1992 Fiscal Year Final Research Report Summary
Glutamate receptor channels in hippocampal neurons and their development
| Project/Area Number |
02454119
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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 |
Neurophysiology and muscle physiology
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| Research Institution | Gunma University |
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Principal Investigator |
OZAWA Seiji Gunma University, School of Medicine, Professor, 医学部, 教授 (40049044)
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| Project Period (FY) |
1990 – 1992
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| Keywords | Glutamate receptor / Hippocampal neuron / AMPA / Kainate / NMDA / Calcium ion / Rectification / Excitatory synapse |
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| Research Abstract |
Glutamate receptor channels in the mammalian central nervous system are classified into three subtypes; NMDA, AMPA/kainate (KA) and KA-selective receptor channels. AMPA/KA receptor channels are activated by both AMPA and KA. In this study, we investigated mainly the properties of AMPA/KA receptors and their development in cultured rat hippocampal neurons prepared from 17- to 19-day-old rat embryos. The results are summarized as follows. 1) Cultured hippocampal neurons became sensitive to KA and AMPA within 7 days after plating. This is due to the development of AMPA/KA receptors, but not of KA-selective receptors. Thereafter, the amplitude of KA- or AMPA-induced current increased gradually. 2) AMPA/KA receptors were classified into two types. The type I receptor exhibited an outwardly-rectifying current-voltage (I-V) relation with little Ca^<2+> permeability. In contrast, the type II receptor was characterized by a remarkable inward rectification and a prominent Ca^<2+> permeability. C
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ombining whole-cell patch-clamp recordings and the PCR amplification of the mRNA harvested from a single neuron, we determined the subunit composition of the type I and type II AMPA/KA receptors expressed in hippocampal neurons. The type I receptor was composed of the GluR1 and GluR2 subunits, whereas the type II receptor of the GluR1 and GluR4 subunits. 3) The type II AMPA/KA receptor appeared exclusively in small neurons with elliptical somata and fine neurites throughout 1-5 weeks after plating. These neurons seem to be GABA ergic interneurons, since GAD was detected in these neurons. 4) When the excitatory synapse was established between dissociated CA1 pyramidal cells and neurons from the CA3/CA4 regions, high-density AMPA spots were detected on the apical dendrite of the postsynaptic CA1 neuron. Both the fast EPSC and the AMPA response on these spots showed almost linear I-V relations. This suggests that the type I AMPA/KA receptor is more responsible for generating the fast EPSC in this excitatory synapse than the type II AMPA/KA receptor. Less
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