Naohiro Tamura

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Publications (3)3.74 Total impact

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    Article: Influence of brain-derived neurotrophic factor on pathfinding of dentate granule cell axons, the hippocampal mossy fibers.
    Makoto Tamura, Naohiro Tamura, Takamitsu Ikeda, Ryuta Koyama, Yuji Ikegaya, Norio Matsuki, Maki K Yamada
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    ABSTRACT: Mossy fibers, the dentate granule cell axons, are generated throughout an animal's lifetime. Mossy fiber paths and synapses are primarily restricted to the stratum lucidum within the CA3 region. Brain-derived neurotrophic factor (BDNF), a neurotrophin family protein that activates Trk neurotrophin receptors, is highly expressed in the stratum lucidum in an activity-dependent manner. The addition of a Trk neurotrophin receptor inhibitor, K252a, to cultured hippocampal slices induced aberrant extension of mossy fibers into ectopic regions. BDNF overexpression in granule cells ameliorated the mossy fiber pathway abnormalities caused by a submaximal dose of K252a. A similar rescue was observed when BDNF was expressed in CA3 pyramidal cells, most notably in mossy fibers distal to the expression site. These findings are the first to clarify the role of BDNF in mossy fiber pathfinding, not as an attractant cue but as a regulator, possibly acting in a paracrine manner. This effect of BDNF may be as a signal for new fibers to fasciculate and extend further to form synapses with neurons that are far from active BDNF-expressing synapses. This mechanism would ensure the emergence of new independent dentate gyrus-CA3 circuits by the axons of new-born granule cells.
    Molecular Brain 02/2009; 2:2.
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    Article: A low-cost method for brain slice cultures.
    Ryuta Koyama, Rieko Muramatsu, Takuya Sasaki, Rie Kimura, Chihiro Ueyama, Makoto Tamura, Naohiro Tamura, Junya Ichikawa, Naoya Takahashi, Atsushi Usami, Maki K Yamada, Norio Matsuki, Yuji Ikegaya
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    ABSTRACT: Low-cost, simple procedures for organotypic tissue cultures are desirable for high-throughput biological experiments such as large-scale medical/drug screening. We present a practical and economical method to cultivate brain slices using hydrophilic filtration membranes. With a cost reduction of more than 90%, this technique allows us to prepare hippocampal slice cultures that are morphologically and functionally indistinguishable from those obtained by the widely used Millicell-CM method.
    Journal of Pharmacological Sciences 07/2007; 104(2):191-4. · 2.08 Impact Factor
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    Article: Conserved role of brain-derived neurotrophic factor in Val66Met: target-selective reinforcement of GABAergic synapses.
    Takamitsu Ikeda, Naohiro Tamura, Norio Matsuki, Maki K Yamada
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    ABSTRACT: Brain-derived neurotrophic factor has been implicated in higher cognitive functions, and several neurological and psychiatric disorders. Recently, a variant brain-derived neurotrophic factor (BDNFMet), having a substitution referred to as Val66Met, was reported as a product of a bdnf allele with a common single nucleotide polymorphism. It has been reported that BDNFMet is impaired in its potential for activity-dependent release. We sparsely transfected cultured hippocampal neurons with BDNFMet or wild-type BDNFVal cDNAs and examined the amount of GABA-synthetic enzyme glutamic acid decarboxylase 65 (GAD65) in the adjacent region, probably in the GABAergic synapses. BDNFMet transfection increased the GAD65 level to the same extent as transfection with BDNFVal. Our findings suggest that the activity-independent secretion of brain-derived neurotrophic factor may be sufficient to induce inhibitory regulation.
    Neuroreport 01/2007; 17(18):1847-51. · 1.66 Impact Factor
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