[THE STRUCTURAL ASPECTS OF THE PARTICIPATION OF THE BRAINSTEM NUCLEI IN THE PROCESSING OF THE FUNCTIONALY DIFFERENT INFORMATIONAL FLOWS GOING THROUGH THE BASAL GANGLIA].

The structural foundation of processing of the information in the basal ganglia morphofunctional system was examined on the basis of the analysis of the investigated by the method of retrograde axonal transport projections between the functionally different parts of brain steam and basal ganglia' functionally various segments. The elements of the topic, showing to opportunity of segregated carrying of the information between the limbic and motor segments of the brain steam and the basal ganglia' similar regions were revealed in the organization of the projections between the named structures in dog. But, in the considered projection systems prevail the convergent carrying of the information testified about the possibility of the integration different modal information not only in the basic, but and in the all nuclei of the basal ganglia' morpho-functional system. The labeled «reticular¼ neurons with sparsely branching dendrites and long axons, which are projected to the basal ganglia, also testify about the integrative function of the investigated nucleus. The opportunity of the utilization of the received dates for making of the new models, which allow to understand better the mechanism of basal ganglia functioning in norm and pathology are discussed.

[THE ORGANIZATION OF PROJECTIONS OF MIDBRAIN LATERAL TEGMENTAL NUCLEI THE TO BRAIN BASAL GANGLIA IN DOGS].

The organization of the projections of midbrain lateral tegmental nuclei (peripeduncular nucleus, paralemniscal nucleus, nucleus of the brachium of inferior colliculus) to functionally diverse nuclei of the basal ganglia system was studied in dogs (n = 34) by the method of retrograde axonal transport of horse-radish peroxidase. It was found that the midbrain nuclei studied were involved in functionally different circuits, containing the basal ganglia as their components. These nuclei innervate the regions of the putamen, globus pallidus, cuneate nucleus, subcuneate nucleus, which are the motor or the limbic structures on the basis of their predominant connections with the motor or the limbic brain nuclei, and also regions of the caudate nucleus, nucleus accumbens, entopeduncular nucleus, compact part of the pedunculopontine nucleus, which receive the projections from the functionally various structures. The analysis of Nissl-stained frontal sections allowed to refine the anatomical topography of the individual nuclei of the midbrain lateral tegmentum. The cholinergic nature of their neurons was demonstrated based on of the positive histochemical reaction to NADPH diaphorase.

[Organization of the pallidal projections of the rostromedial tegmental nucleus in the dog brain].

The method of retrograde and anterograde transport of horse-radish peroxidase was used to study the organization of the projections of the rostromedial tegmental nucleus (RMTN) to functionally distinct regions of pallidal structures of brain in dogs (n = 13). It was found that the fibers formed by the neurons of the limbic medial segments of RMTN rostral and caudal regions projected to the limbic pallidal regions--ventral globus pallidus and ventral pallidum. The reciprocal projections were detected between the ventral pallidum and medial segment of the rostral RMTN. These data indicate the possibility of the segregated conduction of the limbic information in the examined projection systems. However, in the majority of the pallidal structures, the convergence of the projection fibers originating from the neurons of functionally different parts of RMTN was observed. Thus, the projection fibers formed by the neurons of motor lateral and limbic medial parts of RMTN are directed to the limbic ventral segment of the globus pallidus and to the entopeduncular nucleus, which is innervated by the fibers formed by the neurons of functionally diverse structures. The possible pathways for conduction of functionally different information and its integration in the projection systems investigated are discussed.

[The organization of the projections of the rostromedial tegmental nucleus to the striatum in canine brain].

Method of retrograde axonal transport of horseradish peroxidase and fluorochromes was used to study the organization of the projections of the rostromedial tegmental nucleus (RMTN) to the functionally diverse regions of striatal structures of dog brain (n=26). It was found that the projection fibers of the neurons of RMTN limbic medial part were directed only to the ventral limbic segments of the nucleus caudatus, the putamen and the nucleus accumbens. However, the convergence of the projection fibers originating from the neurons of functionally different RMTN parts was observed in the majority of the segments of the striatal structures. Thus, the projection fibers of the motor lateral and the limbic medial RMTN parts were directed to the motor dorso-lateral segment of the caudate nucleus and also to the striatal segments, which were innervated by the fibers from the neurons of functionally diverse structures (ventro-lateral segment of the caudate nucleus and the lateral segment of the nucleus accumbens). Possible pathways conducting functionally different information and its integration in the investigated projection systems are discussed.

[Organization of the projections of the structures of the basal ganglia morpho-functional system to the individual substructures of the deep mesencephalic nucleus complex of dog brain].

The method of retrograde axonal transport of horseradish peroxidase was used to study the organization of the projections of the morpho-functional system of the basal ganglia nuclei to the individual substructures of the of deep mesencephalic nucleus complex (DMNC) of dog brain (n = 9). It was found that the nucleus accumbens was the only striatum structure containing the neurons that sent projection fibers to the subcuneate nucleus. The projections of the output structures of the basal ganglia--pallidum, substantia nigra, zona incerta, pedunculopontine nucleus were more numerous in DMNC. It was demonstrated that not all DMNC substructures received projection fibers from the neurons of all the nuclei of the basal ganglia structures mentioned. Thus, the fibers from the neurons of the globus pallidus and the ventral pallidum innervated the cuneiform and the subcuneiform nuclei, while those from the entopeduncular nucleus projected to all the DMNC substructures. The projection fibers from the zona incerta neurons were directed to the subcuneate nucleus and to the deep mesencephalic nucleus, while those from the pedunculopontine nucleus projected to the cuneate and the subcuneate nuclei. The projections from the substantia nigra neurons were directed to all the substructures of DMNC.

Connections between the zona incerta of the dog diencephalon and the substantia nigra, ventral tegmental field, and pedunculopontine tegmental nucleus.

Studies using technique based on retrograde and anterograde transport of horseradish peroxidase were performed to address the organization of the connections of different sectors of the zone incerta (ZI) of the diencephalon with substructures of the substantia nigra, ventral tegmental field, and pedunculopontine nucleus of the midbrain in dogs. These structures were found to be interconnected. The organization of these connections included elements demonstrating that segregated conduction of functionally diverse information can be transmitted via these pathways. In addition, the convergence of projections fibers from neurons in substructures of the midbrain nucleus described in all sectors of the ZI and to these neurons from neurons in all ZI sectors is evidence that functionally diverse information can be integrated both at the level of the ZI and at the level of the midbrain structures studied here.

Organization of projections of the zona incerta of the diencephalon to pallidal structures in the dog brain.

Detailed studies of the organization of individual sectors in the zona incerta of the diencephalon to functionally diverse pallidal structures in the dog brain were performed by antero- and retrograde axon transport of horseradish peroxidase. The results showed that neurons in the caudal sector of the zona incerta innervate the globus pallidus and entopeduncular nucleus, which receive more extensive innervation from motor structures. The same pallidal structures receive projections from occasional neurons in the dorsal and causal sectors of the zona incerta. No connections of the zona incerta with the limbic ventral pallidum were found.

Projections of the basal ganglia to the zona incerta of the dog diencephalon.

Retrograde axonal transport of horseradish peroxidase was used to show that the projections of the globus pallidus, entopeduncular nucleus, substantia nigra, and pedunculopontine tegmental nucleus in dogs are directed to all segments of the zone incerta. The experiments reported here identified no topical features in the organization of these projections in dogs, as application of marker to different areas of the zona incerta yielded similar distributions of labeled neurons in the basal ganglia. No striatal projections to the zone incerta were found.

Structural organization of the zona incerta of the dog diencephalon.

Studies performed using the Nissl and Kluver-Barrera methods for analysis of the organization of fibers, morphological neuron types, and neuron density distribution were undertaken to map the zona incerta of the diencephalon of the dog brain; five individual sectors were identified, whose boundaries were further identified by histochemical detection of NADPH-diaphorase-positive neurons.

Projections of striatopallidal structures to the pedunculopontine nucleus of the tegmentum of the midbrain in dogs.

A method based on retrograde axonal transport of horseradish peroxidase was used to study the striatopallidal afferent projections of the pendunculopontine nucleus of the midbrain (PPN) in dogs. The major source of these projections was found to be the pallidum, as both the compact and diffuse zones of this nucleus received projections from all of its structures: the entopeduncular nucleus, the globus pallidus, and the ventral pallidum. The striatal complex, specifically the nucleus accumbens, showed only occasional labeled neurons, projecting exclusively to the compact part of the PPN. Since the distribution of projection fibers arising from the functionally diverse territories of the striatopallidum and directed to individual structural subdivisions of the PPN showed no topical elements, identification of functionally specific (motor and limbic) areas of the PPN was not possible on the basis of the present analysis.

Structural basis of the involvement of the striopallidum and pedunculopontine tegmental nucleus in the organization of adaptive behavior.

Retrograde axonal transport was used to study the organizational characteristics of the afferent and efferent projection systems of individual substructures of the pedunculopontine tegmental nucleus and the functionally diverse (motor, limbic) areas of structures in the striopallidum. The structural bases of the conduction of functionally diverse information and its integration in the basal ganglia system and tegmental area were evaluated. The morphological data obtained here aid our understanding of the morphofunctional bases of the interaction of these structures and their involvement in adaptive behavior.

Organization of the efferent projections of the pedunculopontine tegmental nucleus of the midbrain of the dog pallidum.

Studies of the pedunculopontinopallidal projections of the dog brain based on the retrograde axonal transport of horseradish peroxidase demonstrated that the compact zone (PPNc) and the lateral area of the diffuse zone (PPNd) of the pedunculopontine tegmental nucleus (PPN) of the midbrain project to the globus pallidus, entopeduncular nucleus, and ventral pallidum. The medial area of the PPNd, adjacent to the chiasm of the upper cerebellar peduncles and seen in other animals as the mesencephalic extrapyramidal area (MEA), projects only to the globus pallidus. In dogs, this area of the tegmentum is not a major source of projections to the striopallidum, such that it is inappropriate to regard it as a separate structure, comment being restricted to the topical organization of PPNd projections to the pallidum. Projection fibers to pallidal structures arise from both cholinergic and non-cholinergic PPN neurons.

Organization of efferent projections of the pedunculopontine nucleus of the tegmentum of the striatum in the dog brain.

A method based on retrograde axonal transport was used to undertake detailed studies of the efferent projections of individual substructures of the pedunculopontine nucleus of the midbrain tegmentum to functionally diverse segments of striatal structures in dogs. The compact and diffuse zones of this nucleus were found to project to segments of the putamen, caudate nucleus, and nucleus accumbens, which are components of the limbic and motor systems. The medial part of the diffuse zone, adjacent to the decussation of the superior cerebellar peduncles (presumptively the mesencephalic extrapyramidal field) projected only to the dorsal segments of the caudate nucleus and putamen, which are parts of the motor system.

Structural organization of the pedunculopontine nucleus of the tegmentum of the dog midbrain.

The aim of the present work was to perform cytoarchitectonic studies of the pedunculopontine nucleus (PPN) of the tegmentum of the midbrain in dogs to define the margins of this structure and to describe its separate substructures. The Nissl and Kluver-Barrera methods and histochemical detection of NADPH-diaphorase, this being a selective marker for cholinergic neurons in the tegmentum, were used to analyze the fiber organization, the morphological types of neurons, and the neuron density in the PPN of the tegmentum. This yielded a map of this nucleus in the dog with descriptions of the margins of its component zones: the compact and the diffuse. The mesencephalic extrapyramidal part could not be discriminated from the general composition of the PPN of the tegmentum.

Organization of the thalamic projections of the striopallidum of the dog brain.

Experiments based on double luminescent labeling were performed to study the distribution of labeled neurons in the thalamic nuclei depending on the injection sites of luminescent markers into functionally similar or functionally different areas of the striopallidum of 16 dogs. The organizational characteristics of the thalamo-striopallidal projection system in dogs provide evidence for its high level of specificity, as not only the motor and limbic areas of the striopallidum, but also its functionally related areas, receive separate inputs mainly from diverse cellular groups. The centromedian nucleus contained groups of diffusely mixed cells, labeled with different markers and innervating functionally diverse segments of the caudate nucleus. In the centromedian, parafascicular, central medial, and medial dorsal nuclei of the thalamus, projection neurons form analogous cell populations innervating different segments of the striopallidal structures belonging to the same functional system. These striopallidal areas receive projections from small numbers of neurons via axon collaterals.

Analysis of the morphological substrate for information processing in the striatum based on the organizational characteristics of its afferent projections.

Retrograde axonal transport of markers was used to study the afferent projections arising from functionally diverse cortical and subcortical structures and running to various segments of the caudate nucleus, nucleus accumbens, and putamen of the dog brain. The characteristics of the spatial organization of these projections were used to analyze the morphological aspects of the segregated and convergent conduction and processing of information in the striatum which underlie striatal function.

Analysis of the structural bases of information processing in the basal ganglia: the spatial organization of thalamocortical projections in the dog brain.

Analysis of the architectonics of the thalamic projection systems of the caudate nucleus, putamen, and nucleus accumbens using axonal transport of retrograde markers was performed to study the morphological substrate for information processing in the striatum of the dog brain. The striatal nuclei contained areas through which segregated conduction of motor (dorsal segments of the caudate nucleus and putamen) and limbic (medial segment of the nucleus accumbens) information could occur, along with areas (ventral segments of the caudate nucleus and putamen, lateral segment of the nucleus accumbens) in which convergent conduction of functionally diverse information processed in the thalamic nuclei could occur. These data make a significant contribution to our understanding of the anatomical aspects of both the functional heterogeneity of the basal ganglia and integrative information processing occurring within them, which underlies the mechanisms organizing adaptive behavior.

Dopamine-dependent inhibition of glycine release in the nucleus accumbens of the rat brain during food consumption.

Studies of Sprague-Dawley rats using in vivo intracerebral dialysis and high-performance liquid chromatography with electrochemical detection were used to investigate glycine release into the intercellular space of the nucleus accumbens during food consumption. The results showed that food consumption led to decreases in glycine levels in the intercellular space of the nucleus accumbens. Administration of the sodium channel blocker tetrodotoxin (1 microM), but not the glutamate reuptake blocker D,L-threo-hydroxyaspartate (1 mM), prevented the food-related behavior-induced decrease in glycine levels in the nucleus accumbens. Eating of food after administration of the dopamine D2 receptor blocker raclopride (10 microM) into the nucleus accumbens was accompanied by an increase in the glycine level in the intercellular space of this structure. These data provide evidence for the neural regulation of glycine release in the nucleus accumbens during food-related behavior, mediated via dopamine D2 receptors.