Search Results - (Author, Cooperation:V. K. Berezovskii)

2015-03-06

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

1573-899X

caudate nucleus ; thalamus ; electrocorticogram ; carbachol

Springer Online Journal Archives 1860-2000

Biology

Medicine

Abstract The effect of local injections of carbachol into the caudate nucleus and individual nuclei of the thalamus on the electrocorticogram of the anterior portion of the brain was investigated in unanesthetized, immobilized cats. It was shown that chemical stimulation of subcortical structures, like electrical stimulation, can induce spindle-like activity and a recruitment response. The appearance of these reactions after injections of carbachol both into the caudate nucleus and into individual nuclei of the thalamus indicates the existence of a functionally unified caudate-thalamic cholinoreceptive system, responsible for the slow wave rhythmic activity.

Electronic Resource

1573-9007

Springer Online Journal Archives 1860-2000

Medicine

Electronic Resource

1573-9007

Springer Online Journal Archives 1860-2000

Medicine

Abstract Sections of the medulla known as the locomotor strip were investigated during cat experiments using the horseradish peroxidase retrograde transport technique. The enzyme was administered under functional control (stimulating the injection site evoked locomotion). Results showed no evidence of a hypothetical column of cells either along the locomotor strip or medially to the strip. This would cast doubts on the existence of such a strip as a separate structural formation. It was shown by comparing findings from morphological research and experiments involving electrical stimulation that the bulbar locomotor strip may in fact consist of the spinal trigeminal tract and its nucleus. It is postulated that non-specific afferent activation of the brainstem reticular formation plays a crucial role in initiating locomotion.

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1573-9007

Springer Online Journal Archives 1860-2000

Medicine

Abstract The origin of spinal locomotor strip fibers was investigated in cats by applying electrical stimulation and the retrograde axonal horseradish peroxidase transport technique. It was found to be mainly composed of corticospinal tract fibers. Moderate numbers of reticulospinal tract and trigeminal spinal tract fibers were also observed. Descending projections from brain stem catecholaminergic neuronal groups do not pass through the test sites of the dorsolateral funiculus, nor, apparently, do they go to make up the spinal locomotor strip. Specificity of the brain stem and spinal locomotor region is discussed.

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1573-899X

Springer Online Journal Archives 1860-2000

Biology

Medicine

Electronic Resource

1573-9007

Springer Online Journal Archives 1860-2000

Medicine

Abstract The location of neurons forming fiber systems descending into the brain-stem reticular formation, red nucleus, and relay nuclei of the dorsal columns was studied in cats by the retrograde axonal transport of horseradish peroxidase method. The cortical projection regions, structures of the limbic system, and the hypothalamus were shown to form fiber systems that descend to the brain stem, whereas the orbito-frontal cortex is the chief source of cortico-reticular projections. The possible functional role of these descending systems in the central control of somatic and visceral functions is discussed.

Electronic Resource

1573-9007

Springer Online Journal Archives 1860-2000

Medicine

Abstract The location of sources of direct projections to the hypothalamic locomotor region, electrical stimulation of which in the lightly anesthetized animal induced stepping along a moving treadmill, was studied by the retrograde axonal transport of horseradish peroxidase method in the cat brain stem. Different formations in the brain stem were shown to have direct connections with hypothalamic locomotor regions on both sides. Most sources of these afferent projections were located at sites of catecholamine- (nucl. reticularis lateralis, locus coeruleus, nucl. tractus solitarii) and serotonin-containing (nucl. raphe and substantia grisea centralis) neurons, parabrachial nuclei, and various sensory nuclei. Hypothalamic locomotor regions of both sides form bilateral connections.

Electronic Resource

1573-9007

Springer Online Journal Archives 1860-2000

Medicine

Abstract Efferent neuronal projections of the mesencephalic locomotor region were investigated in cats using a horseradish peroxidase retrograde axonal transport technique. It was found that neurons located within the locomotor area form ascending and descending projections to many structures of the spinal cord and the brain but that short-axon connections running to the reticular formation of the midbrain and the medulla predominate. Small numbers of long-axon fibers may merge into the locomotor strips of the medulla and the spinal cord. The locomotor regions of the two halves of the midbrain are interlinked.

Electronic Resource

1573-9007

Springer Online Journal Archives 1860-2000

Medicine

Abstract Nigrothalamic neurons were identified in the reticular part of thesubstantia nigra using labelling by the retrograde axonal transport of horseradish peroxidase. Nine parameters of the synaptic contacts (n=195) were analyzed, including the size and shape of terminals and size and type of synaptic vesicies. Sixty-six percent of axon terminals studied formed symmetric contacts and contained large polymorphic vesicles (group I). Two-thirds of these synapses were located on the distal dendrites, while one-third was distributed on the perikarya and proximal dendrites. Synapses of group II (29% of all synapses analyzed) exhibited asymmetric contacts and contained round agranular vesicles. Among these synapses, 79% were located on the distal dendrites, 19% were located on the proximal dendrites, and only 2% were located on the neuronal perikarya. Axon terminals of group III (5% of total population) exhibited symmetric contact and contained small polymorphic vesicles. High-resolution immunogold EM histochemistry indicated that 63% of the group-I axon terminals were GABA-positive. The majority of synapses on the labelled nigrothalamic neurons (21 contacts of 25) belonged to group I. Among these 21 synapses, 19 were axo-somatic and mostly GABA-positive. Within group II, 30% of synapses showed slightly expressed GABA-positivity.

Electronic Resource

1573-899X

Springer Online Journal Archives 1860-2000

Biology

Medicine

Electronic Resource

1573-899X

Springer Online Journal Archives 1860-2000

Biology

Medicine

Electronic Resource

1573-9007

Springer Online Journal Archives 1860-2000

Medicine

Electronic Resource

1573-9007

Springer Online Journal Archives 1860-2000

Medicine

Abstract Sources of direct and indirect afferent connections of the caudate nucleus were investigated in cats by the retrograde axonal transport of horseradish peroxidase method. Different parts of the neocortex were shown to form different types of projections to the caudate nucleus; the sources of these projections have a laminar organization. Connections of the globus pallidus with the caudate nucleus, not previously described, were found. Among the sources of the thalamo-caudate projections, besides nuclei of the intralaminar complex, an important place is occupied by the ventral anterior and mediodorsal nuclei. After injection of horseradish peroxidase into the caudate nucleus, retrograde axonal transport of the enzyme was observed in the caudal direction, as far as cells of the locus coeruleus. ON the basis of these results a general scheme of afferent projections to the caudate nucleus is drawn up, including its connections with the spinal cord mediated by the thalamic nuclei and mesencephalic reticular formation.

Electronic Resource

1573-9007

Springer Online Journal Archives 1860-2000

Medicine

Abstract Efferent projections of the thalamic locomotor region were investigated using the horseradish peroxidase technique of retrograde axonal transport. This enzyme was injected into different brain structures. Function was monitored during a micro-injection into the locomotor areas. It was found that direct descending projections from the hypothalamic locomotor region lead mainly to ipsilateral structures and reach the lumbar sections of the spinal cord. Neurons of the locomotor area of the hypothalamus make their major connections with thelocus coeruleus area and the medial brainstem reticular formation. Projections were observed from the hypothalamic locomotor region to the mesencephalic locomotor area and the locomotor strip.

Electronic Resource

1573-9007

Springer Online Journal Archives 1860-2000

Medicine

Abstract Descending projections from the cortex and basal ganglia to the hypothalamic locomotor region were studied in cats by the retrograde axonal transport of horse-radish peroxidase method. Neurons forming direct projections to the physiologically identified hypothalamic locomotor region are diffusely scattered over different gyri, but predominantly in areas 4 and 6 of the motor cortex, and also in the entopeduncular nucleus. Powerful cortico- and pallido-hypothalamic projections mainly do not reach as far as the most caudal zones of the hypothalamus, where the region whose electrical stimulation evokes locomotion lies.

Electronic Resource

1573-9007

Springer Online Journal Archives 1860-2000

Medicine

Abstract Afferent projections to the functionally identified mesencephalic locomotor region were investigated in cats using the horseradish peroxidase retrograde axonal transport technique. Sources of afferent projections to this region were discovered in different structures of the fore-, mid-, and hindbrain. Numbers of horseradish peroxidase-labeled neurons were calculated in different brain structures after injecting this enzyme into the mesencephalic locomotor region. Apart from the endopeduncular nucleus, different hypothalamic structures, and the substantia nigra, labeled neurons were discovered in the central tegmental region, the central gray, raphe and vestibular nuclei, the solitary tract nucleus, and the brain stem reticular formation. Neurons accumulating horseradish peroxidase were also discovered in nuclei where ascending sensory tracts originate. This fact serves to bring out the structural inhomogeneity of the midbrain locomotor region; electrical stimulation of this area is an effect which may be attributed to excitation of neurons found within it and activation of accompanying fiber tracts.

Electronic Resource

1573-9007

Springer Online Journal Archives 1860-2000

Medicine

Conclusion This overview of the brainstem pathways of the initiation of locomotion can be summarized as follows. There are locomotor regions (hypothalamic and mesencephalic) whose stimulation leads to the appearance of rhythmic stepping movements. These regions are nonuniform in composition: transient fibers as well as cells are found. The locomotor effects of electrical stimulation of these regions can largely be explained on the basis of the presence of efferent projections of the neurons to the medial reticular formation, as well as the activation of the transient fibers of other brain systems. The ventromedial parts of the reticular formation of the medulla oblongata, including areas of the macrocellular and (to a lesser extent) gigantocellular nuclei, form the final element in the suprasegmental system of locomotion initiation. The inconclusive data of different scientists who have used chemical microinjections into the locomotor regions make it impossible at present to specify precisely the neurochemical mechanisms underlying the initiation of locomotion. NMDA has been found to play an important role. The activation of the reticular formation during the triggering of stepping movements can take place either from the locomotor regions or by means of signals coming from the collaterals of the ascending sensory tracts. The wide spectrum of possible pathways of the initiation of locomotion apparently affords the organism a choice of ways by which to realize this process and is an important factor in its adaptation to its environment.

Electronic Resource

1573-9007

Springer Online Journal Archives 1860-2000

Medicine

Abstract Nigrothalamic neurons were identified into thesubstantia nigra by their retrograde labelling with horseradish peroxidase. Axon terminals that contain glutamate (the excitatory transmitter) were revealed immunocytochemically with an immunogold electron microscopic technique. Ultrastructural parameters (the large and small diameters of axon terminals, area of their profiles, coefficient of form of profiles, large and small diameters of synaptic vesicles) were analyzed in all 240 synapses under study. Synaptic contacts localized on both nigrothalamic and unidentified neurons belonged to three morphologically specific groups. Synapses of the groups I and III, according to classification by Rinvik and Grofova, were characterized by a symmetric type of synaptic contact and contained polymorphic synaptic vesicles. Contacts in group-II synapses were asymmetric, and respective terminals contained round vesicles. Among the studied synapses, 65.8% were classified as group-I contacts, 25.0% belonged to group II, and 9.2% belonged to group III. Glutamate-positive axon terminals formed predominantly group-II synapses; such connections constituted 70% of this group's synapses. Sixty percent of glutamate-positive synapses were localized on the distal dendrites and 23% on the proximal dendrites, while 17% of such synapses were distributed on the somata of nigral neurons. Such a pattern of distribution of glutamate-positive synapses was observed on both nigrothalamic and unidentified nigral neurons. About 7% of glutamate-positive synapses were formed by very large axon terminals containing round synaptic vesicles; yet, the contacts of these terminals were of a symmetric type. Twenty percent of group-I synapses, i.e., synapses considered inhibitory connections, were found to manifest a weak immune reaction to glutamate.

Electronic Resource

1573-9007

Springer Online Journal Archives 1860-2000

Medicine

Abstract Synchronized activity (spindles, augmentation response) evoked by stimulation of thalamic nonspecific, association, and specific nuclei was investigated in chronic experiments on 11 cats before and after successive destruction of the caudate nuclei. After destruction of the caudate nuclei the duration of spindle activity in the frontal cortex and subcortical formations (thalamic nuclei, globus pallidus, putamen) was reduced to only three or four oscillations. In the subcortical nuclei its amplitude fell significantly (by 50±10%); in the cortex the decrease in amplitude was smaller and in some cases was not significant. Different changes were observed in the amplitude of the augmentation response, depending on where it was recorded. In the subcortical formations it was considerably and persistently reduced (by 50±10%); in the cortex these changes were unstable in character. Unilateral destruction of the caudate nucleus inhibited synchronized activity evoked by stimulation of the thalamic nuclei on the side of the operation only. Destruction of the basal ganglia (caudate nucleus, globus pallidus, entopeduncular nucleus, and putamen) did not prevent the appearance of synchronized activity; just as after isolated destruction of the caudate nucleus, after this operation synchronized activity was simply reduced in duration and amplitude. It is suggested that the caudate nucleus exerts an ipsilateral facilitatory influence on the nonspecific system of the thalamus during the development of evoked synchronized activity.

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