-66. [PMID: 11893026 DOI: 10.1089/08977150252806992] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Glutamate toxicity is a viable hypothesis to explain the expanding tissue degeneration occurring after traumatic or ischemic spinal cord injury. One important component in this process is the acute, excessive release of glutamate. In the current communication, the glycolytic inhibitor iodoacetate was used to induce metabolic inhibition in spinal cord slices and thereby provide an in vitro model to study the mechanisms of pathological glutamate release in the spinal cord. The evoked glutamate release was not Ca2+-dependent. Exclusion of NaCl reduced the evoked release of endogenous glutamate by 56%, while excluding Na+ increased release. Glutamate release was also reduced by the PLA2 inhibitors indomethacin (40%), arachidonyltrifluoromethyl ketone (45%) and 4-bromophenacyl bromide (36%). Blocking reverse glutamate transport by preincubation with 1 mM dihydrokainic acid reduced evoked release by 41%. However, when the dihydrokainic acid and arachidonyltrifluoromethyl ketone treatments were combined, no additive effect of the two substances was seen. These findings suggest that glutamate is released by three mechanisms from the energy compromised spinal cord: (1) in response to cellular swelling, most likely by the regulatory volume decrease, (2) by PLA2-mediated breakdown of the cell membrane and diffusion of glutamate down its concentration gradient, and (3) through reversal of the glutamate transporter.
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Affiliation(s)
- Erik Sundström
- Section of Experimental Geriatrics, Neurotec Department, Karolinska Institutet, Stockholm, Sweden.
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5
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Herrero I, Miras-Portugal MT, Sánchez-Prieto J. PKC-independent inhibition of glutamate exocytosis by arachidonic acid in rat cerebrocortical synaptosomes. FEBS Lett 2002; 296:317-9. [PMID: 1347020 DOI: 10.1016/0014-5793(92)80312-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In rat cerebrocortical synaptosomes, the addition of 4 beta-phorbol dibutyrate (4 beta-PDBu) and arachidonic acid enhances and decreases, respectively, the glutamate release evoked by 4-aminopyridine. Pretreatment of synaptosomes with 12-O-tetradecanoylphorbol 13-acetate (TPA) or pre-incubation with staurosporine, prevent the stimulatory effect of 4 beta-PDBu, but are without effect on the inhibitory action of arachidonic acid. Moreover, methyl arachidonate, which is not effective as a PKC activator, also strongly inhibits glutamate exocytosis. These results suggest that PKC is not involved in the inhibition of glutamate release by arachidonic acid.
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Affiliation(s)
- I Herrero
- Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain
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6
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Janáky R, Dohovics R, Hermann A, Oja SS, Saransaari P. Effects of metabotropic glutamate receptor agonists and antagonists on D-aspartate release from mouse cerebral cortical and striatal slices. Neurochem Res 2001; 26:1217-24. [PMID: 11874203 DOI: 10.1023/a:1013963222332] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The cytosolic release of L-glutamate has been held to be responsible for the increase in extracellular glutamate to toxic levels in the brain. The mechanism and regulation of this release was now studied in cerebral cortical and striatal slices with D-[3H]aspartate, a non-metabolized analogue of L-glutamate and a poor substrate for vesicular uptake. L-Glutamate and D-aspartate strongly stimulated the release in a concentration-dependent manner. Of the ionotropic glutamate receptor agonists, only kainate enhanced the basal release in the striatum. Of the metabotropic glutamate receptor ligands, the group I agonist (S)-3,5-dihydroxyphenylglycine (S-DHPG) failed to affect the basal release but inhibited the D-aspartate-evoked release in the striatum. The group I antagonist (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA) had no effect on the basal release in either preparation but enhanced the L-glutamate-evoked release and inhibited the D-aspartate-evoked release in the striatum, not however in the cerebral cortex. The group II agonist (2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)glycine (DCG IV) and the group II antagonist (2S)-2-ethylglutamate (EGLU) were without effect on the basal, D-aspartate- and L-glutamate-evoked releases of D-[3H]aspartate in either preparation. The group III agonist L-serine-O-phosphate (L-SOP) failed to affect the basal release but reduced the D-aspartate-evoked release in the striatum. The group III antagonist (RS)alpha-methylserine-O-phosphate (MSOP) failed to affect the basal release but increased the glutamate-evoked release and inhibited the D-aspartate-evoked release in the striatum. Both L-trans-pyrrolidine-2,4-dicarboxylate (L-trans-PDC) and (2S,1'S,2'R)-2-carboxycyclopropyl)glycine (L-CCG-III), transportable inhibitors of the high-affinity glutamate uptake, enhanced the basal release, more strongly in the striatum than in the cerebral cortex. L-CCG-III also increased the L-glutamate-evoked release in the striatum. Nontransportable dihydrokainate enhanced the basal release much less and failed to affect the glutamate-evoked release. The results indicate that the release of glutamate from cytosolic pools is carrier-mediated via homoexchange. This process is regulated in the striatum by metabotropic group I and group III receptors in a manner different from the regulation of the vesicular release of glutamate from presynaptic terminals.
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Affiliation(s)
- R Janáky
- Brain Research Center, University of Tampere Medical School, Finland.
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7
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Saransaari P, Oja SS. Characteristics of hippocampal glycine release in cell-damaging conditions in the adult and developing mouse. Neurochem Res 2001; 26:845-52. [PMID: 11565618 DOI: 10.1023/a:1011624421505] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The release of preloaded [3H]glycine from hippocampal slices from 7-day-old and 3-month-old (adult) mice was studied in different cell-damaging conditions, including hypoxia, hypoglycemia, ischemia, oxidative stress and the presence of free radicals and metabolic poisons, using a superfusion system. Glycine release was greatly enhanced in all the above conditions in both age groups, with the exception of hypoxia in developing mice. This coincides with the increased susceptibility to seizures and excitotoxicity during postnatal development. The ischemia-induced release of glycine was Ca2+-independent at both ages. The release was potentiated by exogenously applied glycine but not in Na+-free conditions, indicating the involvement of Na+-dependent transporters operating outwards. The Cl- channel blockers 4-acetamido-4'-isothiocyanostilbene-2,2'-disulphonate and diisothiocyanostilbene-2,2'-disulphonate generally reduced the ischemia-induced release, suggesting that this occurs through anion channels in both developing and adult mice. Furthermore, in the adult hippocampus riluzole and amiloride inhibited the release, indicating that Na+ channels also contribute to the ischemia-evoked release. Since glycine is an essential factor in glutamate-induced Ca2+ channel opening at the N-methyl-D-aspartate receptor, the elevated levels of glycine, together with the increased release of excitatory amino acids, must obviously collaborate in the development of ischemic neuronal damage.
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Affiliation(s)
- P Saransaari
- Tampere Brain Research Center, Medical School, University of Tampere, Finland.
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8
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Abstract
Superfused synaptosomes have been utilized in studies of neurotransmitter release during 25 years. This review summarizes the aspects of neurotransmission that have been and could be successfully investigated with this technique. The major aim of the article is to draw attention on the versatility of superfused synaptosomes and to suggest how the system could be exploited in clarifying several aspects of synaptic neurochemistry including neurotransmitter transport, receptor localization, receptor-receptor interactions, functional aspects of multi-sited receptor complexes, receptor heterogeneity and mechanisms of neurotransmitter exocytosis-endocytosis.
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Affiliation(s)
- L Raiteri
- Dipartimento di Medicina Sperimentale, Genova, Italy
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9
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Abstract
Mitochondria play a central role in the survival and death of neurons. The detailed bioenergetic mechanisms by which isolated mitochondria generate ATP, sequester Ca(2+), generate reactive oxygen species, and undergo Ca(2+)-dependent permeabilization of their inner membrane are currently being applied to the function of mitochondria in situ within neurons under physiological and pathophysiological conditions. Here we review the functional bioenergetics of isolated mitochondria, with emphasis on the chemiosmotic proton circuit and the application (and occasional misapplication) of these principles to intact neurons. Mitochondria play an integral role in both necrotic and apoptotic neuronal cell death, and the bioenergetic principles underlying current studies are reviewed.
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Affiliation(s)
- D G Nicholls
- Department of Pharmacology, University of Dundee, Dundee, Scotland.
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10
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Martin RL. Block of rapid depolarization induced by in vitro energy depletion of rat dorsal vagal motoneurones. J Physiol 1999; 519 Pt 1:131-41. [PMID: 10432344 PMCID: PMC2269489 DOI: 10.1111/j.1469-7793.1999.0131o.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/1999] [Accepted: 04/28/1999] [Indexed: 11/28/2022] Open
Abstract
1. The ionic mechanisms contributing to the rapid depolarization (RD) induced by in vitro ischaemia have been studied in dorsal vagal motoneurones (DVMs) of brainstem slices. Compared with CA1 hippocampal neurones, RD of DVMs was slower, generally occurred from a more depolarized membrane potential and was accompanied by smaller increases in [K+]o. 2. RD was not induced by elevation of [K+]o to values measured around DVMs during in vitro ischaemia or by a combination of raised [K+]o and 2-5 microM ouabain. 3. Neither TTX (5-10 microM) nor TTX combined with bepridil (10-30 microM), a Na+-Ca2+ exchange inhibitor, slowed RD. Block of voltage-dependent Ca2+ channels with Cd2+ (0.2 mM) and Ni2+ (0.3 mM) led to an earlier onset of RD, possibly because [K+]o was higher than that measured during in vitro ischaemia in the absence of divalent ions. 4. When [Na+]o was reduced to 11.25-25 mM, RD did not occur, although a slow depolarization was observed. RD was slowed (i) by 10 mM Mg2+ and 0.5 mM Ca2+, (ii) by a combination of TTX (1.5-5 microM), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 10 microM) and D-2-amino-5-phosphonovalerate (AP5, 50 microM) and (iii) by TTX (1.5-5 microM) and AP5 (50 microM). 5. Ni2+ at concentrations of 0.6 or 1.33 mM blocked RD whereas 0.6 mM Cd2+ did not. A combination of Cd2+ (0.2 mM), Ni2+ (0.3 mM), AP5 (50 microM) and bepridil (10 microM) was largely able to mimic the effects of high concentrations of Ni2+. 6. It is concluded that RD is due to Na+ entry, predominantly through N-methyl-D-aspartate receptor ionophores, and to Ca2+ entry through voltage-dependent Ca2+ channels. These results are consistent with known changes in the concentrations of extracellular ions when ischaemia-induced rapid depolarization occurs.
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Affiliation(s)
- R L Martin
- Division of Botany and Zoology, Australian National University, Canberra ACT 0200, Australia.
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11
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Saransaari P, Oja SS. Mechanisms of D-aspartate release under ischemic conditions in mouse hippocampal slices. Neurochem Res 1999; 24:1009-16. [PMID: 10478940 DOI: 10.1023/a:1021052725921] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The release of preloaded D-[3H]aspartate, an unmetabolizable analogue of L-glutamate, was studied in superfused hippocampal slices from 7-day-old and 3-month-old (adult) mice under various cell-damaging conditions, including hypoxia, hypoglycemia, ischemia, oxidative stress and the presence of free radicals and metabolic poisons. The release was generally markedly enhanced in most of the above conditions, the responses being greater in adults than in developing mice. The presence of dinitrophenol had the most pronounced effect at both ages, followed by NaCN- and free-radical-containing media and ischemia. Hypoxia did not affect release in the immature hippocampus. Under most conditions K+ stimulation (50 mM) was still able markedly to enhance D-aspartate release. This potentiation under cell-damaging conditions in both adult and developing hippocampus signifies that increased L-glutamate release contributes to excitotoxicity and subsequent cell death. The mechanisms of ischemia-induced release of D-aspartate were analyzed in the adult hippocampus using ion channel inhibitors and modified superfusion media. The induced release proved to be partly Ca(2+)-dependent and partly Ca(2+)-independent. The results obtained with Na+ omission and homo- and heteroexchange with D-aspartate and L-glutamate demonstrated that a part of the release in normoxia and ischemia is mediated by the reversal of Na(+)-dependent glutamate transporters. The Na+ channel blockers amiloride and riluzole reduced the ischemia-induced release, also indicating the involvement of Na+ channels. In addition to this, the enhanced release of D-aspartate may comprise a swelling-induced component through chloride channels.
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Affiliation(s)
- P Saransaari
- Tampere Brain Research Center, University of Tampere Medical School, Finland.
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12
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Büyükuysal RL, Mete B. Anoxia-induced dopamine release from rat striatal slices: involvement of reverse transport mechanism. J Neurochem 1999; 72:1507-15. [PMID: 10098855 DOI: 10.1046/j.1471-4159.1999.721507.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Incubation of rat striatal slices in the absence of oxygen (anoxia), glucose (aglycemia), or oxygen plus glucose (ischemia) caused significant increases in dopamine (DA) release. Whereas anoxia decreased extracellular 3,4-dihydroxyphenylacetic acid levels by 50%, aglycemia doubled it, and ischemia returned this aglycemia-induced enhancement to its control level. Although nomifensine, a DA uptake blocker, completely protected the slices against anoxia-induced DA depletion, aglycemia- and ischemia-induced increases were not altered. Moreover, hypothermia differentially affected DA release stimulated by anoxia, aglycemia, and ischemia. Involvement of glutamate in DA release induced by each experimental condition was tested by using MK-801 and also by comparing the glutamate-induced DA release with that during anoxia, aglycemia, or ischemia. MK-801 decreased the anoxia-induced DA depletion in a dose-dependent manner. This treatment, however, showed a partial protection in aglycemic conditions but failed to improve ischemia-induced DA depletion. Like anoxia, DA release induced by exogenous glutamate was also sensitive to nomifensine and hypothermia. These results indicate that anoxia enhances DA release by a mechanism involving both the reversed DA transporter and endogenous glutamate. Partial or complete lack of effect of nomifensine, hypothermia, or MK-801 in the absence of glucose or oxygen plus glucose also suggests that experimental conditions, such as the degree of anoxia/ischemia, may alter the mechanism(s) involved in DA depletion.
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Affiliation(s)
- R L Büyükuysal
- Department of Pharmacology and Clinical Pharmacology, Uludağ University Medical School, Bursa, Turkey
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Arias RL, Tasse JR, Bowlby MR. Neuroprotective interaction effects of NMDA and AMPA receptor antagonists in an in vitro model of cerebral ischemia. Brain Res 1999; 816:299-308. [PMID: 9878799 DOI: 10.1016/s0006-8993(98)01051-8] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
An in vitro model of ischemia was developed and characterized using the acute rat hippocampal slice preparation. Neuroprotective concentrations of several competitive and noncompetitive glutamate subtype-selective antagonists (CGS-19755, MK-801, YM90K and GYKI-52466) were initially determined in anoxia-enhanced agonist-induced excitotoxicity experiments. Concentrations which proved to be effective in these studies were subsequently tested for their effectiveness against an ischemic episode. Ischemia was defined as a 30-min exposure to aglycemic media ending in 5 min of concurrent anoxia, a protocol which was arrived at by empirically determining the effect of various hypoglycemic and anoxic insults on the ability of hippocampal slices to retain their electrophysiological viability. Exposure to such an ischemic episode resulted in a loss of viability by most slices, an effect which was strongly dependent on extracellular calcium. AMPA antagonists applied alone produced no neuroprotective effect in the present model of in vitro ischemia, while NMDA antagonists applied alone had a modest neuroprotective effect. In contrast, the coapplication of 10 microM MK-801 and 300 microM GYKI-52466, noncompetitive NMDA and AMPA receptor antagonists, respectively, resulted in almost complete neuroprotection. This protection was comparable to that obtained by withholding extracellular calcium, indicating that the toxic effects of glutamate receptor overstimulation can be accounted for solely by calcium influx. The effect of this combination treatment on the survival rate of hippocampal slices was synergistic, that is greater than the sum of the effects of the individual compounds. The results indicate that neuroprotection against acute ischemic insults may require a combination therapy approach.
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Affiliation(s)
- R L Arias
- CNS Disorders Division, Wyeth-Ayerst Research, CN-8000, Princeton, NJ 08543-8000, USA.
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Skogvall S, Grampp W. Physiological oxygen concentration gives an oscillating spontaneous tone in guinea-pig tracheal preparations. ACTA PHYSIOLOGICA SCANDINAVICA 1999; 165:81-93. [PMID: 10072101 DOI: 10.1046/j.1365-201x.1999.00472.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The spontaneous tone in isolated six-segment preparations of guinea-pig trachea was examined. In 12% oxygen (corresponding to normal systemic arterial oxygen pressure) the preparations developed a spontaneous tone with regular oscillations (6.6 min(-1)), usually grouped in so-called complexes (7.5 h(-1)). The average tone during an entire complex amounted to 12% of a maximum KCl-induced contraction. The complex tone was highly stable during observation periods of at least 4 h, and was reversibly transformed to the 'classical', smooth type when exposed to 94% oxygen. Stretch of preparations in low oxygen resulted in a fast, stable change of tone, while preparations in traditionally high oxygen reacted slower, and lost 40% of the active tension during the hour following stretch. Indomethacin (10 microM) did not eliminate the oscillating behaviour, but reduced the average size of the tone by 44%. Exposure to the C-fibre blocking agent capsaicin (50 microM) and the local anaesthetic lidocaine (1 mM) completely eliminated the oscillations and complexes, although the preparations retained a smooth tone. Atropine, propranolol and tetrodotoxin did not affect the complex tone. This study demonstrates for the first time that guinea-pig tracheal preparations that are exposed to near-physiological oxygen concentrations develop a new type of oscillating spontaneous tone, which is largely prostaglandin-independent, but appears to require transmitter release from sensory C-fibres. We argue that the complex tone is physiological, and that traditionally high oxygen (95%) probably results in non-physiological hyperoxic changes in this preparation.
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Affiliation(s)
- S Skogvall
- Department of Physiology and Neuroscience, Lund University, Sweden
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Abstract
Taurine release in the hippocampus is markedly potentiated in various cell-damaging conditions, including ischemia and excitotoxic damage produced by glutamate. The increase in the levels of taurine may provide an important protective mechanism against excitotoxicity. The mechanisms of the enhanced release were now studied in mouse hippocampal slices using a superfusion system. The basal release of [3H]taurine was significantly increased in Na+-deficient media in normal conditions, whereas the ischemia-evoked release was decreased, indicating the participation of Na+-dependent transport processes. The involvement of taurine transport carriers in the release was confirmed with the structural analogs, hypotaurine and beta-alanine. These amino acids potentiated the release by trans-stimulation in normoxia. In Na+-free conditions, this heteroexchange was not discernible, the carriers not being functional without Na+. In ischemia, the marked potentiation of taurine release by hypotaurine and beta-alanine further indicates that the Na+-requiring transporters also operate in ischemia. The effects of membrane disruption on taurine release due to activation of phospholipases were estimated using phospholipase and protein kinase inhibitors, which had no marked effects on hippocampal taurine release. The chloride channel blockers, 4-acetamido-4'-isothiocyanostilbene-2, 2'-disulphonate (SITS) and diisothiocyanostilbene-2,2'-disulphonate (DIDS), reduced the ischemia-induced release, suggesting that taurine diffusion through an anion channel is partially responsible for the enhanced release in ischemia.
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Affiliation(s)
- P Saransaari
- Tampere Brain Research Center, University of Tampere Medical School, Box 607, FIN-33101, Tampere, Finland.
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Goda H, Ooboshi H, Nakane H, Ibayashi S, Sadoshima S, Fujishima M. Modulation of ischemia-evoked release of excitatory and inhibitory amino acids by adenosine A1 receptor agonist. Eur J Pharmacol 1998; 357:149-55. [PMID: 9797030 DOI: 10.1016/s0014-2999(98)00559-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Adenosine has been reported to have beneficial effects against ischemic brain damage, although the mechanisms are not fully clarified. To examine the role of adenosine on the ischemia-evoked release of neurotransmitters, we applied a highly selective agonist for adenosine A1 receptor, 2-chloro-N6-cyclopentyladenosine (CCPA), into the ischemic brain using in vivo brain dialysis, which directly delivered the agonist to the local brain area. Concentrations of extracellular amino acids (glutamate, aspartate, gamma-aminobutyric acid (GABA) and taurine) and regional blood flow in the striatum of spontaneously hypertensive rats (SHRs) were monitored during cerebral ischemia elicited by bilateral carotid artery occlusion for 40 min and recirculation. Striatal blood flow and basal levels of amino acids were not affected by direct perfusion of CCPA (10 microM or 100 microM). During ischemia, concentrations of glutamate, aspartate, GABA and taurine increased up to 37-, 30-, 96- and 31-fold, respectively, when vehicle alone was administered. Administration of CCPA did not affect the changes in regional blood flow during ischemia and reperfusion. Perfusion of CCPA (100 microM), however, significantly attenuated the ischemia-evoked release of aspartate (by 70%) and glutamate (by 73%). The ischemia-induced increase of GABA tended to be decreased by CCPA, although it was not statistically significant. In contrast, both low and high concentrations of CCPA had little effect on the release of taurine during ischemia. These results suggest that stimulation of adenosine A1 receptors selectively attenuated the ischemia-evoked release of excitatory amino acids, but not of inhibitory amino acids without affecting blood flow. This modulation of the release of amino acids by adenosine A1 receptor agonists may play a protective role against ischemic neuronal damage.
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Affiliation(s)
- H Goda
- Second Department of Internal Medicine, Faculty of Medicine, Kyushu University, Fukuoka, Japan
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Sistiaga A, Miras-Portugal MT, Sánchez-Prieto J. Modulation of glutamate release by a nitric oxide/cyclic GMP-dependent pathway. Eur J Pharmacol 1997; 321:247-57. [PMID: 9063695 DOI: 10.1016/s0014-2999(96)00937-5] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The mechanism by which changes in cyclic GMP (cGMP) regulate glutamate release was investigated in rat cerebrocortical nerve terminals. The elevation of cGMP levels by inhibition of cGMP-phosphodiesterase with 2-o-propoxy-phenyl-8-azapurin-6-one (zaprinast) reduced the Ca(2+)-dependent glutamate release evoked by depolarization with 30 mM KCl or 1 mM 4-aminopyridine. The nitric oxide (NO) donor S-nitroso-N-acetylpenicillamine also enhanced cGMP and reduced glutamate release. In addition, the membrane-permeable analogs 8-bromoguanosine 3':5'-cyclic monophosphate (8-Br-cGMP) and N,2'-o-dibutyrylguanosine (dbcGMP) at 10 microM also mimic glutamate release inhibition. The reduction in glutamate release was observed with no modifications in the ATP/ADP ratio, and was reversed in the presence of the protein kinases inhibitor [N-[2-(methylamino)ethyl]-5-isoquinoline sulfonamide, HCl] (H-8). Interestingly, higher concentrations of dbcGMP (1 mM) abolished the inhibition observed with low concentrations although no facilitation was observed. This finding seems to indicate the existence of a dual role for cGMP in the control of glutamate exocytosis.
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Affiliation(s)
- A Sistiaga
- Departamento de Bioquímica, Faculatad de Veterinaria, Universidad Complutense, Madrid, Spain
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Yoshimoto K, Yayama K, Sorimachi Y, Tani J, Uemara K, Yoshida T, Ogata M, Nishimura A, Ueda S, Komura S. Effects of ion channel blockers on rapid postmortem changes in extracellular dopamine and serotonin levels in the rat nucleus accumbens. Forensic Sci Int 1997; 85:29-39. [PMID: 9050219 DOI: 10.1016/s0379-0738(96)02077-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
In the present study, we used in vivo brain microdialysis to examine the effects of ion channel blockers tetrodotoxin (TTX), EGTA-free Ca2+ and verapamil on rapid postmortem changes in extracellular levels of dopamine (DA), serotonin (5-HT) and their metabolites dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindoleacetic acid (5-HIAA) in the ACC of freely moving rats. Extracellular ACC DA levels decreased following the perfusion of the three ion channel blockers in freely moving rats, and then, at death by cervical dislocation, maximum respective 220-, 60- and 90-fold increases were observed in the extracellular output of DA in animals treated with EGTA, verapamil and TTX, respectively. Also, ACC 5-HT decreased following perfusion with the three blockers in the freely moving rats, and then maximum increases of 80-, 30- and 45-fold in the extracellular output of 5-HT were observed at death in animals treated with EGTA, verapamil and TTX, respectively, compared to the baseline. Cervical dislocation-induced rapid postmortem changes were inhibited markedly by perfusion with CSF containing the CA2+ entry blocker verapamil. These observations suggested that rapid postmortem changes in ACC DA and 5-HT release were associated with the action of calcium ion channels and/or voltage gated channels in the CNS.
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Affiliation(s)
- K Yoshimoto
- Department of Legal Medicine, Kyoto Prefectural University of Medicine, Japan
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19
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Roettger V, Lipton P. Mechanism of glutamate release from rat hippocampal slices during in vitro ischemia. Neuroscience 1996; 75:677-85. [PMID: 8951864 DOI: 10.1016/0306-4522(96)00314-4] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
There was a large release of endogenous glutamate and of pre-accumulated [3H]-D-aspartate from rat hippocampal slices during deprivation of oxygen and glucose (in vitro ischemia). The role of Na(+)-dependent glutamate transporters in this process was investigated. The release of both glutamate and [3H]-D-aspartate was largely blocked by two competitive substrate analogues of the Na(+)-dependent glutamate transporters (L-trans-pyrrolidine-2,4-dicarboxylate and D,L-threo-B-hydroxyaspartate) if the substrate analogues were intracellularly loaded prior to the ischemia. The pre-loaded analogue, D,L-threo-B-hydroxyaspartate, did not block exocytotic release of glutamate, induced by high-potassium. Dihydrokainate, an inhibitor of a subset of the Na(+)-dependent transporters, did not inhibit ischemia-induced release of glutamate or [3H]-D-aspartate. However, it did block release induced by veratridine, which was also blocked by the pre-loaded substrate analogues. Dihydrokainate could still inhibit veratridine-induced release during ischemia, showing that conditions during ischemia did not reduce its efficacy. It is concluded that release of glutamate during ischemia is largely via reversal of the Na(+)-dependent glutamate transport system. The differential effects of dihydrokainate and the competitive substrate analogues on ischemia-induced release indicate that this release occurs via a subset of the glutamate transporters that are present in the hippocampus.
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Affiliation(s)
- V Roettger
- Department of Physiology, University of Wisconsin-Madison 53706, USA
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20
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Vázquez E, Herrero I, Miras-Portugal MT, Sánchez-Prieto J. Developmental change from inhibition to facilitation in the presynaptic control of glutamate exocytosis by metabotropic glutamate receptors. Neuroscience 1995; 68:117-24. [PMID: 7477917 DOI: 10.1016/0306-4522(95)00121-x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
We have addressed the role of presynaptic metabotropic glutamate receptors in the control of glutamate release from cerebrocortical nerve terminals. The metabotropic glutamate receptor agonist (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid enhances the release evoked by a submaximal depolarization in the presence of low concentrations of arachidonic acid and in a staurosporine-sensitive manner. In contrast, (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid and L(+)-2-amino-4-phosphonobutyrate inhibit the release evoked by a maximal depolarization, in the absence of arachidonic acid and by a staurosporine-insensitive mechanism. Interestingly, the effects of the metabotropic glutamate receptors that inhibit glutamate release are only observed in the nerve terminals from young rats (one to three weeks), while the facilitatory effects are better seen in latter developmental stages (three to four weeks) and adult (two to three months) rats, coinciding with the development of the maximal capacity of glutamate uptake. These results indicate the existence of important developmental changes in the presynaptic control of glutamate release.
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Affiliation(s)
- E Vázquez
- Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain
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21
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Patel PM, Goskowicz RL, Drummond JC, Cole DJ. Etomidate Reduces Ischemia-Induced Glutamate Release in the Hippocampus in Rats Subjected to Incomplete Forebrain Ischemia. Anesth Analg 1995. [DOI: 10.1213/00000539-199505000-00013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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22
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Patel PM, Goskowicz RL, Drummond JC, Cole DJ. Etomidate reduces ischemia-induced glutamate release in the hippocampus in rats subjected to incomplete forebrain ischemia. Anesth Analg 1995; 80:933-9. [PMID: 7726435 DOI: 10.1097/00000539-199505000-00013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Etomidate and thiopental reduce ischemic neuronal injury but the mechanism by which they do so is not clear. Ischemia-induced release of the excitatory neurotransmitters glutamate and glycine is thought to play a major role in the pathophysiology of ischemic injury. To determine how etomidate and thiopental modulate excitatory transmitter release, their effect on the release of glycine and glutamate during ischemia was evaluated by microdialysis in the hippocampus and cortex of rats. Three groups of Wistar-Kyoto rats (n = 5/group) were studied. In the etomidate and thiopental groups, electroencephalogram (EEG) burst-suppression was achieved and maintained by a continuous infusion of either etomidate (0.6 mg.kg-1.min-1) or thiopental (3 mg.kg-1.min-1) 40 min prior to ischemia. Halothane anesthetized (1 minimum alveolar anesthetic concentration [MAC]) rats served as controls. Ischemia was induced in all three groups by bilateral carotid artery occlusion with simultaneous hypotension to 35 mm Hg for 10 min. Pericranial temperature was controlled at 38 degrees C. Dialysate was collected before, during, and after ischemia. The levels of glutamate and glycine in the dialysate were measured by high-performance liquid chromatography. Within the hippocampus, both glutamate and glycine levels increased significantly in the thiopental and control groups. By contrast, in the etomidate group, glutamate and glycine levels did not increase during ischemia, and peak levels were significantly less than those in the thiopental group. Peak glutamate levels in the thiopental group were significantly larger than in the control group, whereas the peak glycine levels were not different among the groups.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- P M Patel
- Department of Anesthesiology, University of California, San Diego, USA
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23
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Janáky R, Varga V, Oja SS, Saransaari P. Release of [3H]GABA evoked by glutamate agonists from hippocampal slices: effects of dithiothreitol and glutathione. Neurochem Int 1994; 24:575-82. [PMID: 7981640 DOI: 10.1016/0197-0186(94)90010-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The effects of dithiothreitol (DTT) and, reduced (GSH) and oxidized (GSSG), glutathione on the release of [3H]GABA evoked by glutamate and its agonists were studied in rat hippocampal slices. DTT had no effect on the basal release of [3H]GABA but it enhanced and prolonged the glutamate agonist-evoked release. This effect was abolished by (+)-5-methyl-10,11-dihydro-5H-dibenzo(a,d)cyclohept-5,10-imine hydrogen maleate (MK-801), a noncompetitive NMDA antagonist, and blocked by Mg2+ ions. It was only slightly attenuated by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a non-NMDA receptor antagonist, and not affected by L-(+)-2-amino-3-phosphonopropionate (L-AP3), a selective antagonist of the metabotropic glutamate receptor. The effect of DTT on the NMDA-evoked release of GABA was only slightly affected by extracellular Ca2+ but completely blocked by verapamil even in the absence of Ca2+. GSH and GSSG attenuated or abolished the effects of DTT on the agonist-induced release of [3H]GABA. The results imply that the enhanced and prolonged release of GABA evoked by the coexistence of DTT and excitatory amino acids and attenuated by endogenous GSH and GSSG is a consequence of sustained activation of the NMDA receptor-governed ionophores, which contain functional thiol groups. DTT, GSH and GSSG may regulate the redox state and accessibility of these groups. In addition to the influx of extracellular Ca2+, DTT mobilizes Ca2+ from intracellular pools distinct from those regulated by metabotropic glutamate receptors.
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Affiliation(s)
- R Janáky
- Tampere Brain Research Center, Department of Biomedical Sciences, University of Tampere, Finland
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24
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Gilman SC, Bonner MJ, Pellmar TC. Free radicals enhance basal release of D-[3H]aspartate from cerebral cortical synaptosomes. J Neurochem 1994; 62:1757-63. [PMID: 8158126 DOI: 10.1046/j.1471-4159.1994.62051757.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Excessive generation of free radicals has been implicated in several pathological conditions. We demonstrated previously that peroxide-generated free radicals decrease calcium-dependent high K(+)-evoked L[3H]-glutamate release from synaptosomes while increasing calcium-independent basal release. The present study evaluates the nonvesicular release of excitatory amino acid neurotransmitters, using D-[3H]aspartate as an exogenous label of the cytoplasmic pool of L-glutamate and L-aspartate. Isolated presynaptic nerve terminals from the guinea pig cerebral cortex were used to examine the actions and interactions of peroxide, iron, and desferrioxamine. Pretreatment with peroxide, iron alone, or peroxide with iron significantly increased the calcium-independent basal release of D-[3H]aspartate. Pretreatment with desferrioxamine had little effect on its own but significantly limited the enhancement by peroxide. High K(+)-evoked release in the presence of Ca2+ was enhanced by peroxide but not by iron. These data suggest that peroxide increases nonvesicular basal release of excitatory amino acids through Fenton-generated hydroxyl radicals. This release could cause accumulation of extracellular excitatory amino acids and contribute to the excitotoxicity associated with some pathologies.
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Affiliation(s)
- S C Gilman
- Department of Physiology, Armed Forces Radiobiology Research Institute, Bethesda, Maryland 20889-5603
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25
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Sánchez-Prieto J, Herrero I, Miras-Portugal MT, Mora F. Unchanged exocytotic release of glutamic acid in cortex and neostriatum of the rat during aging. Brain Res Bull 1994; 33:357-9. [PMID: 7904891 DOI: 10.1016/0361-9230(94)90206-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The Ca(2+)-dependent release of glutamate induced by 4-aminopyridine in synaptosomes prepared both from the cerebral cortex and basal ganglia was unchanged in aged rats (27-30 months) when compared to adults rats (3 months). Consistent with the absence of changes in glutamate exocytosis during aging, the rise in the cytosolic free Ca2+ concentration, [Ca2+]c, induced by depolarization in synaptosomes from aged rats was similar to that found in control adult rats. The results suggest that during aging the nerve terminals from the cerebral cortex and basal ganglia maintain an intact ability to release glutamate by exocytosis.
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Affiliation(s)
- J Sánchez-Prieto
- Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain
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26
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Herrero I, Miras-Portugal MT, Sánchez-Prieto J. Rapid desensitization of the metabotropic glutamate receptor that facilitates glutamate release in rat cerebrocortical nerve terminals. Eur J Neurosci 1994; 6:115-20. [PMID: 7907519 DOI: 10.1111/j.1460-9568.1994.tb00253.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The metabotropic autoreceptor of glutamatergic nerve terminals from the cerebral cortex of adult rats has been characterized. Receptor activation involves a rapid and transient increase in diacylglycerol, which is sensitive to L-2-amino-3-phosphonopropionate (L-AP3) and L-2-amino-4-phosphonobutanoic acid (L-AP4) and is partially blocked by pertussis toxin. Protein kinase C (PKC) has a negative feedback control in this transduction pathway because the activation of the kinase, either by phorbol esters or by the endogenous diacylglycerol produced by the receptor, results in a reversible receptor desensitization, with loss of the ability to further facilitate glutamate release. It is concluded that the facilitatory metabotropic receptor located at the glutamatergic nerve endings belongs to the subclass coupled to phosphoinositide hydrolysis and that the rapid and use-dependent desensitization of the facilitatory pathway may underlie a mechanism to prevent its permanent activation and thereby to avoid neurotoxicity.
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Affiliation(s)
- I Herrero
- Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain
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27
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Pavlásek J, Haburcák M, Masánová C, Orlický J. Increase of catecholamine content in the extracellular space of the rat's brain cortex during spreading depression wave as determined by voltammetry. Brain Res 1993; 628:145-8. [PMID: 8313141 DOI: 10.1016/0006-8993(93)90949-n] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The effect of chemically initiated (KCl) spreading cortical depression on catecholamine content in the extracellular cortical space was examined using voltammetry technique in chloralhydrate-anaesthetized rats. Correlation between alterations in catechol-oxidative current (CA.OC) and the time-course of the slow potential (SP) change (one of the chief features of the spreading depression) showed that spreading depression wave was accompanied by the significant increase in CA.OC content (up to 158 +/- 43%, mean +/- S.D., P < 0.001). The rise of the negative SP preceded significant CA.OC increase by 20 +/- 8 s. This fact provides the evidence that catecholamine overflow cannot participate in triggering spreading depression wave; nevertheless it can be an important link of the spreading depression mechanism.
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Affiliation(s)
- J Pavlásek
- Institute of Normal and Pathological Physiology, Slovak Academy of Sciences, Bratislava
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28
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Dickie BG, Davies JA. Modulation of calcium-dependent and -independent components of veratridine-evoked release of glutamate from rat cerebellum. Brain Res 1993; 619:247-54. [PMID: 7690673 DOI: 10.1016/0006-8993(93)91618-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The entry of Ca2+ into the presynaptic neuronal terminal is considered to be a prerequisite for exocytosis. However, reports suggest that a Ca(2+)-independent component of release can exist for some neurotransmitters. In this study we have used veratridine-stimulated release of glutamate from rat cerebellar slices to investigate Ca(2+)-dependent and -independent release. A 1-min pulse of veratridine (10 microM) induced release of glutamate in both Ca(2+)-replete and Ca(2+)-free ACSF. Both modes of release, however, could be elicited in a sequential manner following a single application of veratridine in Ca(2+)-free ACSF, with return to Ca(2+)-replete conditions 5 min post-pulse. This separation permitted the modulation of either, or both, phases of release. Apamin and dihydrokainate had little effect on Ca(2+)-independent release but produced enhancement of the Ca(2+)-dependent phase. Tetrodotoxin abolished both phases of release when applied with the veratridine pulse, but had no effect on the Ca(2+)-dependent phase alone. The Ca(2+)-dependent phase was partially sensitive to Co2+, although the Ca2+ channel blockers verapamil, amiloride, omega-conotoxin and ruthenium red were ineffective, suggesting a lack of involvement of L-, N- or T-type channels. The possible mechanisms mediating the Ca(2+)-dependent and -independent components of endogenous glutamate release from cerebellar slices are discussed.
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Affiliation(s)
- B G Dickie
- Department of Pharmacology and Therapeutics, University of Wales College of Medicine, Cardiff, UK
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29
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Matsumoto M, Scheller MS, Zornow MH, Strnat MA. Effect of S-emopamil, nimodipine, and mild hypothermia on hippocampal glutamate concentrations after repeated cerebral ischemia in rabbits. Stroke 1993; 24:1228-34. [PMID: 8102022 DOI: 10.1161/01.str.24.8.1228] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
BACKGROUND AND PURPOSE We sought to determine the effects of two different calcium channel antagonists, S-emopamil and nimodipine, on hippocampal glutamate and glycine release and to compare their effects to those of mild hypothermia. METHODS New Zealand White rabbits were subjected to two 7.5-minute episodes of global cerebral ischemia at a 1-hour interval produced by neck tourniquet inflation (20 psi) combined with hypotension during halothane anesthesia. Hippocampal extracellular concentrations of glutamate and glycine were monitored using in vivo microdialysis. Animals were randomized to receive either S-emopamil (1 mg.kg-1 bolus, 0.1 mg.kg-1.min-1 infusion), nimodipine (10 micrograms.kg-1 bolus, 1 microgram.kg-1.min-1 infusion), hypothermia (32 degrees C), or saline (control) before ischemia. Drug infusion and hypothermia were continued throughout the study periods. RESULTS In all four groups, both ischemic episodes resulted in significant elevations of hippocampal extracellular concentrations of glutamate and glycine (baseline vs peak, P < .01 in all groups). However, glutamate levels were significantly lower in the S-emopamil (P = .0001) and hypothermia (P = .0003) groups when compared with the control group after the onset of the first ischemic episode through 1 hour after the second ischemic episode. There was no significant difference between the four groups in the concentrations of glycine. There was no significant difference between the peak concentrations of glutamate or glycine after each ischemic period. CONCLUSIONS These results suggest that preischemic administration of S-emopamil, but not nimodipine, attenuates the increase in hippocampal extracellular concentrations of glutamate in the peri-ischemic period in this model, and that this effect is also observed when mild hypothermia is instituted before ischemia. Decreased concentrations of glutamate after ischemic episodes may be a possible mechanism for the observed neuroprotective properties of S-emopamil and mild hypothermia (32 degrees C).
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Affiliation(s)
- M Matsumoto
- Department of Anesthesiology, University of California, San Diego, La Jolla 92093-0629
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30
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Yoshimoto K, Irizawa Y, Komura S. Rapid postmortem changes of rat striatum dopamine, serotonin, and their metabolites as monitored by brain microdialysis. Forensic Sci Int 1993; 60:183-8. [PMID: 7693559 DOI: 10.1016/0379-0738(93)90237-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Brain microdialysis was used to monitor changes in extracellular dopamine (DA), serotonin (5-HT), and their metabolite levels in the rat striatum at death by cervical dislocation. Maximum respective 450-fold and 150-fold increases in the extracellular output of DA and 5-HT were observed within the first 30 min of death. DA and 5-HT outputs remained elevated over the following 2 h at levels about 100-fold and 50-fold above pre-death values, respectively. In contrast with monoamine outputs, the outputs of the DA metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC), and the 5-HT metabolite, 5-hydroxyindoleacetic acid (5-HIAA), rapidly decreased by 10% and 20%, respectively 1 h after death. 5-Hydroxytryptophol (5-HTOL) gradually decreased after death. Before death both the extracellular DOPAC/DA and 5-HIAA/5-HT ratios were about 400; after death these ratios dropped to 0.56 and 4.0, respectively at 30 min. These observations suggested that regulation of neurotransmitter releases through the neuronal membrane and metabolisms in the rat striatum were seriously disrupted at death. This finding may be helpful in the determination of death in the field of forensic medicine.
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Affiliation(s)
- K Yoshimoto
- Department of Legal Medicine, Kyoto Prefectural University of Medicine, Japan
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31
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Zini S, Roisin MP, Armengaud C, Ben-Ari Y. Effect of potassium channel modulators on the release of glutamate induced by ischaemic-like conditions in rat hippocampal slices. Neurosci Lett 1993; 153:202-5. [PMID: 8100991 DOI: 10.1016/0304-3940(93)90322-c] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The effects of the potassium channel openers lemakalim, RP 52891 and galanin and the potassium channel blockers glibenclamide and gliquidone were evaluated by the release of endogenous glutamate from rat hippocampal slices subjected to a brief period of ischaemia (2-10 min). Ischaemia was mimicked by incubating slices in a glucose free medium equilibrated with 95% N2/5% CO2. These conditions evoked a release of glutamate which was insensitive to tetrodotoxin and Ca2+ indicating a non-vesicular origin. The release of glutamate evoked by a 6- or 8-min period of ischaemia was reduced by 25-40% in the presence of lemakalim (10 microM), RP 52891 (10 microM) or galanin (0.3 microM), whereas it was enhanced by 60 to 100% in the presence of glibenclamide (1 microM) and gliquidone (2 microM). These observations suggest that cellular damage resulting from ischaemia induced excessive release of glutamate in the hippocampus may be partly reduced by potassium channel openers, and conversely increased by sulfonylureas.
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Affiliation(s)
- S Zini
- Laboratoire de Neurobiologie et Physiopathologie du Développement, INSERM U29, Paris, France
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32
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Affiliation(s)
- D G Nicholls
- Department of Biochemistry, University of Dundee, Scotland
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33
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Collard KJ, Menon-Johansson AS. Effects of short-term hypoxia on [3H]glutamate release from preloaded hippocampal and cortical synaptosomes. Neurochem Res 1993; 18:165-70. [PMID: 8097288 DOI: 10.1007/bf01474680] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The effect of short-term hypoxia on the release of [3H]glutamate from preloaded hippocampal and cortical synaptosomes was studied in a rapid superfusion system. The technique minimised the loss of released glutamate by reuptake. The results indicated that the effects of short term hypoxia were qualitatively similar to those reported in previous studies using more long-term hypoxia, but were significantly smaller. The non-Ca(2+)-dependent efflux of glutamate from cortical synaptosomes was increased by hypoxia as was the Ca(2+)-dependent release from hippocampal tissue. Possible mechanisms for these findings were discussed. The small amplitude of these changes in comparison to the effects seen in slowly perfused tissue in vitro and in vivo indicated that the contribution made by changes in neuronal efflux to the overall increase in extracellular glutamate seen in hypoxia is relatively minor.
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Affiliation(s)
- K J Collard
- Department of Physiology, University of Wales College of Cardiff
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34
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Sánchez-Prieto J, Herrero I, Miras-Portugal MT. Modulation of the exocytotic release of neurotransmitter glutamate by protein kinase C. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1993; 341:95-105. [PMID: 7906916 DOI: 10.1007/978-1-4615-2484-7_9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- J Sánchez-Prieto
- Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain
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35
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McIntosh TK. Novel pharmacologic therapies in the treatment of experimental traumatic brain injury: a review. J Neurotrauma 1993; 10:215-61. [PMID: 8258838 DOI: 10.1089/neu.1993.10.215] [Citation(s) in RCA: 197] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Delayed or secondary neuronal damage following traumatic injury to the central nervous system (CNS) may result from pathologic changes in the brain's endogenous neurochemical systems. Although the precise mechanisms mediating secondary damage are poorly understood, posttraumatic neurochemical changes may include overactivation of neurotransmitter release or re-uptake, changes in presynaptic or postsynaptic receptor binding, or the pathologic release or synthesis of endogenous "autodestructive" factors. The identification and characterization of these factors and the timing of the neurochemical cascade after CNS injury provides a window of opportunity for treatment with pharmacologic agents that modify synthesis, release, receptor binding, or physiologic activity with subsequent attenuation of neuronal damage and improvement in outcome. Over the past decade, a number of studies have suggested that modification of postinjury events through pharmacologic intervention can promote functional recovery in both a variety of animal models and clinical CNS injury. This article summarizes recent work suggesting that pharmacologic manipulation of endogenous systems by such diverse pharmacologic agents as anticholinergics, excitatory amino acid antagonists, endogenous opioid antagonists, catecholamines, serotonin antagonists, modulators of arachidonic acid, antioxidants and free radical scavengers, steroid and lipid peroxidation inhibitors, platelet activating factor antagonists, anion exchange inhibitors, magnesium, gangliosides, and calcium channel antagonists may improve functional outcome after brain injury.
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Affiliation(s)
- T K McIntosh
- Department of Surgery, University of Pennsylvania, Philadelphia
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36
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Herrero I, Miras-Portugal MT, Sánchez-Prieto J. Positive feedback of glutamate exocytosis by metabotropic presynaptic receptor stimulation. Nature 1992; 360:163-6. [PMID: 1359425 DOI: 10.1038/360163a0] [Citation(s) in RCA: 287] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Glutamate is important in several forms of synaptic plasticity such as long-term potentiation, and in neuronal cell degeneration. Glutamate activates several types of receptors, including a metabotropic receptor that is sensitive to trans-1-amino-cyclopenthyl-1,3-dicarboxylate, coupled to G protein(s) and linked to inositol phospholipid metabolism. The activation of the metabotropic receptor in neurons generates inositol 1,4,5-trisphosphate, which causes the release of Ca2+ from intracellular stores and diacylglycerol, which activates protein kinase C. In nerve terminals, the activation of presynaptic protein kinase C with phorbol esters enhances glutamate release. But the presynaptic receptor involved in this protein kinase C-mediated increase in the release of glutamate has not yet been identified. Here we demonstrate the presence of a presynaptic glutamate receptor of the metabotropic type that mediates an enhancement of glutamate exocytosis in cerebrocortical nerve terminals. Interestingly, this potentiation of glutamate release is observed only in the presence of arachidonic acid, which may reflect that this positive feedback control of glutamate exocytosis operates in concert with other pre- or post-synaptic events of the glutamatergic neurotransmission that generate arachidonic acid. This presynaptic glutamate receptor may have a physiological role in the maintenance of long-term potentiation where there is an increase in glutamate release mediated by postsynaptically generated arachidonic acid.
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Affiliation(s)
- I Herrero
- Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain
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Herrero I, Miras-Portugal MT, Sánchez-Prieto J. Activation of Protein Kinase C by Phorbol Esters and Arachidonic Acid Required for the Optimal Potentiation of Glutamate Exocytosis. J Neurochem 1992; 59:1574-7. [PMID: 1357097 DOI: 10.1111/j.1471-4159.1992.tb08478.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The effects of arachidonic acid and phorbol esters in the Ca(2+)-dependent release of glutamate evoked by 4-aminopyridine (4-AP) in rat cerebrocortical synaptosomes were studied. In the absence of arachidonic acid, high concentrations (500 nM) of 4 beta-phorbol dibutyrate (4 beta-PDBu) were required to enhance the release of glutamate. However, in the presence of arachidonic acid, low concentrations of 4 beta-PDBu (1-50 nM) were effective in potentiating glutamate exocytosis. This potentiation of glutamate release by phorbol esters was not observed with the methyl ester of arachidonic acid, which does not activate protein kinase C. Moreover, pretreatment of synaptosomes with the protein kinase inhibitor staurosporine also prevented the stimulatory effect by arachidonic acid and phorbol esters. These results suggest that the activation of protein kinase C by both arachidonic acid and phorbol esters may play a role in the potentiation of glutamate exocytosis.
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Affiliation(s)
- I Herrero
- Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain
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