1992 Fiscal Year Final Research Report Summary
Significance of abnormal dendritic activities for epileptogenesis in hippocampal kindled rabbits
| Project/Area Number |
02670060
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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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 | Nippon Medical School |
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Principal Investigator |
MARU Eiichi Nippon Medical School, Department of Physiology, Associate Professor, 医学部, 助教授 (80221597)
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| Project Period (FY) |
1990 – 1992
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| Keywords | Dendritic spikes / Hippocampal pyramidal cells / Seizure activity / Kindling / Current source density analysis / CSD / Rabbits / Epileptogenesis |
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| Research Abstract |
1. Changes in the dendritic and somatic activities of hippocampal CAl pyramidal cells during seizures and kindling development were examined with an improved current source density (CSD) analysis. Laminar field potentials were simultaneously recorded from behaving rabbits implanted with a stimulating electrode in the ventral hippocampal commissure (VHM) and a recording electrode array in the CAl region. The latter had 8 or 9 recording tips separated by 100 mum along the somato-dendritic axis of pyramidal cells.
2. In the normal hippocampus, the population spike (synchronized action potentials) originated in the distal apical dendrite (400 mum from the pyramidal cell layr) following kindling and conducted toward the cell body with a velocity of 0.1-1.0m/sec.
3. During the VMH kindling stimulation (5 Hz, 10 sec) and afterdischarge, the burst discharge of action potentials occurred at the cell body and/or the proximal dendrite, white the initiation of action potentials at the middle and distal dendritic regions was strongly inhibited. Most of the action potentials originating in the somatic or proximal dendritic regions during seizures propagated back as far as the middle region of apical dendrites. Within 2-3 sec of the kindling stimulation at 5 Hz, slow EPSPs lasting more than 30 msec appeared gradually in a form of frequency potentiation at the most distal region of appical dendrites. These abnormal activities during seizures were gradually enhanced as kindling progressed.
4. It appears, thus, that both of the slow EPSPs (probably mediated by NMDA receptor activation) and the inactivation of dendritic membrane may play an critical role in seizure activities and kindling development.
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