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[The topical organization of the nuclear projections of the amygdaloid body, the ventral tegmental field and the substantia nigra into the striopallidum of the cat].

The work has generalized and compared results of studying the topical organization of projections of the amygdaloid body, ventral tegmental area and substantia nigra in the extrapyramidal system of the cat's brain. Methods of retrograde axon transport of horseradish peroxidase and fluochrome were used. In the basal ganglia the limbic and motor areas were found with prevailing projections from structures belonging to the limbic system or from the formations bearing a relation to motor activity. Parallel with this, in considerable areas of the basal ganglia there occur overlapping projection fields of the axons belonging to neurons of the both structures. This fact as well as the widely represented in the striopallidal system divergence of axons of neurons belonging to many structures are discussed in association with the hypothesis of the interaction of the limbic and motor systems in the basal ganglia. General features found in the topical organization of projections from the structures under investigation onto the striopallidum nuclei and specific features for each of the nuclei are discussed in connection with similar and different manifestations of behavioral reactions or clinical disturbances in neurological diseases.

Amygdala↗

Structural and quantitative characteristics of the dendrites of neurons in the posterior zone of the amygdaloid body in the rat brain.

The aim of the present work was to study the structure of the dendritic tree of the main groups of neurons in the posterior zone of the amygdaloid body and to analyze their quantitative characteristics. Frontal sections of rat brain impregnated with Golgi silver nitrate were used to study the characteristics of neuronal organization. Classification of neurons was based on criteria developed by Leontovich (1978) and Polyakov (1973). The main groups of neurons were long-axon, rarely branched cells, long-axon, densely branched subcortical cells, and long-axon, densely branched cortical cells. Quantitative studies of seven measures of the dendrite tree showed that the most informative parameters for differences between the main groups of neurons were the number of branching points and the number of free dendrite tips. The contents of rarely and densely branched neuron systems in the nuclei, paleocortex, and intermediate formations are described.

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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.

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[Afferent connections of the adjoining nucleus with the amygdaloid body and dopaminergic mesencephalic structures of the cat brain].

By means of the retrograde axonal transport of horseradish peroxidase and luminescent markers the data have been obtained on topical organization of projections of the basal nucleus of the amygdaloid body, of the ventral field of the operculum and of the substantia nigra nuclei to the adjoining nucleus. In the medial and lateral segments of the adjoining nucleus the terminal fields of these structures overlap and have collaterals in the nuclei of the striopallidum. The interaction of limbic and motor informations in the adjoining nucleus is discussed.

Afferent Pathways↗

The pattern of synaptophysin changes during the maturation of the amygdaloid body and hippocampal hilus in the rat.

Synaptophysin is an integral membrane protein associated with small, electron-lucent synaptic vesicles. Immunohistochemistry for this protein is a sensitive method to study subtle changes in synaptic density and distribution in various brain regions. In the present study, the synaptogenesis was examined in the rat basolateral amygdala in comparison with the hippocampal hilus, from the day of birth to adulthood. A total of 41 brains at various ages starting from P0 to P90 (P--postnatal day) were examined. After perfusional fixation the brains were frozen and cut in the coronal plane and stained either with cresyl violet or standard immunohistochemical methods using the anti-synaptophysin antibody. Synaptophysin positive granules appeared just after birth in both structures, but their number was very low (about 0.28 x 10(6) and 0.13 x 10(6) per mm3 in the amygdala and hippocampus, respectively). In the basolateral amygdala the number of synapses increased rapidly reaching the maximum at P14 (1.6 x 10(6) per mm3) followed by about 45% decrease in number up to P30 and later being stabile. In the hippocampus two increases of the synaptogenesis were observed. The first at P7 (about 1.7 x 10(6) of synapses per 1 mm3) which was followed by dramatic decrease up to 0.7 x 10(6) per mm3 at P14. The second increase appeared later (about P90) and reached 1.7 x 10(6) per mm3. After that time the density of synapses was stabile. It may be supposed that the first characteristic wave of synaptogenesis observed in the hippocampus and amygdaloid body is due to the overproduction of synapses observed at that time in other cortical regions. The late wave of synaptogenesis found in the hippocampus is related to the great plasticity of the interneuronal connections in this period of development.

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Differential input from the amygdaloid body to the ventromedial hypothalamic nucleus in the rat.

Differential amygdaloid afferents to anterior dorsal, anterior ventral, posterior dorsal and posterior ventral subdivisions of the ventromedial hypothalamic nucleus (VMH) were studied by means of retrograde transport of horseradish peroxidase (HRP). Injections of tracer confined to the VMH subdivisions mentioned, and enhancement of tracer uptake and transport were achieved by iontophoretic delivery of an HRP solution containing poly-L-alpha-ornithine. It was shown that the medial, central, basolateral, basomedial, lateroposterior and intercalated nuclei of the amygdala constitute afferent input sources to the ventromedial nucleus in a topographic pattern related to the various subdivisions of the VMH. This topographically organized amygdala-VMH projection is discussed against the background of the functional role that both amygdala and VMH play in the control of feeding, apart from various other autonomous functions that both brain centers are known to be concerned with.

Afferent Pathways↗

The distribution of axon terminals with flattened vesicles in the nuclei of the amygdaloid body of the cat.

The morphology of synapses in the amygdaloid nuclei was studied in 10 cats. On the basis of the percentage of axon terminals with flattened vesicles (F-type) nuclei were distinguished, in which these terminals are as sparsely distributed as in most areas of the central nervous system, from other nuclei in which they are abundant (about one-third to one-half of all synaptic boutons). The lateral, basal dorsal and basal ventral nuclei belong to the first, the medial and central nucleus and the anterior amygdaloid area--to the second group. The cortical nucleus, which generally has a small number of boutons of F-type has some parts seemingly belonging to the first, and others to the second group. In all amygdaloid nuclei axon terminals of F-type form symmetrical synaptic contacts. In nuclei with a low percentage of F-type terminals these boutons are predominantly small and synapse either with perikarya or with large dendrites. The amygdaloid nuclei having numerous F-type terminals contain not only small but also larger terminals with flattened vesicles. Both, the larger and smaller axon terminals form in these nuclei synaptic contacts with various parts of dendrites even with very small ones and with dendritic spines. The subdivision of amygdala into two parts, one with a low and another with a high number of F-type boutons would seem to support the hypothesis that amygdala may be subdivided physiologically into a dorsomedial--"excitatory" and basolateral--"inhibitory" portion.

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[The amygdaloid body of the brain: some topics for discussion and little-studied problems].

Features of functional morphology of the amygdaloid brain complex (ABC) are analyzed in a new light presenting the notion of the ABC as a nucleo-paleocortical structure. The analysis of the structural organization of ABC could imply the presence of phylogenetically differentiated parts: the ancient, the old and the new amygdala. The presentation carries original data on the morphometric and histophysiological studies under various experimental alterations of the endocrine system. A concept is developed of the existence of a rostrocaudal gradient in the expression of sex-dependent structural and functional features of the amygdaloid complex as a neuroendocrine brain centre. Provided is technical recommendation for use in biological studies of amygdaloid brain complex mathematical models based on the theory of image identification. An original technique has also been recommended for selective dissection of the ABC with its eventual removal from nonfixed brain, which allows studies to be made of the ABC neurophysiological and neurochemical properties on surviving slices. Evidence is adduced indicating involvement of the ABC in the process of the brain sex differentiation.

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[Characteristics of the response of the white rami communicantes to stimulation of different sections of the amygdaloid body].

Electrical responses in L2-L3 white rami to stimulation of cortico-medial, baso-lateral and central amygdaloid nuclei were studied in anesthetized and immobilized cats. The stimulation evoked a similar pattern of sympathetic discharge mostly consisting of a wave with a mean latency of 69.04 +/- 1.31 ms. No strict topographical location of sympatho-activating structures was found in different areas of the amygdala. In simultaneous recording of arterial BP and amygdalo-sympathetic discharges, 10-sec period of tetanic (100/sec) stimulation of the amygdalo led to a short-latency component facilitation or appearance, the late component of the amygdalo-sympathetic discharge being depressed. The duration of the latter inhibition corresponded to the period of the BP reaction and therefore was of a baroreceptor origin. Possible mechanisms of amygdaloid regulation of the activity of sympathetic preganglionic neurons are discussed.

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[Relationship between the limbic system and gonadal function. 3. Quantifiable prepuberal morphokinesis of the basolateral amygdaloid body and the ventral hippocampus formation].

In juvenile female rats the neurons of the limbic system which are attached to the basolateral amygdaloid nucleus and to a circumscribed area of ventral hippocampal formation are characterised by markedly quantifiable morphokinesis between the 21st day of age and onset of the first oestrus. This morphokinesis will take the form of consecutively occurring highly significant volume alterations of the cell nuclei which, in turn, reflect variation in neuronal activity. Some of such variation represents a expression of the general maturation and differentiation of central nervous neurons. The time of occurrence of such variation as well as its peculiar nature also appear to suggest the existence of some special relationship to sexual maturation. This seems to support the conclusion that the basolateral amygdaloid nucleus and the ventral hippocampal formation are attached to the extrahypothalamic central nervous structures of the cerebro-hypophyseal-gonadal axis, in addition to the medial and cortical amygdaloid nuclei. However, the very nature of relationships that may exist between the two investigated components of the limbic system, on the one hand, and sexual maturation as well as gonadal function, on the other, cannot be derived from the results reported in this paper.

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[Characteristics of neurons from the anterior region of the rat amygdaloid body by electron microscopy].

Dark and light neurons with morphological signs of secretory activity are described within one of the major sexually dimorphic zones of brain amygdaloid nucleus (anterior cortical nucleus). Dark neurons are of medium size, they have large nuclei and well developed perikarya. The latter contain numerous free ribosomes and mitochondria, dilated rough endoplasmic reticulum cisterns, hypertrophied Golgi complex with forming secretory granules. Elementary neurosecretory granules (ENG) 75-300 nm in size were found in light neurosecretory cells, which seem to be similar to dark cells but are at different phase of functional activity. Synapses of all types known, containing small light vesicles, vesicles with dense core and ENG, were found in active neuropil.

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[Changes in the concentration of various collagen fractions after electric stimulation and electrocoagulation of the rabbit amygdaloid body].

Content of catecholamines, 11-hydroxycorticosteroids, free and bound hydroxyproline in blood as well as metabolism of collagen in rabbit aorta wall were studied after electrostimulation and bilateral electrocoagulation of brain amygdaloid complex. The stimulation was shown to alter the content of adrenal gland hormones and activated the collagen metabolism in aorta wall. After electrocoagulation within the first month content of noradrenaline, 11-hydroxycorticosteroids and accumulation of collagen in aorta tissue were decreased.

11-Hydroxycorticosteroids↗

Tegmental afferents of the amygdaloid body in the rat.

Horseradish peroxidase (HRP) was injected to various parts of the amygdala in 50 rats. Retrograde axonal transport revealed that tegmental areas containing biogenic amines: dorsal and median raphe nuclei, locus coeruleus and ventral tegmental area, project diffusely to various amygdaloid areas. Moreover, HRP labeled cells were found in the parabrachial nucleus (following injection of the lateral amygdaloid nucleus) and in tegmental dorsolateral nucleus (after injection of the central nucleus of amygdala).

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Tracing of two-neuron pathways in the olfactory system by the aid of transneuronal degeneration: projections to the amygdaloid body and hippocampal formation.

Following an olfactory bulb lesion in guinea pig (2 to 3 days), neuronal degeneration occurs in several olfactory-bulb-related areas, primarily in the piriform cortex. The degenerating neurons, which are argyrophilic, are also found in the posterolateral cortical amygdaloid nucleus and the ventrolateral entorhinal cortex. It is suggested that the neurons degenerate because of a transneuronal effect due to a sudden loss of afferent input from the olfactory bulb, although a retrograde effect acting in concert with transneuronal factors cannot be excluded. Terminal degeneration can be identified in several areas outside the olfactory bulb projection area, and is interpreted as degeneration in the axons of the degenerating cortical neurons. Such terminal degeneration, which is best seen 3 to 4 days postoperatively, has been identified in part of the basolateral amygdaloid complex, in the basomedial amygdaloid nucleus, and in the temporal parts of the fascia dentata of the hippocampal formation. Terminal degeneration has also been observed in the deep layers of the anterior olfactory nucleus, the olfactory tubercle, the nucleus of the lateral olfactory tract, and the anterior amygdaloid area. All these projections, apparently, represent the second link in two-neuron pathways, where mitral or tufted cells in the olfactory bulb make up the first neuron. This interpretation was confirmed in control experiments in which areas of argyrophilic neurons coincided with the location of retrogradely labeled neurons following injection of fluorescent substances into several of the above-mentioned areas of terminal degeneration.

Afferent Pathways↗

Connections of the hypothalamus and preoptic area with nuclei of the amygdaloid body in the rat; HRP retrograde transport study.

Horseradish peroxidase (HRP) was injected into various nuclei of the amygdala in 50 rats. The retrograde axonal transport of HRP showed various connections arising from the hypothalamic nuclei and the basal forebrain. Neurons of the magnocellular preoptic nucleus send out amygdalopetal axons to all amygdaloid nuclei except the lateral nucleus. The amygdalopetal projections emerge from the large neurons situated dorsally in the most lateral preoptic area (probably substantia innominata) and terminate in the basal dorsal and the central amygdaloid nuclei. Neurons in the lateral division of the hypothalamus (the lateral hypothalamic area proper and the perifarnical region) send out axons which terminate in the medial and central nuclei and in the posterior part of the cortical amygdaloid nucleus. Axons emerging from the ventromedial hypothalamic nucleus end mainly in the medial nucleus and in the central amygdaloid nucleus. Amygdalopetal fibers arising from neurons of the ventral premammillary and dorsal hypothalamic nuclei reach the medial amygdaloid nucleus and perhaps a few of them end in the posterior part of the cortical amygdaloid nucleus. Neurons of the bed nucleus of the stria terminalis project to the medial, the posterior part of the cortical and probably to the basal dorsal amygdaloid nuclei.

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