[Paleoamygdala: a comparative analysis of structural and functional organization in wAG/Rij and Wistar rats].

A comparative analysis of structural and functional organization of paleoamygdala was performed in 22 male WAG/Rij and Wistar rats using light microscopy (Nissl staining method and computer morphometric analysis), electron microscopy (using the criteria of the evaluation of the functional state of neurons) and the TUNEL method for apoptotic cell labeling. The results obtained suggest the involvement of the limbic brain structures in the pathogenesis of absence epilepsy. It was shown that the area occupied in the sections by amygdala was significantly greater in WAG/Rij rats (model of absence epilepsy). The assessment of ultrastructural characteristics of neurons in all the structures of paleoamygdala (dorsomedial, posterior medial and posterior cortical nuclei) has shown the signs of the reduction of their functional activity in WAG/Rij rats. In addition, WAG/Rij rats demonstrated the increased numbers of pyknomorphic neurons with the signs of apoptosis, as identified by the TUNEL method, which is indicative of the destructive processes.

Structural organization, neurochemical characteristics, and connections of the reticular nucleus of the thalamus.

This review analyzes current concepts of the structural organization and ultrastructure of the reticular nucleus of the thalamus (RNT) and the neurochemical characteristics of its neurons. The topography, cytoarchitectonics, and neuronal organization of this nucleus are considered in detail, as are questions of its neurogenesis. Neurochemical data clarifying the representation of neurotransmitter systems in the RNT and data on neuropeptides synthesized in its neurons are systematized. The complex ultrastructural organization of the RNT is characterized in terms of recent data from state-of-the-art immunocytochemical methods allowing localization of glutamatergic and GABAergic receptors on synaptic elements. Data on the afferent and efferent connections of the RNT demonstrate its influences on various parts of the brain and the specific features of its interactions with cortical formations.

Characteristics of small neurons of the reticular thalamic nucleus in WAG/Rij rats.

The aim of the present work was to study the ultrastructure of small neurons in the reticular thalamic nucleus (RTN) in WAG/Rij rats, which are used as a model of absence epilepsy. A total of 24 rats were studied. The brains of 10 rats were used for studies of the cytoarchitectonics and cytological characteristics of neurons, for which paraffin sections were stained with cresyl violet by the Nissl method. Electron microscopic studies were performed by microscope-controlled harvesting of the RTN with fixation in 2.5% glutaraldehyde in phosphate buffer pH 7.4. Small neurons were found to account for 5-8% of all neurons in the RTN. These had oval bodies, sparse and pale-staining cytoplasm, and were frequently located in pairs. The ultrastructure of these neurons was characterized by poor development of cell membranes, branching of the axon close to the cell body, and multiple axon contacts with the body and dendrites. It is suggested that these neurons are short-axon neurons.

[Characteristics of small neurons in the reticular thalamic nucleus of WAG/Rij rat].

The aim of this investigation was to study the ultrastructure of small neurons in the reticular thalamic nucleus (RTN) in rats of the WAG/Rij strain, which is a recognized model for human absence epilepsy. 24 rats were used in these studies. The paraffin sections of the brain taken from 10 rats were stained with Nissl's cresyl violet and were used for the study of neuronal cytoarchitecture and cytological characteristics. For electron microscopic study, RTN was dissected under microscopic control and fixed in cooled 2.5% glutaraldehyde solution in 0.1 M sodium phosphate buffer (pH 7.4). Small neurons were found to constitute 5-8% of the total number of RTN neurons. They had ovoid cell body, scanty pale-staining cytoplasm, often were seen in pairs. The ultrastructure of these neurons was characterized by poor development of membranes, axonal branching close to the cell body, multiple contacts of axon with cell body and dendrites. It is suggested that the neurons described are short-axonal.

[Structural organization of the reticular thalamic nucleus].

This review presents an analysis of current data on the structural organization of the reticular thalamic nucleus (RTN). In contains a detailed discussion on topography, cytoarchitecture, neuronal organization and neurogenesis in this nucleus. The materials on RTN neurochemistry are systematized specifying the topographic representation of neurotransmitter systems and neuropeptides which are synthesized in RTN neurons. Complex ultrastructural organization of RTN is characterized on the basis of modern immunocytochemical methods, which allow to detect the localization of glutamatergic and GABAergic receptors on synaptic elements. Data on afferent and efferent connections of RTN demonstrate its influence on various brain regions and the specificity of RTN interrelations with some cortical formations.

[Ultrastructural characteristics of the reticular thalamic nucleus neurons in WAG/Rij rats].

The aim of this study was to investigate the ultrastructure of the reticular thalamic nucleus (RTN) in rats of WAG/Rij strain, an established model for human absence epilepsy. Most RTN neurons are medium-to large-sized and have either dark or light appearance, depending on their functional state. Moreover, small-sized neurons with short axons are present, their characteristics being described for the first time.

Synaptology of the rostral reticular thalamic nucleus of absence epileptic WAG/Rij rats.

The adult WAG/Rij rat is a well-established animal model for human absence epilepsy characterized by the presence of spike-wave discharges (SWDs). The pacemaking activity of the rostral reticular thalamic nucleus (rRTN) has been demonstrated to be essential for SWD maintenance. We investigated if SWD maintenance can be related to the synaptic organization of the rRTN, by studying the ultrastructure of the rRTN of absence epileptic WAG/Rij rats in comparison with that of non-epileptic, age-matched ACI control rats. In WAG/Rij rats, D-, L- and F-type terminals constitute the synaptic organization of the rRTN. D-type synapses, especially axo-dendritic ones, occur frequently. L- and F-type terminals are common but less frequent than D-type terminals. Semi-quantitative observations indicate that all terminal types are present on different parts of the postsynaptic neuron, but in different numbers: they are frequent on dendrites, common on somata and axons, and occur occasionally on dendritic spines. In addition, occasionally an F-type terminal was observed on the axon hillock. The three terminal types are also involved in multiple synaptic configurations, convergent as well as divergent, with dendrites, somata, axon hillocks and axons as postsynaptic structures. Convergent synaptic configurations outnumber divergent ones. The synaptic organization of the rRTN of the non-epileptic ACI rat appears to be very similar to that of the epileptic WAG/Rij rat. This indicates that SWD maintenance in the WAG/Rij rat does not depend on a different synaptic organization of the rRTN.

[Cytologic characteristics of "dark" and "light" cells in the brain amygdaloid complex]. / Tsitologicheskie kharakteristiki "temnykh" i "svetlykh" kletok mindalevidnogo kompleksa mozga.

This paper reports data on cytological peculiarities of neurons of two main zones of sexual dimorphism in brain amygdala (dorsomedial nucleus and anterior cortical nucleus). The main attention was paid to some characteristics of "dark" and "pale" cells found in the amygdaloid complex for the first time. It is supposed that the dark and pale cells are targets for gonadal steroids, whose cyclic changes in concentration in the blood difined their functional states. Though the ultrastructure of dark and pale cells of the amygdaloid complex is similar to that of neurosecretory cells of hypothalamus, there are necessary electron microscopic and cytochemical evidences.

[Electron-microscopic characteristics of the dorsomedial nucleus of the brain amygdala]. / Elektronno-mikroskopicheskaia kharakteristika dorsomedial'nogo iadra mindalevidnogo tela mozga.

Dark and light neurons with morphological signs of secretory activity were discovered for the first time in one of the main zones of sexual dimorphism of brain amygdala (dorsomedial nucleus). Dark neurons were of small and medium sizes, contained large nuclei and incompletely developed perikaryon. The latter contained a large number of free ribosomes, dilated cisterns of endoplasmic reticulum, hypertrophied Golgi complex with forming secretory granules and numerous mitochondria. Elementary neurosecretory granules (ENG) 75-180 nm in size were found in light neurosecretory cells that are likely to represent dark neurons at the specific phase of functional activity. Synapses of all known types, containing small light vesicles in their terminals and vesicles with electron-opaque centre and ENG were detected in the extremely active neuropil.

[Structural and functional organization of sexual dimorphism zones of the amygdala in the normal state and in alloxan diabetes]. / Strukturo-funktsional'naia organizatsiia zon polovogo dimorfizma mindalevidnogo tela mozga v norme i pri alloksanovom diabete.

Cytoarchitectonics and neuronal organization of sexual dimorphism zones (ZSD) of amygdala, one of the brain higher neuroendocrine centres were studied and reactive changes of this zone neurons were analysed in rats with chronic alloxan diabetes that modulate type I diabetes mellitus in man. Structural organization of main ZSD of amygdala--dorsomedial, anterior and basolateral nuclei displays its characteristic topographical and cytoarchitectonic peculiarities. Neuronal organisation of main amygdala zones is characterized by different ratio of intensely and sparsely dendritic long-axonal neurons. Neurons of all ZSD respond to insulin deficiency--induced disturbances of carbohydrate metabolism in the same type. Reactive changes of neurons defined consist in chromatophilia development and neuron shrinkage and also in significant decline in cell nuclear volume.