bluuebunny/crossref_metadata_2025 huggingface dataset:
Organisation of subcortical pathways for sensory projections to the limbic cortex. II. Afferent projections to the thalamic lateral dorsal nucleus in the rat
Authors: Thompson Scott M. , Robertson Richard T.
Published: January 2005

Afferent projections to the thalamic lateral dorsal nucleus were examined in the rat by the use of retrograde axonal transport techniques. Small iontophoretic injections of horseradish peroxidase were placed at various locations within the lateral dorsal nucleus, and the location and morphology of cells of origin of afferent projections were identified by retrograde labeling.

For all cases examined, subcortical retrogradely labeled neurons were most prominant in the pretectal complex, the intermediate layers of the superior colliculus, and the ventral lateral geniculate nucleus. Labeled cells were also seen in the thalamic reticular nucleus and the zona incerta. Within the cerebral cortex, labeled cells were prominent in the retrosplenial areas (areas 29b, 29c, and 29d) and the presubiculum. Labeled cells were also seen in areas 17 and 18 of occipital cortex. Peroxidase injections in the dorsal lateral part of the lateral dorsal nucleus result in labeled neurons in all of the ipsilateral pretectal nuclei, but especially those that receive direct retinal afferents. Labeled cells were also seen in the ventral lateral geniculate nucleus and the rostral tip of laminae IV‐VI of the superior colliculus. In contrast, peroxidase injections in ventral medial portions of the lateral dorsal nucleus result in fewer labeled pretectal cells, and these labeled cells are found exclusively in the pretectal nuclei that do not receive retinal afferents. Other labeled cells following injections in the rostral and medial portions of the lateral dorsal nucleus are seen contralaterally in the medial pretectal region and nucleus of the posterior commissure, and bilaterally in the rostral tips of laminae IV and V of the superior colliculus. Camera lucida drawings of HRP labeled cells reveal that projecting cells in each pretectal nucleus have a characteristic soma size and dendritic branching pattern.

These results are discussed with regard to the type of sensory information that may reach the lateral dorsal nucleus and then be relayed on to the medial limbic cortex.
Frontal eye field as defined by intracortical microstimulation in squirrel monkeys, owl monkeys, and macaque monkeys II. cortical connections
Authors: Huerta Michael F. , Krubitzer Leah A. , Kaas Jon H.
Published: January 2005

Physiological (intracortical microstimulation) and anatomical (transport of horseradish peroxidase conjugated to wheat germ agglutinin as shown by tetramethyl benzidine) approaches were combined in the same animals to reveal the locations, extents, and cortical connections of the frontal eye fields (FEF) in squirrel, owl, and macaque monkeys. In some of the same owl and macaque monkeys, intracortical microstimulation was also used to evoke eye movements from dorsomedial frontal cortex (the supplementary motor area). In addition, in all of the owl and squirrel monkeys, intracortical microstimulation was also used to evoke body movements from the premotor and motor cortex situated between the central dimple and the FEF. These microstimulation data were directly compared to the distribution of anterogradely and retrogradely transported label resulting from injections of tracer into the FEF in each monkey. Since the injection sites were limited to the physiologically defined FEF, the demonstrated connections were solely those of the FEF. To aid in the interpretation of areal patterns of connections, the relatively smooth cortex of owl and squirrel monkeys was unfolded, flattened, and cut parallel to the flattened surface. Cortex of macaque monkeys, which has numerous deep sulci, was cut coronally.

Reciprocal connections with the ipsilateral frontal lobe were similar in all three species: dorsomedial cortex (supplementary motor area), cortex just rostral (periprincipal prefrontal cortex) to the FEF, and cortex just caudal (premotor cortex) to the FEF. In squirrel and owl monkeys, extensive reciprocal connections were made with cortex throughout the caudal half of the lateral fissure and, to a much lesser extent, cortex around the superior temporal sulcus. In macaque monkeys, only sparse connections were present with cortex of the lateral fissure, but extensive and dense connections were made with cortex throughout the caudal one‐third to one‐half of the superior temporal sulcus. In addition, very dense reciprocal connections were made with the cortex of the lateral, or inferior, bank of the intraparietal sulcus. Contralateral reciprocal connections in all three species were virtually limited to regions that correspond in location to the FEF and the supplementary motor area.

The results of this study reveal connections between the physiologically defined frontal eye field and cortical regions known to participate in higher order visual processing, short‐term memory, multimodal, visuomotor, and skeletomotor functions. Some of the demonstrated pathways may contribute to functional interactions between oculomotor and skeletomotor systems, perhaps facilitating the planning and coordination of related eye, head, and hand movements.
Morphological features of layer V pyramidal neurons in the cat parietal cortex: An intracellular HRP study
Authors: Yamamoto Tetsuro , Samejima Akio , Oka Hiroshi
Published: January 2005

Layer V pyramidal neurons in the cat parietal cortex (areas 5 and 7) were investigated with intracellular HRP staining. Antidromic responses were recorded intracellularly as well as extracellularly with pontine stimulation under Nembutal anesthesia. The relationship between the latency of antidromic responses and the morphology of HRP‐stained neurons was analyzed. A total of 65 neurons were stained with HRP, and sixteen of these neurons were activated antidromically with pontine stimulation.

Two distinct groups of layer V pyramidal neurons were detected morphologically by intracellular HRP staining; i.e., one (F type) consisted of neurons with relatively large somata (58.4±8.1 μm × 24.5±5.1 μm, N = 11) and aspiny or sparsely spinous apical dendrites, and the other (S type) consisted of neurons with smaller somata (44.6±7.6 μm × 19.3±3.9 μm, N = 22) and richly spinous apical dendrites. These two groups showed different electrophysiological properties; i.e., the former responded antidromically to pontine stimulation at a latency shorter than 1.5 ms (namely, with a conduction velocity faster than 18 m/second) and the latter responded at a latency longer than 1.5 ms.

The two neuronal types in the parietal cortex corresponded respectively to fast and slow pyramidal tract neurons (PTNs) investigated in the sensorimotor cortex. Although their morphological features were almost similar to those of PTNs, the branching pattern of apical dendrites of the F‐type pyramidal neuron seemed to be different from that of fast PTNs. In the parietal cortex, apical dendrites of F‐type neurons showed rather frequent branching in layer I. This was simialr to the pattern of branching in slow PTNs. Such a characteristic branching pattern suggested that, in the cat parietal cortex, layer V pyramidal neurons of both types are adapted to receive cerebellar inputs through the ventroanterior (VA) thalamic nucleus to the superficial cortical layers.
Golgi study of the primate substantia nigra. II. Spatial organization of dendritic arborizations in relation to the cytoarchitectonic boundaries and to the striatonigral bundle
Authors: François Chantal , Yelnik Jerome , Percheron Gerard
Published: January 2005

The spatial organization of Golgi‐stained dendritic arborizations of the substantia nigra was studied in three dimensions by using a video computer system. Dendritic orientation was analyzed in relation to the cytoarchitectonic boundaries and to the direction of the axons of the striato‐pallidonigral bundle. All the brains, humans and macaques, were sectioned according to the same ventricular planes. The striatal bundle is made up of dense fascicles of very thin parallel axons. Sixty neurons located in the pars reticulata, lateralis, and compacta were reconstructed from serial sections. In the anterior pars reticulata and lateralis, the dendritic arborizations spread in all directions inside the striatal bundle. Below the pars compacta fringes, the dendrites of pars reticulata neurons extend ventrolaterally in the bundle. Because one nigral arborization can cover the whole thickness of the striatal bundle, we are led to believe that nigral neurons exert a role of convergence of the corticostriatal information similar to that of pallidal neurons (Percheron et al., '84a,b). The pars reticulata neurons appear to receive information mainly from the associative striatal territory. The pars lateralis neurons, conversely, appear to receive information from the sensorimotor territory. The anterior pars compacta neurons are organized in such a way that their ventral dendrites, located inside the pars reticulata, are ventrolaterally oriented, perpendicular to the striatal bundle. Their dorsal dendrites remaining in the pars compacta can receive other input. At more caudal levels, the posterior pars compacta neurons have dendrites radiating outside the striatal bundle.
Distribution of afferent fibers in the brainstem from end organs in the ear and lateral line in the european eel
Authors: Meredith G. E. , Roberts B. L. , Maslam Suharti
Published: January 2005

Sensory nerve fibers from the lateral line system and labyrinth of Anguilla anguilla were labeled with horseradish peroxidase and traced to various targets in the ipsilateral brainstem.

The three rami of the anterior lateral line nerve and the supratemporal ramus of the posterior lateral line nerve form overlapping terminal zones in the ventral portion of nucleus medialis. The posterior lateral line nerve on the body is represented exclusively in the dorsal half of the nucleus medialis. Eighth nerve fibers from the otolithic end organs in the inner ear send fibers into dorsal portions of three octavus nuclei: anterior, magnocellular, and descending, and saccular fibers lie most medial and utricular fibers most lateral. Fibers from vestibular organs, especially the semicircular canals and utricle, end densely in ventral portions of these nuclei and in the tangential nucleus. All labyrinthine sense organs send fibers into the region of a Mauthner‐like neuron, and all except the saccule terminate in the reticular formation, tangential nucleus, and eminentia granularis of the cerebellum. Primary sensory input to the octavolateralis efferent nucleus comes only from the labyrinth, and fibers from the saccule alone penetrate the region of efferent neuronal somata. Fibers from labyrinthine end organs except the saccule project to the reticular formation where they may contact the dendrites of efferent somata. Fibers from the lateral line and the eighth nerve overlap most extensively at the rostral pole of the nucleus medialis and in the eminentia granularis of the cerebellum.
Immunocytochemical analysis of the dopamine system in the forebrain and midbrain of Raja radiata: Evidence for a substantia nigra and ventral tegmental area in cartilaginous fish
Authors: Meredith Gloria E. , Smeets Wilhelmus J. A. J.
Published: January 2005

The distribution of dopamine‐containing cell somata and fibers in the forebrain and midbrain of a cartilaginous fish, Raja radiata, was investigated by means of antibodies directed against dopamine. Many small dopamine immunoreactive neurons are distributed throughout the telencephalon, including the olfactory bulbs. Within the diencephalon and particularly in the hypothalamus, i.e., in the nucleus preopticus, nucleus suprachiasmaticus, the paraventricular organ, lateral hypothalamic area, recessus mamillaris, and nucleus tuberculi posterioris, numerous cell somata stain for dopamine. In the mesencephalon, two distinct cell masses are found, which on the basis of their immunoreactivity for dopamine and their location, may be homologous to the substantia nigra and ventral tegmental area of other vertebrates, Dopamine immunoreactive fibers are found in the glomeruli of the olfactory bulbs, in ventral portions of the telencephalon, where a dense dopaminergic plexus innervates the area superficialis basalis and striatum, and in the diencephalon, where the inferior lobe is the most densely innervated structure. In the mesencephalon, the dopamine immunoreactive fibers are confined predominantly to the periventricular zone and lateral portions of the tectum.

We conclude that much of the dopaminergic system in Raja radiata is strikingly similar to that seen in amniotes.
Effect of different optic nerve lesions on retinal ganglion cell death in the frog Rana pipiens
Authors: Humphrey Martin F.
Published: January 2005

Following optic nerve crush in various species of frog, a proportion of the retinal ganglion cells re‐establishes functional contact with the optic tectum. However, as much as 50% of the retinal ganglion cells die during this process. The determinants of an individual ganglion cell's fate have not been established. In this study of Rana pipiens, cell survival after optic nerve crush was compared with that after nerve cut followed by stump separation, a procedure that considerably delayed entry of optic axons to the brain. It was also ascertained, in the case of delayed ingrowth, whether application of nerve growth factor immediately after lesion influenced the cell death process.

This study confirmed that retinal ganglion cell death is a relatively late event in regeneration, because in several animals‐where anterograde HRP labeling demonstrated regenerating axons within the tectum, no cell death had occurred. There was no statistically significant difference in cell death at 75 days after lesion between animals receiving nerve crush and those receiving nerve cut with stump separation, even though most crush animals had regenerated a complete visual projection, whereas most nerve cut animals had not. The application of NGF did not influence the level of cell death at 75 days after lesion.

These results suggest that contact of optic axons with the optic tract or tectum is not necessary for retinal ganglion cell death to occur. However, this does not necessarily mean that contact with the brain is not involved with cell death during regeneration following nerve crush because it is possible that the mechanisms of cell death are different when axons are prevented from regenerating. Further investigations are therefore required to establish the reasons for this cell death.
Spinocerebellar projections from the central cervical nucleus in the cat, as studied by anterograde transport of wheat germ agglutinin‐horseradish peroxidase
Authors: Matsushita Matsuo , Tanami Toshio
Published: January 2005

The projection of the Spinocerebellar, tract arising from the central cervical nucleus with crossed ascending axons was studied by the anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP) in the cat.

Following injections of WGA‐HRP into the C1 to the C4 or C5 segments, labeled terminals were seen in lobules I–VI, sublobule VIIb, lobules VIII and IX, the paramedian lobule, crus I and crus II, and the simple lobule. About 67–80% of the total number of labeled terminals were in the anterior lobe and 20–33% in the posterior lobe; the labeled terminals were abundant in lobules I (11–20%), II (11–28%), III (5.7–9.6%), IV (8.6–15.4%), and VIH (9–12%). The labeled terminals were densely distributed in the basal half or basal two‐thirds of sublobules IIa‐Va and VIf–VIb in their apicobasal extent and the transitional areas between neighboring sublobules. In sublobules Ia, Ib, and Vg they were distributed over the entire sublobule. The labeled terminals were most abundant within 0.5 mm of the midline (30–55% of the total number in each sublobule). Results in cases with injections into the C2–C4 segments, preceded by hemisection between the C1 and C2 segments, revealed that the projections were bilateral but predominantly contralateral to the cells of origin; the proportion of the quantity of the contralateral projection to that of the ipsilateral was about 60:40% in sublobules Ia–Vb and sublobules Ve–Vg.

The projection field in the horizontal plane of the lobule was reconstructed from a series of cross sections through each sublobule. The labeled terminals were distributed in three major longitudinal areas named areas 1, 2, and 3, respectively. These areas were confined in the basal half to two‐thirds of lobules III–V: area 1 located in zone A1 of Voogd (within 0.25 mm of the midline); area 2 located in zones A1 to A2 (at around 0.5 mm lateral to the midline); and area 3 located in the lateral part of zone A2 to zone B (between 0.75 mm and 1.5 mm lateral to the midline in lobule III, and between 1.0 mm and 2.0 mm lateral to the midline in lobules IV–VI). An indefinite area 4 appeared in zones B and C of some lobules. In sublobules Ia, Ib, Vf, and Vg the three areas extended throughout the apicobasal length.

The present study demonstrates that the central cervical nucleus projects bilaterally to the anterior lobe, sublobules VIf‐VIc, lobule VIIb, lobules VIII and IX, the paramedian lobule, crus I and crus II, and the simple lobule. The projections were localized to three major longitudinal areas in the vermis of the anterior lobe and lobule VI of the posterior lobe.
Banding of lateral superior olivary nucleus afferents in the inferior colliculus: A possible substrate for sensory integration
Authors: Shneiderman Amiram , Henkel Craig K.
Published: January 2005

In this study the organization of the projection from the lateral superior olivary nucleus (LSO) to the inferior colliculus was investigated in the cat by using anterograde tract‐tracing techniques. The findings indicated that LSO projected bilaterally to the central nucleus of the inferior colliculus as well as to the ventrolateral and rostral pole nuclei. In the central nucleus a larger medial component of the projection ended in pars medialis and centralis. A smaller lateral component ended in the region of the pars lateralis. Both components of the projection appeared to be topographically organized, but in the lateral component the low‐frequency part of LSO appeared to have greater representation.

The uncrossed and crossed LSO projections to the inferior colliculus exhibited several important differences in their distribution. First, periodic bands of dense labeling were more prominent in the distribution of the uncrossed projection. The bands measured 150–200 μ in thickness and in some cases interruptions or gaps were present along the length of the bands. The distribution of the crossed projection was more diffuse, but some banding was also apparent. Second, the positions of the bands of dense labeling on the two sides were not homotopic as determined by labeling projections from the ipsilateral and contralateral LSO in the same tissue. The dense bands labeled with WGA‐HRP from an injection in LSO on one side and bands labeled with 3H‐leucine from an injection in LSO on the other side either were interdigitating or were only partially overlapping. Finally, the area over which the uncrossed projection distributed endings varied in size with respect to that of the crossed projection. The variation in size of the area of the projections was a function of the frequency representation. A model based on the three‐dimensional reconstruction of bands as projection sheets is proposed as a substrate for selective integration of afferents in the inferior colliculus.
Spinomesencephalic tract: Projections from the lumbosacral spinal cord of the rat, cat, and monkey
Authors: Yezierski Robert P.
Published: January 2005

Anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase was used to determine the terminal domain of the projection from the lumbosacral spinal cord to the midbrain in the rat, cat, and monkey. Results have shown that several midbrain regions receiving afferent input from this level of the spinal cord are common to the three species examined. Structures innervated by this projection were located throughout the full rostrocaudal extent of the midbrain. The strongest projections were to the intercollicular region and caudal midbrain contralateral to injection sites in the spinal cord. Terminal labeling in the rostral midbrain, except that observed in the nucleus of Darkschewitsch, was substantially less than that observed at more caudal midbrain levels. Structures receiving the strongest input from the spinal cord included the central gray, nucleus cuneiformis, the deep and intermediate layers of the superior colliculus, and the intercollicular nucleus. Other structures receiving afferent input from the lumbosacral spinal cord included the anterior and posterior pretectal nuclei, red nucleus, Edinger‐Westphal nucleus, interstitial nucleus of Cajal, and the mesencephalic reticular formation. It is concluded that the spinal projection to the midbrain is a multicomponent projection consisting of several pathways terminating in discrete midbrain regions. Considering the diverse functions associated with midbrain regions receiving spinal input and the response and receptive field properties of cells belonging to this pathway, the results of the present study are discussed in relation to the potential role of the spinomesencephalic tract in somatic, visceral, and motor function.
Synaptic organization of cholinergic amacrine cells in the rhesus monkey retina
Authors: Mariani Andrew P. , Hersh Louis B.
Published: January 2005

In the rhesus monkey retina, choline acetyltransferase (ChAT) immunoreactivity has been used to study the localization and synaptic organization of cholinergic neurons by both light and electron microscopy with peroxidase‐antiperoxidase immunohistochemistry. ChAT‐containing neurons are a type of amacrine cell with 97.5% of their cell bodies localized to the ganglion cell layer and the remainder in the inner nuclear layer. Their processes arborize in a single narrow band in the inner plexiform layer in a plane diving the outer two‐thirds from the inner one‐third of this synaptic region. With electron microscopy, ChAT‐immunoreactive amacrine cell processes were observed to be primarily postsynaptic to the diffuse invaginating cone bipolar cells and presynaptic to ganglion cells, although they are both post‐ and presynaptic to immunohistochemically unlabeled amacrine cell profiles and to ChAT‐containing amacrine cell processes as well.
Monoclonal antibodies react with neuronal subpopulations in the human nervous system
Authors: Hinton David R. , Henderson Victor W. , Blanks Janet C. , Rudnicka Maria , Miller Carol A.
Published: January 2005

Monoclonal antibody probes were used to identify antigenic cross reactivities among neuronal subpopulations and to dissect the human nervous system at several levels of organization. Six monoclonal antibodies, prepared with immunogens from Drosophila melanogaster or human nervous tissue, were used to localize antigens immunocytochemically in normal adult human neocortex, hippocampus, cerebellum, spinal cord, and retina. Four of the six antibodies were neural specific in their reactivity and each stained a unique combination of neurons. The antibodies reacted with at least three subpopulations of cerebral cortical neurons, including discrete populations of pyramidal and nonpyramidal cells. Components of a widely distributed functional system within the spinal cord and cerebellum were labelled by one antibody, which reacted with neurons in the nucleus dorsalis of Clarke, deep cerebellar nuclei, and Purkinje cells. At the single‐cell level, three of the monoclonals differentially labelled the photoreceptor cell outer segment, inner segment, and perikaryon. Three of the six antibodies were reactive with specific protein bands, on immunoblots of tissue homogenates. This monoclonal antibody panel provides a novel and potentially useful method of analysis of the organization of the normal and diseased human nervous system.
Distribution and Morphological Characteristics of Dopamine‐Immunoreactive Neurons in the Midbrain of the Squirrel Monkey (Saimiri sciureus)
Authors: Arsenault M.‐Y. , Parent A. , Séguéla P. , Descarries L.
Published: January 2005

The distribution and morphological characteristics of dopamine (DA) neurons in the midbrain of the squirrel monkey (Saimiri sciureus) were investigated by peroxidase‐antiperoxidase (PAP) immunohistochemistry with a highly specific antiserum raised against DA‐glutaraldehyde‐lysyl‐protein conjugate (donated by M. Geffard). Four contiguous areas contained DA‐immunostained nerve cell bodies: (1) the substantia nigra, pars compacta (SNc), (2) the ventral tegmental area (VTA), (3) the retrorubral area (RRA), and (4) the periaqueductal gray (PAG). The SNc composed the vast majority of DA‐immunostained neurons. Most of these neurons were relatively large (mean diameters: 35 × 15 μm) and varied in shape from fusiform to polygonal, but a few smaller (16 × 10.5 μm) globular cells were dispersed among them. The caudal two‐thirds of the SNc was particularly rich in DA somata. Rostrally, these DA cells formed several distinct columns impinging deeply upon the underlying pars reticulata. Large oval sectors mostly devoid of immunoreactivity were delineated by these trabeculae. The long dendritic processes of DA neurons in the SNc were generally oriented in prominent dorsoventral bundles the ventralmost portion of which arborized diffusely along the dorsal surface of the cerebral peduncle. In the VTA, the DA neurons were regrouped in a triangular zone located dorsal to the interpeduncular nucleus, medial to the substantia nigra and ventral to the oculomotor nucleus. These DA cells were of medium size (19 × 10.5 μm), globular or fusiform, and usually showed one or two thick primary dendrites oriented dorsoventrally. The DA cells in the RRA lay in continuity with the most caudal DA‐containing elements of the substantia nigra but could be distinguished by their smaller size (26 × 12 μm), shorter and more profusely branched dendrites, and darker immunostaining. These DA neurons were characteristically scattered among and medial to the fibers of the medial lemniscus, and a few could be observed as far caudally as the pedunculopontine nucleus. In the PAG, DA‐immunostained neurons were seen in the rostral half of the mesencephalic central gray and predominated in its ventral half. These cells were of medium size (22.5 × 10 μm) and some of them were found in proximity to the ventricular lining. At caudal levels, the DA‐positive cells in the PAG did not intermingle with dorsal raphe neurons. Complementary electron microscopic observations of the medial portion of the SNc revealed that (1) the DA‐immunoreactive somata were endowed with spiny dendrites synaptically contacted by numerous immunonegative axon terminals; (2) immunostained axons in this region were myelinated; and (3) axonal varicosities or terminal boutons did not exhibit detectable DA immunoreactivity in the SNc sector examined. These data provide a basis for future hodological and functional studies of the organization of the DA‐ containing neuronal systems in primates.
Topologic and connectional analysis of the dorsal thalamus of Triturus alpestris (Amphibia, Urodela, Salamandridae)
Authors: Wicht Helmut , Himstedt Werner
Published: January 2005

A morphological and connectional analysis was performed on the dorsal thalamus of the alpine newt, Triturus alpestris. We have used a graphic reconstruction technique for the evaluation of the connectional (HRP) data. On the basis of these reconstructions, we propose a subdivision of the salamandrid dorsal thalamus into subhabenular, anteroventral, and posterodorsal zones. Each of these zones is defined by its telencephalic projections (“ascending thalamofugal systems”). The posterodorsal zone projects to the striatum, the anteroventral zone to the pallium. The subhabenular zone projects to the subpallial telencephalon and to the tegmentum. This zonal subdivision allows a more detailed comparison of the salamandrid dorsal thalamic features with ranid dorsal thalamic structures. We compare our dorsal thalamic zones to the ones proposed by Herrick (J. Comp. Neurol. 62:239–261, '35, The Brain of the Tiger Salamander. Chicago: The University of Chicago Press, ′48). Furthermore, using the same reconstructive technique, we undertook an analysis of the spatial relations of various inputs to the salamandrid dorsal thalamus (“thalamopetal systems”) Besides the well‐known retinal inputs, we identified the tectum and the tegmentum as sources of inputs to the thalamus. We provide evidence that there is no extensive multi‐ or unimodal overlap of these thalamopetal systems.
Developmental changes in density and distribution of serotoninergic fibers in the chick spinal cord
Authors: Kojima Tokuzo , Homma Shunsaku , Sako Hiroko , Shimizu Iwao , Okada Akira , Okado Nobuo
Published: January 2005

Developmental changes of serotoninergic innervation in the chick spinal cord (third lumbosacral segment) were examined with an immunohistochemical technique using an antiserum to serotonin.

In the 1‐day‐old hatched chick, serotoninergic fibers were located in laminae I, II, VII, IX, and X. A large number of serotonin‐positive fibers and terminals were found around somal profiles of large neurons and in the neuropil of the medial and lateral parts of the lateral motor column (LMC).

In the 1‐week‐old chick, the density of serotoninergic fibers was greatly increased in the posterior columns, and serotoninergic fibers were most densely aggregated in the dorsolateral part of the LMC.

In the 2‐week‐old chick, a considerable decrease in the density of serotoninergic fibers was observed in the lateral funiculus and the gray matter (laminae I, II, VII, IX, and X). In the LMC, serotonin‐positive fibers and terminals were largely absent from the neuropil, but were found preferentially around the somal profiles of large neurons. Between 1 and 2 weeks after hatching the density of varicosities and terminals in the neuropil of the dorsolateral and medial parts of the LMC decreased by 33% and 56%, respectively.

In the 3‐month‐old chick, the density of serotoninergic fibers in laminae I, II, V, VII, and X had increased compared to younger ages. Serotonin‐positive fibers were not evenly distributed in the LMC of the adult chicken; rather, they were densely aggregated around the soma and proximal dendrites of motoneurons in the dorsolateral LMC. Many neuronal soma in the medial and intermediate regions of the LMC lacked serotoninergic fibers.
Immunohistochemical study of glutaminase‐containing neurons in the cerebral cortex and thalamus of the rat
Authors: Kaneko Takeshi , Mizuno Noboru
Published: January 2005

In an attempt to identify glutamatergic neurons, the cerebral cortex and thalamus of the rat were examined immunohistochemically by using a monoclonal antibody against phosphate‐activated glutaminase (PAG), a major synthetic enzyme of transmitter glutamate in the central nervous system. In both the neocortex and mesocortex, pyramidal cells in layers V and VI showed intense PAG‐like immunoreactivity (PAG‐LI), whereas neuronal cell bodies in layers I–IV showed weak PAG‐LI. At the deep border of layer VI, neurons with horizontally elongated cell bodies showed PAG‐LI. In the pyriform and entorhinal cortices, neurons with intense to moderate PAG‐LI were seen in layer II as well as in the deeper layers. In the hippocampal formation, pyramidal cells in CA1, CA2, and CA3 and polymorphic cells in CA4 showed PAG‐LI; PAG‐LI was most intense in pyramidal cells of CA3. Fine granules with weak PAG‐LI were also seen on and/or within the cell bodies of granule cells in the dentate gyrus. In the thalamus, neurons with PAG‐LI were distributed in all nuclei, although regional differences were observed in the distribution pattern of neurons with PAG‐LI and in the intensity of PAG‐LI in individual neurons. The largest neurons in each thalamic nucleus showed intense PAG‐LI; these were considered to be projection neurons. In addition to perikaryal labeling, many fine, PAG‐like immunoreactive granules were distributed in the neuropil of both the cerebral cortex and thalamic nuclei. Some of these fine granules with PAG‐LI in the neuropil were assumed to represent fiber terminals with PAG‐LI, because the distribution pattern of the deposits in the primary somatosensory and primary visual cortices resembled that of thalamocortical fiber terminals.

Glutamate is rather ubiquitous in the mammalian central nervous system, and it is still debatable whether the monoclonal antibody to PAG from brain mitochondria can distinguish transmitter‐related glutaminase from the other metabolism‐related ones. In the present study, however, large neurons in the thalamic nuclei, as well as pyramidal neurons in the cerebral cortex, showed PAG‐LI most intensely, supporting the assumption that projection neurons of the cerebral cortex and thalamus are primarily glutamatergic.
Asymmetric distribution of retinal ganglion cells in goldfish
Authors: Mednick Adam S. , Springer Alan D.
Published: January 2005

The distribution of retinal ganglion cells (RGCs) in goldfish was determined by removing an eye and applying cobaltous‐lysine to the optic nerve for 24 hr. This procedure allowed the cobalt label to be in continuous contact with the cut ends of the optic axons and thereby backfilled many RGCs. RGC density was determined across three different sizes of retinae by using fish with different eye sizes.

Confirming earlier work, we found that RGC density diminished as retinal area increased. However, irrespective of the retinal size, the density of RGCs was elevated along the temporal boundary between the dorsal and the ventral retina. A conservative estimate indicated that the RGC density in the temporal retina was at least 1.8–2.5 times higher than the mean RGC density of the entire retina. Thus, the goldfish retina does not appear to have a homogeneous distribution of RGCs as was previously considered.

Small and large retinae differed with respect to the percentage of cells in the RGC layer that was RGCs. In small retinae, even when the noncobaltfilled cells (glia and displaced amacrine cells) were added to the cobalt‐filled RGCs, the density of all cell types was elevated in the temporal retina relative to the remainder of the retina. Furthermore, in small retinae, the percentage of cells in the RGC layer that was RGCs (75%) was constant across the radial and circumferential aspects of the retina. In marked contrast, in medium‐large retinae, a homogeneous distribution of cells across the entire retina resulted when the noncobalt‐filled cells were added to the cobalt‐filled cells. However, the percentage of cells that was cobalt‐filled RGCs was significantly greater in the temporal retina (50%) than in the remainder of the retina (35%). In large retinae, as in small retinae, the percentage of cells that was RGCs did not vary as a function of distance from the optic disc. These data suggest that, in the course of retinal maturation, cell density in the temporal retina is elevated initially and then declines subsequently to the level of the surrounding retina. Over time, more displaced amacrine cells may be added to the tissue surrounding the temporal retina. Alternatively, more RGCs outside the temporal retina may become displaced amacrine cells. Such events could account for the growth‐associated, disproportionate decrease in the percentage of cells that is RGCs in the tissue surrounding the temporal retina.

Cobalt‐filled RGCs had a mean somata area of 50 μm2 and ranged in size from 20 to 310 μm2. Temporal and nasal RGCs had the same mean soma areas. Estimates of the total number of RGCs suggested that the number of RGCs increased as the retinal area increased. This relationship was linear in small retinae (i.e., up to 15 mm2). However, progressive twofold increases in retinal area were only accompanied by 20% increases in the number of RGCs. Thus, additional factors, beyond RGC addition at the retinal margin, must account for the expansion of larger retinae.
Ultrastructural evidence that horizontal cell axon terminals are presynaptic in the human retina
Authors: Linberg Kenneth A. , Fisher Steven K.
Published: January 2005

The organization of the rod spherule and of the horizontal cell axon terminals within the invagination of the rod spherule in the human retina was examined in serial sections by electron microscopy. Twenty‐one rod spherules were reconstructed in this study. Axon terminal processes of type I horizontal cells consistently make one or two small punctate synapses onto each rod spherule within the invagination. In addition, these axon terminal processes make distinct synapses upon rod bipolar dendrites outside the spherule before both processes enter the invagination.

This is the first positive description of a synapse from a horizontal cell axon terminal process onto a photoreceptor terminal and the first identification of a synapse from a horizontal cell to a rod bipolar cell in the mammalian outer plexiform layer. We speculate that the axon terminal‐to‐rod synapse is responsible for feedback while the synapse upon the rod bipolar cell is feed‐forward and serves to expand the receptive field of the rod bipolar cell beyond its dendritic field. Alternatively, the latter may contribute to a center‐surround organization of the rod bipolar's receptive field.
Functionally distinct groups of X‐cells in the lateral geniculate nucleus of the cat
Authors: Humphrey Allen L. , Weller Rosalyn E.
Published: January 2005

The latencies and visual response properties of 202 X‐cells in the A‐laminae of the cat dorsal lateral geniculate nucleus (LGN) were examined to investigate the recent claim (Mastronarde, '85,'87a) that functionally different groups of X‐cells reside there. Two groups of X‐cells were found, which differed in their extracellularly recorded responses to spots of light flashed within their receptive fields. One group, constituting one‐third of the sample, responded to spot onset with a profound and often long‐lasting dip in discharge rate, such that cell discharge usually did not reach half maximum until ≥ 100 msec after spot onset. About 70% of these cells also displayed a transient discharge at spot offset. These cells correspond to Mastronarde's lagged X‐cells, and we similarly refer to them as XL‐cells. The second group, constituting the remainder of the X‐cell population, generally responded to spot onset with a short latency (≤ 60 msec) brisk discharge, no detectable XL‐type dip, and a rapid reduction in firing at spot offset. We refer to these neurons as nonlagged (XN) X‐cells; this group probably encompasses all of Mastronarde's non‐XL‐cells.

Despite some overlap, the XL‐ and XN‐cells differed in numerous other features. Compared to XN‐cells, XL‐cells exhibited: 1) lower peak rates of discharge and more uniform firing during spot onset; 2) slightly longer latencies and markedly lower probabilities of discharge to optic chiasm stimulation; 3) consistently lower geniculocortical conduction velocities; and 4) markedly lower optimal temporal frequencies when tested with drifting sine wave gratings. No differences were found between the two cell groups in optimal spatial frequency, spatial resolution, or receptive field center size, and there were equal proportions of on‐ and off‐center types of XL‐ and XN‐cells.

Analyses of one‐ and two‐dimensional plots of the physiological measures indicate that XL‐ and XN‐cells constitute a physiological continuum. However, the two groups occupy opposite sides of the continuum on many of the measures, with little overlap and with few (< 5%) cells with intermediate properties. Therefore, XL‐cells may be considered a distinct, readily identifiable group.

These findings confirm and extend Mastronarde's ('87a) observations on functional differences among geniculate X‐cells. The existence of XL‐cells in the LGN and their apparent absence in the retina (Mastronarde, '87b) add support to the view that the LGN operates as more than a simple relay nucleus, passing on to the cortex in largely unaltered form the signals received from the retina. The differences between XL‐ and XN‐cells suggest that an important transformation occurs in the LGN among XL‐cells, and that it is in the temporal domain rather than in the spatial domain.
Distribution and development of VIP immunoreactive neurons in the spinal cord of the embryonic and newly hatched chick
Authors: Du Fu , Chayvialle Jean‐Alain , Dubois Paul
Published: January 2005

The distribution and development of vasoactive intestinal polypeptide (VIP) immunoreactive elements were studied in the spinal cord of embryonic and newly hatched chicks with the indirect immunofluorescence method. VIP neurons were first detectable in the presumed dorsal horn at stages 27–28 (incubation day 5). Subsequently they increased in number, and by stage 39 (day 12) many occurred in lamina I, in the nucleus of the dorsolateral funiculus, and in the lateral portion of the neck of the dorsal horn throughout the cord. However, at the thoracic level many were also situated lateral to the central canal, with their processes running to the ipsilateral lateral and contralateral ventral funiculi. The pattern described above remained visible in both embryonic and colchicine‐pretreated newly hatched chicks.

During development, VIP fibers appeared later than cell bodies. In the gray matter, they were mainly scattered in the intermediate zone, especially around the central canal at all levels examined. In the white matter, however, longitudinal fibers were observed in the lateral funiculus throughout the cord, but mostly at the cervical level, though some also occurred in the ventral funiculus. This finding supports the idea that spinal VIP neurons might project rostrally via the lateral funiculus.

In addition, no VIP immunoreactivity was found in the spinal ganglia, but examination of the sympathetic paravertebral ganglia showed immunoreactivity as described by others.
Morphological response of axotomized septal neurons to nerve growth factor
Authors: Gage Fred H. , Armstrong David M. , Williams Lawrence R. , Varon Silvio
Published: January 2005

Septal efferent fibers from, the neurons in the medial septal nucleus are destroyed by fimbria‐fornix aspirative lesion. In the present study we used quantitative morphometric techniques to evaluate the response of these axotomized septal neurons to a constant infusion of nerve growth factor (NGF). By 2 weeks following the lesion, approximately 75% of the cholinergic neurons had degenerated in the untreated rats. The remaining cholinergic neurons showed few signs of the effect of the lesion when stained for a polyclonal antibody to ChAT and examined in 40‐μm‐thick sections. In 1‐μm‐thick sections the remaining ChAT‐immunoreactive (IR) neurons also appeared no different from the intact ChAT neurons. However, non‐ChAT‐IR neurons had a shrunken nucleus, while all other morphometric parameters appeared normal. NGF infusion protected most of the ChAT‐IR neurons from degenerating. The saved neurons had the same parameters as the undamaged ChAT‐IR neurons when examined in either 40‐μm‐ or 1‐μm‐thick sections. In addition, the shrunken appearance of the non‐ChAT‐IR neurons' nuclei was avoided by the NGF infusions.

Enlarged ChAT‐IR processes were evident in the dorsolateral quadrant of the septum following damage to the fimbria‐fornix. NGF‐infusions prevented the formation of these processes. Instead, in the treated animals the dorsal lateral quadrant contained a dense plexus of fine ChAT‐IR varicosities.

Taken together these results demonstrate that NGF not only can protect the cholinergic neurons from axotomy‐induced degeneration but can also cause the saved neurons to maintain the same morphometric appearance as intact ChAT‐IR neurons. In addition, the lesion‐induced appearance of enlarged ChAT‐IR processes was avoided, and NGF prevents some of the degenerative changes that occur in non‐ChAT‐IR septal neurons after fimbria‐fornix aspiration.
Quantitative synaptology of feline motoneurones to external anal sphincter muscle
Authors: Pullen A. H.
Published: January 2005

Motoneurones innervating the cat external anal sphincter muscle were labelled retrogradely following intramuscular injections with horseradish peroxidase (HRP). Labelled motoneurones were examined by correlative light and electron microscopy (LM and EM) with special regard to a qualitative and morphometric analysis of the axon terminals resident on the neuronal membrane.

By LM, labelled motoneurones were (1) ipsilateral to the injections; (2) all in S1‐S2; (3) found only in the superior dorsomedial region of Onuf's nucleus; and (4) exhibited a broad spectrum of diameters (25–72 μm, mean 47.4 ± 11.3 μm).

By EM, axon terminals on the neuronal membrane when classified according to size, vesicle shape, and synaptic complex ultrastructure conformed to the S‐, F‐, T‐, M‐, and C‐type terminals previously described for cat lumbosacral motoneurones. C‐terminals confirmed these sphincteric motoneurones to be skeletomotor. Pooled data from midnuclear sections through 15 random labelled motoneurones (20–64‐μm diameter) revealed that S‐ and F‐type terminals predominated, with numerically few M and C types. Notwithstanding their low frequency (0.3/100 μm membrane) C‐terminals contributed 1% of the mean areal coverage by terminals, which implies a potentially larger synaptic influence relative to other terminal types. Linear relationships occurred between terminal frequency (or cover) and motoneurone diameter. While motoneurones >40μm in diameter exhibited all five terminal types, labelled motoneurones ≤30 μ generally possessed only S‐, F‐, and occasional T‐type terminals, and in this respect resembled gamma motoneurones.
Spatial organization of the retinal projection to the avian lentiform nucleus of the mesencephalon
Authors: Bodnarenko Stefan R. , Rojas Ximena , McKenna Olivia C.
Published: January 2005

Utilizing the horseradish peroxidase retrograde tracing technique and the 2‐deoxy‐D‐glucose metabolic mapping technique, we have demonstrated in chickens the distribution of retinal ganglion cells that project to the lentiform nucleus of the mesencephalon (LM) and the retinotopic organization of the projection in the LM. Retinal ganglion cells labeled after a nearly complete injection into the LM were found in the four quadrants, distributed in a wide horizontal belt lying along both sides of the retinal equator and stretching from the temporal to the nasal retina. The HRP‐labeled cells, which appeared round or oval, ranged from 25 to 840 μm2 in size with most in the smaller size range. Results of partial HRP injections into the LM and metabolic mapping patterns in the LM produced by stimulation of half the retina with horizontal visual motion suggest that there is an orderly mapping of the retina onto the LM. The inferior temporal quadrant projects to the rostrodorsal LM; the inferior nasal quadrant projects to the caudodorsal LM. The superior temporal quadrant projects to the middle and ventral LM, extending from the rostral to the caudal pole, whereas the superior nasal quadrant projects to a small zone in the caudal LM. The mapping of the retinal quadrants in the LM is remarkably similar to that reported in the optic tectum of birds. We suggest that a common embryological anlage with the optic tectum and the arrangement of retinal axons in the optic tract are important factors in establishing the retinotopic organization of the LM.