会議発表用資料 DIAMETER CHANGES TO CEREBRAL BLOOD VESSELS DURING NEURAL ACTIVATION AND DEACTIVATION MEASURED BY TWO-PHOTON MICROSCOPY IN AWAKE MICE

田桑, 弘之

2015-06-29
内容記述
Objectives: Neural activation monitored with positron emission tomography (PET) has been reported to a cause larger increase in cerebral blood flow (CBF) than cerebral blood volume (CBV) in humans [1]. It has also been reported that neural activation evokes larger increases in red blood cell (RBC) velocity than RBC concentration in mice when measured with Laser-Doppler flowmetry (LDF) [2]. Crossed cerebellar diaschisis (CCD) caused by contralateral supratentorial lesions can be considered to be a model of neural deactivation, and hemodynamic changes in CCD measured with PET in humans have been reported to show similar percentage decreases in CBF and CBV [3]. Recently, we developed a mouse model of CCD induced by middle cerebral artery occlusion (MCAO) that also showed similar percentage decreases in CBF and RBC concentration [4]. On the other hand, changes to the diameter of microvessels during neural activation and deactivation are still unclear. Using two-photon microscopy, we investigate microvessels diameter changes in these mouse models of neural activation and deactivation.Methods:Two-photon microscopic imaging was performed on mouse models of neural activation and deactivation (C57BL/6Jmice, 7-9weeks, N=5). Neural activation was induced by air-puff stimulation and a permanent occlusion of the MCAO was used to mimic deactivation. Microvessels were fluorescently labeled with sulforhodamine 101 and changes to the diameter of arterioles, capillaries and venula were measured in cerebral cortex (activation) and cerebellar cortex (deactivation). Baseline diameters of arterioles, capillaries and venula in cerebral cortex were 17 ± 20µm, 6 ± 7µm and 17 ± 17µm, respectively (mean ± SD). Baseline diameters of the same vessels in cerebellar cortex were 16 ± 12µm, 6 ± 6µm and 14 ± 13µm, respectively. The two-photon imaging was performed on awake animals immobilized using a hand-made fixation apparatus [5]. Results:Using two-photon imaging of mouse brain in the awake state, vasodilation and vasoconstriction were observed during neural activation and deactivation, respectively. Percentage changes in diameter during whisker stimulation were +19 ± 3%, +8 ± 4%, and +3 ± 1% for arterioles, capillaries and venula, respectively. Percentage changes in diameter during CCD were -23 ± 3%, -11 ± 3%, and -2 ± 7% for arterioles, capillaries and venula, respectively. Conclusions:In the case of microvessels, the degree of vasoconstriction under neural deactivation was similar to the degree of vasodilation under neural activation. These results only partially agree with our previous results obtained PET and LDF [1], [2], [3], [4]. PET and LDF measure hemodynamic changes in a broad brain region that includes large arteries and veins which differs from situation measured with two-photon imaging in this study. Therefore, changes in microvessels may different from changes in large vessels during the neural activation and deactivation. References[1] Ito H, et al. J Cereb Blood Flow Metab 2005; 25: 371-377.[2] Takuwa H, et al. Brain Res. 2012; 1472: 107-112[3] Ito H, et al. Ann Nucl Med 2002; 16: 249-254.[4] Takuwa H, et al. Brain Res. 2013; 1537: 350-355[5] Takuwa H, et al. Brain Res. 2011; 1369: 103-111
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