Peculiarities of Cyto- and Chemoarchitectonics of Human Entorhinal Cortex during the Fetal Period

We studied peculiarities of the structure of human entorhinal cortex at weeks 20-26 of gestation (10 hemispheres). The samples were Nissl-stained and immunohistochemically treated with antibodies to parvalbumin, calretinin, calbindin, and cytoskeleton proteins (MAP2 and N200). 3D-reconstruction of the entorhinal cortex from serial sections was performed, caudomedial and rostrolateral areas were isolated. Parvalbumin⁺ cells in layer I, discrete distribution of layer II cells with colocalization of MAP2 and calretinin at the border with layer I, and two sublayers Va and Vb with MAP2⁺ neurons were typical for the caudomedial area. Rostrolateral area was characterized by the homogenous layer II with big amount of cells, high density of MAP2⁺ neurons only in layer III, and the unique layer V. Reelin⁺ Cajal—Retzius cells and N200⁺ fiber plexus in layer I were observed in the caudomedial and rostrolateral areas of the entorhial cortex. Layer IV was represented by a cell-free desiccant.