Neuronal responses of the reticular and anterior ventral thalamic nuclei to stimulation of the thalamic ventrolateral nucleus and motor cortex

Responses of 137 neurons of the rostral pole of the reticular and anterior ventral thalamic nuclei to electrical stimulation of the ventrolateral nucleus and motor cortex were studied in 17 cats immobilized with D-tubocurarine. The number of neurons responding antidromically to stimulation of the ventrolateral nucleus was 10.5% of all cells tested (latent period of response 0.7–3.0 msec), whereas to stimulation of the motor cortex it was 11.0% (latent period of response 0.4–4.0 msec). Neurons with a dividing axon, one branch of which terminated in the thalamic ventrolateral nuclei, the other in the motor cortex, were found. Orthodromic excitation was observed in 78.9% of neurons tested during stimulation of the ventrolateral nucleus and in 52.5% of neurons during stimulation of the motor cortex. Altogether 55.6% of cells responded to stimulation of the ventrolateral nucleus with a discharge of 3 to 20 action potentials with a frequency of 130–350 Hz. Similar discharges in response to stimulation of the motor cortex were observed in 30.5% of neurons tested. An inhibitory response was recorded in only 6.8% of cells. Convergence of influences from the thalamic ventrolateral nucleus and motor cortex was observed in 55.7% of neurons. The corticofugal influence of the motor cortex on responses arising in these cells to testing stimulation of the ventrolateral nucleus could be either inhibitory or facilitatory.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 10, No. 5, pp. 460–468, September–October, 1978.     

Ultrastructure of mitotically dividing cells with signs of neurons in the rat brain

Ultrastructure of mitotically dividing cells in the sensomotor cerebral cortex of mature rats has been investigated, after transplantation into them embryonal nervous tissue of 17-day-old embryos. In 4 days after the operation in the recipient's nervous tissue, arranging around the developing transplant, among various proliferating cells with mitotic figures, some cells with signs of neurons (oval bodies, electron opaque cytoplasm with developed organelles and RNP-particles, specific for the nervous cell, with axonal terminals on the body) have been found. These cells are surrounded with the satellite glia. There are no mitotic figures in the pyramidal neurons.     

Correction of changes induced by toluene in the cortical and subcortical structures of albino rat brain

The number and weight of cells in the cortical and subcortical structures of the cerebral and cerebellar motor system in albino rats after a long-term exposure to toluene were determined. Toluene intoxication proved to kill projection neurons and interneurons in the sensorimotor cortex, ventrolateral thalamic nucleus, caudate nucleus, pallidum, red nucleus, and inferior olivary complex. The decreased number of cerebellar cells was mediated by atrophic changes as indicated by the decrease in the area and dry weight of Purkinje cells. The addition of plaferon LB to the diet attenuated the cytotoxic effect of toluene.     

Structural and functional features of caudatocortical connections

Efferent connections of the caudate nucleus were studied experimentally in 13 cats after electrolytic destruction of various parts of it. Preparations were stained by the methods of Nauta, Knook, and Fink-Heimer. Direct caudatocortical connections with a definite topical organization were discovered: a ventrodorsal projection in the cortex corresponds to a rostrocaudal and ventrodorsal distribution of neurons in the caudate nucleus. Striatocortical fibers are few in number and very thin. Their predeterminals were found in both the deep and the superficial layers of the cortex on granule cells and pyramidal cells of different sizes. The results are in agreement with those of most of the recent physiological investigations indicating a close functional connection between the caudate nucleus and the cortex.     

磷酸化的p44/42MAPK在成年猫端脑和间脑内的分布

为研究丝裂原激活的蛋白激酶（p44/42mitogen-activated protein kinase,缩写为p44/42MAPK)在正常动物脑内的功能,用免疫组织化学方法对正常家猫端脑和间脑内,磷酸化p44/42MAPK的分布进行了研究,结果表明在正常猫端脑和间脑内,磷酸化p44/42MAPK的存在范围比较广泛,嗅球,岛叶,梨状皮质,外侧隔区,海马锥体细胞层,下丘脑腹内侧核及弓状核内均有较多的阳性神经元,杏仁核存在中等量的阳性神经元,另外,新皮质Ⅱ层,内侧隔区,齿状回,纹状体,后脑室旁核和外侧缰核,下丘脑室旁核有散在分布的阳性神经元,外侧膝状体和丘脑腹后核有许多胶质细胞呈免疫阳性染色。咱束内有浓密的阳性纤维。本研究结果表明p44/42MAPK存在于与嗅觉,情绪,内分泌和记忆活动等功能有关的脑区和核团,提示其参与这些功能过程,本文还提示p44/42MAPK既与神经细胞,也与神经胶质细胞的信号转导有关。     

Expression of Bcl-2 in Adult Human Brain Regions with Special Reference to Neurodegenerative Disorders

Abstract: The expression of the protooncogene bcl-2 , an inhibitor of apoptosis in various cells, was examined in the adult human brain. Several experimental criteria were used to verify its presence; mRNA was analyzed by northern blot with parallel experiments in mouse tissues, by RNase protection, and by in situ hybridization histochemistry. Bcl-2 protein was detected by western blot analysis and immunohistochemistry. Two bcl-2 mRNA species were identified in the human brain. The pattern of distribution of bcl-2 mRNA at the cellular level showed labeling in neurons but not glia. The in situ hybridization signal was stronger in the pyramidal neurons of the cerebral cortex and in the cholinergic neurons of the nucleus basalis of Meynert than in the Purkinje neurons of the cerebellum. Both melanized and nonmelanized neurons were labeled in the substantia nigra. In the striatum, bcl-2 mRNA was detected in some but not all neurons. In the regions examined for Bcl-2 protein, the expression pattern correlated with the mRNA results. In patients with Alzheimer's and Parkinson's diseases, quantification of bcl-2 mRNA in the nucleus basalis of Meynert and substantia nigra, respectively, showed that the expression was unaltered compared with controls, raising the possibility that the expression of other components of apoptosis is modulated.     

Aspects of synaptic reorganization in the cat sensorimotor cortex after lesion of the symmetrically contralateral hemisphere

During the course of acute experiments, response in cortico-spinal neurons (CSN) to stimulating the ipsilateral ventral thalamic nucleus was investigated by extracellular recording techniques in intact adult cats and others with lesioning inflicted on the contralateral sensorimotor cortex 6–18 months previously. An accelerated stage of growth was noted in monosynaptic IPSP and CSN with slow-conducting axons in animals with surgically-induced lesion, suggesting reorganization of synaptic contacts within the CSN somatodendritic membrane. The collision test was applied to make a complete examination of arborization and of other aspects of CSN axons, as well as the presence of collaterals running to the ventrolateral thalamic nucleus and helping to form the ipsilateral pyramidal tract. The significance is discussed of plastic synaptic rearrangement in the ipsilateral thalamo-cortical reverberating system for formation of the efferent spike train during partial interhemisphere cortical deafferentation.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 22, No. 5, pp. 612–621, September–October, 1990.     

Course and termination of the pyramidal tract in the pig

To study the pyramidal tract in the pig, the motor cerebral cortex of one side was defined electrophysiologically and subsequently excised. The animals operated were killed after 7, 11 and 14 days, and the cerebral hemisphere of the operated side, brain stem and spinal cord were removed for histological examination. The pyramidal tract proved to run ipsilaterally as far as the oral extremity of the 12th cranial nerve nucleus. The decussation, which exhausted itself almost completely at the level of the rostral extremity of the 1st cervical metamere, started here. After the limit just mentioned only rare isolated fibres were visible. Along its course, the pyramidal tract sent a small number of axons to the ipsilateral and contralateral nucleus of the 7th cranial nerve, while the fibres running from the opposite side to the reticular formation and to the hypoglossal nerve nucleus, cuneatus, gracilis and trigeminal spinal tract nuclei were more numerous.     

Role of the solitary tract nucleus and caudal ventrolateral medulla in temperature responses in endotoxemic rats

In experiments on conscious rats it was found that preliminary microinjection of 100 nl 100 microM glutamic acid to the rostral commissural part of the solitary tract nucleus or to the caudal ventrolateral medulla increased a rise in colonic temperature induced by systemically applied endotoxin (3 microg/kg Escherichia coli lipopolysaccharide, i.p.) as compared to animals with intrabulbar injection of vehicle (control group). Preliminary microinjection of glutamate to the caudal commissural part of the solitary tract nucleus levelled the endotoxin-induced temperature response. After glutamate treatment of the caudal ventrolateral medulla there was a significant decrease in the noradrenaline content and decrease in the adrenaline level in the caudal (not significant) and rostral ventrolateral medulla (significant), as well as a small rise in noradrenergic activity at the solitary tract nucleus as compared to control animals. The post-mortem measurement of the optical density of brainstem tissues revealed its significant attenuation at the solitary tract nucleus and caudal ventrolateral medulla after glutamate as compared with these structures after vehicle. The involvement of monoaminergic systems of both structures under study in the initiation and control of temperature responses during endotoxemia is suggested.     

Lifelong Expression of Apolipoprotein D in the Human Brainstem: Correlation with Reduced Age-Related Neurodegeneration

The lipocalin apolipoprotein D (Apo D) is upregulated in peripheral nerves following injury and in regions of the central nervous system, such as the cerebral cortex, hippocampus, and cerebellum, during aging and progression of certain neurological diseases. In contrast, few studies have examined Apo D expression in the brainstem, a region necessary for survival and generally less prone to age-related degeneration. We measured Apo D expression in whole human brainstem lysates by slot-blot and at higher spatial resolution by quantitative immunohistochemistry in eleven brainstem nuclei (the 4 nuclei of the vestibular nuclear complex, inferior olive, hypoglossal nucleus, oculomotor nucleus, facial motor nucleus, nucleus of the solitary tract, dorsal motor nucleus of the vagus nerve, and Roller`s nucleus). In contrast to cortex, hippocampus, and cerebellum, apolipoprotein D was highly expressed in brainstem tissue from subjects (N = 26, 32−96 years of age) with no history of neurological disease, and expression showed little variation with age. Expression was significantly stronger in somatomotor nuclei (hypoglossal, oculomotor, facial) than visceromotor or sensory nuclei. Both neurons and glia expressed Apo D, particularly neurons with larger somata and glia in the periphery of these brainstem centers. Immunostaining was strongest in the neuronal perinuclear region and absent in the nucleus. We propose that strong brainstem expression of Apo D throughout adult life contributes to resistance against neurodegenerative disease and age-related degeneration, possibly by preventing oxidative stress and ensuing lipid peroxidation.     

Interaction of direct afferent and recurrent signals in cat motor cortex neurons

Intracellular activity was recorded from the functionally identified motor cortex neurons (MI, area 4) in acute experiments on myorelaxin-immobilized cats under calypsol anesthesia. Changes in neuronal responses to testing stimulation of the ventrolateral thalamic nucleus or pyramidal tract fibers were studied; the same or another input was used for a conditioning stimulation. Excitatory and inhibitory components of test responses of variousMI neurons were found to be either facilitated or depressed. The facilitation of orthodromic excitation was more frequent in the case of thalamic testing stimulation. The depression of both excitatory and inhibitory components of the response was more pronounced with paired stimulation of the pyramidal tract fibers. The peculiarities of interaction between direct afferent and recurrent signals in theMI neurons are thought to be determined by different distribution of thalamocortical fiber terminals and recurrent collaterals of corticofugal axons in the cortex and nonuniform localization of their synapses on dendrites and somata of the studied cells. It seems possible that these peculiarities also are connected with different chemical mechanisms of synaptic transmission in the above synapses and different properties of postsynaptic membrane receptors.Neirofiziologiya/Neurophysiology, Vol. 26, No. 3, pp. 203–210, May–June, 1994.     

Use of fluorescent carbocyanine dyes in the study of the organization of the pathways in autopsy material of the human brain

Our report provides evidence that fluorescent carbocyanine dyes (diI and diO) can be used in experimental anatomical studies of the fixed autopsy human brain. The dyes transported in both anterograde and retrograde directions, providing labeling of axons with collaterals and neurons including dendrites. To study the retrograde labeling of pyramidal neurons and anterogradely labeling of afferent fibers in human motor cortex, we applied diI and diO to the white matter, I and III layers of cortex. During 2 months there was no evidence of passive diffusion from labeled fibers and neurons to other neurons or glia. This method will be useful for identifying alterations of neuronal connections associated with neurological and psychiatric disorders.     

Transport of horseradish peroxidase by processes of radial glia from the pial surface into the mouse brain

Summary The transport of horseradish peroxidase (HRP) applied to exposed pial surfaces of the brain was studied in newborn, 4-, 7- and 12-day-old, and adult mice. In the telencephalon the cell bodies of radial glia were found to accumulate the tracer. Labeled cells occurred in the subventricular zone of the lateral ventricle during the first postnatal week; they became gradually restricted to an area around the stria terminalis (ventrolateral ventricular corner) by day 12. At later stages no HRP transport could be traced from the surface of the telencephalon. In the cerebellum, HRP was transported from the surface to the cell bodies of Bergmann glia in all age groups studied including adult animals. It is concluded that radial glia and their derivatives share the capacity of transporting material between various cerebrospinal fluid compartments.     

The motor nuclei of the glossopharyngeal-vagal and the accessorius nerves in the rat

Retrograde cobalt labeling was performed by incubating the rootlets of cranial nerves IX, X and XI, or the central stumps of the same nerves, in a cobaltic lysine complex solution, and the distribution of efferent neurons sending their axons into these nerves was investigated in serial sections of the medulla and the cervical spinal cord in young rats. The following neuron groups were identified. The inferior salivatory nucleus lies in the dorsal part of the tegmentum at the rostral part of facial nucleus. It consists of a group of medium-sized and a group of small neurons. Their axons make a hair-pin loop at the midline and join the glossopharyngeal nerve. The dorsal motor nucleus of the vagus situates in the dorsomedial part of the tegmentum. Its rostral tip coincides with the first appearance of sensory fibres of the glossopharyngeal nerve, the caudal end extends into the pyramidal decussation. The constituting cells have globular or fusiform perikarya and they are the smallest known efferent neurons. The ambiguous nucleus is in the ventrolateral part of the tegmentum. The rostral tip lies dorsal to the facial nucleus, and the caudal tip extends to the level of the pyramidal decussation. The rostral one third of the ambiguous nucleus is composed of tightly-packed medium sized neurons, while larger neurons are arranged more diffusely in the caudal two thirds. The long dendrites are predominantly oriented in the dorsoventral direction. The dorsally-oriented axons take a ventral bend anywhere between the ambiguous nucleus and dorsal motor nucleus of the vagus. The motoneurons of the accessorius nerve are arranged in a medial, a lateral and a weak ventral cell column. The medial column begins at the caudal aspect of the pyramidal decussation and terminates in C2 spinal cord segment. The lateral and ventral columns begin in C2 segment and extend into C6 segment. The neurons have large polygonal perikarya and characteristic cross-shaped dendritic arborizations. The axons follow a dorsally-arched pathway between the ventral and dorsal horns. The accessorius motoneurons have no positional relation to any of the vagal efferent neurons. It is concluded that the topography and neuronal morphology of accessorius motoneurons do not warrant the designation of a bulbar accessorius nucleus and a bulbar accessorius nerve.     

Thalamic inputs to the motor cortex studied in cats by retrograde axonal horseradish peroxidase transport

Thalamic afferent inputs of the motor cortex (area 4) were studied in cats by retrograde axonal transport of horseradish peroxidase (HRP). The main concentration of HRP-labeled neurons was found in rostral zones of the relay nuclei (of the ventrolateral and ventrobasal complex). A few labeled neurons were found in the mediodorsal association nucleus, where their distribution is quite local. HRP-labeled neurons of nonspecific intralaminar nuclei, projecting into the motor cortex, are present only in single numbers and show no tendency toward grouping in any parts of these nuclei. The results are evidence that the motor cortex receives heterogeneous afferentation from various thalamic nuclei, and it is evidently this which guarantees the reliability of transmission of incoming information.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 17, No. 2, pp. 250–255, March–April, 1985.     

Characterization of central nervous system structures by magnetic resonance diffusion anisotropy

Diffusion-weighted magnetic resonance imaging (MRI) provides information about tissue water diffusion. Diffusion anisotropy, which can be measured with diffusion tensor MRI, is a quantitative measure of the directional dependence of the diffusion restriction that is introduced by biological structures such as nerve fibers. Diffusion tensor MRI data was obtained in the brain, brain stem, and cervical spinal cord. For each region, scans were performed in four normal volunteers. Fractional anisotropy (FA), an index of diffusion anisotropy, was measured within regions of interest located in the corpus callosum, capsula interna, thalamus, caudate nucleus, putamen, brain cortex, pyramidal tract of the medulla, accessory olivary nucleus, dorsal olivary nucleus, inferior olivary nucleus, spinal white and gray matter. The highest FA value was measured in the corpus callosum (81 +/- 3%). The values of the other areas decreased in the following order: pyramidal tract in the medulla (72 +/- 1%), spinal white matter (65 +/- 4%), capsula interna (62 +/- 3%), accessory olivary nucleus (36 +/- 2%), spinal gray matter (35 +/- 5%), dorsal olivary nucleus in the medulla (29 +/- 2%), thalamus (28 +/- 2%), inferior olivary nucleus (15 +/- 2%), putamen (13 +/- 2%), caudate nucleus (13 +/- 2%), and brain cortex (9 +/- 1%). Our results indicate that the underlying fiber architecture, fiber density, and uniformity of nerve fiber direction affect anisotropy values of the various structures. Characterization of various central nervous system structures with diffusion anisotropy is possible and may be useful to monitor degenerative diseases in the central nervous system.     

The thalamus in the motor system.

The ventrolateral (VL) and anterior (VA) are the main thalamic relay for cerebellar and pallidal efferents going to the motor cortex. Four aspects of the function of these nuclei are briefly considered. (1) It is well known that these thalamic structures are not a simple relay on the way to the motor cortex, but that they have a gating function for the cerebellar afferents. The gating mechanism is active during slow-wave sleep, with deafferentation and with the use of various anesthetics. Possibly, it might play a role in the central organization of movement. (2) The organization at the unitary level of the projections between VL and motor cortex is examined and their role in the command of motor synergies through the motor cortex is strongly suggested. (3). It appears that unitary activity of VL neurons is not only related to movement but also to postural changes associated with movement. (4) The sensory input to VL nucleus is briefly analyzed. The inefficacy of exteroceptive stimulation in awake animals, in contrast with the effect of the same stimulation in anesthetized preparations, is discussed.     

The amygdala of the cat: A golgi study

Summary The amygdaloid complex in the cat was studied in a series of Golgi preparations. Both the lateral and the basal nucleus are composed of the same two cell types, one of which (type P) resembles the pyramidal and the other (type S) the stellate neuron of the cortex. The cortical nucleus can be divided into three layers (I, II, and III–IV) which are made up of cells similar to those in the periamygdaloid cortex. In addition, there are sufficient differences in the organization of these layers to justify a subdivision of the cortical nucleus into lateral and medial parts. The dendrites of neurons in the medial part of the central nucleus, the medial nucleus and the anterior amygdaloid area undergo less branching and carry fewer spines than those of the type P cell. The neurons in the nucleus of the lateral olfactory tract are all of the pyramidal or modified pyramidal type. These findings are discussed in relation to those of previous investigators who employed the Nissl and Golgi methods.This investigation was supported by the Medical Research Council of Canada, Grant M.T. 870. The author wishes to thank Miss Elizabeth Korzeniowski for her technical assistance.     

Unit responses in area 5b of the suprasylvian gyrus to stimulation of the posterior lateral thalmamic nucleus

In response to stimulation of the posterior lateral nucleus in unanesthetized cats immobilized with D-tubocurarine an evoked potential consisting of three components with a latent period of 3–5 msec appeared in area 5b of the suprasylvian gyrus. All three components were reversed at about the same depth in the cortex (1500–1600 µ). Reversal of the potential shows that it is generated in that area by neurons evidently located in deeper layers of the cortex and is not conducted to it physically from other regions. Responses of 53 spontaneously active neurons in the same area of the cortex to stimulation of the posterior lateral nucleus were investigated. A characteristic feature of these reponses was that inhibition occurred nearly all of them. In 22 neurons the responses began with inhibition, which lasted from 30 to 400 msec. In 30 neurons inhibition appeared immediately after excitation while one neuron responded by excitation alone. The latent periods of the excitatory responses varied from 3 to 28 msec. The short latent period of the evoked potentials and of some single units responses (3–6 msec) confirms morphological evidence of direct connections between the posterior lateral nucleus and area 5b of the suprasylvian gyrus. Repetitive stimulation of that nucleus led to strengthening of both excitation and inhibition. Influences of the posterior lateral nucleus were opposite to those of the specific nuclei: the posterior ventrolateral nucleus and the lateral and medial geniculate bodies. Stimulation of the nonspecific reticular nucleus, however, evoked discharges from neurons like those produced by stimulation of the posterior lateral nucleus.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 5, No. 5, pp. 502–509, September–October, 1973.