Wei L, Otsuka T, Acuff V, Bereczki D, Pettigrew K, Patlak C, Fenstermacher J
Department of Neurological Surgery, State University of New York, Stony Brook 11794-8122.
J Cereb Blood Flow Metab. 1993 May;13(3):487-97. doi: 10.1038/jcbfm.1993.63.
Local cerebral blood flow is lowered in many brain areas of the rat by high-dose pentobarbital (50 mg/kg). In the present study, the mechanism of this flow change was examined by measuring the distribution of radiolabeled red blood cells (RBCs) and albumin (RISA) in small parenchymal microvessels and calculating the microvascular distribution spaces and mean transit times of RBCs, RISA, and blood. In most brain areas, pentobarbital slightly decreased the RISA space, modestly increased the RBC space, and did not alter the blood space. The mean transit times of RBCs, RISA, and blood through the perfused microvessels were considerably greater in treated rats than in controls. These findings indicate that the mechanism by which high-dose pentobarbital diminishes local cerebral blood flow in rat brain is, in the main, a lowered linear velocity of plasma and RBC flow through small parenchymal microvessels and not decreased percentage of perfused capillaries (capillary retirement). This response is probably driven mainly by lowered local metabolism and may well entail a slight increase in the number of small microvessels that are perfused by RBCs.
高剂量戊巴比妥（50毫克/千克）可使大鼠许多脑区的局部脑血流量降低。在本研究中，通过测量放射性标记红细胞（RBC）和白蛋白（RISA）在实质微血管中的分布，并计算RBC、RISA和血液的微血管分布空间及平均通过时间，来研究这种血流变化的机制。在大多数脑区，戊巴比妥使RISA空间略有减小，使RBC空间适度增加，而不改变血液空间。与对照组相比，经处理大鼠的RBC、RISA和血液通过灌注微血管的平均通过时间显著更长。这些发现表明，高剂量戊巴比妥降低大鼠脑局部脑血流量的机制主要是血浆和RBC通过实质微血管的线性流速降低，而非灌注毛细血管百分比降低（毛细血管退缩）。这种反应可能主要由局部代谢降低驱动，并且很可能导致被RBC灌注的小微血管数量略有增加。
