Branching-pattern analysis of the dendritic arborization in the thalamic nuclei of the rat brain

We investigated the dendritic patterns of rapid Golgi-impregnated, highly similar multipolar neurons from two functionally different thalamic regions of the rat brain: two dorsal nuclei (the nucleus laterodorsalis thalami, pars dorsomedialis and the nucleus laterodorsalis thalami, pars ventrolateralis), and two ventral nuclei (the nucleus ventrolateralis thalami and the nucleus ventromedialis thalami). The analysis involved conventional morphometric parameters (height and size) and a new parameter derived from graph theory, the relative imbalance (RI), derived from the branching patterns of the dendrites, which permits quantitative characterization of the dendritic arborization of a neuron. On this basis, neurons can be grouped into three fundamentally different types: type A, or highly-polarized (imbalanced) neurons (RI values close to 1); type B, or medium-polarized neurons (RI values around 0.5); and type C, or balanced neurons with low polarization (RI values close to 0). The orientations of the dendritic arbor, and thus the receptive fields, of the dorsal and ventral thalamic neurons, were mutually perpendicular. The H and S values indicated that the neurons in the dorsal and ventral thalamic nuclei differed significantly. However, their RI values demonstrated that they were similar neurons of type B. Our data reveal that 1 ) the dendritic arbor cannot be reliably characterized purely on the basis of height and size, and 2) RI is a valuable morphometric parameter that identifies the true nature of the dendritic arborization.     

GABA-immunohistological observations, at the electron-microscopical level, of the neurons of isthmic nuclei in chicken, Gallus domesticus

Following a demonstration of Golgi-impregnated neurons and their terminal axon arborization in the optic tectum, the neurons of the nucleus parvocellularis and magnocellularis isthmi were studied by means of postembedded electron-microscopical (EM) γ-aminobutyric acid (GABA)-immunogold staining. In the parvocellular nucleus, none of the neuronal cell bodies or dendrites displayed GABA-like immunoreactivity in EM preparations stained by postembedded GABA-immunogold. However, numerous GABA-like immunoreactive and also unlabeled terminals established synapses with GABA-negative neurons. GABA-like immunoreactive terminals were usually found at the dendritic origin. Around the dendritic profiles, isolated synapses of both GABA-like immunoreactive and immunonegative terminals established glomerulus-like structures enclosed by glial processes. All giant and large neurons of the magnocellular nucleus of the isthmi displayed GABA-like immunoreactivity. Their cell surface was completely covered by GABA-like immunoreactive and unlabeled terminals that established synapses with the neurons. These neurons are thought to send axon collaterals to the parvocellular nucleus; their axons enter the tectum opticum. The morphological characteristics of neurons of both isthmic nuclei are like those of interneurons, because of their numerous axosomatic synapses with both asymmetrical and symmetrical features. These neurons are not located among their target neurons and exert their modulatory effect on optic transmission in the optic tectum at a distance.     

Convergence between projections from different thalamic nuclei to columns of the rat somatosensory cortex

Primuline fluorochrome retrograde transport technique was used to investigate sources of thalamocortical projections to a single rat somatosensory cortex column connected with the projection of the C₃ vibrissa. Labeled cells were identified in eight different thalamic nuclei: two specific, five nonspecific, and one association nucleus. Labeled neurons differed in the degree of stain accumulated as well as cell numbers and density of distribution from one nucleus to another, indicative of the different arborization patterns of their axons within the cortex. Highest numbers of heavily stained cells as well as highest density of distribution were observed in the ventral thalamic nucleus. The convergence seen between different thalamocortical inputs on to a single somatosensory cortex column explains the functional differences observed between neurons belonging to the same column and makes the formation of functionally distinct neuronal groupings appear possible on this structural basis.Neurocybernetics Research Institute, Rostov-on-Don. Translated from Neirofiziologiya, Vol. 21, No. 2, pp. 168–174, March–April, 1989.     

The intrinsic neuronal organisation of the nucleus of the basal optic root in the domestic chicken; a light and electron microscopic study using anterograde tracers and postembedding GABA-immunostaining

The intrinsic neuronal organisation in the nucleus of the basal optic root of chickens was investigated. The divergent connections with various areas and the functional complexity of the nucleus require a complex intrinsic structural arrangement. Therefore, an analysis of Golgi impregnated material, ultrastructure, GABA-immunocytochemistry and biotinylated dextran-amine anterograde tracer analysis of the nucleus was carried out. In the Golgi analysis, a characteristic dendritic ramification pattern of two types of putative projection neurons was observed. These neurons form dendritic nests with their overlapping dendritic terminal sections, that develop synaptic fields with the optic fibre terminals. These synaptic fields were confirmed by electron microscopy. GABA-immunopositive terminals synapse with distinct loci of the dendritic trees of projection neurons; they may therefore play an important role in the inhibitory-modulatory system of the nucleus of the basal optic root. The GABA-immunopositive terminals derive from small and/or elongated local circuit neurons which receive retinal afferents, and from myelinated fibres afferents to the nucleus of unknown origin.     

Effects of lingual nerve section on morphometric characteristics of reticular nucleus neurons in the kitten brain stem

Computerized morphometric techniques were used to investigate each of 23 parameters in three types of brain stem reticular nucleus neurons in Golgi-stained frontal slices from the brain of 30-day-old kittens after uni- and bilateral lingual nerve section 5–7 days after birth. Particular statistically significant differences in some parameters were discovered in all types of cell. Certain group-specific differences in parameters could be most frequently distinguished in each category: distribution of loose dendritic endings through the dendritic area in reticular neurons, length of dendritic segments in branching cells, and distribution of foci of dendritic arborization in giant multipolar neurons. Unilateral lingual nerve section results in quantitatively more marked deviation from the normal state. It was only under these circumstances, moreover, that differences in overall length of dendrites could be seen, which could indicate a difference in the surface area of the cell.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 23, No. 4, pp. 409–418, July–August, 1991.     

Neuronal differentiation in the thalamic area triangularis of a lizard

Development of neurons in the area triangularis of Gallotia galloti was investigated in Golgi-impregnated brain tissue. Four major neuronal types present in adults were found to originate from two migratory neuroblast types, which were followed from embryonic stage S.32. One type has a thick main medial process, whereas the second type has a long main lateral process. As they migrate toward the periphery of the nucleus, morphological characteristics of maturation appear, including growth cones, filopodia, and outgrowth of axons. Neuroblasts with a main lateral process differentiate into two immature neuronal types, bipolars and pyramidals, observed at S.33 and thereafter. The neuroblasts with a main medial process undergo some somatic translocation through a transitory tangential shaft. Then they develop into monopolar immature forms with a long varicose medial, process, appearing from S.36. onward. Immature bipolar neurons do not experience great changes in their dendritic arborization during development to the adult stage, but pyramidals and monopolars undergo a rapid development of the dendritic tree after S.36. By S.38 archetypes of adult neuronal forms are established. Hairlike appendages first appear on neurons at S.36 They decrease suddenly in S.38 and then proliferate in S.39 when spines first appear. Around the time of hatching, the hairlike appendages begin to disappear and spines become established. Reduction of spines occurs after hatching and continues to the adult stage. Possible influences of several external factors on neuronal maturation are discussed.     

Types of thalamo-cortical relay neurons in the anteroventral nucleus of the cat

Summary Neurons displaying a thalamo-cortical projection were marked by means of the retrograde transport of horseradish peroxidase (HRP), and the labeled elements were compared with neurons impregnated by the Golgi technique. Injections of HRP into the posterior area of the limbic cortex resulted in its uptake by various anterior thalamic nuclei, especially the anteroventral nucleus. HRP-positive cells are characterized by their position, dendritic orientation, and the shape and size of their somata. On the basis of the combined HRP- and Golgi-analysis three different types of thalamo-cortical relay neurons can be distinguished.     

Intrinsic organization of the paramedian pontine reticular formation of the cat.

A morphoquantitative analysis was carried out to clarify the cytoarchitectural organization of the paramedian pontine reticular formation (PPRF) which is considered to be an important site in the control of eye movements. The study was carried out on the cat, using the Golgi staining method. The topographic position and detailed structure of the neurons were demonstrated using morphoquantitative methods. On the basis of their neuronal arborization, fusiform neurons and two types of multipolar cells were identified. Fusiform neurons show dendrites which are given off from the two poles of the small- to medium-sized cell body. The arborization generally runs caudorostrally, ending inside the PPRF. These neurons are ubiquitous. Type 1 multipolar neurons, the most frequent elements of the neuronal population (60%), have a small- to large-sized cell body from which 2 or 3 primary spiny dendrites and the axon emerge. Their dendritic field is oval and generally oriented in the vertical plane. These neurons are scattered everywhere in the PPRF. Type 2 multipolar cells are large neurons endowed with numerous primary spiny dendrites constituting a wide round dendritic field and with a thick axon. They are located almost exclusively at the boundaries of the PPRF and preferentially in the caudal region. The characteristics of the neurons suggest that the fusiform cells may play an interneuronal role, while the multipolar neurons could have both a projective function and an important receptive role for the afferent fibers to the PPRF. The lack of homogeneity found among the multipolar neurons is in agreement with the variety of projective elements shown by functional investigations.(ABSTRACT TRUNCATED AT 250 WORDS)     

Morphological characteristics of different types of neurons in the ventrooralis anterior,ventrooralis internus,and ventrooralis posterior nuclei in the human thalamus

1. Golgi-Kopsch preparations of the oral ventral nuclei of human thalamus were analyzed in an attempt to classify the neuronal types. 2. Three types of neurons are described for the first time in humans. Type I neurons are large or medium in size and bear dendrites with protrusions, spines, and short hair-like appendages. Some have a radiate dendritic arbor and others have dendrites grouped in tufts. The dendritic trees of these neurons are dense. 3. Type II neurons are medium or small in size with less dense dendritic trees. These cells have somatic as well as dendritic appendages of different forms. 4. Relatively rare is a type of very small neurons, type III, with few and sparsely branching dendrites.     

Accessory oculomotor nuclei of man. II. The interstitial nucleus of Cajal: a Nissl and Golgi study.

The interstitial nucleus of Cajal (INC) is an important premotor centre related to the control of eye and head movements. The aim of the present research was to draw a detailed picture of the cytoarchitecture of the human INC, in particular taking into consideration the morphological features of the neurons and their functional implications. Within the neuronal population, two groups of cells were identified: one group (the most substantial) was made up of small and medium-sized neurons showing different soma shapes and both light and moderate basophilia. The second group consisted of a limited number (about 25%) of large cells dispersed throughout the whole INC, showing polygonal soma and intense basophilia. The hypothesis that these large cells represent a different cellular population inside the INC is advanced. On the basis of the dendritic emergence pattern, two types of cells were identified: multipolar and fusiform cells. The multipolar cells (59%) had small to large nerve cell bodies giving off 2-3 dendrites radiating in all directions. Dendrites and axons were often seen spreading outside the INC. The fusiform cells were small or medium sized and two dendrites emerged from the opposite poles of their elongated perikaryon. Their dendrites and axons always lay inside the INC. The fusiform cells were interpreted as neurons carrying out a mainly local integrative function, while the multipolar cells could also probably carry out an important projective role. The structural data reported are in agreement with the functional studies indicating the INC as both an integrative and a projective center.     

Pathological changes in dendrites of substantia nigra neurons in Parkinson's disease: a Golgi study.

Neurons of the substantia nigra show severe morphological changes in Parkinson's disease. Pathological alterations of cell bodies have been described, whereas those of neuronal processes have hardly been investigated. Golgi impregnation has been the chosen method for demonstrating neuronal processes and dendritic and somatic spines. We therefore used the Golgi-Braitenberg method to qualitatively and semi-quantitatively study the substantia nigra of eight patients with Parkinson's disease compared with eight control cases. Golgi impregnation of substantia nigra neurons was good in all control cases. In full agreement with the analysis of Braak and Braak (1986) three neuronal types within the substantia nigra were found. In cases of Parkinson's disease, severe pathological changes such as decrease of dendritic length, loss of dendritic spines and several types of dendritic varicosities were found only in the melanin-containing pars compacta neurons. Pars reticulata nerve cells were intact. These findings support the predominant role played by the dopaminergic efferent pathway in the degenerative process. The afferent pathway was not affected. This suggests that the substantia nigra lesion is primary in Parkinson's disease. Loss of neurons found in H & E sections corresponded to a lesser amount of impregnated pars compacta neurons in cases with Parkinson's disease when compared to controls. Evidences exist that the duration of the disease may be related to the extent of pathologically altered Golgi-impregnated pars compacta cells. The amount of Lewy bodies in H & E sections corresponded to the quantity of round varicosities in impregnated pars compacta neurons. These round dendritic varicosities were considered to be Lewy body inclusions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Neuronal responses evoked in the bulbar respiratory center by stimulation of the anterior ventral and mediodorsal thalamic nuclei

The effects of rhythmical low- and high-frequency stimulation of specific nonsensory anterior ventral and associative mediodorsal thalamic nuclei (AV and MD, respectively) on the activity of neuronal units in the medullary ventral respiratory nucleus were studied in acute experiments on anesthetized, spontaneously breathing cats. Both inhibitory and excitatory influences on spike activity of inspiratory and expiratory neurons were found, with suppression effects being markedly predominant. Thresholds for inspiratory neuronal responses were lower as compared with those for expiratory cells. Electrical AV stimulation mainly produced an inhibitory effect on the activity of nonspecific reticular neurons (without respiratory activity), whereas during MD stimulation activating effects on these neurons dominated. Possible mechanisms underlying the realization of thalamorespiratory influences are discussed.Neirofiziologiya/Neurophysiology, Vol. 25, No. 3, pp. 218–223, May–June, 1993.     

The dorsomedial nuclear group of cranial nerves in the frog.

The dorsomedial motor nuclei were demonstrated by the cobalt-labeling technique applied to the so-called somatic motor cranial nerves. The motoneurons constituting these nuclei are oval-shaped and smaller than the motoneurons in the ventrolateral motor nuclei. They give rise to ventral and dorsal dendrite groups which have extensive arborization areas. A dorsolateral cell group in the rostral three quarters of the oculomotorius nucleus innervates ipsilateral eye muscles (m.obl.inf., m.rect.inf., m.rect.med.) and a ventromedial cell group innervates the contralateral m. rectus superior. Ipsilateral axons originate from ventral dendrites, contralateral axons emerge from the medial aspect of cell bodies, or from dorsal dendrites, and form a "knee" as they turn around the nucleus on their way to join the ipsilateral axons. A few labeled small cells found dorsal and lateral to the main nucleus in the central gray matter are regarded as representing the nucleus of Edinger-Westphal. The trochlearis nucleus is continuous with the ventromedial cell group of the oculomotorius nucleus. The axons originate in dorsal dendrites, run dorsally along the border of the gray matter and pierce the velum medullare on the contralateral side. A compact dendritic bundle of oculomotorius neurons traverse the nucleus, and side branches appear to be in close apposition to the trochlearis neurons. A dorsomedial and a ventrolateral cell group becomes labeled via the abducens nerve. The former supplies the m. rectus lateralis, while the latter corresponds to the accessorius abducens nucleus which innervates the mm. rectractores. Neurons in this latter nucleus are large and multipolar, resembling the neurons in the ventrolateral motor nuclei. Their axons originate from dorsal dendrites and form a "knee" around the dorsomedial aspect of the abducens nucleus. Cobalt applied to the hypoglossus nerve reaches a dorsomedial cell group (the nucleus proper), spinal motoneurons and sympathetic preganglionic neurons. Of the dorsomedial motor cells, the hypoglossus neurons are the largest, and a branch of their ventral dendrites terminates on the contralateral side. Some functional and developmental biological aspects of the morphological findings, such as the crossing axons and the peculiar morphology of the accessory abducens nucleus, are discussed.     

Frizzled-5 Receptor Is Involved in Neuronal Polarity and Morphogenesis of Hippocampal Neurons

The Wnt signaling pathway plays important roles during different stages of neuronal development, including neuronal polarization and dendritic and axonal outgrowth. However, little is known about the identity of the Frizzled receptors mediating these processes. In the present study, we investigated the role of Frizzled-5 (Fzd5) on neuronal development in cultured Sprague-Dawley rat hippocampal neurons. We found that Fzd5 is expressed early in cultured neurons on actin-rich structures localized at minor neurites and axonal growth cones. At 4 DIV, Fzd5 polarizes towards the axon, where its expression is detected mainly at the peripheral zone of axonal growth cones, with no obvious staining at dendrites; suggesting a role of Fzd5 in neuronal polarization. Overexpression of Fzd5 during the acquisition of neuronal polarity induces mislocalization of the receptor and a loss of polarized axonal markers. Fzd5 knock-down leads to loss of axonal proteins, suggesting an impaired neuronal polarity. In contrast, overexpression of Fzd5 in neurons that are already polarized did not alter polarity, but decreased the total length of axons and increased total dendrite length and arborization. Fzd5 activated JNK in HEK293 cells and the effects triggered by Fzd5 overexpression in neurons were partially prevented by inhibition of JNK, suggesting that a non-canonical Wnt signaling mechanism might be involved. Our results suggest that, Fzd5 has a role in the establishment of neuronal polarity, and in the morphogenesis of neuronal processes, in part through the activation of the non-canonical Wnt mechanism involving JNK.     

Morphology of neurons and axon terminals associated with descending and ascending pathways of the lateral forebrain bundle in Rana esculenta

Summary The cells of origin of afferent and efferent pathways of the lateral forebrain bundle were studied with the aid of the cobalt-filling technique. Ascending afferents originated from the lateral thalamic nucleus, central thalamic nucleus, posterior tuberculum and the cerebellar nucleus. They terminated in the anterior entopeduncular nucleus, amygdala and the striatum. Telencephalic projection neurons, which are related to the lateral forebrain bundle, were located mainly in the ventral striatum and the anterior entopeduncular nucleus, but were not so numerous in the dorsal striatum. Irrespective of their location, most of the neurons projecting axons into the lateral forebrain bundle had piriform or pyramidal perikarya. Long apical dendrites usually arborized in a narrow space, whereas widely arborizing secondary dendrites originated from short dendritic trunks. The other neurons that contributed to the lateral forebrain bundle were fusiform or multipolar cells. Striatal efferents terminated in the pretectal area and in the anterodorsal, anteroventral and posteroventral tegmental nuclei.     

Persistent larval sensory neurons in adult Drosophila melanogaster

Using a combination of lineage tracing and laser ablation, we have identified a segmentally repeated array of embryonically produced sensory neurons that persist through metamorphosis into adult stages of Drosophila development. The persistent sensory neurons are found in all unfused abdominal segments, but there is segment-specific variation in the number of neurons observed. There are 12 persistent neurons in the first abdominal segment (A1), 18 in the second (A2), and 16 in segments A3-A7. Most are internal sensory neurons (dendritic arborization neurons and bipolar dendrite neurons), but two are associated with external sensilla on the sternite. All of these neurons and their axons define specific adult sensory pathways in the periphery and their locations and persistence through metamorphosis suggest a role in guiding the growth of adult sensory and motor axons.     

Golgi-type I and Golgi-type II Neurons in the Ventral Anterior Thalamic Nucleus of the Adult Human: Morphological Features and Quantitative Analysis

The morphological and quantitative features of neurons in the adult human ventral anterior thalamic nucleus were studied in Golgi preparations. Two neuronal types were found and their quantitative features were studied. Golgi-type I neurons were medium to large cells with dense dendritic trees and dendritic protrusions and short hair-like appendages. They have somatic mean diameter of 30.8 μm (±9.4, n = 85). They have an average 100.3 dendritic branches, 48.97 dendritic branching points, and 58.85 dendritic tips. The mean diameters of their primary, secondary, and tertiary dendrites were 3.1 μm (±1, n = 80), 1.85 μm (±0.8, n = 145), and 1.5 μm (±0.4, n = 160), respectively. Golgi-type II neurons were small to medium cells with few sparsely branching dendrites and dendritic stalked appendages with or without terminal swellings. They have somatic mean diameters of 22.2 μm (±5.8, n = 120). They have an average 33.76 dendritic branches, 16.49 dendritic branching points, and 21.97 dendritic tips. The mean diameters of their primary, secondary, and tertiary dendrites were 1.6 μm (±0.86, n = 70), 1.15 μm (±0.55, n = 118), and 1 μm (±0.70, n = 95), respectively. These quantitative data may form the basis for further quantitative studies involving aging or some degenerative diseases that may affect cell bodies and/or dendritic trees of the Golgi-type I and/or Golgi-type II thalamic neurons.     

Synaptic interaction of serotonergic axons and corticotropin releasing factor (CRF) synthesizing neurons in the hypothalamic paraventricular nucleus of the rat. A light and electron microscopic immunocytochemical study

The morphological interrelationship between the central serotonergic and hypothalamic corticotropin-releasing factor (CRF) synthesizing systems was studied in the hypothalamic paraventricular nucleus (PVN) of colchicine pretreated male rats. The simultaneous immunocytochemical localization of the transmitter and peptide employed the peroxidase-antiperoxidase complex (PAP) technique using the silver-gold intensified (SGI) and non-intensified forms of the oxidized 3,3'-diaminobenzidine (DAB) chromogen. The paraventricular nucleus received a moderate serotonergic innervation as compared with other diencephalic structures. The distribution and arborization of serotonergic axons were more prominent in the parvocellular subnuclei than in the magnocellular units of the nucleus. Serotonin containing axons formed terminal bouton and en passant type synapses with dendrites and somata of parvocellular neurons. The immunocytochemical double labelling technique revealed the overlapping of serotonergic axons and CRF-immunoreactive neurons. Vibratome (40 micron) and semithin (1 micron) sections indicated that the interneuronal communication may take place on both dendrites and cell bodies of CRF-immunoreactive neurons. Ultrastructural analysis demonstrated that serotonin-containing terminals formed axo-dendritic and axo-somatic synapses with CRF-immunoreactive neurons. These findings indicate that the central serotonergic neuronal system can influence the function of the pituitary-adrenal endocrine axis via a direct action upon the hypophysiotrophic CRF synthesizing neurons.     

Dendritic structure in neurons of embryo amygdala grafts

Brain preparations stained by Golgi's technique in grafts of rat embryo basolateral amygdaloid nucleus were transplanted into the intact brain and the cavity produced by electrolytic destruction of the adult rat amygdala, revealing two types of neurons — sparsely and densely arborizing cells. It was found from comparing grafted with intact units that length and arborization of the cell had increased in sparsely arborizing cells after grafting, whereas the cell body had decreased in size and dendrites lengthened in densely arborizing units; neuronal arborization had also increased considerably. It was found from analyzing polar histograms of dendritic density distribution that neurites of transplanted neurons are selectively orientated depending on the area where the graft has united with the host brain. Altered neuronal geometry is assumed to be a factor determining the graft's ability to contribute to compensatory functions of the lesioned brain.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 22, No. 5, pp. 579–586, September–October, 1990.     

Ultrastructural features of the lateral preoptic area,median eminence and arcuate nucleus of the rat

Summary The arcuate nucleus, median eminence, and the lateral preoptic area from the brains of aldehyde-perfused male and female rats were examined by electron microscopy. In the lateral preoptic area, three neuronal types are described: a small light neuron, a larger light one, and a dark neuron resembling the larger light one in size and nuclear shape. Many myelinated axons are interposed among single neurons or neuronal pairs. The relationship of structures to each other is discussed. Several observations not previously reported are illustrated from tissue of the arcuate nucleus and median eminence.