Publications (6)10.8 Total impact
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Article: Synaptic plasticity in hippocampal CA1 neurons and learning behavior in transient ischemia-loaded gerbils.
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ABSTRACT: We studied the synaptic plasticity of hippocampal CA1 neurons and spatial learning behavior in gerbils that had been loaded with a transient cerebral ischemia caused by 5 min or 10 min occlusion of the bilateral carotid arteries. The stimulus threshold to elicit the field responses after a transient cerebral ischemia was not different from that in controls, but there was a significant decrease in the magnitude of synaptic responses, which might result from the observed loss of neurons. Long-term potentiation (LTP) and depotentiation after a 10 min cerebral ischemia expressed as a percentage of the pre-tetanus or pre-low frequency stimulation value were almost the same as those in controls, although the actual magnitude of the LTP and depotentiation was lower than in controls. Gerbils that were loaded with a 10 min cerebral ischemia showed impairment in a spatial learning test when this was started 10 days after the cerebral ischemia, but not when it was started 20 days after the same cerebral ischemia. These results suggest that the changes in electrophysiological properties of hippocampal CA1 neurons seen at 10 days after a 10 min cerebral ischemia contribute to the impairment of spatial learning of gerbils seen at this time, and that the extra-CA1 regions might be involved in the recovery of spatial learning seen at 20 days after cerebral ischemia.Biomedical Research 01/2013; 34(2):75-85. · 1.15 Impact Factor -
Article: Suppressive effect of preconditioning low-frequency stimulation on subsequent induction of long-term potentiation by high frequency stimulation in hippocampal CA3 neurons.
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ABSTRACT: We investigated the role of inositol 1, 4, 5-trisphosphate receptors (IP3Rs), activated during preconditioning low-frequency afferent stimulation (LFS), in the subsequent induction of long-term potentiation (LTP) in CA3 neurons in hippocampal slices from mature guinea pigs. Induction of LTP in the field excitatory postsynaptic potential (EPSP) by the delivery of high-frequency stimulation (HFS, a tetanus of two trains of 100 pulses at 100Hz with a 10s interval) to mossy fiber-CA3 neuron synapses was suppressed when CA3 synapses were preconditioned by the LFS of 1000 pulses at 2Hz and this effect was inhibited when the LFS preconditioning was performed in the presence of an IP3R antagonist or a protein phosphatase inhibitor. Furthermore, activation of group 1 metabotropic glutamate receptors (mGluRs) during HFS canceled the effects of an IP3R antagonist given during preconditioning LFS on the subsequent LTP induction at mossy fiber-CA3 synapses. These results suggest that, in hippocampal mossy fiber-CA3 neuron synapses, activation of IP3Rs during a preconditioning LFS results in dephosphorylation events that lead to failure of the HFS to induce subsequent LTP.Brain research 02/2012; 1449:15-23. · 2.46 Impact Factor -
Article: Impairment of hippocampal long-term potentiation and failure of learning in mice treated with d-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol.
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ABSTRACT: Gangliosides (sialic acid-containing glycosphingolipids) play important roles in many physiological functions, including synaptic plasticity in the hippocampus, which has been suggested as the basal cellular process of learning and memory in the brain. In the present study, long-term potentiation (LTP) and long-term depression (LTD) in CA1 hippocampal neurons and learning behavior were examined in mice treated with (D)-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol ((D)-PDMP), an inhibitor of ganglioside biosynthesis. Mice treated with (D)-PDMP, but not those treated with (L)-PDMP, showed impairment of LTP induction in hippocampal CA1 neurons without any significant change in LTD formation and also showed a failure of learning in the 4-pellet taking test. These results indicate that de novo synthesis of gangliosides in the brain is involved in synaptic plasticity of LTP in mouse hippocampal CA1 neurons and plays important roles in learning and memory.Biomedical Research 01/2012; 33(5):265-71. · 1.15 Impact Factor -
Article: Impaired hippocampal long-term potentiation and failure of learning in β1,4-N-acetylgalactosaminyltransferase gene transgenic mice.
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ABSTRACT: Gangliosides (sialic acid-containing glycosphingolipids) play important roles in many physiological functions, including synaptic plasticity in the hippocampus, which is considered as a cellular mechanism of learning and memory. In the present study, three types of synaptic plasticity, long-term potentiation (LTP), long-term depression (LTD) and reversal of LTP (depotentiation, DP), in the field excitatory post-synaptic potential in CA1 hippocampal neurons and learning behavior were examined in β1,4-N-acetylgalactosaminyltransferase (β1,4 GalNAc-T; GM2/GD2 synthase) gene transgenic (TG) mice, which showed a marked decrease in b-pathway gangliosides (GQ1b, GT1b and GD1b) in the brain and isolated hippocampus compared with wild-type (WT) mice. The magnitude of the LTP induced by tetanus (100 pulses at 100 Hz) in TG mice was significantly smaller than that in control WT mice, whereas there was no difference in the magnitude of the LTD induced by three short trains of low-frequency stimulation (LFS) (200 pulses at 1 Hz) at 20 min intervals between the two groups of mice. The reduction in the LTP produced by delivering three trains of LFS (200 pulses at 1 Hz, 20 min intervals) was significantly greater in the TG mice than in the WT mice. Learning was impaired in the four-pellet taking test (4PTT) in TG mice, with no significant difference in daily activity or activity during the 4PTT between TG and WT mice. These results suggest that the overexpression of β1,4 GalNAc-T resulted in altered synaptic plasticity of LTP and DP in hippocampal CA1 neurons and learning in the 4PTT, and this is attributable to the shift from b-pathway gangliosides to a-pathway gangliosides.Glycobiology 07/2011; 21(10):1373-81. · 3.58 Impact Factor -
Article: Role of inositol 1, 4, 5-trisphosphate receptors in the postsynaptic expression of guinea pig hippocampal mossy fiber depotentiation.
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ABSTRACT: Long-term potentiation (LTP) at hippocampal mossy fiber-CA3 pyramidal neuron synapses was induced in the field excitatory postsynaptic potential (EPSP) by the delivery of HFS (a tetanus of two trains of 100 pulses at 100 Hz with a 10s interval) and was reversed (depotentiated) by a train of LFS of 1000 pulses at 2 Hz applied 60 min later. This depotentiation was triggered by activation of inositol 1, 4, 5-trisphosphate receptors (IP3Rs) during HFS, which may increase the postsynaptic intracellular Ca(2+) concentration, leading to a cellular process responsible for modification of LTP expression at mossy fiber-CA3 synapses. Furthermore, we found that activation of IP3Rs or protein phosphatase during LFS was required for the reversal of LTP expressed at mossy fiber-CA3 synapses. These results suggest that, in hippocampal mossy fiber-CA3 neuron synapses, activation of IP3Rs by a preconditioning HFS results in modulation of IP3R activation and/or postsynaptic protein phosphorylation during a subsequent LFS, leading to a decrease in the field EPSP and the erasure of LTP.Brain research 03/2011; 1387:19-28. · 2.46 Impact Factor -
Article: ＜Poster＞Modulation of neuronal activities by interactions between neurons and glial cells
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ABSTRACT: Action potentials are the fundamental signals for relaying information from one region to another in the nervous system. Action potentials are propagated along axons without decrease of their amplitudes and are conducted with constant velocity depending on axonal diameter and myelin. It is considered that the modulation of fi ring patterns of action potentials in the neural circuit infl uences the information processing in the brain. We investigated the modulatory eff ects of glial cells on the fi ring pattern and the axonal conduction of action potentials using rat hippocampal slice preparation. In our previous study, we focused on interneuron / perineuronal glial cell pairs in CA1 region and reported that perineuronal glial cells could be classifi ed into two groups, one group belong astrocytes （perineuronal astrocytes） and the other group oligodendrocytes （perineuronal oligodendrocytes）, based on their membrane properties and immunohistochemical study. Direct depolarization of perineuronal astrocytes modulated the directly induced fi ring pattern of the interneuron, with initial facilitation and subsequent suppression. We also studied the oligodendrocytes in the alveus and examined their modulatory effects on the conduction of action potentials along axons of CA1 pyramidal cells. Direct repetitive depolarization of oligodendrocytes shortened the latencies of action potentials evoked by antidromic stimulation. These results indicate that glial cells infl uence the firing pattern and axonal conduction of action potentials, and that their effects involve both facilitation and suppression.
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