Abstract
The aim of this studywas to compare the pyramidal neurons, their processes and synapses in the stratum lucidum, stratum radiatum and stratum lacunosum of the molecular layer of the field CA3 of the hippocampus of the brain of white rats in the normal state and after acute ischemia caused by a 20-minute occlusion of the common carotid arteries.Materials and methods.In the experiment, using histological methods (hematoxylin and eosin, staining by Nissle and immunohistochemistry for p38, MAP-2) and electron microscopy, the pyramidal neurons of field CA3, their processes and synapses in stratum lucidum, stratum radiatum and stratum lacunosum of the molecular layer were studied. The main group included animals in the reperfusion period (1, 3, 7, 14, 21, and 30 days;n=30), comparison group — falsely operated animals (n=20). Morphometric analysis was performed using ImageJ 1.46, the verification of statistical hypotheses — Statistica 8.0.Results.After occlusion of the common carotid arteries (CCAO) in the field CA3 of hippocampus, reactive, compensatory and reparative reorganization of pyramidal neurons and their communication structures was noted. On day 1, there was a decrease, and then (days 3—14) restoration of the total number of synapses and of P38-positive material within the area of synapses. According to electron microscopy, in the early post-ischemic period, the total numerical density of synaptic contacts in the stratum lacunosum of the molecular layer decreased by 44.8%, and after 14 days recovered to control. In stratum lucidum, the area of P38-positive material decreased by 8.8% after 1 day, and recovered after 3—7 days.Conclusion.After the CCAO, the communication systems of the pyramid neurons of the field CA3 hippocampus of white rats were reorganized. Neurons of the field CA3 had high tolerance to ischemia and ability to restore interneural relations after reperfusion. In the surviving neurons, high levels of the cytoskeleton (MAP-2) marker and synaptic vesicles (p38) were detected. Data demonstrate structural and functional safety of all components of the communication system of a significant part of pyramidal neurons in acute ischemia. After reperfusion, the most significant alterations included the reconstructed interneuron synapses in the stratum radiatum and the lacunosum molecular layer.
Highlights
The pyramid neurons in hippocampus field CA3 are represented by large cells with a large nucleus, 1–2 nucleoli, located loosely within the pericarrion area — 125.3 (113.7–165.5) mm2
The bodies and apical dendrites of these neurons are covered with densely located synapses, the terminals of which are filled with granules of labeled synaptophysin
The communication of the pyramidal neurons of field CA3 with other parts of the brain become visible due to axosomatic, axodendritic and axospine synapses, which are located in the layer of the bodies of pyramidal neurons, in the stratum radiatum and lacunosum of the molecular layer
Summary
Что мощные апикальные дендриты пирамидных нейронов поля СА3 разделяются недалеко от перикариона и покрыты гигантскими шипиковыми выростами. Эти шипики пирамидных нейронов СА3 образуют синаптические контакты с гигантскими аксонами гранулярных нейронов зубчатой фасции (мшистыми волокнами). Аксоны пирамидных нейронов СА3 дают так называемые коллатерали Шаффера, контактирующие с апикальными дендритами пирамид СА1. Упомянутые связи являются двумя основными ассоциативными путями гиппокампа, соединяющими воедино его основные элементы, и составляют так называемый трисинаптический путь. Поле СА3 гиппокампа является точкой конвергенции потоков информации от ассоциативной коры и филогенетически древних образований ствола мозга [1,2,3,4,5,6]. Хорошо изучены нейромедиаторные системы гиппокампа [7]. Большое значение для реорганизации межнейронных отношений и коммуникации пирамидных нейронов гиппокампа имеет его высокая синаптическая пластичность [8]
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