bluuebunny/crossref_metadata_2025 huggingface dataset:
Selective retrograde labeling with D‐[3H]‐aspartate in afferents to the mammalian superior colliculus
Authors: Matute Carlos , Streit Peter
Published: May 2005

The selectivity previously reported for retrograde labeling patterns obtained following D‐[3H]‐aspartate injections and proposed to be related to the transmitter specificity of the labeled pathways was tested in afferents to the superior colliculus (SC) of rats and rabbits.

In rats selectivity was assessed by comparing retrograde perikaryal labeling patterns observed in D‐[3H]‐aspartate experiments with those found after administration of a nonselective tracer, horseradish‐peroxidase‐labeled wheat germ agglutinin (HRP‐WGA), and of the tritiated neurotrasmitter γ‐aminobutyric acid (GABA). Following D‐[3H]‐aspartate injections into the SC labeling was intense in a large number of cortical and hypothalamic neurons. Other afferents to the SC, however, such as those originating from the ventrolateral geniculate nucleus, the pars reticulata of the substantia nigra, the locus coeruleus, the pontine nuclei, or the retinal ganglion cells, were not labeled. Similar results were obtained in rabbits.

In cats, the analysis was focused on the cerebral cortex, since in an earlier investigation no retrograde labeling had been detectedin the visual cortex following D‐[3H]‐aspartate injectionsin the SC. In the present work, however, retrogradely labeled neuronswere observed in various cortical areas including a few in visual cortex.

This report shows selective retrograde labeling for a part of the afferents to the SC. This selectivity does not display major differences among the mammalian species studied. Moreover, according to the information available about the distribution of neurotransmittersin the brain, the findings reported here favour the idea that D‐[3H]‐aspartate is a retrograde tracer selective for glutamatergic and/or aspartatergic pathways.
The structure of the brainstem and cervical spinal cord in lungless salamanders (family plethodontidae) and its relation to feeding
Authors: Roth Gerhard , Wake David B.
Published: May 2005

We present an HRP study of the sensory tracts and motor nuclei associated with feeding (especially use of the tongue) in plethodontid salamanders (mainly Batrachoseps attenuatus, Bolitoglossa subpalmata, Desmognathus ochrophaeus, Eurycea bislineata, and Plethodon jordani). The nerves studied are VII (ramus hyomandibularis only), IX, X, XI, the first spinal nerve (hypoglossus), and the second spinal nerve. Two types of sensory projections are universally found in the brainstem: superficial somatosensory projections of VII, IX, and X, and deeper visceral sensory projections of IX and X to the fasciculus solitarius. The first spinal nerve and the spinal accessory nerve (XI) have no sensory projections, but the second spinal nerve has typical projections along the dorsal funiculus of the spinal cord.

The motor nuclei of VII ramus hyomandibularis, IX, and X form a combined nucleus situated at the level of the IX/X root complex. The nucleus of the first spinal nerve is well separated from the combined nucleus and is situated rostral and caudal to the obex. The rostral part of the motor nucleus of the second spinal modestly overlaps that of the first. The motor nucleus of the spinal accessory nerve is more or less restricted to the region of the second spinal nerve. Its fibers leave the brain through the last root of the IX/X complex and the related ganglion. Bolitoglossine and nonbolitoglossine differ in the architecture of the spinal nuclei. Two distinct types of motor neurons occur in spinal nuclei of nonbolitoglossine species–some of those with tongue projection–but only one type is found amongthe tongue‐projecting bolitoglossine group.
The development of the dentate area and the hippocampal mossy fiber projection of the rat
Authors: Gaarskjaer Frank B.
Published: May 2005

The development of the dentate area and the hippocampal mossy fiber system of the rat has been investigated at the light microscopic level by using fluorescent tracing, Nissl, and Timm's histochemical methods. Although the cytoarchitectonic development of the dentate granular layer is mainly a postnatal phenomenon, the initial events take place before birth. The aggregation and maturation of the cells in the granular layer proceed in a graded fashion from the lateral to the medial and from the superficial to the deep aspects of the layer. The earliest‐formed granule cells are probably derived directly from the cells of the ventricular zone. They start to form mossy fibers prenatally, either during the relatively long period of migration to the granular layer or soon after their arrival. However, most of the granule cells are derived from a secondary proliferative center in the hilus. They start to produce mossy fibers postnatally a while after arriving at the granular layer. The total complement of granule cells starts to grow mossy fibers in a sequence that is related to the final position of the cells of origin within the granular layer. This sequence also proceeds in a graded fashion from the lateral to the medial and from the superficial to the deep aspects of the layer.

In the beginning the mossy fibers elongate relatively rapidly. Already at birth the Timm‐stained mossy fiber zone occupies the anterolateral part of the hilus and the adjacent suprapyramidal parts of the regio inferior. Once the mossy fibers have reached the distal end of the regio inferior they elongate along the longitudinal axis of the hippocampus more slowly. At the same time the Timm‐stainability of the mossy fiber zone, which, during the first postnatal week, is weaker toward the regio superior, develops a mature pattern in which the distal part of the zone stains most intensely. Throughout development, fibers from the granule cells that form first are longer and diverge more in the septotemporal dimension than fibers from later‐forming granule cells. In contrast to other axonal systems which appear to be sculptured from a diffuse set of connections the results presented here provide evidence that the topographic relationships of the mossy fiber system develop in a stepwise fashion.
The projection of the visual field onto the lateral geniculate nucleus of the ferret
Authors: Zahs Kathleen R. , Stryker Michael P.
Published: May 2005

The projection of the visual field onto the dorsal lateral geniculate nucleus (LGN) of the ferret was mapped electrophysiologically. The nucleus contains a single orderly map of the contralateral visual hemifield. The upper visual field is represented dorsally and rostrally in the nucleus; central fields are found in the medial and caudal sections of the LGN; and peripheral fields are represented most laterally. The ipsilateral eye is represented in laminae Al and Cl up to eccentricities of 20–30°. Lines of projection run perpendicular to the laminar borders. The ferret LGN resembles that of the cat rotated approximately 110° clockwise in the sagittal plane, viewing the right nucleus from its lateral aspect; it differs from the cat in having a larger monocular segment.
An autoradiographic study of projections ascending from the midbrain central gray, and from the region lateral to it, in the rat
Authors: Eberhart J. A. , Morrell J. I. , Krieger M. S. , Pfaff D. W.
Published: May 2005

Ascending projections from the midbrain central gray (CG) and from the region lateral to it were traced in the rat using tritiated amino acid autoradiography. Leucine or a cocktail of amino acids (leucine, proline, lysine, histidine, and tyrosine) were used as tracers.

In addition to projections within the midbrain, ascending fibers follow three trajectories. The ventral projection passes through the ventral tegmental region of Tsai and the medial forebrain bundle to reach the hypothalamus, preoptic area, caudoputamen, substantia innominata, stria terminalis, and amygdala. There are labeled fibers in the diagonal bands of Broca and medial septum, and terminal labeling in the lateral septum, nucleus accumbens, olfactory tubercle, and frontal cortex. The dorsal periventricular projection terminates in the midline and intralaminar thalamic nuclei. The ventral periventricular projection follows the ventral component of the third ventricle into the hypothalamus, passing primarily through the dorsal hypothalamic area and labeling the rostral hypothalamus and preoptic area.

Projections from the region lateral to the CG are similar, but exhibit stronger proximal, and weaker distal, projections. Rostral levels of the CG send heavier projections to the fields of Forel and the zona incerta, but fewer fibers through the supraoptic decussation, than do caudal levels.

Ascending projections from the CG are both strong and widespread. Strong projections to the limbic system and the intralaminar thalamic nuclei provide an anatomical substrate for CG involvement in nociception and affective responses.
Vasoactive intestinal polypeptide and substance P in primary afferent pathways to the sacral spinal cord of the cat
Authors: Kawatani Masahito , Erdman Susan L. , de Groat William
Published: May 2005

An analysis of vasoactive intestinal polypeptide immunoreactivity (VIP‐IR) and substance P‐IR in the cat spinal cord has revealed marked differences in the distribution of the two peptides. While substance P‐IR was located at all levels of the cord, VIP‐IR was most prominent in the sacral segments in Lissauer's tract and lamina I on the lateral edge of the dorsal horn. VIP‐IR was also present in the sacral cord in (1) laminae V, VII, and X, (2) a thin band on the medial side of the dorsal horn, (3) the dorsal commissure, (4) the lateral band of the sacral parasympathetic ucleus, and (5) in a few animals in Onuf's nucleus. In other segments of the spinal cord VIP‐IR was much less prominent but was present in Lissauer's tract and laminae I, II, and X. Substance P‐IR was more uniformly distributed at all segmental levels in laminae I–III, V, VII, and X and in the dorsal commissure.

In ventrolateral lamina I of the sacral spinal cord both VIP‐IR and substance P‐IR exhibited a distinctive periodic pattern in te rostrocaudal axis. The peptides were associated with bundles of dorsoventrally oriented axons and varicosities spaced at approximately 210‐μm intervals center to center along the length of the spinal cord. The bundles in lamina I continued into lamina V where they further divided into smaller bundles that extended medially through laminae V and VII. The most prominent bundles of VIP axons passed ventrally from lateral laminae V and VII to enter lamina X and the ventral part of te dorsal gray commissure. On the other hand the maority of substance P axons in lamina V turned dorsally to join wth axons on the medial side of the dorsal horn and to pass into the dorsal part of the dorsal gray commissure. Rostrocaudal VIP axons were present not only in Lissauer's tract but also in dorsolateral lamina I, in the lateral funiculus and in the ependymal cell layer of the central canal.

Following unilateral transectionofthe sacral dorsal roots (2 weeks–22 months) the density of VIP axons and terminals was markedly reduced in ipsilateral Lissauer's trat and lateral laminae I and V; however, no change was detected in lamina X. Sacral deafferentation reduced substance P‐IR in the dorsal gray commissure and in lateral laminae I and V.

It is concluded that VIP‐IR and substance P‐IR are present at all levels of the cat spinal cord, but that VIP‐IR is most prominent in sacral afferent pathways. The distribution of VIP‐IR in spinal cord was very similar to the central projections of sacral visceral afferents. These findings are consistent with data from other experiments indicating that VIP may be a transmitter in visceral afferent pathways.
Cerebral cortical projections to the reticular regions around the trigeminal motor nucleus in the cat
Authors: Yasui Yukihiko , Itoh Kazuo , Mitani Akira , Takada Masahiko , Mizuno Noboru
Published: May 2005

Cerebral cortical regions which send projection fibers to the reticular regions around the trigeminal motor nucleus were identified in the cat by the horseradish peroxidase (HRP) method. The reticular region around the trigeminal motor nucleus are known to contain many interneurons for masticatory motoneurons. After injections of HRP into the reticular regions around the trigeminal motor nucleus, HRP‐labeled neuronal cell bodies in the cerebral cortex were found in layer V. They were distributed bilaterally in the orbitofrontal cortical regions, mainly in the rostral extension of the orbital gyrus close to the presylvian sulcus; more were located in the floor and lateral bank of the presylvian sulcus than in the crown of the orbital gyrus. After injections of HRP conjugated with wheat germ agglutinin (WGA‐HRP) into these cortical regions, many labeled presumed axon terminals were distributed bilaterally in the reticular regions around the trigeminal motor nucleus; mainly in the region ventral to the trigeminal motor nucleus and in the intertrigeminal region between the main sensory trigeminal nucleus and the trigeminal motor nucleus. Terminal labeling in these regions was more prominent after WGA‐HRP injection into the lateral bank of the presylvian sulcus than after WGA‐HRP injection into the crown of the orbital gyrus. Thus, the present results indicate that the main part of the cortical region projecting directly to the reticular regions around the trigeminal motor nucleus in the cat is folded into the presylvian sulcus.
Ontogeny of substance P‐like immunoreactive fibers in the taste buds and their surrounding epithelium of the circumvallate papillae of the rat. II. Electron microscopic analysis
Authors: Yamasaki Hiroshi , Tohyama Masaya
Published: May 2005

We studied the ontogeny of the fine structure of substance P‐like immunoreactive (SPI) fibers in the extragemmal epithelium and taste buds of the circurnvallate papillae in the rat tongue by electron microscopy and by the unlabeled antibody‐enzyme method. SPI fibers in the lamina propria first appeared at gestational day 19, and those in the extragemmal epithelium and in the taste buds at day 21. These fibers did not form synaptic contact with underlying cells. In addition, the occurrence of nonimmunoreactive fibers in these areas preceded that of SPI fibers. Our findings suggest that SPI fibers are not primarilly involved in the differentiation of the extragemmal epithelium and taste bud cells.
Morphology of physiologically identified slowly adapting lung stretch receptor afferents stained with intra‐axonal horseradish peroxidase in the nucleus of the tractus solitarius of the cat. I. A light microscopic analysis
Authors: Kalia Madhu , Richter Diethelm
Published: May 2005

The present series of experiments was designed to study the organization of preterminai processes and synaptic boutons of single physiologically identified slowly adapting receptor (SAR) pulmonary stretch afferent fibers. Intra‐axonally injected horseradish peroxidase‐wheat germ agglutinin (HRP‐WGA) conjugate was used as the label. In the first paper, we describe the pattern of arborization of axon collaterals from single physiologically identified SAR afferent fibers evident in the various subnuclei of the nucleus of the tractus solitarius (nTS). In the second paper, details are presented regarding the ultrastructure of these synaptic boutons and axon collaterals.

A number of significant findings resulted from this study: (1) A single lung stretch SAR afferent fiber arborized over a considerable distance rostrocaudally in the brain stem (1,700–2,100 μm). (2) A single lung stretch SAR afferent fiber terminated as hundreds of bouton terminals (650–1,180). (3) There was a remarkable consistency in the subnuclei of the nTS that received these terminal arborizations of SAR afferents. (4) The ventral (vnTS), intermediate (nI), ventrolateral (vInTS), and interstitial (ni) subnuclei of the nTS were the only regions of the nTS receiving bouton terminals of SAR afferent fibers. (5) Under the light microscope the pattern of termination of SAR afferents was similar in all the axons studied in this series. (6) The injected parent axon in each case could be followed in the TS at all levels and remained consistent with regard to position and orientation and could be traced rostrally to levels as far as 3.5 mm rostral to the obex whereas the region of terminal arborization was located around 1.7–2.1 mm rostral to the obex. This pattern indicates that a single lung stretch SAR afferent fiber descends caudally upon entering the nTS. In the cat vagal afferent fibers are known to enter the medulla at levels between 0.5 mm and 3.2 mm rostral to the obex (Kalia and Mesulam, '80a).

The results of the light microscopic analysis presented in this article indicate that lung stretch (SAR) afferents from the lungs and tracheobronchial tree have distinctly localized patterns of distribution in the nTS. In addition, these findings support the concept that representation of pulmonary afferents in the medulla is constituted by a differentiated distribution of nerve terminals in the various subnuclei of the nTS. Modality‐specific localization (SAR afferents in this case) appears to be predominant in the n'1'S. The widespread rostrocaudal distribution of the terminal field of a single lung stretch SAR afferent is remarkable. In addition, the finding that the terminals of different SAR afferents are localized in only a few subnuclei of the nTS suggests that specificity exists in this afferent system which could provide the morphological substrate for focussed physiological effects.
Morphology of physiologically identified slowly adapting lung stretch receptor afferents stained with intra‐axonal horseradish peroxidase in the nucleus of the tractus solitarius of the cat. II. An ultrastructural analysis
Authors: Kalia Madhu , Richter Diethelm
Published: May 2005

The nucleus of the tractus solitarius is a site for termination of primary afferents originating from a variety of visceral receptors. The localization of bouton terminals of slowly adapting lung stretch (SAR) afferent fibers originating from the tracheobronchial tree have been described in the companion paper (Kalia and Richter, '85). The most conspicuous finding regarding the location of SAR terminals is that they are concentrated within specific subnuclear groups of the nucleus of the tractus solitarius (nTS) and are distributed widely in the rostrocaudal plane of the medulla oblongata. These light microscopic features have provided us with valuable information with regard to the organization of visceral afferents in the central nervous system. The synaptic profiles formed by the 476 bouton terminals of these HRP‐labeled afferents have been described in this paper in serial thin sections. All of the bouton terminals examined under the electron microscope were found to contain round synaptic vesicles. Synaptic boutons (1.0–3.0) /μm in diameter were usually of the en passant variety and made contact with different structures depending upon the subnucleus which was examined. In the ventral (v) and the ventrolateral (vl) subnuclei of the nTS, asymmetrical (type I) synaptic contacts containing round, clear synaptic vesicles of 35–50 ion μm in diameter were found and these contacts were made with (1) the soma of cell bodies located in that subnucleus; (2) spiny dendrites in that nucleus; (3) vesicle‐containing axon terminals that were presynaptic to the HRP‐labeled bouton terminal; and (4) vesicle‐containing dendrites in which the HRP profile was presynaptically located. The terminal axon remained my‐elinated till the last 1 μm before the bouton terminal was formed. There was no distinct, unmyelinated portion of the terminal axon. The synaptic bouton received axon‐axonal synapses from unlabeled bouton terminals containing round, clear vesicles.

This is the first report of the localization of these afferent fibers as well as of the regional variations in the ultrastructure of boutons of physiologically identified terminals. It appears likely that the lung stretch afferent fibers, by having axon‐axonal as well as axon‐somatic contact in the ventral, ventrolateral, and intermediate subnuclei of the nTS, can interact in a variety of different ways in this region. The significance of these features in relation to the precise influence of respiratory afferents on central respiratory mechanisms needs to be evaluated further.
The efferent projections from the reticular formation and the locus coeruleus studied by anterograde and retrograde axonal transport in the rat
Authors: Jones Barbara E. , Yang Tian‐Zhu
Published: May 2005

Following injections of [3H]leucine into the formatio reticularis gigantocellularis (Rgc), reticularis pontis caudalis (Rpc), reticularis pontis oralis (Rpo), reticularis mesencephali (Rmes), or the locus coeruleus (LC) of the rat, autoradiographic study revealed prominent reticuloreticular projections from all areas and secondary projections onto cranial nerve motor nuclei from most areas within the brain stem. Common long descending projections extended the full length of the spinal cord terminating in the ventromedial ventral horn and intermediate zone and more sparsely in the base of the dorsal horn and (particularly from Rgc) the region of the motoneurons. Common long ascending projections extended into the forebrain via Forel's tegmental fascicles. A dorsal branch of fibers innervated the intralaminar and midline nuclei of the thalamus. The major fiber system continued forward through Forel's fields and ascended into the pallidum from Rpo, Rmes, and LC and into the neostriatum from Rmes and LC. Fascicles from all areas also ascended in the medial forebrain bundle through the lateral hypothalamus to the lateral preoptic area, substantia innominata, and nuclei of the diagonal band. From Rpo, Rmes, and LC, fibers continued forward to reach the cerebral cortex, where the innervation was sparse and discrete from Rpo and Rmes but moderate and ubiquitous from LC.

Retrograde transport of true blue and/or nuclear yellow revealed inverse gradients along the brain stem longitudinal axis of interdigitated cells respectively projecting caudally into the spinal cord (with the greatest number of cells in Rgc, Rpc, and Rpo) and rostrally into the diencephalon (with the greatest number of cells in Rmes and LC), with very few cells projecting both to the spinal cord and the diencephalon. From the basal forebrain, a large number of reticular and LC cells were retrogradely labelled, whereas from the frontal cortex, a much smaller number of reticular cells was labelled. These results document the widespread efferent projections from the reticular formation and overlapping, yet more extensive, projections from the LC.
The cerebellar and vestibular nuclear complexes in the turtle. I. Projections to mesencephalon, rhombencephalon, and spinal cord
Authors: Künzle H.
Published: May 2005

Cerebellar and vestibular projections were investigated in the turtle Pseudemys scripta elegans following injection of 35S‐methionine into the cerebellar and vestibular nuclear complexes at various locations.

Fibers arising from the cerebellar nuclei were traced via the cerebellar commissure to the contralateral vestibular nuclear complex (particularly the n. vestibularis inferior and n. vestibularis ventrolateralis) and caudal rhombencephalic tegmentum. Ascending projections crossing the midline in the ventral isthmomesencephalic tegmentum terminated in the contralateral red nucleus and nuclei of the fasciculus longitudinalis medialis (flm).

Vestibular projections ascending mainly via the flm terminated in the nuclei of the flm, the nuclei of the posterior commissure, and particularly the extraocular motor nuclei. Vestibulo‐ocular projections arising from the rostral vestibular nuclear complex were almost exclusively ipsilateral; those from the caudal vestibular nuclear complex were bilateral. Evidence for a topographic organization of the projections to the trochlear and oculomotor nuclei was also obtained. There were some vestibular projections to the contralateral rhombencephalic tegmentum and n. vestibularis inferior. Spinal projections coursing within the ipsilateral ventral descending tract and the ipsilateral fasciculus longitudinalis medialis were found to arise from both rostral and caudal vestibular regions. The caudal vestibular nuclear complex in addition gave rise to fibers descending in the contralateral fasciculus longitudinalis medialis. Evidence for the existence of labeled fibers crossing at spinal levels was also obtained. Vestibulospinal terminations appeared restricted to the ventral horn.
The cerebellar and vestibular nuclear complexes in the turtle. II. Projections to the prosencephalon
Authors: Künzle H.
Published: May 2005

Prosencephalic projections from the cerebellar and vestibular nuclear complexes in the turtle Pseudemys scripta elegans were investigated with anterograde tracing. Following injections of 35S‐methionine at various locations within the cerebellar and vestibular nuclear complexes, labeled ascending fibers were found to arise from the lateral cerebellar and the rostral (superior and/or dorsolateral) vestibular nuclei. The great majority of these fibers coursed within the ipsilateral ascending periventricular tract.

There were possible terminations in the hypothalamosuprapeduncular region, the ovalis‐complex, and the nucleus commissuralis anterior, but scarcely any indication of terminal labeling within the dorsal thalamus. The labeled fibers, however, continued rostralward, entered the lateral forebrain bundle, and terminated in the anterior dorsal ventricular ridge—in all but one case, exclusively ipsilaterally. The terminal area within the lateral division (referred to as area L) of the anterior dorsal ventricular ridge was sharply delimited, being situated ventrolateral to the visually oriented area D of the anterior dorsal ventricular ridge (Balaban and Ulinski, '81), medial to the lateral cortex, and ventral to the pallial thickening (motor pallium of Johnston, '16).

The findings are compared with related ones in mammals, particularly those pertaining to telencephalic somatosensorimotor regions and their interactions with the vestibular nuclear complex and the cerebellum.
Immunohistochemical study of subclasses of olfactory nerve fibers and their projections to the olfactory bulb in the rabbit
Authors: Mori Kensaku , Fujita Shinobu C. , Imamura Kazuyuki , Obata Kunihiko
Published: May 2005

The organization of the olfactory nerve projection to the olfactory bulb was studied immunohistochemically in the rabbit by using monoclonal antibodies (MAbs). Out of 42 MAbs raised against the homogenate of the olfactory bulb, two types of MAbs that strongly stained the olfactory nerve fibers (axons of olfactory receptor cells) were selected and their staining patterns were analysed in detail. MAbs of one type (represented by MAb R2D5) specifically labeled all olfactory receptor cells in the nasal epithelium and all olfactory nerve fibers and their terminal portions in the bulb.

The other type of MAbs (represented by MAb R4B12) recognized only a subgroup of olfactory nerve fibers. The R41312‐positive fibers were distributed over the ventrolateral areas but not in the dorsomedial areas of the epithelium. Similarly in the bulb, the R41312‐positive fibers terminated in the glomeruli in the ventrolateral and the caudal regions but not in the dorsomedial region. These results demonstrate for the first time the cellular heterogeneity among olfactory receptor neurons at the molecular level. The segregated distribution of the subtypes of olfactory receptor cell axons both in the epithelium and the bulb indicates a defined topographical organization of the olfactory nerve projection. These results also suggest a functional division between dorsomedial and ventrolateral areas both in the epithelium and the bulb.
Wide‐spreading terminal axons in the inner plexiform layer of the cat's retina: Evidence for intrinsic axon collaterals of ganglion cells
Authors: Dacey Dennis M.
Published: May 2005

Extracellular, iontophoretic injections of horseradish peroxidase (HRP) were made directly into the cat's retina. The retinas were processed with the cobalt‐enhanced diaminobenzidine method and prepared as whole mounts. These retinas reveal HRP‐filled axons that extend widely and terminate within the inner plexiform layer. The axons are morphologically distinct from ganglion and amacrine cell dendritic trees that were retrogradely labelled from the same injection sites.

The axons are long and straight, approximately 1 μm in diameter, and in some cases can be traced for several millimeters in the inner plexiform layer. Each axon gives rise to many short, terminal branches that extend, on average, 100 μm from the parent axon and bear clusters of boutons. The terminal branches are widely spaced so that the bouton clusters are distributed in small, isolated patches along the length of the axon. Bouton clusters vary in size and contain from two to over 100 loosely arranged boutons. Single boutons are frequently large, up to 3 μm in diameter.

In one case a terminal axon was traced to its origin from the parent axon of an HRP‐filled ganglion cell. It is suggested, therefore, that these axons are intrinsic to the retina and originate as primary collaterals of ganglion cells.
Catecholamine innervation of the caudal spinal cord in the rat
Authors: Schrøder Henrik Daa , Skagerberg Gunnar
Published: May 2005

By means of the aluminum‐formaldehyde (ALFA) fluorescence technique for monoamine visualization the distribution of catecholamines was studied in the caudal spinal cord, particularly in relation to motoneurons innervating pelvic structures.

In the lumbosacral cord all parts of the spinal gray matter were found to contain catecholamines. In the dorsal horn the most intense fluorescence was seen in the superficial layers. The motoneuron neuropil exhibited the most prominent catecholamine‐fluorescence of the ventral horn layers. In the sixth lumbar segment, which contains the motor nuclei that innervate the pelvic striated muscles as well as one innervating muscles in the lower limb, a differential distribution of the density of catecholamine fluorescence was presented by the individual nuclei.

The catecholamine fibers in the motoneuron neuropil were seen closely surrounding the motoneuron somata, suggesting the existence of axosomatic contacts, and by utilizing the fluorescent retrograde tracer True Blue in combination with the ALFA method tentative axosomatic noradrenergic synapses on identified neurons innervating small striated pelvic muscles could be visualized in the light microscope.

In the intermediate gray the intermediolateral nucleus in thoracic and upper lumbar segments was the most heavily innervated area, followed by the medial lumbar sympathetic group, which contains the majority of the sympathetic preganglionic neurons innervating the pelvic organs. The parasympathetic intermediolateral nucleus in the upper sacral segments received a catecholamine innvervation of moderate density.

The catecholamine innervation pattern is discussed in relation to the patterns of other putative transmitters. The distribution of catecholamine fluorescence in relation to nuclei that control the pelvic organs differs from the arrangement of other transmitters in this region. The complexity of the innervation of the pelvic organs and their related striated muscles is thus further stressed.
The dorsal cochlear nucleus of the mouse: A light microscopic analysis of neurons that project to the inferior colliculus
Authors: Ryugo D. K. , Willard F. H.
Published: May 2005

In the mouse dorsal cochlear nucleus (DCN), all members of a distinct class of large multipolar neurons were shown to project to the contralateral inferior colliculus by using retrograde horseradish peroxidase techniques. Typically, these multipolar neurons have the largest cell bodies in the nucleus and are distributed in layers II, III, and IV. Each contains a round, pale nucleus with a prominent nucleolus and conspicuous Nissl bodies. In Golgi preparations, however, two types of large cells could be distinguished on the basis of dendritic characteristics. Pyramidal cells form relatively flattened, slablike dendritic fields whose alignment contributes to the laminar organization of the DCN. They represent 75–80% of the large cell population and are found in layer II and the superficial region of layer III. Giant cells represent the other type of large multipolar neuron and are distributed in the deeper regions of layer III and in layer IV. Their ellipsoidal dendritic fields are formed by long and relatively unbranched dendrites that project across the laminae. The differences in dendritic morphology imply that each cell class segregates its afferent input in distinct ways and subserves different auditory functions.
Topographic representation of visceral target organs within the dorsal motor nucleus of the vagus nerve of the pigeon Columba livia
Authors: Katz David Miles , Karten Harvey J.
Published: May 2005

Our previous work (Katz and Karten, '83a J. Comp. Neurol. 217:31–46) demonstrated that the dorsal motor nucleus of the vagus nerve (DMN complex) in the pigeon is composed of cytoarchitecturally distinct subnuclei that are distinguished by the size, shape, position, and cytochemical characteristics of their constituent neurons. In view of the diversity of target organs innervated by the vagus nerve, we sought to determine whether the subnuclear heterogeneity of the DMN complex is related to the pattern of target innervation. To test this possibility, retrograde tracing techniques were used to define the subnuclear localization of vagal motoneurons that innervate individual vagal target organs.

The distribution of horseradish peroxidase (HRP)‐labeled motoneurons within the DMN complex was studied following application of HRP to the cut central end of individual vagal nerve branches and after injection of the tracer into vagal target tissues. In addition, we examined the distribution of acetylcholinesterase depletion within the DMN complex following transection of individual vagal branches.

Our data demonstrate that individual vagal target organs have discrete and topographic representations within cytoarchitecturally distinct subnuclei of the DMN complex. Therefore, in the pigeon, the subnuclear distribution of vagal motoneurons plays a critical role in the organization of descending vagal motor pathways. Segregation of visceral representations within the DMN complex may provide a mechanism for organizing functionally diverse afferent inputs to target‐specific populations of vagal motoneurons.
Neurogenesis of the cat's primary visual cortex
Authors: Luskin Marla B. , Shatz Carla J.
Published: May 2005

The 3H‐thymidine method of birth‐dating was used to determine when the cells belonging to each of the principal cellular layers of the cat's primary visual cortex are generated. In order to detect systematic differences in the position of radioactively labeled cells following 3H‐thymidine administration at different prenatal ages, a geometric method was devised to represent the distribution of labeled cells in the form of depth histograms. Results show that visual cortical neurogenesis occurs largely during the second half of gestation between embryonic day 31 (E31) and E57. Cells of layer 6 are generated early, between E31 and E38, whereas cells destined for successively more superficial layers are generated at progressively later times. Layer 4 cells, the principal targets of geniculocortical afferents, are generated between E37 and E44. In addition, a special population of cells embedded in the white matter below layer 6 was found to be produced throughout the week‐long period immediately prior to the onset of layer 6 neurogenesis. Overall, this radial pattern of cortical neurogenesis closely resembles the inside‐first, outside‐last, spatiotemporal sequence of development described for the monkey's primary visual cortex (Rakic, '74).

In addition to finding this pronounced gradient in the radial dimension, we were also able to detect a less pronounced gradient along the tangential dimension: neurons destined for any given layer in the anterior part of the cortex (inferior visual, field representation) are generated slightly in advance of neurons destined for more posterior regions (superior visual field). However even our more quantitative histogram analysis failed to reveal a mediolateral (central to peripheral visual field) gradient within area 17.

In the cat, layers 6, 5, and 4 each take about a week to be generated, although their total cell numbers and packing densities differ in the adult. About 2 weeks are required to produce the cells of layers 2 and 3 combined. Furthermore, we found that neurons belonging to different layers and different morphological classes can be generated simultaneously. This suggests that the identity of a cortical neuron is not solely a function of the time of neurogenesis.
Location of motoneurones projecting to the cat distal forelimb. I. Deep radial motornuclei
Authors: Fritz Norbert , Illert Michael , Saggau Peter
Published: May 2005

The position of the motornuclei projecting through the dorsal interosseus (DR) nerve to the distal forelimb muscles has been investigated in the cat. Horseradish peroxidase (HRP) and fluorescent (Fl) compounds have been used as retrograde tracers. They were either injected into forelimb muscles or applied to the proximal end of transected forelimb nerves. Limb muscles that were not investigated have been carefully denervated. HRP was used to trace the position and the architecture of the individual motornuclei. The topographical relations between the nuclei were established with application of up to three F compounds in the same animal. The position of the labeled motornuclei was reconstructed with a computer‐assisted approach which is described in the appendix. The DR representation area extends from the caudal C5 to the caudal Thl segments. In C6 it forms a dorsoventrally oriented narrow region at the lateral border of the ventral horn; in C7 and rostral C8 it forms a broad column in the dorsolateral corner of the ventral horn. In caudal C8 and Thl this column is shifted into a ventral direction. The motoneurones projecting to the individual DR muscles are not randomly distributed in this area, but arranged in long, slender columns. These motornuclei occupy specific positions with only minimal interindividual variations. Three nuclei (brachioradialis, extensor carpi radialis, and supinator) are located in the C6 and C7 segments. They compose about onethird of the DR cell population. The nuclei to the other radial muscles are all located in C8 and Thl. Thus most of the DR motoneurones are located in these two segments. These results, together with those from the companion paper on the location of the median and ulnar motornuclei, provide important anatomical knowledge for the investigation of the cat brachial enlargement.
Ontogenetic change in the distribution of callosal projection neurons in the postcentral gyrus of the fetal rhesus monkey
Authors: Killackey Herbert P. , Chalupa Leo M.
Published: May 2005

In the postcentral gyrus of the mature rhesus monkey the distribution of callosal projection neurons is discontinuous. The density of callosal projection neurons, which are mainly located in the supragranular layers, varies both within and across cytoarchitectonic areas (Killackey et al., '83). In the present study, we investigated the ontogeny of corpus callosum projections of the postcentral gyrus in five fetal rhesus monkeys, ranging in age from embryonic day (E) 108 to E 133. Multiple large injections of horseradish peroxidase that involved the underlying white matter were made into the postcentral gyrus of one hemisphere and the distribution of labeled neurons in the ipsilateral thalamus and the other hemisphere was determined. The pattern of thalamic label indicated that the tracer was effectively transported from all portions of the postcentral gyrus.

We found that the areal distribution pattern of labeled callosal projection neurons varied at the different fetal ages. At early fetal ages (E 108, E 111, and E 119) callosal projection neurons were continuously distributed throughout the postcentral gyrus. As in the adult animal, the vast majority of labeled callosal projection neurons were found in the supragranular layers, although a few labeled cells were located in the infragranular layers. From the earliest age, there was regional variation in the width of the band of labeled supragranular callosal projection neurons. The difference between the precentral and postcentral gyrus was most obvious, but there was also a difference between anterior and posterior portions of the postcentral gyrus. The first indication of some discontinuity in the distribution of callosal projection neurons was noted at E 126. By E 133, approximately 1 month before birth, the distribution of callosal projection neurons appeared remarkably mature.

On E 119 aggregations of anterograde label could be detected in restricted portions of the posterior postcentral gyrus beneath the cortical layers. By E 133 anterograde label was found within the cortical layers (most densely in layer IV) in these regions of the postcentral gyrus. Thus, the emergence of the discrete pattern of callosal projection neurons appears to be temporally correlated with the ingrowth of callosal afferents.

On the basis of these observations, as well as those of others (discussed in the text), we propose that the ontogenetic changes in the distribution of callosal projection neurons reflect the unique strategy employed by cortical projection neurons in establishing their patterns of connectivity. It is hypothesized that this strategy may involve multiple processes.
Morphology of local “Stridulation” interneurons in the metathoracic ganglion of the acridid grasshopper Omocestus viridulus L
Authors: Gramoll Siglinde , Elsner Norbert
Published: May 2005

The morphological characteristics of five types of local spiking interneurons in the metathoracic ganglion of the acridid grasshopper Omocestus viridulus L. have been revealed by intracellular injection of the fluorescent dye Lucifer Yellow. All these neurons are active during induced stridulation and discharge in the stridulation rhythm. They are structurally unlike any of the metathoracic local interneurons previously described in the Acrididae.

Type 1: Unilateral interneurons in the metathoracic neuromere; soma in anterior position; arborization dorsal, in anterolateral, posterolateral, and midline regions.

Type 2: Unilateral interneurons in the metathoracic neuromere; neurite with characteristic hairpin bend; soma in lateral position; arborization through the lateral neuropil region.

Type 3: Unilateral interneurons in the metathoracic and abdominal neurons; soma anterior at the base of the connective; arborization dorsal, in anterolateral, posterolateral, and midline regions, with ladderlike branches into the abdominal neuromeres.

Type 4: Symmetrically bilateral neurons; soma in ventral median position; arborization dorsal, in anterolateral, posterolateral, and midline regions. Ipsilateral branches mostly smooth, contralateral mostly varicose.

Type 5: Asymmetrically bilateral neurons, soma in ventral median position; ipsilateral branches mostly smooth, contralateral mostly varicose. The ipsilateral branches in particular penetrate all layers of the ganglion.

The main arborizations of interneurons of types 1 and 4, and to some extent those of types 3 and 5, occupy the same region, which extends very far dorsally into the vicinity of the median and lateral tracts. There are additional antero‐ and posterolateral branches in the metathoracic neuromere, in positions where in principle they can overlap with the arborizations of the motoneurons. The interneurons of type 2, and to some extent type 5, arborize mainly in a lateral region that also includes deeper layers of the ganglion and hence encompasses the projections of mechanoreceptive proprioceptors.

The interneurons of types 1, 3, and 4 have so‐called “sister” neurons, identical to the typical neurons in their metathoracic arborizations but with additional collaterals that pass into the mesothoracic ganglion.
Postnatal development of microtubules and neurofilaments in the rat optic nerve: A quantitative study
Authors: Cuenca N. , Fernandez E. , de Juan J. , Carreres J. , Iniguez C.
Published: May 2005

In this paper the postnatal changes in the cytoskeleton of the rat optic nerve fibers are described and quantified. These changes are also compared with other parameters such as myelination and axonal caliber with the aim of describing a general pattern of optic nerve maturation from a morphological point of view. The results showed that during the first postnatal week microtubules outnumbered neurofilaments but between days 8 and 20 the neurofilaments rapidly increased and on day 20 were about twice as numerous as microtubules. This proportion remained almost unaltered from the end of the third weak to the 44th postnatal day. The comparison with other parameters suggested that the cytoskeleton, and in particular the proportion between its components, may be a more reliable index for measuring optic nerve maturation than other variables commonly used.
Frontal eye field efferents in the macaque monkey: I. Subcortical pathways and topography of striatal and thalamic terminal fields
Authors: Stanton G. B. , Goldberg M. E. , Bruce C. J.
Published: May 2005

Anterograde tracers (tritiated leucine, proline, fucose; WGA‐HRP) were injected into sites within the frontal eye fields (FEF) of nine macaque monkeys. Low thresholds (≤50 μA) for electrically evoking saccadic eye movements were used to locate injection sites in four monkeys. Cases were grouped according to the amplitude of saccades evoked or predicted at the injection site. Dorsomedial prearcuate injection sites where large saccades were elicited were classified as lFEF cases, whereas ventrolateral prearcuate sites where small saccades were evoked were designated sFEF cases. One control case was injected in the medial postarcuate area 6.

We found five descending fiber bundles from FEF; fibers to the striatum, which enter the caudate nucleus at or just rostral to the genu of the internal capsule; fibers to the claustrum, which travel in the external capsule; and transthalamic, subthalamic, and pedunculopontine fibers. Our results indicate that transthalamic and subthalamic pathways supply all terminal sites in the thalamus, subthalamus, and tegmentum of the midbrain and pons, whereas pedunculopontine fibers appear to terminate in the pontine and reticularis tegmenti pontis nucleus exclusively.

Frontal eye field terminal fields in the striatum were topographically organized: lFEF projections terminated dorsal and rostral to sFEF projections. Thus, lFEF terminal fields were located centrally in the head and body of the caudate nucleus and a small dorsomedial portion of the putamen, whereas sFEF terminal fields were located in ventrolateral parts of the caudate body and ventromedial parts of the putamen. In the claustrum, lFEF projections terminated dorsal and rostral to sFEF projections. Projections from FEF terminated in ventral and caudal parts of the subthalamic nucleus without a clear topography. By comparison, terminal fields from medial postarcuate area 6 were located more caudally and laterally in the striatum and claustrum than projections from FEF, and more centrally in the subthalamic nucleus.

In the thalamus, FEF terminal patches in some thalamic nuclei were also topographically organized. Projections from lFEF terminated in dorsal area X, dorsolateral medial dorsal nucleus, pars parvicellularis (MDpc), and the caudal pole of MDpc, whereas projections from sFEF terminated in ventral area X, medial dorsal nucleus, pars multiformis, and caudal medial dorsal nucleus pars densocellularis. Characteristically, projections from postarcuate area 6 terminated in central ventral lateral nucleus, pars caudalis, ventral posterior lateral nucleus, pars oralis. Projections from dorsomedial postarcuate area 6 terminated in the paracentral and central lateral nuclei.