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 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 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 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.

[Basal ganglia projections to zona incerta of dog diencephalon].

Using the method of the retrograde axonal transport of horseradish peroxidase, it was determined that in dog, the projections from globus pallidus, nucleus entopeduncularis, substantia nigra and pedunculopontine nucleus were directed to all the regions of zona incerta. In the present study, no topical features were detected in the organization of these projections in dog, since after the injections of the marker in different regions of zona incerta, similar distribution of labeled neurons was observed in basal ganglia. The projections from the striatum to zona incerta were not found.

[Structural organization of the zona incerta in the dog diencephalon].

Zona incerta in dog diencephalon was studied by the methods of Nissl and Kluver-Barrera. As a result of this study, 5 individual sectors were identified on the basis of the analysis of fiber Organization, morphological types of neurons and the density of their distribution. The mapping of zona incerta was performed, and the borders of the sectors were accurately determined by histochemical demonstration of NADPH-diaphorase-positive neurons.

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.

[Striopallidum projections to the pedunculopontine tegmental nucleus in the dog mesencephalon].

Using the method based on the retrograde axonal transport of the horseradish peroxidase, striopallidal afferent projections to the pedunculopontine tegmental nucleus (PPN) of the dog brain were studied. It was shown that the main source of these projections was pallidum, since the projections were directed both to the compact and diffuse parts of this nucleus from all its structures: nucleus entopeduncularis, globus pallidus and ventral pallidum. In the striatal complex, namely in the nucleus accumbens, only single labeled neurons projecting exceptionally to the compact part of the PPN, were detected Since in the distribution of the projection fibers, originating from the functionally various territorries of the striopallidum and directed to the individual substructures of the PPN, no topical elements were detected, the separation of the functionally specific (motor and limbic) regions in the PPN, on the basis of findings obtained, appears impossible.

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 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.

[The organization of the efferent projections of the pedunculo-pontine tegmental nucleus to the dog pallidum ].

The study of pedunculo-pontine-pallidum projections in the dog's brain, which was performed using the method of retrograde axonal transport, has demonstrated the projections of a compact part (PPNc) and the lateral area of a diffuse part (PPNd) of midbrain pedunculo-pontine tegmental nucleus (PPN) to the globus pallidus, nucleus entopeduncularis and the ventral pallidum. PPNd medial area adjacent to decussation of the superior cerebellar peduncules, which is distinguished in other animals as the mesencephalic extrapiramydal area (MEA), projects only to the globus pallidus. In the dog, this tegmental area is not the major source of projections to striopallidum, therefore it appears not to be valid to distinguish it as an individual structure, it is reasonable to indicate only a topical organization PPNd projections to the pallidum. It was detected that the structures of pallidum received the projections from both cholinergic and non cholinergic initial PPN neurons.

Analysis of the morphological substrate for information processing in the pallidal nuclear complex of the dog brain in terms of the organizational characteristics of its afferent projections.

Axonal transport of retrograde markers was used to study the distribution of the afferent projections of the nuclei of the pallidal complex (the globus pallidus, the entopeduncular nucleus, and the ventral pallidum) from functionally diverse cortical and subcortical structures (cortical fields, substantia nigra, ventral tegmental field, and thalamus) in the dog brain. The results were used to analyze the morphological aspects both of the functional heterogeneity of the pallidum and integrative information processing, which underlie the mechanisms of adaptive behavior.

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.

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.

Structural basis for the functional specialization of the pallidal complex of the cat brain.

Experiments carried out on 30 cats using retrograde axonal transport of markers (horseradish peroxidase and luminophores) were used to study the organization of the afferent projection system of the pallidal complex (the globus pallidum, the entopeduncular nucleus, the ventral pallidum) formed by fibers from functionally different cortical and subcortical structures (the ventral tegmental area, the substantia nigra, the amygdaloid body). The distribution of afferent projection fibers in this complex of nuclei led to identification of the following zones: a "limbic" zone, corresponding to the ventral pallidum, and a "motor" zone, corresponding to the caudal part of the globus pallidum. On the one hand, the features of the afferent organization as demonstrated here can be regarded as a structural basis for the functional heterogeneity of the pallidal complex; on the other, significant regions within these structures (the rostral part of the globus pallidum and the entopeduncular nucleus) were found to receive projection fibers from functionally different structures, suggesting the existence of convergence and integration processes in these regions.

Corticostriatal mechanisms of behavior.

This article presents the results of three series of experiments on cats, dogs, and lower primates, performed to investigate the structural, neurophysiological, and mediator mechanisms of the corticostriatal systems involved in the organization of behavior. Morphological studies of corticostriatal connections showed that along with the diffuse distribution of afferent terminals within the striatum, there were also elements of topical organization defined by anteroposterior and mediolateral gradients. Neurophysiological experiments on dogs and lower primates were used to study the spike activity of the prefrontal region of the cortex and the head of the caudate nucleus during training to conditioned first- and second-order reflexes and during the solution of complex problems involving delayed spatial selection. Studies demonstrated that while in dogs, most of the neurons recorded showed a transition to responses to the conditioned signal at a particular stage of carrying out a conditioned response, in monkeys all cells recorded showed specific responses at different periods of solving the task at all stages of the study. Neuropharmacological experiments on dogs showed that agents blocking glutamine receptors in the caudate nucleus had more pronounced effects at the phase of developing conditioned movement reflexes. Administration of these agents during the reflex reinforcement phase affected only the differentiation of inhibition. These results lead to the conclusion that the prefrontal area of the cortex and, to some extent, the caudate nuclei, act on incoming information specifying the current dominant need and the states of the external and internal environments, to carry out programmed actions and assess the results of these actions.

[Changes in RNA synthesis in neurons depending on the intensity of their synaptic activity]. / Izmeneniia sinteza RHK v neironakh v zavisimosti ot intensivnosti ikh sinapticheskoi aktivatsii.

A prolonged synaptic activation of the frog spinal motoneurons increases the intensity of 3H-uridine incorporation into nuclei and nucleoli of the nerve cells. The higher the frequency of neuronal synaptic activation, the higher the incorporation intensity during the post-activation period.

[Spatial organization of the corticopalladial projection system of dog brain]. / Prostranstvennaia organizatsiia kortiko-pallidarnoi proektsionnoi sistemy mozga sobaki.

Spatial organization of corticopallidal projectional system was studied in 11 outbred dogs by method based on horse radish peroxidase transport. It was demonstrated that globus pallidum receives projections predominantly from neocortical zones (motor, premotor, somatosensory, parietal and auditory and from insular field of mesocortex. Mesocortical (prelimbic, orbital and insular) and allocortical (entorhinal, piriform and periamygdalar) including archicortex (subicular part of hippocampal formations) fields project onto ventral pallidum. Entopeduncular nucleus receives projections from neocortical zones (motor, premotor, somatosensory, parietal and auditory), mesocortex (prelimbic, orbital, insular and cingular fields) and allocortex (entorhinal and periamygdalar fields). The data obtained indicate specificity of distribution of cortical afferent projectional fibres in each of nuclei studied which allows to consider globes pallidum as motor zone and ventral pallidum as limbic zone of paladial complex. As projections from functionally different cortical fields were revealed in entopeduncular nucleus it may be suggested that this is the exact site for interaction of functionally different information, including the one received from the cortex.

[The spatial organization of the cortical projection system of the nucleus accumbens in the canine brain]. / Prostranstvennaia organizatsiia kortikal'noi proektsionnoi sistemy prilezhashchego iadra mozga sobaki.

The study was performed in 10 outbred dogs by method based on retrograde axonal transport of horseradish peroxidase. Spatial organization of cortical projection system was examined. The structure was shown to receive projections from meso- and allocortex. Neocortical projections were not found. Mesocortical ones from prelimbic, infralimbic, orbital, insular and cingular zones were demonstrated to extend throughout both segments of dog nucleus accumbens, while projections from allocortex (periamygdaloid and entorhinal cortical zones, as well as hippocampal formation subicular part) were found only in medial part of the structure studied. Thus, features of mediodorsal topography were discovered in organization of nucleus accumbens afferent cortical projection system, while rostrocaudal topography elements were not found. Cortical initial neurons projections to the dog nucleus accumbens are located multilaminarly.

[The organization of the cortical projection system of the putamen in dogs]. / Organizatsiia kortikal'noi proektsionnoi sistemy u sobak.

Organization of cortical projections in dorsal and ventral segments of putamen rostral and caudal regions was studied in dogs using retrograde axonal transport of horse radish peroxidase. Dorsal region was shown to receive projections from neo- and mesocortex, while ventral is linked with all cortical units: neo-, meso- and allocortex. Dorsal part of putamen is to greater extent connected with cortical fields, relating to motor aspects of behavior (motor, premotor and somatosensory). Ventral region basically receives projections from the so called limbic cortical fields (cingular, insulary, orbital, periamygdalary and perirhinal). However, results of the present study do not allow to conclude on absolute division of projections of functionally different systems and only indicate the prevalence of one of them in certain topographic zone of the structure studied, i.e. elements of distinctive topography. consisting in presence of dorsal motor and ventral limbic morpho-functional regions are characteristic for dog putamen. No diversities in distribution of cortical projectional fibres along rostrocaudal axis of the structure were revealed. Initial neurons, projecting in putamen are of multilaminary localisation in the cortex.