[Ultrastructural research on the sensorimotor cortex in adult rats. I. Intranuclear inclusions in the neurons and astrocytes].

The morphological peculiarities of neurones and astrocytes in the sensorimotor cortex of mature (over 3 months) and elderly (over 24 months) rats were studied at electron microscopic level. Intranuclear inclusions are found in the nuclei of pyramidal neurones from the third and fifth layer. On the basis of their fine structure they could be grouped into the following types: 1. Filamentous bundles. 2. Filamentous crystalloids. 3. Granulofilamentous bodies. 4. Membrane-enclosed inclusions. 5. Combined intranuclear inclusions. Filamentous crystalloids are found in two varieties, composed of filaments with various diameter and way of arrangement. Membrane-enclosed bodies are formed as small vesicles or large vacuoles. Combinations from various types of inclusions in the nucleus of a neurone are discovered frequently. Only intranuclear inclusions of the type of membrane-enclosed bodies are observed in the nuclei of astrocytes. These bodies are found only in the nuclei of astrocytes of elderly animals. On the basis of the comparative analysis between ultrastructural characteristics and frequency of intranuclear inclusions in pyramidal neurones and astrocytes in sensorimotor cortex of mature and elderly rats their probable connection with age changes in the central nervous system is discussed.