| Project/Area Number |
14370024
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Environmental physiology (including Physical medicine and Nutritional physiology)
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| Research Institution | University of Miyazaki (2004)
宮崎医科大学 (2002-2003) |
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Principal Investigator |
KANNAN Hiroshi University of Miyazaki, Faculty of Medicine, Department of Medical Sciences, Section of Integrative Physiology, Professor, 医学部, 教授 (00049058)
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| Co-Investigator(Kenkyū-buntansha) |
KUNITAKE Takato University of Miyazaki, Dept.Physiol., Assistant, 医学部, 助手 (20234461)
KATO Kazuo University of Miyazaki, Dept.Physiol., Assistant, 医学部, 助手 (80284834)
ISHIZUKA Yuta University of Miyazaki, Dept.Psychiatry, Lecture, 医学部, 講師 (20264377)
SHIRASAKA Tetsuro University of Miyazaki, Dept.Anesthesiology, Assistant, 医学部, 助手 (00274788)
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| Project Period (FY) |
2002 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥13,900,000 (Direct Cost: ¥13,900,000)
Fiscal Year 2004: ¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 2003: ¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 2002: ¥7,700,000 (Direct Cost: ¥7,700,000)
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| Keywords | Fos-immunohistochemical / hypertonic saline / Vasopressin / in vivo microdialysis / NO / paraventricular nucleus / Stress / brain slice / ニューロメジンU / 自由行動・意識下ラット / 心血管系 / 交感神経活動 / 脳スライス実験 / パッチクランプ法 / I_h電流 |
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| Research Abstract |
To elucidate the mechanisms responsible for adaptive responses following intracerebroventricular(i.c.v.) administration of hypertonic saline(HS), in vivo and in vitro studies have been performed using immunohistochemical, neurochemical, and electrophysiological methods. The results obtained are as follows :
(1)The quantitative relationship between the intracerebroventricularly(i.c.v.) administered HS concentration and the expression of Fos-like immunoreactivity(FLI) in brain regions involved in the homeostasis of body fluid has been examined. The regions examined were the organum vasculosum lamina terminalis(OVLT), the median preoptic nucleus(MnPO), the subfornical organ(SFO), the paraventricular nucleus(PVN), the supraoptic nucleus(SON) of the hypothalamus, the nucleus of the solitary tract(NTS), and the area postrema(AP). HS was delivered in conscious rats with attention to the actual changes in central [Na^+]. The changes in cerebrospinal fluid [Na^+] during i.c.v. administration of
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HS were compatible with those expected for thermal dehydration. FLI increased in a dose-dependent manner in the PVN and NTS. Although the pressor responses during central salt loading were not significantly affected by pretreatment with vasopressin V_1 receptor antagonist OPC-21268, FLI expression in the PVN was significantly augmented. The result suggests that the peripheral vasopressin system participates in negative feedback to modulate neuronal activities in the PVN, probably through direct action at the PVN in response to central osmotic and /or Na stimulation.
(2)Direct perfusion of the PVN region with HS was performed in conscious rats by using an in vivo brain microdialysis technique. The extracellular concentration of nitric oxide(NO) metabolites was measured, as were the blood pressure(BP) and heart rate(HR). HS perfusion increased the BP, HR, and NO metabolite levels in the PVN. Pretreatment with N^g-methyl-L-arginine (L-NMMA), an inhibitor of NO synthase, attenuated the increases in the BP and HR induced by direct infusion of HS. The result suggests that local perfusion of the PVN region with HS elicits a local release of NO, which may mediate the production of cardiovascular responses.
(3)Extracellular recordings of neurons in the PVN of consciously, freely moving male rats were performed using a movable electrode system. Single-unit activities were examined for their spontaneous firing patterns, as well as responses to intero-and extero-ceptive stressors, including disturbance in BP, water deprivation, air-jet stimulation, and systemic administration of cholecystoknin-8(CCK). On the basis of the responses to these stressors, putative vasopressin-secreting neurons could be identified. This technique may contribute to understanding of local neural mechanisms within the PVN that are responsible for stress responses in conscious rats. Less
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