Development of visualization system for neural activity and microcirculation of cerebral cortex.

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Analysis of cerebral microcirculation is of importance, as higher function of cerebral cortex is completely dependent on blood flow. The purpose of this study was to develop in vivo visualization system for microcirculation and neural activity of cerebral cortex by using needle probe CCD intravital microscope. During the first year we focused on visualization of arteriole and venule and developed a new system, and checked feasibility of the system. This system is composed of a needle-probe with relay lens, three-plate CCD and high difinition monitor. Time and space resolution of this system is 33ms and 2mum, respectively, and distortion of image was not found. In anesthetized dogs, we could clearly observe pial arteriole and venule and movement of red blood cell. Furthermore, we could observe microvessels within cortex by insertion of the needle-probe.In the next year, we investigated the mechanism (s) of regulation of cerebral blood flow. Inhalation of 10% CO_2, intracarotid injection of nitrol or adenosine remarkably increased carotid blood flow. In accordance with this increase, pial arteriole remarkably dilated. Relatively smaller arteriole (diameter<75mum) dilated much, but relatively larger arteriole (diameter*75mum) did not dilate significantly. In conclusion local cerebral blood flow is regulated mainly by relatevely smaller arteriole (<75mum). This mechamism may be beneficial for fine regulation of local cerebral blood flow.