2003 Fiscal Year Final Research Report Summary
Functional properties of the Na^+-sensitive Na^+ channel in tanycytes
| Project/Area Number |
14570042
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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 |
General physiology
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| Research Institution | Kinki University |
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Principal Investigator |
YOSHIDA Shigeru Kinki University, Faculty of Science & Technology, Professor, 理工学部, 教授 (60145224)
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| Co-Investigator(Kenkyū-buntansha) |
MOHRI Tatsuma Okazaki National Institute for Physiological Sciences, Department of Molecular Physiology, Assistant Professor, 生理学研究所・分子生理研究系, 助手 (60290912)
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| Project Period (FY) |
2002 – 2003
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| Keywords | mouse / tanycyte / Na^+-sensitive Na^+channel / Na^+ sensor / osmolality sensor / median eminence |
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| Research Abstract |
Methods : Brain slices, sectioned coronally at the level of the median eminence(ME) with 200μm thickness, were obtained from adult mice(C57BL/6J). Slices were loaded with the Na^+-sensitive fluorescent dye SBFI(sodium-binding benzofuran isophthalate), and intracellular Na^+ images were monitored using an image analyzer ARGUS-50(Hamamatsu Photonics, Japan).
Resulfls : 1)In all areas studied, the intracellular Na^+ concentration([Na^+]_i) was greatly increased by 1mM ouabain(a Na^+ pump blocker). 2)[Na^+]_i was decreased either by 1-10μM benzamil(a blocker of Na^+/Ca^<2+> exchanger), 100μM amiloride(an inhibitor of epithelial Na^+ channels(ENaCs)) or 1mM phloridzin(a blocker of Na^+/ghicose co-transporter). 3)When [Na^+]_o was raised from a control value of 140mM to 160-200mM, a sustained elevation in [Na^+]_i was observed in ME but only small responses were observed in the other regions. 4)The responses were abolished when Na^+ was substituted with choline or mannitol. 5)Very small changes were seen in [Na^+]_i when [Na^+]_o was decreased from 140mM to 100mM. 6)The transitional area between the lateral wall of third ventricle (3V) and the ME responded inversely, i.e. this area showed a decrease in [Na^+]_i when [Na^+]_o was elevated.
Conclusions : The data indicate that (a)the basal level of [Na^+]_i in the brain regions lining 3V and ME is maintained chiefly by Na^+ pumps, Na^+/Ca^<2+> exchangers, ENaCs and Na^+/glucose co-transporters, and (b)a Na^+-level sensor, present in ME where the blood-brain barrier is absent, works when [Na^+]_o Aviates from the maintained [Na^+]_i level.
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Research Products
(4 results)
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[Publications] Hiyama, T.Y., Watanabe, E., Ono, K., Inenaga, K., Tamkun, M.M., Yoshida S., Noda, M.: "Na_x channel involved in CNS sodium-level sensing."Vol.2. 511-512 (2002)
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