[Ultrastructural characteristics of the 1st cortical layer of the cingulate area of the brain in rats].

The limiting membrane, participating in formation of the liquor- and hematoencephalic barrier on the brain surface, and specialized intercellular contacts are considered as factors regulating entrance of substances from liquor and blood into the intercellular medium. Heteromorphism of the cingulate cortex first layer takes place: in the 1-b sublayer a large amount of myelinated fibres is revealed, in the 1-c sublayer numerous longitudinal sections of dendrites are seen, they arrange perpendicularly or tangentially to the brain surface. In the 1-a sublayer, more often than in others, multifocal axodendritic synapses are observed they are of convergent or divergent types, several synapses occur. In the first layer of the cingulate cortex, axonal profiles are revealed, they resemble axons of the neurosecretory cells described in the literature. This cannot exclude any hormonal mechanisms affecting the neurons of the cingulate cortex. Numerous synaptic contacts, formed by afferent fibers that come from different brain structures, with processes of the first layer cells and ascending dendrites of deeper layers are considered as a morphological substrate of integrative and modulating activity of the first layer.