In vivo observation of the brain microvessels by needle-probe CCD intravital microscope *
In vivo observation of cerebral arterioles and venules is important for the analysis of the mechanism(s) of cerebral blood flow regulation. It has been possible to observe pial microvessels by using a cranial window and a intravital microscope. However, accession areas are limited and the microvessels within cortex are not visualized. A needle-probe CCD intravital microscope was developed with the cooperation of Nihon Koden Co Ltd. Tokyo, Japan and is used to observe microvessels. By observing the movement of red blood cells, blood flow is also visualized. We used two different types of needle-probe CCD intravital microscope. The one consists of a straight-type system with a relay lens probe and a triple-plate CCD of 1,140,000 pixels, which is used for observation of microvessels on the brain surface. The other consists of a side-type system with a prism on the tip of the probe and a single plate CCD of 380,000 pixels, which is used for observations of microvessels within the cortex. Dogs of both sexes weighing 7-12 kg were anesthetized with intravenous (i.v.) pentobarbital (25 mg/kg) and paralyzed with i.v. gallamine triethiodide (0.1 mg/kg). Through a midline incision of the skin, a piece of one side of the skull was removed. A needle probe of CCD videomicroscope was placed gently on the surface of the brain. Catheters were inserted into the carotid artery via the thyroid artery and the femoral vein for injection of drugs and femoral artery for measurement of blood pressure. Blood flow in the carotid artery was monitored by transit time ultrasound flowmetry. I tried to observe the changes in the microvessels during hypercapnia and after injection of adenosine (0.5 mg), nitroglycerin (0. 5 mg), angiotensin Ⅱ (5 fig) into the carotid artery. The carotid flow markedly increased during hypercapnia and after injection of adenosine and nitroglycerin. The microvessels on the brain surface showed diffuse dilation with the vessels of a smaller diameter (<75μm) showing more dilation. In contrast, after injection of Angiotensin Ⅱ , the carotid flow was reduced to 1/3, microvessels showed a mixture of segmental constriction and dilation. This vessel diameter response was also more prominant in the smaller vessels (< 75 μm). I inserted the side type needle probe in depth of 0.5-1.5 mm into the brain cortex for the observation of the microvessels within the cortex. I suggest that the brain blood flow may be mainly regulated by the arterioles of up to 75 μm diameter. (Accepted on September 8, 1998) Kawasaki Igakkaishi 24(3) : 131 - 140, 1998
