Characteristic of the cerebral cortex microcirculation after ischemia

Abstract

Introduction. The outcome of ischemia is depending on a condition of microcirculatory bed. The important factor in development of cerebral ischemia is regulation of microvascular function, influencing both perfusion and oxygenation of cerebral tissue. The aim of the current study was to examine the time course of micirculatory changes in rat cerebral cortex, as well as to assess the changes in oscillatory components of myogenic, neurogenic and endothelial levels of cortical microvessel tone within 21 days after ischemia. Methods. Transient global cerebral ischemia was induced in anesthetized Wistar rats by clamping of both common carotid arteries for 12 min with simultaneous controlled hypotension to 45±3 mm Hg, followed by blood reinfusion and recovering from anesthesia. Five different groups of rats were re-anesthetized at 1 hour and 2, 7, 14 or 21 days after ischemia and subjected to studies using continuous wavelet transform analysis of laser Doppler flowmetry. Results. In the first 7 days of the post-ischemic period, peripheral resistance was reduced in the cerebral cortex, which was associated with domination of nutritive blood flow. By 14th day after ischemia it resulted in the blood stagnation connected with development of endothelial dysfunction. From 14th to 21st day post-ischemia, the increase of shunt blood flow was noted. It was possibly a consequence of blood shunting processes happening in a cerebral cortex bypassing a nutritive level that prevents microcirculation from congestion. Conclusions. It is established that transient global cerebral ischemia results in significant changes of microcirculation in cerebral cortex lasting at least 3 weeks after ischemia. Initial dominant nutritive blood flow is probably due to blood congestion because of endothelial dysfunction. Three weeks post-ischemia, it is followed by increase in shunt blood flow that can prevent blood congestion in microcirculatory vascular bed.