Reactive Changes in the Cellular Elements of the Rat Brain in Different Conditions of Circulatory Hypoxia

摘要

The aim of the present work was to identify structural, spatial, and quantitative changes in elements of the paranigral nucleus (PNN) of the midbrain and anterior cingulate field (ACF) of the telencephalon in different conditions of circulatory hypoxia. The anterior medial part of the PNN and layers V-VI of the ACF were studied in healthy rats seven days (n = 4) after occlusion of both common carotid arteries and in intact (control 1, n = 4) and sham-operated (control 2, n = 4) rats. Histological sections stained with cresyl violet by the Nissl method and processed for detection of glial fibrillary acidic protein and Iba1 protein were used to identify the ratio of essentially unchanged, hypochromic, pyknomorphic, and ghost neurons, along with the numbers of astrocytes, oligodendrocytes, microgliocytes, and endotheliocytes. The areas of neurons and gliocyte bodies were measured, along with the distances from these cells to capillary walls, and gliocyte:neuron indexes were calculated. The results showed that after exposure to different conditions of circulatory hypoxia, the cellular elements of the brain showed a spectrum of characteristic pathological changes. Neurons showed signs of nuclear pyknosis, lysis, and conversion to “ghost” cells. Cells in the nuclear zone of hypoxia tended to undergo death or pyknosis. Neurons located outside the hypoxic area and exposed only to the humoral actions of the responses of the glutamate-calcium cascade often showed acute swelling. The reactions of microgliocytes, with minor increases in numbers and structural signs of activation, represented early diffuse signs of focal hypoxia in the forebrain. Endotheliocyte proliferation seen at seven days of ischemia was not associated with the chain of cascade reactions, but occurred only in the focus of hypoxia. The concentrations of viable neurons and astrocytes close to blood capillaries and the increase in the number of satellite types of glial cells represent an adaptive mechanism and a constitute a condition for cell survival in the conditions of various types of cerebral ischemia.