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 differentiat ion 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.
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