1998 Fiscal Year Final Research Report Summary
Function of voltage-dependent Ca^<2+> channels in central nervous system neurons.
| Project/Area Number |
09680822
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
神経・脳内生理学
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| Research Institution | Tokyo University of Pharmacy and Life Science |
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Principal Investigator |
MIYAKAWA Hiroyoshi Tokyo Univ.Pharm.LifeSch., Sch.Life Sci., Assoc.Pro., 生命科学部, 助教授 (90166124)
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| Project Period (FY) |
1997 – 1998
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| Keywords | central nervous system neuron / deudrite / voltage-dependent Ca^<2+> channel / Ca^<2+> imaging |
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| Research Abstract |
The objective of this project was to study spatial distribution of functional voltage-gated Ca^<2+> channels in the dendrites of central nervous system neurons in slice preparations using a Ca^<2+> imaging technique in order to understand the roles of Ca^<2+> channels. Several different types of voltage-gated Ca^<2+> has been shown to be distributed in central nervous system neurons and classified according to their pharmacological and kinetic properties. Those include T, N, L, and P-type of Ca^<2+> channels.
It has been reported from the studies using isolated or cultured neurons that cerebellar Purkinje neurons are rich in P-type Ca^<2+> channels, and that low-threshold Ca^<2+> channels are also distributed in Purkinje neurons. We made cerebellar slices from rats and stained individual Purkinje neurons with fluorescent Ca^<2+> indicator dye using whole-cell pipetts. The dendrites of Purkinje neurons were stimulated by depolarizing the cell body in the presence of TTX, a Na^+ channel b
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locker, and the change in intracellular Ca^<2+> level was measured with a cooled CCD camera. Addition of a blocker for P-type channel abolished Ca^<2+> dependent action spikes and accompanying transient Ca^<2+> increase leaving a significant Ca^<2+> rise in the dendrites. Ca^<2+> imaging study showed that this Ca^<2+> rise was due to activation of low-threshold Ca^<2+> channels and that under a condition where voltage-gated K^+ channels were pharmacologically blocked, this Ca^<2+> rise was suppressed by Ni^<2+> , a blocker for low-threshold Ca^<2+> channels. Based on these findings we concluded that low-threshold Ca^<2+> channels and low-threshold K^+ channels are distributed along the dendrites of cerebellar Purkinje neurons. A simulation study to computationally reconstruct Purkinje neurons using a compartmental model suggested that those low-threshold Ca^<2+> and K^+ channels are responsible for the Ca^<2+>-dependent plateau potential.
Further studies are needed to understand how these low-threshold ion channels in the dendrites contribute the mechanisms for integrating synaptic inputs in central nervous system neurons. Less
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Research Products
(2 results)
