1994 Fiscal Year Final Research Report Summary
Effects of extra and intracellular pH on the toxicity of excitatory amino acid to CNS neurons
| Project/Area Number |
05454418
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Anesthesiology/Resuscitation studies
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| Research Institution | Niigata University |
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Principal Investigator |
FUJIWARA Naoshi Niigata University Hospital Lecturer, 医学部・附属病院, 講師 (70181419)
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| Project Period (FY) |
1993 – 1994
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| Keywords | N-methy1-D-aspartate / ischemia in vitro / hippocampal slice / intracellular Ca^<2+> / acidosis / ammonium / membrane potential / 膜電位 |
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| Research Abstract |
(1) To investigate the effect of acidosis on acute neuronal damage in ischemic brain, we examined changes in intracellular free Ca^<2+> concentration ([Ca^<2+>] _i) and electrical activities in hippocampal slices exposed to oxygen-glucose deprivations (ischemia in vitro) . Hippocampal slices from Wistar rats were loaded with fura-2 and superfused with Krebs solution at 36-37ﾟC.Changes in [Ca^<2+>] _i were estimated by fluorescence measurements. Field potentials and membrane potential were recorded from the CA1 pyramidal cells. In normal pH (pH 7.4) solution, a characteristic rapid increase in [Ca^<2+>] _i and a rapid depolarization of membrane potential were observed at 6-7 min in response to ischemia in vitro. Field potentials were not recovered following 10 min of ischemia in vitro. In acidic solution (pH6.8) , both of the characteristic rapid [Ca^<2+>] _i-increase and the rapid depolarization were significantly retarded and slown. Field potentials following ischemia in vitro were reappeared in 7 of 9 slices. The results suggest that acidosis protects functions of CA1 neurons against ischemic damage.
(2) Actions of NMDA on neuronal activities and intracellular Ca^<2+> and effects of ammonium on the NMDA-induced changes in neuronal activities were investigated by using hippocampal slices of the rat. Application of NMDA (50muM,30sec) induced an increase in [Ca^<2+>] _i of the CA1 area. Duration of the [Ca^<2+>] _i-increase induced by NMDA elongated in the presence of 5 mM NH_4Cl. Membrane potential of the CA1 neuron was depolarized by NMDA (20muM,10sec) , and this NMDA-induced membrane depolarization was enhanced and elongated in the presence of NH_4Cl. On the other hand, NH_4Cl inhibited both e.p.s.p.and i.p.s.p.evoked by stimulation of the Schaffer collateral. These results suggest that ammonium aggravate ischemic neuronal damage by enhancing the NMDA-induced neuronal excitation.
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Research Products
(16 results)
