1995 Fiscal Year Final Research Report Summary
A role of nitric oxide in regulation of the cerebral microcirculation
| Project/Area Number |
06671384
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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 |
Cerebral neurosurgery
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| Research Institution | Nagoya University |
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Principal Investigator |
TAKAYASU M Nagoya Univ., Medical School, Res. Assoc., 医学部, 助手 (60216794)
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| Co-Investigator(Kenkyū-buntansha) |
森 美雅 名古屋大学, 医学部, 医員
MORI M Nagoya Univ., Medical School, Postdoc.Fellow
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| Project Period (FY) |
1994 – 1995
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| Keywords | Cerebral arterioles / Nitric oxide / Cerebral microcirculation / N^G-monomethyl-L-arginine / L-arginine / Oxyhemoglobin / Vasopressin |
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| Research Abstract |
Nitric oxide (NO) is a potent vasodilator that plays a substantial role in the regulation of cerebral circulation. However, little is known about its effects on the cerebral microcirculation. Therefore, we investigated a role of NO in regulation of the cerebral microcirculation, using isolated intracerebral arterioles from rats. The arterioles were cannulated on the stage of the inverted microscope and pressurized to 60 mmHg. The inner diameter was determined by a video micro-scaler. At first, regulation of basal tone of the arterioles by NO was examined using NO inhibitor, N^G-monomethyl-L-arginine (L-NMMA) and substrate of NO,L-arginine. L-NMMA (10^<-3>M) produced vasoconstriction of 14% in arterioles originated from the middle cerebral artery, and 23% in arterioles from the basilar artery. On the other hand, L-arginine (10^<-3>M) produced vasodilatation of 11% in arterioles originated from the middle cerebral artery, and 24% in arterioles from the basilar artery. These findings sugg
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est that the roles of NO in vasomotor control differ by regions in the brain, and it may be greater in vessels of the posterior than of the anterior circulation. Next, as a model of the pathological condition, the arterioles were pretreated with oxyhemoglobin (OxyHb) and vasopressin, an endogenous vasoactive substance, was applied to the arterioles. Vasopressin produced a triphasic, dose-dependent response consisting of casodilation (10^<-11>M), vasoconstriction (10^<-9>-10^<-8>M) and a decrease in casoconstriction (10^<-7>-10^<-6>M). Pretreatment with OxyHb (10^<-4>M) abolished the vasodilation induced by the lower dose of vasopressin and doubled the vasoconstriction induced by the higher dose. These results suggest that nitric oxide play an important roles in regulation of the cerebral microciriculation directly and indirectly through the effects of the other vasoactive substances both in the physiological and pathological conditions. Finally we attempted to measure the levels of NO,which was released from the isolated and cannulated single arteriole after administration of L-arginine in vitro. However, No could not be detected in this moment because the mechanical noise level seemed much higher than the level of NO. Less
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