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Objectives. Intravital studies have shown that alterations to myelination in the gray matter of the cortex in schizophrenia are the most marked in the prefrontal cortex. The authors have previously observed a decrease in the number density of oligodendrocytes (ND OL) in layers 3 and 5 of field 10 of the prefrontal cortex in schizophrenia. Proliferation of oligodendrocyte precursors in the brains of adult animals and humans is known to lead to the formation of oligodendrocyte clusters (OLC) and this process is linked with function-dependent axon myelination. The aim of the present work was to determine ND OLC and the ratio of ND OLC to ND OL in the functionally diverse supra- and infragranular layers of field 10 in health and schizophrenia. Materials and methods. ND OLC was determined in layers 3a, 3b, and 3c (supragranular) and 5a (infragranular) of field 10 using an optical dissector on Nissl-stained sections in 17 cases of schizophrenia and 20 people without mental disorders. Results and conclusions. Decreases in ND OLC were seen in both the supra- (by 32%, p < 0.02, Duncan test) and the infragranular (by 50%, p < 0.001) sublayers of field 10 in schizophrenia as compared with the control group. A decrease in the ND OLC/ND OL ratio was significant only for sublayers 2a (p = 0.015) and 5a (p < 0.001). In the control group, ND OLC showed a significant correlation with ND OL in sublayers 3b, 3c, and 5a (R ≥ 0.59, p ≤ 0.006), while in the schizophrenia group only layer 5a showed a persisting positive correlation (R = 0.8, p = 0.00001) between measures. A deficit of OLC in field 10 in schizophrenia may be due to impaired proliferation and/or differentiation of OL precursors. The nature of the interaction between ND OLC and ND OL presumptively depends on the characteristics of the connections between the corresponding cortical sublayers and their changes in schizophrenia.

The scientific literature contains several hypotheses for the pathogenesis of schizophrenia. The most widespread hypotheses for schizophrenia are the dopaminergic, serotoninergic, and glutamatergic hypotheses. There is also the suggestion that other neurochemical systems are involved in the pathogenesis of schizophrenia, particularly the GABAergic. This review considers published data on derangements of GABAergic interneurons in schizophrenia, taking account of data on post-mortem, neuroimaging, molecular-genetic, and electrophysiological research. A hypothesis for the pathogenesis of schizophrenia based on impairments to the myelination of GABAergic interneurons is proposed, these impairments leading to decreases in the numbers of intra- and interhemisphere coherent connections and the appearance of symptoms of the disease.

The spatial organization of oligodendrocytes and pyramidal neurons in the anterior limbic cortex in health and schizophrenia was studied using automated two-dimensional image analysis. Layer III of this area of the cortex in schizophrenia showed a 20% reduction in the minimal distance between oligodendrocytes and their nearest neurons and 10% and 9% reductions, respectively, in the mean maximum distance between neurons and their nearest oligodendrocytes. Thus, this automatic image analysis method allows assessment of the spatial organization of neurons and glial cells in the cerebral cortex not only in health, but also in mental pathology.

The aim of the present work was to produce organotypic cultures of human embryo brain tissues, as needed for investigation of the effects of serum factors on mental diseases and their pharmacological treatment. Cultures were made using slices of medulla oblongata from human embryos aged 9-10 weeks, obtained from medical abortions. Free-floating slices were cultured using a modified roller method for four weeks. Light and electron microscopy, along with immunocytochemistry, demonstrated that cultured slices showed differentiation and growth of neurons, astro- and microgliocytes, with formation of the synaptic contacts and glioneuronal interactions typical of organotypic cultures. However, along with differentiated neurons and glial cells, there was some persistence of undifferentiated cellular elements with signs of stem cells and neuron and gliocyte precursor cells. These experiments showed that organotypic roller cultivation of free-floating slices of human embryo brain tissue can be used to study the processes of neuron and gliocyte development, the mechanisms of neurotoxicity and neuroprotection using a variety of morphological (including stereological) and biochemical study methods.

Electron-cytochemical methods were used to study the distribution of acetylcholinesterase (ACE) activity in the brain in postmortem cases of Alzheimer's disease. The findings showed a decreased number of ACE-positive neural fibers in the upper cortical layers. The reduction was most pronounced in the temporal and parietal lobes of the cortex and absent in the occipital lobe. The disclosed cytochemical changes confirm the presence of disorders in the cholinergic system in the brain cortex in Alzheimer's disease.