The central nucleus of the amygdaloid body of the brain: cytoarchitectonics, neuronal organization, connections

This review considers the questions of the structural-functional organization of the central nucleus (CN) of the amygdaloid body (AB) of the brain in relation to new data on its involvement in the formation of stress reactions and adaptive behavior in animals. Data are presented on the distribution of neuropeptides, neurotransmitters, and modulators in the CN. It is noted that the CN, appearing at the earliest stages of establishment of the AB, is reorganized with it and reflects the evolution of the whole AB. Detailed data are presented on the cytoarchitectonics of the CN of the AB, its heteromorphousness, and subdivision into zones (subnuclei) based on the use of different study methods and assessment criteria. The neuronal organization of the CN and its subnuclei is considered; detailed descriptions of different types of neurons are provided, with consideration of their topographies, sizes, and shapes and of their perikarya, the orientation and type of branching of their dendrites, the organization of the spine apparatus, and axon structure. The characteristics of the development of the CN of the AB in the ontogenesis of mammals and man are discussed. Analysis of published data and our own results supports the role of the CN not only as an intra-amygdalar integrative center, but also as one of the major channels for the afferent and efferent connections of the AB with the rest of the brain.

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.

Dendroarchitectonics of neurons in the posterior cortical nucleus of the amygdaloid body of the rat brain as influenced by gender and neonatal androgenization

The aim of the present work was to identify gender-related differences in the dendroarchitectonics of neurons in the posterior cortical nucleus of the amygdaloid body and the role of androgens in forming the dendroarchitectonics during the period of sexual differentiation of the rat brain. Golgi staining showed that long-axon, sparsely branched neurons in males had large numbers of primary dendrites, while long-axon densely branched neurons had a greater total dendrite length in females. Administration of testosterone propionate (1250 microg) to females on postnatal day 5 increased the number of primary dendrites in long-axon, sparsely branched neurons in adults as compared with the number in control females; treatment also produced a significant increase in dendrite length in long-axon, densely branched neurons, leading to an increase in the area of the dendritic field.

Expression of CART peptide in the paleoamygdala neurons and its relationship with sex hormone levels

The location of CART peptide in the paleoamygdala neurons was studied by immunocytochemical reaction. Significant differences in the number of immunoreactive cells and optical density of CART-positive neurons detected over the course of the estrous cycle indicate modulating effects of sex steroids on the expression of CART peptide.

Paleoamygdala and biogenic amines: effect of gender factor and sex steroid content on their content and metabolism

The content of biogenic amines and their metabolism in the ancient part of the amygdala (paleoamygdala) differ in male and female rats and depended on the phase of the estrous cycle.

Structural organization of the amygdaloid complex of the rat brain

The amygdaloid complex, traditionally regarded as part of the system of basal endbrain nuclei, has a unique structure in that it combines the two major principles of organization of the gray matter--the nuclear and the screening. Working from the studies of Zavarzin on the nuclear and screening centers, the authors suggest a classification of its structures into nuclei, paleocortex, and intermediate 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.

The paleoamygdala: cytoarchitectonics, organization, and the cytological characteristics of its neurons

The aim of the present work was to compare the cytoarchitectonics, neuronal organization, and cytological characteristics of the dorsomedial, posterior medial, and posterior cortical nuclei of the amygdaloid body (AB) of the rat brain. Series of frontal brain sections stained with cresyl violet and silver nitrate impregnation by the Golgi method were studied. The results showed that rearrangements of the nuclear principle of organization of the gray matter of the nervous system into the screened organization occur within the territory of this complex of nuclei; it consists of a sparsely branched neuron system and contains neuroendocrine cells. It is concluded that this complex of nuclei is unique in terms of its structural organization and the mechanism of development of this part of the AB, which forms in the earliest stages of AB development; it is termed the "paleoamygdala."

Morphogenesis of the dorsomedial nucleus of the amygdaloid complex in early juvenile period in rats

We studied the dynamics and gender differences in the formation of the dorsomedial nucleus of the amygdaloid complex in early juvenile period (postnatal days 21, 24, 28 and 31) by determining its planimetric parameters, count of neural and glial cells, and glial and apoptotic indexes.

Paleoamygdala: morphogenesis of the posterior cortical nucleus of the rat amygdaloid complex of the brain during the early juvenile period

Sex-related differences and the dynamic of formation of the posterior cortical nucleus of the rat amygdaloid complex were revealed in the early juvenile period by planimetric characteristics, numbers of neurons and glial cells, and glial and apoptotic indexes reflecting morphological restructuring on postnatal days 21, 24, 28, and 31.

Neurosecretory cells of the amygdaloid complex during estrous cycle

Ultrastructure of neurosecretory cells of the dorsomedial nucleus of the cerebral amygdaloid complex (one of the main zones of sexual dimorphism) was studied in different phases of the estrous cycle. The characteristics of the "light" and "dark" cells change depending on the concentrations of sex steroids during estrus and metestrus.

Structural Organization of Cerebral Basolateral Nucleus of the Amygdaloid Complex in WAG-Rij Rats with Different Genotypes by the TAQ 1A Locus of Dopamine 2 Receptor Gene (DRD2)

Anxiety levels and structural organization of the basolateral nucleus of the amygdaloid complex were analyzed in WAG/Rij rats with genotypes A₁/A₁ and A₂/A₂ by DRD2 locus Taq 1A. Association of anxious behavior with A₂/A₂ genotype and the relationship between the structural organization of the nucleus and polymorphic variants of this locus are detected.

Structural and functional characteristics of the dorsomedial nucleus of the cerebral amygdaloid complex in male rats

We developed a classification of neuroendocrine neurons of the dorsomedial nucleus of the cerebral amigdaloid complex of male rats; characteristics of these cells are presented.

Neuronal organization of structures in the central part of the amygdaloid body of the brain

The features of neurons in the central part of a amygdaloid body (AB) were studied and compared with published data on similar measures of cells in the anterior and posterior parts of the amygdaloid complex. Neurons were impregnated with silver nitrate using the Golgi method. Neurons were classified and measured as described by Leontovich (1978). Long-axon and short-axon neurons were identified and their quantitative characteristics were described.

[Experimental approaches to investigation into the role of the genotype by the locus TAG 1A of dopamine D2-receptors in epileptogenesis]

The effect of genotype in locus TAG 1A of gene receptor dopamine second type on characteristics of peak-and-wave EEG pattern in somatosensory, parietal and occipital areas of the cortex was studied in two groups of rats. Quantitative analysis showed that the peak-wave discharge of the first type in rats with A1/A1 genotype had a significantly longer duration, occurred more frequently leading to a significant increase in their peak-wave index. The results are of clinical interest creating a theoretical basis for improved diagnosis of absence epilepsy and selection of anticonvulsants.